US20160201403A1

US20160201403A1 - Composite Sucker Rod Assemblies

Info

Publication number: US20160201403A1
Application number: US14/969,034
Authority: US
Inventors: Ashish Sen; Michael L. Wesley; David W. Eastep
Original assignee: Ticona LLC
Current assignee: Ticona LLC
Priority date: 2015-01-13
Filing date: 2015-12-15
Publication date: 2016-07-14

Abstract

Sucker rod assemblies are provided. A sucker rod assembly includes one or more continuous fiber reinforced thermoplastic rods. Each rod has a core comprising a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin. A sucker rod assembly further includes a first end fitting and a second end fitting, at least one of which is connected to the plurality of continuous fiber reinforced thermoplastic rods. Each rod has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, and the continuous fibers have a ratio of ultimate tensile strength to mass per unit length of greater than about 1,000 Megapascals per gram per meter. The continuous fibers constitute from about 25 wt. % to about 80 wt. % of each rod, and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of each rod.

Description

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Application Ser. No. 62/102,796, filed on Jan. 13, 2015, which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

A sucker rod is a rod uses in the oil and gas industry to join together surface and downhole components of a reciprocating piston pump installed in an oil well. In most cases, a number of sucker rods are connected together, end-to-end, to obtain the necessary length between the surface and downhole components. Each sucker rod can including fittings on each end of the rod in order to facilitate the connection to other sucker rods and the surface and downhole components.
Many known sucker rods are formed from metals, such as steel. However, there are significant problems with the use of such sucker rods. For example, metal sucker rods are heavy and have relatively small strength-to-weight ratios. Additionally, the chemical and temperature resistance capabilities of metal sucker rods are relatively low, particularly when subjected to oil well environments. Further, metal sucker rods are very susceptible to mechanical wear during operation. Still further, the requirement that a number of sucker rods of limited lengths be connected together to obtain longer necessary lengths introduces weak spots into the assembly, due to the connection joints between the various sucker rods.
More recently, fiberglass sucker rods have been introduced. While these sucker rods have addressed some of the issues raised above, many concerns remain. Additionally, known fiberglass sucker rods are relatively stiff, and thus cannot be spooled for transportation purposes, etc.
Accordingly, improved sucker rods are desired in the art. In particular, sucker rods which have improved strength-to-weight ratios, chemical and temperature resistance capabilities, mechanical wear resistance, and flexibility, and which can have relatively longer lengths which meet application requirements, would be advantageous.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present disclosure, a sucker rod assembly is provided. The sucker rod assembly includes a plurality of continuous fiber reinforced thermoplastic rods arranged in a stranded bundle. Each of the plurality of continuous fiber reinforced thermoplastic rods has a core which includes a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin. The sucker rod assembly further includes a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the plurality of continuous fiber reinforced thermoplastic rods. Each of the plurality of rods has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch. The continuous fibers constitute from about 25 wt. % to about 80 wt. % of each of the plurality of rods and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of each of the plurality of rods.
In accordance with another embodiment of the present disclosure, a sucker rod assembly is provided. The sucker rod assembly includes a single monolithic continuous fiber reinforced thermoplastic rod. The continuous fiber reinforced thermoplastic rod has a core which includes a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin. The sucker rod assembly further includes a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the continuous fiber reinforced thermoplastic rod. The continuous fiber reinforced thermoplastic rod has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch. The continuous fibers constitute from about 25 wt. % to about 80 wt. % of the rod and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of the rod.
In some exemplary embodiments, the continuous fibers of a rod of a sucker rod assembly of the present disclosure have a ratio of ultimate tensile strength to mass per unit length of greater than about 1,000 Megapascals per gram per meter. For example, in some exemplary embodiments, the continuous fibers of a rod of a sucker rod assembly of the present disclosure are carbon fibers.
In some exemplary embodiments, the thermoplastic resin of a rod of a sucker rod assembly of the present disclosure includes a polyarylene sulfide, such as polyphenylene sulfide.
In some exemplary embodiments, a rod of a sucker rod assembly of the present disclosure includes a capping layer surrounding the core of the rod. For example, in some exemplary embodiments, the capping layer may include polyetherether ketone and be free from fibers.
Other features and aspects of the present invention are set forth in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a side view, partially in cross-section, of a wellbore having a sucker rod assembly connected between a pump and a pump drive according to one embodiment of the present disclosure;

FIG. 2 is a perspective broken view of a sucker rod assembly according to one embodiment of the present disclosure;

FIG. 3 is a perspective broken view of a sucker rod assembly according to another embodiment of the present disclosure;

FIG. 4 is a schematic illustration of an impregnation system in accordance with one embodiment of the present disclosure;

FIG. 5 is a perspective view of a die in accordance with one embodiment of the present disclosure;

FIG. 6 is a cross-sectional view of the die shown in FIG. 5;

FIG. 7 is an exploded view of a manifold assembly and gate passage for a die in accordance with one embodiment of the present disclosure;

FIG. 8 is a perspective view of one embodiment of a second impregnation plate at least partially defining an impregnation zone in accordance with one embodiment of the present disclosure;

FIG. 9 is a close-up cross-sectional view of a portion of an impregnation zone in accordance with one embodiment of the present disclosure;

FIG. 10 is a close-up cross-sectional view of a downstream end portion of an impregnation zone in accordance with one embodiment of the present disclosure;

FIG. 11 is a perspective view of a land zone in accordance with one embodiment of the present disclosure;

FIG. 12 is a perspective view of a land zone in accordance with one embodiment of the present disclosure;

FIG. 13 is a schematic illustration of one embodiment of a pultrusion system that may be employed in the present invention;

FIG. 14 is a top cross-sectional view of one embodiment of various calibration dies that may be employed in accordance with the present invention;

FIG. 15 is a side cross-sectional view of one embodiment of a calibration die that may be employed in accordance with the present invention;

FIG. 16 is a front view of a portion of one embodiment of a calibration die that may be employed in accordance with the present invention;

FIG. 17 is a front view of one embodiment of forming rollers that may be employed in accordance with the present invention;

FIG. 18 is a perspective view of a tape in accordance with one embodiment of the present disclosure;

FIG. 19 is a cross-sectional view of a tape in accordance with one embodiment of the present disclosure; and

FIG. 20 is a perspective cross-sectional view of a composite rod formed in accordance with one embodiment of the present disclosure.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.
Generally speaking, the present disclosure is directed to sucker rod assemblies. A sucker rod assembly in accordance with the present disclosure is formed from one or more continuous fiber reinforced thermoplastic (“CFRT”) rods. In some embodiments, a plurality of CFRT rods may be utilized, with the rods arranged for example in a stranded bundle. In other embodiments, a single monolithic CFRT rod may be utilized. In exemplary embodiments, the CFRT rods may include a polyarylene sulfide, such as polyphenylene sulfide, in or as the thermoplastic resin. Further, in exemplary embodiments, the CFRT rods may utilize carbon fibers embedded in the thermoplastic resin.
The use of such rods in sucker rod assemblies in accordance with the present disclosure provides numerous advantages over previously known sucker rods. For example, the use of CFRT materials provides lightweight and strong rods, thus increasing the strength-to-weight ratios of the resulting sucker rod assemblies. Further, as discussed herein, CFRT rods formed in accordance with the present disclosure have excellent flexibility, thus allowing spooling of the resulting sucker rod assemblies. Additionally, CFRT rods formed in accordance with the present disclosure can be provided at relatively long lengths, which can be adjusted to meet application requirements. Thus, resulting sucker rod assemblies may advantageously not require increased connections and resulting weak spots, due to the ability of the CFRT rods to have lengths which are adapted to fit the requirements of particular applications.
Still further, CFRT rods formed in accordance with the present disclosure may have improved chemical and temperature resistance capabilities. For example, each rod may include a core and a capping layer surrounding and bonded to the core. This capping layer may protect the rod generally from harsh environmental conditions, and may further improve the wear resistance of the rod. In exemplary embodiments, for example, a capping layer may include polyetherether ketone, and may be free from fibers.
Referring now to FIG. 1, one embodiment of a sucker rod assembly 10 of the present disclosure being utilized in an oil and gas application, and specifically in a downhole application, is illustrated. As shown, sucker rod assembly 10 extends between a pump drive 12 and a pump 14. At least a portion of the sucker rod assembly 10 extends within and through a wellbore 16. As further illustrated, a sucker rod assembly 10 in accordance with the present disclosure may include a first end fitting 20 and a second end fitting 22, which may be connected to the one or more rods of the sucker rod assembly 10. In exemplary embodiments, only a single sucker rod assembly 10 is required for a downhole application, with the fittings 20, 22 coupled to the pump drive 12 and pump 14 as illustrated. In alternative embodiments, however, multiple sucker rod assemblies 10 may be utilized, with the fittings 20, 22 thereof connected to each other to form a string of sucker rod assemblies 10.
FIGS. 2 and 3 illustrate embodiments of a sucker rod assembly 10 in accordance with the present disclosure. For example, FIG. 2 illustrates a sucker rod assembly 10 which includes a single, monolithic composite rod 750 extending between and connected to a first end fitting 20 and a second end fitting 22. The fittings 20, 22 may be connected to the respective ends of the rod 750. As illustrated, for example, the ends of the rod 750 may fit within the fittings 20, 22, and the fittings 20, 22 may generally surround the ends of the rod 750. The ends of the rod 750 may be press-fit within or otherwise connected (via mechanical fasteners, adhesives, etc.) to the fittings 20, 22.
FIG. 3 illustrates a sucker rod assembly 10 which includes a plurality of composite rods 750 arranged in a stranded bundle. Each of the plurality of rods 750 is in contact with neighboring rods 750 within the bundle, as illustrated. Notably, in the arrangement illustrated, seven rods 750 are utilized, with six rods 750 surrounding a central rod 750. In other embodiments, 19 rods 750 can be utilized, such that for example an outer layer of 12 rods surrounds the six rods 750, or 37 or 49 rods 750 having similar arrangements can be utilized. Still further, however, it should be understood that any suitable number of rods 750 may be utilized in any suitable stranded bundle arrangement. The plurality of rods 750 may extend between and be connected to a first end fitting 20 and a second end fitting 22. The fittings 20, 22 may be connected to the respective ends of the rods 750. As illustrated, for example, the ends of the rods 750 may fit within the fittings 20, 22, and the fittings 20, 22 may generally surround the ends of the rods 750. The ends of the rods 750 may be press-fit within or otherwise connected (via mechanical fasteners, adhesives, etc.) to the fittings 20, 22.
Any suitable fittings 20, 22 may be utilized in a sucker rod assembly 10 in accordance with the present disclosure. For example, FIGS. 2 and 3 illustrate simple, tubular fittings. First end fitting 20 is illustrated as a male fitting having male threads, while second end fitting 22 is illustrated as a female fitting having female threads. Alternatively, any suitable fittings having suitable male and/or female coupling apparatus may be utilized for the fittings 20, 22. In exemplary embodiments, the fittings 20, 22 may be formed from a suitable metal, such as steel. Alternatively, however, any suitable materials, include polymers such as thermoplastics as discussed herein, may be utilized.
Referring now to FIG. 20, one embodiment of a rod 750 for use in a sucker rod assembly 10 is presented. As can be seen, the rod 750 includes a core 760 formed from a continuous fiber reinforced thermoplastic (“CFRT”) material and a capping layer 800 that generally surrounds and is bonded to the core 760. Capping layer 800 may extend around the perimeter of the core 760 and define an external surface of the rod 750.
As illustrated, the rod 750 has a generally circular shape and includes a core 760 formed from one or more consolidated rovings 142. By “generally circular”, it is generally meant that the aspect ratio of the rod (height divided by the width) is typically from about 1.0 to about 1.5, and in some embodiments, about 1.0. Due to selective control over the process used to impregnate fiber rovings and form tapes 152, 156 as discussed herein, as well the process for compressing and shaping the tape(s) into a preform and finally into a core 760, as discussed further herein, the rod 750 and core 760 thereof may possess a relatively even distribution of resin 214 across along its entire length. This also means that the continuous fibers are distributed in a generally uniform manner about a longitudinal central axis “L” of the core 760. As shown in FIG. 20, for example, the core 760 includes continuous fibers 400 embedded within a thermoplastic matrix 214. The fibers 400 are distributed generally uniformly about the longitudinal axis “L.” It should be understood that only a few fibers are shown in FIG. 20, and that the core 760 will typically contain a substantially greater number of uniformly distributed fibers.
The cross-sectional thickness (“T”) of the rod 750 may be strategically selected to help achieve a particular strength. For example, the rod 750 may have a thickness (e.g., diameter) of from about 0.1 to about 40 millimeters, in some embodiments from about 0.5 to about 30 millimeters, and in some embodiments, from about 1 to about 10 millimeters. The thickness of the capping layer 800 depends on the intended function of the part, but is typically from about 0.01 to about 10 millimeters, and in some embodiments, from about 0.02 to about 5 millimeters. Regardless, the total cross-sectional thickness or height of the rod typically ranges from about of from about 0.1 to about 50 millimeters, in some embodiments from about 0.5 to about 40 millimeters, and in some embodiments, from about 1 to about 20 millimeters. While the rod 750 may be substantially continuous in length, the length of the rod is often practically limited by the spool onto which it will be wound and stored or the length of the continuous fibers. For example, the length often ranges from about 1000 to about 5000 meters, although even greater lengths are certainly possible.
Referring still to FIG. 20, the CFRT material of the core 760 includes a thermoplastic material or resin and a plurality of continuous fibers embedded therein. Suitable thermoplastic materials for use in rods include, for instance, polyolefins (e.g., polypropylene, propylene-ethylene copolymers, etc.), polyesters (e.g., polybutylene terephalate (“PBT”)), polycarbonates, polyamides (e.g., PA12, Nylon™), polyether ketones (e.g., polyether ether ketone (“PEEK”)), polyetherimides, polyarylene ketones (e.g., polyphenylene diketone (“PPDK”)), liquid crystal polymers, polyarylene sulfides (e.g., polyphenylene sulfide (“PPS”), poly(biphenylene sulfide ketone), poly(phenylene sulfide diketone), poly(biphenylene sulfide), etc.), fluoropolymers (e.g., polytetrafluoroethylene-perfluoromethylvinylether polymer, perfluoro-alkoxyalkane polymer, petrafluoroethylene polymer, ethylene-tetrafluoroethylene polymer, etc.), polyacetals, polyurethanes, polycarbonates, styrenic polymers (e.g., acrylonitrile butadiene styrene (“ABS”)), and so forth.
The thermoplastic material of the core 760 may further include a plurality of fibers embedded therein to reinforce the thermoplastic material. In exemplary embodiments, the CFRT material includes continuous fibers, although it should be understood that long fibers may additionally be included therein. The fibers may be dispersed in the thermoplastic material to form the CFRT material. As used therein, the term “long fibers” generally refers to fibers, filaments, yarns, or rovings that are not continuous, and as opposed to “continuous fibers” which generally refer to fibers, filaments, yarns, or rovings having a length that is generally limited only by the length of a part. The fibers dispersed in the polymer material may be formed from any conventional material known in the art, such as metal fibers, glass fibers (e.g., E-glass, A-glass, C-glass, D-glass, AR-glass, R-glass, S-glass such as S1-glass or S2-glass), carbon fibers (e.g., graphite), boron fibers, ceramic fibers (e.g., alumina or silica), aramid fibers (e.g., Kevlar® marketed by E. I. duPont de Nemours, Wilmington, Del.), synthetic organic fibers (e.g., polyamide, polyethylene, paraphenylene, terephthalamide, polyethylene terephthalate and polyphenylene sulfide), and various other natural or synthetic inorganic or organic fibrous materials known for reinforcing polymer compositions. Glass fibers, carbon fibers, and aramid fibers are particularly desirable. In exemplary embodiments, the continuous fibers may be generally unidirectional.
A rod 750 in accordance with the present disclosure may be formed using any suitable process or apparatus. Exemplary embodiments of suitable processes and apparatus, such as pultrusion processes and apparatus, for forming a tape and rod according to the present disclosure are discussed in detail below.
Referring to FIG. 4, one embodiment of such an extrusion device is shown. More particularly, the apparatus includes an extruder 130 containing a screw shaft 134 mounted inside a barrel 132. A heater 136 (e.g., electrical resistance heater) is mounted outside the barrel 132. During use, a feedstock 137 is supplied to the extruder 130 through a hopper 138. The feedstock is formed from a thermoplastic material as discussed above. The feedstock 137 is conveyed inside the barrel 132 by the screw shaft 134 and heated by frictional forces inside the barrel 132 and by the heater 136. Upon being heated, the feedstock 137 exits the barrel 132 through a barrel flange 138 and enters a die flange 139 of an impregnation die 150.
A continuous fiber roving 142 or a plurality of continuous fiber rovings 142 are supplied from a reel or reels 144 to die 150. The rovings 142 are generally positioned side-by-side, with minimal to no distance between neighboring rovings, before impregnation. The feedstock 137 may further be heated inside the die by heaters 146 mounted in or around the die 150. The die is generally operated at temperatures that are sufficient to cause and/or maintain the proper melt temperature for the thermoplastic material, thus allowing for the desired level of impregnation of the rovings by the thermoplastic material. Typically, the operation temperature of the die is higher than the melt temperature of the thermoplastic material, such as at temperatures from about 200° C. to about 450° C. When processed in this manner, the continuous fiber rovings 142 become embedded in the thermoplastic material, which may be a resin 214 processed from the feedstock 137. The mixture may then exit the impregnation die 150 as wetted composite, extrudate, or tape 152.
As used herein, the term “roving” generally refers to a bundle of individual fibers 400. The fibers 400 contained within the roving can be twisted or can be straight. The rovings may contain a single fiber type or different types of fibers 400. Different fibers may also be contained in individual rovings or, alternatively, each roving may contain a different fiber type. The continuous fibers employed in the rovings possess a high degree of tensile strength relative to their mass. For example, the ultimate tensile strength of the fibers is typically from about 1,000 to about 15,000 Megapascals (“MPa”), in some embodiments from about 2,000 MPa to about 10,000 MPa, and in some embodiments, from about 3,000 MPa to about 6,000 MPa. Such tensile strengths may be achieved even though the fibers are of a relatively light weight, such as a mass per unit length of from about 0.05 to about 2 grams per meter, in some embodiments from about 0.4 to about 1.5 grams per meter. The ratio of ultimate tensile strength to mass per unit length may thus be greater than about 1,000 Megapascals per gram per meter (“MPa/g/m”), in some embodiments greater than about 4,000 MPa/g/m, and in some embodiments from about 5,000 to about 20,000 MPa/g/m. Carbon fibers are particularly suitable for use as the continuous fibers, which typically have a tensile strength to mass ratio in the range of from about 5,000 to about 7,000 MPa/g/m. The continuous fibers often have a nominal diameter of about 4 to about 35 micrometers, and in some embodiments, from about 9 to about 35 micrometers. The number of fibers contained in each roving can be constant or vary from roving to roving. Typically, a roving contains from about 1,000 fibers to about 50,000 individual fibers, and in some embodiments, from about 5,000 to about 30,000 fibers.
A pressure sensor 147 may sense the pressure near the impregnation die 150 to allow control to be exerted over the rate of extrusion by controlling the rotational speed of the screw shaft 134, or the feed rate of the feeder. That is, the pressure sensor 147 is positioned near the impregnation die 150, such as upstream of the manifold assembly 220, so that the extruder 130 can be operated to deliver a correct amount of resin 214 for interaction with the fiber rovings 142. After leaving the impregnation die 150, impregnated rovings 142 or the extrudate or tape 152, which may comprises the CFRT material, may enter an optional pre-shaping or guiding section (not shown) and/or a preheating device to control the temperature of the extrudate before entering a nip formed between two adjacent rollers 190. Although optional, the rollers 190 can help to consolidate the impregnated rovings 142 into a tape 156 or consolidate the tape 152 into a final tape 156, as well as enhance fiber impregnation and squeeze out any excess voids. In addition to the rollers 190, other shaping devices may also be employed, such as a die system. Regardless, the resulting consolidated tape 156 is pulled by tracks 162 and 164 mounted on rollers. The tracks 162 and 164 also pull the impregnated rovings 142 or tape 152 from the impregnation die 150 and through the rollers 190. If desired, the consolidated tape 156 may be wound up at a section 171. Generally speaking, the resulting tapes are relatively thin and typically have a thickness of from about 0.05 to about 1 millimeter, in some embodiments from about 0.1 to about 0.8 millimeters, and in some embodiments, from about 0.1 to about 0.4 millimeters.
Perspective views of one embodiment of a die 150 according to the present disclosure are further shown in FIGS. 4 and 5. As shown, resin 214 is flowed into the die 150 as indicated by resin flow direction 244. The resin 214 is distributed within the die 150 and then interacted with the rovings 142. The rovings 142 are traversed through the die 150 in roving run direction 282, and are coated with resin 214. The rovings 142 are then impregnated with the resin 214, and these impregnated rovings 142 exit the die 150. In some embodiments, as shown in FIG. 4, the impregnated rovings 142 are connected by the resin 214 and thus exit as tape 152. In other embodiments, as shown in FIGS. 5 and 6, the impregnated rovings 142 exit the die separately, each impregnated within resin 214.
Within the impregnation die, it is generally desired that the rovings 142 are traversed through an impregnation zone 250 to impregnate the rovings with the polymer resin 214. In the impregnation zone 250, the polymer resin may be forced generally transversely through the rovings by shear and pressure created in the impregnation zone 250, which significantly enhances the degree of impregnation. This is particularly useful when forming a composite from tapes of high fiber content, such as about 35% weight fraction (“Wf”) or more, and in some embodiments, from about 40% Wf or more. Typically, the die 150 will include a plurality of contact surfaces 252, such as for example at least 2, at least 3, from 4 to 7, from 2 to 20, from 2 to 30, from 2 to 40, from 2 to 50, or more contact surfaces 252, to create a sufficient degree of penetration and pressure on the rovings 142. Although their particular form may vary, the contact surfaces 252 typically possess a curvilinear surface, such as a curved lobe, pin, etc. The contact surfaces 252 are also typically made of a metal material.
FIG. 6 shows a cross-sectional view of an impregnation die 150. As shown, the impregnation die 150 includes a manifold assembly 220 and an impregnation section. The impregnation section includes an impregnation zone 250. In some embodiments, the impregnation section additionally includes a gate passage 270. The manifold assembly 220 is provided for flowing the polymer resin 214 therethrough. For example, the manifold assembly 220 may include a channel 222 or a plurality of channels 222. The resin 214 provided to the impregnation die 150 may flow through the channels 222.
As shown in FIG. 7, in exemplary embodiments, at least a portion of each of the channels 222 may be curvilinear. The curvilinear portions may allow for relatively smooth redirection of the resin 214 in various directions to distribute the resin 214 through the manifold assembly 220, and may allow for relatively smooth flow of the resin 214 through the channels 222. Alternatively, the channels 222 may be linear, and redirection of the resin 214 may be through relatively sharp transition areas between linear portions of the channels 222. It should further be understood that the channels 222 may have any suitable shape, size, and/or contour.
The plurality of channels 222 may, in exemplary embodiments as shown in FIG. 7, be a plurality of branched runners 222. The runners 222 may include a first branched runner group 232. The first branched runner group 232 includes a plurality of runners 222 branching off from an initial channel or channels 222 that provide the resin 214 to the manifold assembly 220. The first branched runner group 232 may include 2, 3, 4 or more runners 222 branching off from the initial channels 222.
If desired, the runners 222 may include a second branched runner group 234 diverging from the first branched runner group 232, as shown. For example, a plurality of runners 222 from the second branched runner group 234 may branch off from one or more of the runners 222 in the first branched runner group 232. The second branched runner group 234 may include 2, 3, 4 or more runners 222 branching off from runners 222 in the first branched runner group 232.
If desired, the runners 222 may include a third branched runner group 236 diverging from the second branched runner group 234, as shown. For example, a plurality of runners 222 from the third branched runner group 236 may branch off from one or more of the runners 222 in the second branched runner group 234. The third branched runner group 236 may include 2, 3, 4 or more runners 222 branching off from runners 222 in the second branched runner group 234.
In some exemplary embodiments, as shown, the plurality of branched runners 222 has a symmetrical orientation along a central axis 224. The branched runners 222 and the symmetrical orientation thereof generally evenly distribute the resin 214, such that the flow of resin 214 exiting the manifold assembly 220 and coating the rovings 142 is substantially uniformly distributed on the rovings 142. This desirably allows for generally uniform impregnation of the rovings 142.
Further, the manifold assembly 220 may in some embodiments define an outlet region 242. The outlet region 242 is that portion of the manifold assembly 220 wherein resin 214 exits the manifold assembly 220. Thus, the outlet region 242 generally encompasses at least a downstream portion of the channels or runners 222 from which the resin 214 exits. In some embodiments, as shown, at least a portion of the channels or runners 222 disposed in the outlet region 242 have an increasing area in a flow direction 244 of the resin 214. The increasing area allows for diffusion and further distribution of the resin 214 as the resin 214 flows through the manifold assembly 220, which further allows for substantially uniform distribution of the resin 214 on the rovings 142. Additionally or alternatively, various channels or runners 222 disposed in the outlet region 242 may have constant areas in the flow direction 244 of the resin 214, or may have decreasing areas in the flow direction 244 of the resin 214.
In some embodiments, as shown, each of the channels or runners 222 disposed in the outlet region 242 is positioned such that resin 214 flowing therefrom is combined with resin 214 from other channels or runners 222 disposed in the outlet region 242. This combination of the resin 214 from the various channels or runners 222 disposed in the outlet region 242 produces a generally singular and uniformly distributed flow of resin 214 from the manifold assembly 220 to substantially uniformly coat the rovings 142. Alternatively, some of the channels or runners 222 disposed in the outlet region 242 may be positioned such that resin 214 flowing therefrom is discrete from the resin 214 from other channels or runners 222 disposed in the outlet region 242. In these embodiments, a plurality of discrete but generally evenly distributed resin flows 214 may be produced by the manifold assembly 220 for substantially uniformly coating the rovings 142.
As shown in FIG. 6, at least a portion of the channels or runners 222 disposed in the outlet region 242 have curvilinear cross-sectional profiles. These curvilinear profiles allow for the resin 214 to be gradually directed from the channels or runners 222 generally downward towards the rovings 142. Alternatively, however, these channels or runners 222 may have any suitable cross-sectional profiles.
As further illustrated in FIGS. 6 and 7, after flowing through the manifold assembly 220, the resin 214 may flow through gate passage 270. Gate passage 270 is positioned between the manifold assembly 220 and the impregnation zone 250, and is provided for flowing the resin 214 from the manifold assembly 220 such that the resin 214 coats the rovings 142. Thus, resin 214 exiting the manifold assembly 220, such as through outlet region 242, may enter gate passage 270 and flow therethrough.
In some embodiments, as shown in FIG. 6, the gate passage 270 extends vertically between the manifold assembly 220 and the impregnation zone 250. Alternatively, however, the gate passage 270 may extend at any suitable angle between vertical and horizontal such that resin 214 is allowed to flow therethrough.
Further, as shown in FIG. 6, in some embodiments at least a portion of the gate passage 270 has a decreasing cross-sectional profile in the flow direction 244 of the resin 214. This taper of at least a portion of the gate passage 270 may increase the flow rate of the resin 214 flowing therethrough before it contacts the rovings 142, which may allow the resin 214 to impinge on the rovings 142. Initial impingement of the rovings 142 by the resin 214 provides for further impregnation of the rovings, as discussed below. Further, tapering of at least a portion of the gate passage 270 may increase backpressure in the gate passage 270 and the manifold assembly 220, which may further provide more even, uniform distribution of the resin 214 to coat the rovings 142. Alternatively, the gate passage 270 may have an increasing or generally constant cross-sectional profile, as desired or required.
Upon exiting the manifold assembly 220 and the gate passage 270 of the die 150 as shown in FIG. 6, the resin 214 contacts the rovings 142 being traversed through the die 150. As discussed above, the resin 214 may substantially uniformly coat the rovings 142, due to distribution of the resin 214 in the manifold assembly 220 and the gate passage 270. Further, in some embodiments, the resin 214 may impinge on an upper surface of each of the rovings 142, or on a lower surface of each of the rovings 142, or on both an upper and lower surface of each of the rovings 142. Initial impingement on the rovings 142 provides for further impregnation of the rovings 142 with the resin 214. Impingement on the rovings 142 may be facilitated by the velocity of the resin 214 when it impacts the rovings 142, the proximity of the rovings 142 to the resin 214 when the resin exits the manifold assembly 220 or gate passage 270, or other various variables.
As shown in FIG. 6, the coated rovings 142 are traversed in run direction 282 through impregnation zone 250. The impregnation zone 250 is in fluid communication with the manifold assembly 220, such as through the gate passage 270 disposed therebetween. The impregnation zone 250 is configured to impregnate the rovings 142 with the resin 214.
For example, as discussed above, in exemplary embodiments as shown in FIGS. 6 and 8 through 10, the impregnation zone 250 includes a plurality of contact surfaces 252. The rovings 142 are traversed over the contact surfaces 252 in the impregnation zone. Impingement of the rovings 142 on the contact surface 252 creates shear and pressure sufficient to impregnate the rovings 142 with the resin 214 coating the rovings 142.
In some embodiments, as shown in FIGS. 6, 9 and 10, the impregnation zone 250 is defined between two spaced apart opposing impregnation plates 256 and 258, which may be included in the impregnation section. First plate 256 defines a first inner surface 257, while second plate 258 defines a second inner surface 259. The impregnation zone 250 is defined between the first plate 256 and the second plate 258. The contact surfaces 252 may be defined on or extend from both the first and second inner surfaces 257 and 259, or only one of the first and second inner surfaces 257 and 259.
In exemplary embodiments, as shown in FIGS. 6, 9 and 10, the contact surfaces 252 may be defined alternately on the first and second surfaces 257 and 259 such that the rovings alternately impinge on contact surfaces 252 on the first and second surfaces 257 and 259. Thus, the rovings 142 may pass contact surfaces 252 in a waveform, tortuous or sinusoidal-type pathway, which enhances shear.
Angle 254 at which the rovings 142 traverse the contact surfaces 252 may be generally high enough to enhance shear and pressure, but not so high to cause excessive forces that will break the fibers. Thus, for example, the angle 254 may be in the range between approximately 1° and approximately 30°, and in some embodiments, between approximately 5° and approximately 25°.
As stated above, contact surfaces 252 typically possess a curvilinear surface, such as a curved lobe, pin, etc. In exemplary embodiments as shown, a plurality of peaks, which may form contact surfaces 252, and valleys are thus defined. Further, in many exemplary embodiments, the impregnation zone 250 has a waveform cross-sectional profile. In one exemplary embodiment as shown in FIGS. 6 and 8 through 10, the contact surfaces 252 are lobes that form portions of the waveform surfaces of both the first and second plates 256 and 258 and define the waveform cross-sectional profile. FIG. 8 illustrates the second plate 258 and the various contact surfaces thereon that form at least a portion of the impregnation zone 250 according to some of these embodiments.
In other embodiments, the contact surfaces 252 are lobes that form portions of a waveform surface of only one of the first or second plate 256 or 258. In these embodiments, impingement occurs only on the contact surfaces 252 on the surface of the one plate. The other plate may generally be flat or otherwise shaped such that no interaction with the coated rovings occurs.
In other alternative embodiments, the impregnation zone 250 may include a plurality of pins (or rods), each pin having a contact surface 252. The pins may be static, freely rotational (not shown), or rotationally driven. Further, the pins may be mounted directly to the surface of the plates defining the impingement zone, or may be spaced from the surface. It should be noted that the pins may be heated by heaters 143, or may be heated individually or otherwise as desired or required. Further, the pins may be contained within the die 150, or may extend outwardly from the die 150 and not be fully encased therein.
In further alternative embodiments, the contact surfaces 252 and impregnation zone 250 may comprise any suitable shapes and/or structures for impregnating the rovings 142 with the resin 214 as desired or required.
As discussed, a roving 142 traversed through an impregnation zone 250 according to the present disclosure may become impregnated by resin 214, thus resulting in an impregnated roving 142, and optionally a tape 152 comprising at least one roving 142, exiting the impregnation zone 250, such as downstream of the contact surfaces 252 in the run direction 282. The impregnated rovings 142 and optional tape 152 exiting the impregnation zone 250 are thus formed from a fiber impregnated polymer material, as discussed above.
As further shown in FIGS. 5 and 6, in some embodiments, a faceplate 290 may adjoin or be adjacent to the impregnation zone 250. The faceplate 290 may be positioned downstream of the impregnation zone 250 and, if included, the land zone 280, in the run direction 282. The faceplate 290 may contact other components of the die 150, such as the impregnation zone 250 or land zone 280, or may be spaced therefrom. Faceplate 290 is generally configured to meter excess resin 214 from the rovings 142. Thus, apertures in the faceplate 290, through which the rovings 142 traverse, may be sized such that when the rovings 142 are traversed therethrough, the size of the apertures causes excess resin 214 to be removed from the rovings 142.
As shown in FIG. 4, in alternative embodiments, the die 150 may lack a faceplate 290. Further, in some embodiments, the formation and maintenance of a tape 152 within and exited from a die 150 of the present disclosure may be facilitated through the lack of or removal of a faceplate from the die 150. Removal of the faceplate 290 allows for a plurality of rovings 142 exiting a die 150 to exit as a single sheet or tape 152, rather than as separated rovings 142 due to metering through the faceplate. This could potentially eliminate the need to later form these rovings 142 into such a sheet or tape 156. Removal of the faceplate 290 may have additional advantages. For example, removal may prevent clogging of the faceplate with resin 214, which can disrupt the traversal of rovings 142 therethrough. Additionally, removal may allow for easier access to the impregnation zone 250, and may thus make it easier to introduce and reintroduce rovings 142 to the impregnation zone 250 during start-up, after temporary disruptions such as due to breakage of a roving 142, or during any other suitable time period.
It should be understood that a tape 152, 156 according to the present disclosure may have any suitable cross-sectional shape and/or size. For example, such tape 152, 156 may have a generally rectangular shape, or a generally oval or circular or other suitable polygonal or otherwise shape. Further, it should be understood that one or more impregnated rovings 142 having been traversed through the impregnation zone 250 may together form the tape 152, 156, with the resin 214 of the various rovings 142 connected to form such tape 152, 156. The various above amounts, ranges, and/or ratios may thus in exemplary embodiments be determined for a tape 152 having any suitable number of impregnated rovings 142 embedded and generally dispersed within resin 214.
To further facilitate impregnation of the rovings 142, they may also be kept under tension while present within the die 150, and specifically within the impregnation zone 250. The tension may, for example, range from about 5 to about 300 Newtons, in some embodiments from about 50 to about 250 Newtons, and in some embodiments, from about 100 to about 200 Newtons per roving 142 or tow of fibers.
As shown in FIGS. 11 and 12, in some embodiments, a land zone 280 may be positioned downstream of the impregnation zone 250 in run direction 282 of the rovings 142. The rovings 142 may traverse through the land zone 280 before exiting the die 150. In some embodiments, as shown in FIG. 11, at least a portion of the land zone 280 may have an increasing cross-sectional profile in run direction 282, such that the area of the land zone 280 increases. The increasing portion may be the downstream portion of the land zone 280 to facilitate the rovings 142 exiting the die 150. Alternatively, the cross-sectional profile or any portion thereof may decrease, or may remain constant as shown in FIG. 12.
Additionally, other components may be optionally employed to assist in the impregnation of the fibers. For example, a “gas jet” assembly may be employed in certain embodiments to help uniformly spread a roving of individual fibers, which may each contain up to as many as 24,000 fibers, across the entire width of the merged tow. This helps achieve uniform distribution of strength properties. Such an assembly may include a supply of compressed air or another gas that impinges in a generally perpendicular fashion on the moving rovings that pass across exit ports. The spread rovings may then be introduced into a die for impregnation, such as described above.
It should be understood that tapes 152, 156 and impregnated rovings 142 thereof according to the present disclosure need not be formed in the dies 150 and other apparatus as discussed above. Such dies 150 and apparatus are merely disclosed as examples of suitable equipment for forming tapes 152, 156. The use of any suitable equipment or process to form tapes 152, 156 is within the scope and spirit of the present disclosure.
A relatively high percentage of fibers may be employed in a tape (and resulting rod), and CFRT material thereof, to provide enhanced strength properties. For instance, fibers typically constitute from about 25 wt. % to about 80 wt. %, in some embodiments from about 30 wt. % to about 75 wt. %, and in some embodiments, from about 35 wt. % to about 70 wt. % of the tape or material thereof. Likewise, polymer(s) typically constitute from about 20 wt. % to about 75 wt. %, in some embodiments from about 25 wt. % to about 70 wt. %, and in some embodiments, from about 30 wt. % to about 65 wt. % of the tape 152, 156. Such percentage of fibers may additionally or alternatively be measured as a volume fraction. For example, in some embodiments, the CFRT material may have a fiber volume fraction between approximately 25% and approximately 80%, in some embodiments between approximately 30% and approximately 70%, in some embodiments between approximately 40% and approximately 60%, and in some embodiments between approximately 45% and approximately 55%.
After formation of a tape 152, 156, the tape 152, 156 may be formed into a core 760 of a rod 750. Any suitable processes and apparatus may be utilized to form a tape 152, 156 into the core 760 of a rod 750. The specific manner in which rovings and tapes 152, 156, are shaped may be carefully controlled to ensure that rods 750 can be formed with an adequate degree of compression and strength properties. Referring to FIG. 13, for example, one particular embodiment of a system and method for forming a rod are shown. In this embodiment, two tapes 152, 156 are initially provided in a wound package on a creel 620. The creel 620 may be an unreeling creel that includes a frame provided with horizontal spindles 622, each supporting a package. A pay-out creel may also be employed, particularly if desired to induce a twist into the fibers. It should also be understood that the tape may also be formed in-line with the formation of the rod. In one embodiment, for example, the tape 152, 156 downstream of the guide assembly 510 may be directly supplied to the system used to form a rod. A tension-regulating device 640 may also be employed to help control the degree of tension in the tapes 152, 156. The device 640 may include inlet plate 630 that lies in a vertical plane parallel to the rotating spindles 622 of the creel 620 and/or perpendicular to the incoming ribbons. The tension-regulating device 640 may contain cylindrical bars 641 arranged in a staggered configuration so that the tape 152, 156 passes over and under these bars to define a wave pattern. The height of the bars can be adjusted to modify the amplitude of the wave pattern and control tension.
The tapes 152, 156 may be heated in an oven 645 before entering a consolidation die. Heating may be conducted using any known type of oven, as in an infrared oven, convection oven, etc. During heating, the fibers in the tapes are unidirectionally oriented to optimize the exposure to the heat and maintain even heat across the entire tape. The temperature to which the tapes 152, 156 are heated is generally high enough to soften the thermoplastic polymer to an extent that the tapes can bond together. However, the temperature is not so high as to destroy the integrity of the material. The temperature may, for example, range from about 100° C. to about 500° C., in some embodiments from about 200° C. to about 400° C., and in some embodiments, from about 250° C. to about 350° C. In one particular embodiment, for example, polyphenylene sulfide (“PPS”) is used as the polymer, and the tapes are heated to or above the melting point of PPS, which is about 285° C.
Upon being heated, the tapes 152, 156 are provided to a consolidation die 650 that compresses them together into a preform 614, as well as aligns and forms the initial shape of the rod. As shown generally in FIG. 13, for example, the tapes 152, 156 are guided through a flow passage 651 of the die 650 in a direction “A” from an inlet 653 to an outlet 655. The passage 651 may have any of a variety of shapes and/or sizes to achieve the rod configuration. For example, the channel and rod configuration may be circular, elliptical, parabolic, etc. Within the die 650, the tapes are generally maintained at a temperature at or above the melting point of the thermoplastic matrix used in the ribbon to ensure adequate consolidation.
The desired heating, compression, and shaping of the tapes 152, 156 may be accomplished through the use of a die 650 having one or multiple sections. For instance, although not shown in detail in FIG. 13, the consolidation die 650 may possess multiple sections that function together to compress and shape the tapes 152, 156 into the desired configuration. For instance, a first section of the passage 651 may be a tapered zone that initially shapes the material as it flows from into the die 650. The tapered zone generally possesses a cross-sectional area that is larger at its inlet than at its outlet. For example, the cross-sectional area of the passage 651 at the inlet of the tapered zone may be about 2% or more, in some embodiments about 5% or more, and in some embodiments, from about 10% to about 20% greater than the cross-sectional area at the outlet of the tapered zone. Regardless, the cross-sectional of the flow passage typically changes gradually and smoothly within the tapered zone so that a balanced flow of the composite material through the die can be maintained. A shaping zone may also follow the tapered zone that compresses the material and provides a generally homogeneous flow therethrough. The shaping zone may also pre-shape the material into an intermediate shape that is similar to that of the rod, but typically of a larger cross-sectional area to allow for expansion of the thermoplastic polymer while heated so as to minimize the risk of backup within the die 650. The shaping zone could also include one or more surface features that impart a directional change to the preform. The directional change forces the material to be redistributed resulting in a more even distribution of the fiber/resin in the final shape. This also reduces the risk of dead spots in the die that can cause burning of the resin. For example, the cross-sectional area of the passage 651 at the shaping zone may be about 2% or more, in some embodiments about 5% or more, and in some embodiments, from about 10% to about 20% greater than the width of the preform 614. A die land may also follow the shaping zone to serve as an outlet for the passage 651. The shaping zone, tapered zone, and/or die land may be heated to a temperature at or above that of the glass transition temperature or melting point of the thermoplastic matrix.
If desired, a second die 660 (e.g., calibration die) may also be employed that compresses the preform 614 into the final shape of the rod. When employed, it is sometimes desired that the preform 614 is allowed to cool briefly after exiting the consolidation die 650 and before entering the optional second die 660. This allows the consolidated preform 614 to retain its initial shape before progressing further through the system. Typically, cooling reduces the temperature of the exterior of the rod below the melting point temperature of the thermoplastic matrix to minimize and substantially prevent the occurrence of melt fracture on the exterior surface of the rod. The internal section of the rod, however, may remain molten to ensure compression when the rod enters the calibration die body. Such cooling may be accomplished by simply exposing the preform 614 to the ambient atmosphere (e.g., room temperature) or through the use of active cooling techniques (e.g., water bath or air cooling) as is known in the art. In one embodiment, for example, air is blown onto the preform 614 (e.g., with an air ring). The cooling between these stages, however, generally occurs over a small period of time to ensure that the preform 614 is still soft enough to be further shaped. For example, after exiting the consolidation die 650, the preform 614 may be exposed to the ambient environment for only from about 1 to about 20 seconds, and in some embodiments, from about 2 to about 10 seconds, before entering the second die 660. Within the die 660, the preform is generally kept at a temperature below the melting point of the thermoplastic matrix used in the ribbon so that the shape of the rod can be maintained. Although referred to above as single dies, it should be understood that the dies 650 and 660 may in fact be formed from multiple individual dies (e.g., face plate dies).
Thus, in some embodiments, multiple individual dies 660 may be utilized to gradually shape the material into the desired configuration. The dies 660 are placed in series, and provide for gradual decreases in the dimensions of the material. Such gradual decreases allow for shrinkage during and between the various steps.
For example, as shown in FIGS. 14 through 16, a first die 660 may include one or more inlets 662 and corresponding outlets 664, as shown. Any number of inlets 662 and corresponding outlets 664 may be included in a die 660, such as four as shown, one, two, three, five, six, or more. An inlet 662 in some embodiments may be generally oval or circle shaped. In other embodiments, the inlet 662 may have a curved rectangular shape, i.e., a rectangular shape with curved corners or a rectangular shape with straight longer sidewalls and curved shorter sidewalls. Further, an outlet 664 may be generally oval or circle shaped, or may have a curved rectangular shape. In some embodiments wherein an oval shaped inlet is utilized, the inlet 662 may have a major axis length 666 to minor axis length 668 ratio in a range between approximately 3 to 1 and approximately 5 to 1. In some embodiments wherein an oval or circular shaped inlet is utilized, the outlet 664 may have a major axis length 666 to minor axis length 668 ratio in a range between approximately 1 to 1 and approximately 3 to 1. In embodiments wherein a curved rectangular shape is utilized, the inlet and outlet may have major axis length 666 to minor axis length 668 ratios (aspect ratios) between approximately 2 to 1 and approximately 7 to 1, with the outlet 664 ratio being less than the inlet 662 ratio.
In further embodiments, the cross-sectional area of an inlet 662 and the cross-sectional area of a corresponding outlet 664 of the first die 660 may have a ratio in a range between approximately 1.5 to 1 and 6 to 1.
The first die 660 thus provides a generally smooth transformation of polymer impregnated fiber material to a shape that is relatively similar to a final shape of the resulting rod, which in exemplary embodiments has a circular or oval shaped cross-section. Subsequent dies, such as a second die 660 and third die 660 as shown in FIG. 14, may provide for further gradual decreases and/or changes in the dimensions of the material, such that the shape of the material is converted to a final cross-sectional shape of the rod. These subsequent dies 660 may both shape and cool the material. For example, in some embodiments, each subsequent die 660 may be maintained at a lower temperature than the previous dies. In exemplary embodiments, all dies 660 are maintained at temperatures that are higher than a softening point temperature for the material.
In further exemplary embodiments, dies 660 having relatively long land lengths 669 may be desired, due to for example desires for proper cooling and solidification, which are critical in achieving a desired rod shape and size. Relatively long land lengths 669 reduce stresses and provide smooth transformations to desired shapes and sizes, and with minimal void fraction and bow characteristics. In some embodiments, for example, a ratio of land length 669 at an outlet 664 to major axis length 666 at the outlet 664 for a die 660 may be in the range between approximately 0 and approximately 20, such as between approximately 2 and approximately 6.
The use of calibration dies 660 according to the present disclosure provides for gradual changes in material cross-section, as discussed. These gradual changes may in exemplary embodiments ensure that the resulting product, such as a rod or other suitable product has a generally uniform fiber distribution with relatively minimal void fraction.
It should be understood that any suitable number of dies 660 may be utilized to gradually form the material into a profile having any suitable cross-sectional shape, as desired or required by various applications.
In addition to the use of one or more dies, other mechanisms may also be employed to help compress the preform 614 into the shape of a core 760 for a rod 750. For example, forming rollers 690, as shown in FIG. 17, may be employed between the consolidation die 650 and the calibration die 660, between the various calibration dies 660, and/or after the calibration dies 660 to further compress the preform 614 before it is converted into its final shape. The rollers may have any configuration, such as pinch rollers, overlapping rollers, etc., and may be vertical as shown or horizontal rollers. Depending on the roller 690 configuration, the surfaces of the rollers 690 may be machined to impart the dimensions of the final product, such as the rod, profile, or other suitable product, to the preform 614. In exemplary embodiment, the pressure of the rollers 690 should be adjustable to optimize the quality of the final product.
The rollers 690 in exemplary embodiments, such as at least the portions contacting the material, may have generally smooth surfaces. For example, relatively hard, polished surfaces are desired in many embodiments. For example, the surface of the rollers may be formed from a relatively smooth chrome or other suitable material. This allows the rollers 690 to manipulate the preform 614 without damaging or undesirably altering the preform 614. For example, such surfaces may prevent the material from sticking to the rollers, and the rollers may impart smooth surfaces onto the materials.
In some embodiments, the temperature of the rollers 690 is controlled. This may be accomplished by heating of the rollers 690 themselves, or by placing the rollers 690 in a temperature controlled environment.
Further, in some embodiments, surface features 692 may be provided on the rollers 690. The surface features 692 may guide and/or control the preform 614 in one or more directions as it is passed through the rollers. For example, surface features 692 may be provided to prevent the preform 614 from folding over on itself as it is passed through the rollers 690. Thus, the surface features 692 may guide and control deformation of the preform 614 in the cross-machine direction relative to the machine direction A as well as in the vertical direction relative to the machine direction A. The preform 614 may thus be pushed together in the cross-machine direction, rather than folded over on itself, as it is passed through the rollers 690 in the machine direction A.
In some embodiments, tension regulation devices may be provided in communication with the rollers. These devices may be utilized with the rollers to apply tension to the preform 614 in the machine direction, cross-machine direction, and/or vertical direction to further guide and/or control the preform.
As indicated above, the resulting rod is also applied with a capping layer to protect it from environmental conditions or to improve wear resistance. Referring again to FIG. 13, for example, such a capping layer may be applied via an extruder oriented at any desired angle to introduce a thermoplastic resin into a capping die 672. To help prevent a galvanic response, it is typically desired that the capping material has a dielectric strength of at least about 1 kilivolt per millimeter (kV/mm), in some embodiments at least about 2 kV/mm, in some embodiments from about 3 kV/mm to about 50 kV/mm, and in some embodiments, from about 4 kV/mm to about 30 kV/mm, such as determined in accordance with ASTM D149-09. Suitable thermoplastic polymers for this purpose may include, for instance, polyolefins (e.g., polypropylene, propylene-ethylene copolymers, etc.), polyesters (e.g., polybutylene terephalate (“PBT”)), polycarbonates, polyamides (e.g., Nylon™), polyether ketones (e.g., polyetherether ketone (“PEEK”)), polyetherimides, polyarylene ketones (e.g., polyphenylene diketone (“PPDK”)), liquid crystal polymers, polyarylene sulfides (e.g., polyphenylene sulfide (“PPS”), poly(biphenylene sulfide ketone), poly(phenylene sulfide diketone), poly(biphenylene sulfide), etc.), fluoropolymers (e.g., polytetrafluoroethylene-perfluoromethylvinylether polymer, perfluoro-alkoxyalkane polymer, petrafluoroethylene polymer, ethylene-tetrafluoroethylene polymer, etc.), polyacetals, polyurethanes, polycarbonates, styrenic polymers (e.g., acrylonitrile butadiene styrene (“ABS”)), acrylic polymers, polyvinyl chloride (PVC), etc. Particularly suitable high dielectric strength capping layer materials may include polyketone (e.g., polyetherether ketone (“PEEK”)), polysulfide (e.g., polyarylene sulfide), or a mixture thereof.
The capping layer is generally free of continuous fibers. That is, the capping layer contains less than about 10 wt. % of continuous fibers, in some embodiments about 5 wt. % or less of continuous fibers, and in some embodiments, about 1 wt. % or less of continuous fibers (e.g., 0 wt. %). Nevertheless, the capping layer may contain other additives for improving the final properties of the rod. Additive materials employed at this stage may include those that are not suitable for incorporating into the continuous fiber material. For instance, it may be desirable to add pigments to reduce finishing labor, or it may be desirable to add flame retardant agents to enhance the flame retarding features of the rod. Because many additive materials are heat sensitive, an excessive amount of heat may cause them to decompose and produce volatile gases. Therefore, if a heat sensitive additive material is extruded with an impregnation resin under high heating conditions, the result may be a complete degradation of the additive material. Additive materials may include, for instance, mineral reinforcing agents, lubricants, flame retardants, blowing agents, foaming agents, ultraviolet light resistant agents, thermal stabilizers, pigments, and combinations thereof. Suitable mineral reinforcing agents may include, for instance, calcium carbonate, silica, mica, clays, talc, calcium silicate, graphite, calcium silicate, alumina trihydrate, barium ferrite, and combinations thereof.
While not shown in detail herein, the capping die 672 may include various features known in the art to help achieve the desired application of the capping layer. For instance, the capping die 672 may include an entrance guide that aligns the incoming rod. The capping die may also include a heating mechanism (e.g., heated plate) that pre-heats the rod before application of the capping layer to help ensure adequate bonding. Following capping, the shaped part 615, or rod 750, is then finally cooled using a cooling system 680 as is known in the art. The cooling system 680 may, for instance, be a sizing system that includes one or more blocks (e.g., aluminum blocks) that completely encapsulate the rod while a vacuum pulls the hot shape out against its walls as it cools. A cooling medium may be supplied to the sizer, such as air or water, to solidify the rod in the correct shape.
Even if a sizing system is not employed, it is generally desired to cool the rod 750 after it exits the capping die (or the consolidation or calibration die if capping is not applied). Cooling may occur using any technique known in the art, such a water tank, cool air stream or air jet, cooling jacket, an internal cooling channel, cooling fluid circulation channels, etc. Regardless, the temperature at which the material is cooled is usually controlled to achieve optimal mechanical properties, part dimensional tolerances, good processing, and an aesthetically pleasing composite. For instance, if the temperature of the cooling station is too high, the material might swell in the tool and interrupt the process. For semi-crystalline materials, too low of a temperature can likewise cause the material to cool down too rapidly and not allow complete crystallization, thereby jeopardizing the mechanical and chemical resistance properties of the composite. Multiple cooling die sections with independent temperature control can be utilized to impart the optimal balance of processing and performance attributes. In one particular embodiment, for example, a water tank is employed that is kept at a temperature of from about 0° C. to about 30° C., in some embodiments from about 1° C. to about 20° C., and in some embodiments, from about 2° C. to about 15° C.
If desired, one or more sizing blocks (not shown) may also be employed, such as after capping. Such blocks contain openings that are cut to the exact rod shape, graduated from oversized at first to the final rod shape. As the rod passes therethrough, any tendency for it to move or sag is counteracted, and it is pushed back (repeatedly) to its correct shape. Once sized, the rod may be cut to the desired length at a cutting station (not shown), such as with a cut-off saw capable of performing cross-sectional cuts or the rod can be wound on a reel in a continuous process. The length of rod will then be limited to the length of the fiber tow.
As will be appreciated, the temperature of the rod as it advances through any section of the system of the present invention may be controlled to yield optimal manufacturing and desired final composite properties. Any or all of the assembly sections may be temperature controlled utilizing electrical cartridge heaters, circulated fluid cooling, etc., or any other temperature controlling device known to those skilled in the art.
Referring again to FIG. 13, a pulling device 682 is positioned downstream from the cooling system 680 that pulls the finished 750 through the system for final sizing of the composite. The pulling device 682 may be any device capable of pulling the rod through the process system at a desired rate. Typical pulling devices include, for example, caterpillar pullers and reciprocating pullers.
The rods 750 that result from use of dies and methods according to the present disclosure may have a very low void fraction, which helps enhance their strength. For instance, the void fraction may be about 5% or less, in some embodiments about 4% or less, in some embodiments about 3% or less, in some embodiments about 2% or less, in some embodiments about 1.5% or less, in some embodiments about 1% or less, and in some embodiments, about 0.5% or less. The void fraction may be measured using techniques well known to those skilled in the art. For example, the void fraction may be measured using a “resin burn off” test in which samples are placed in an oven (e.g., at 600° C. for 3 hours) to burn out the resin. The mass of the remaining fibers may then be measured to calculate the weight and volume fractions. Such “burn off” testing may be performed in accordance with ASTM D 2584-08 to determine the weights of the fibers and the polymer matrix, which may then be used to calculate the “void fraction” based on the following equations:
V _f=100*(ρ_t−ρ_c)/ρ_t
where,
V_fis the void fraction as a percentage;
ρ_cis the density of the composite as measured using known techniques, such as with a liquid or gas pycnometer (e.g., helium pycnometer);
ρ_tis the theoretical density of the composite as is determined by the following equation:
ρ_t=1/[W _f/ρ_f +W _m/ρ_m]
ρ_mis the density of the polymer matrix (e.g., at the appropriate crystallinity);
ρ_fis the density of the fibers;
W_fis the weight fraction of the fibers; and
W_mis the weight fraction of the polymer matrix.
Alternatively, the void fraction may be determined by chemically dissolving the resin in accordance with ASTM D 3171-09. The “burn off” and “dissolution” methods are particularly suitable for glass fibers, which are generally resistant to melting and chemical dissolution. In other cases, however, the void fraction may be indirectly calculated based on the densities of the polymer, fibers, tape and/or rod in accordance with ASTM D 2734-09 (Method A), where the densities may be determined ASTM D792-08 Method A. Of course, the void fraction can also be estimated using conventional microscopy equipment.
As discussed above, after exiting an impregnation die 150, 412, the CFRT material may in some embodiments form a tape 152, 156. The number of rovings employed in each tape 152, 156 may vary. Typically, however, a tape 152, 156 will contain from 2 to 80 rovings, and in some embodiments from 10 to 60 rovings, and in some embodiments, from 20 to 50 rovings. In some embodiments, it may be desired that the rovings are spaced apart approximately the same distance from each other within the tape 152, 156. In other embodiments, however, it may be desired that the rovings are combined, such that the fibers of the rovings are generally evenly distributed throughout the tape 152, 156, such as throughout one or more resin rich portions and a fiber rich portion as discussed above. In these embodiments, the rovings may be generally indistinguishable from each other. Referring to FIGS. 18 and 19, for example, embodiments of a tape 152, 156 are shown that contains rovings that are combined such that the fibers 400 are generally evenly distributed therein. As shown in FIG. 18, in exemplary embodiments, the fibers extend generally unidirectionally, such as along a longitudinal axis of the tape 152, 156.
Through use of apparatus and methods according to the present disclosure and control over the various parameters mentioned above, tapes and rods having a very high strength may be formed. For example, the rods may exhibit a high maximum load. Maximum load may be determined according to ASTM D3039. The maximum load may be, for example, greater than about 290 pounds per square inch (psi), or for example greater than about 130 kilograms per square inch (130 ksi).
The rods may exhibit a relatively high flexural modulus. The term “flexural modulus” generally refers to the ratio of stress to strain in flexural deformation (units of force per area), or the tendency for a material to bend. It is determined from the slope of a stress-strain curve produced by a “three point flexural” test (such as ASTM D790-10, Procedure A), typically at room temperature. For example, the rod of the present invention may exhibit a minimum flexural modulus of about 10 Gigapascals (“GPa”), in some embodiments a flexural modulus from about 12 to about 400 GPa, in some embodiments a flexural modulus from about 15 to about 200 GPa, and in some embodiments a flexural modulus from about 20 to about 150 GPa. Furthermore, the ultimate tensile strength of a rod may be between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, such as between approximately 320,000 pounds per square inch and approximately 370,000 pounds per square inch. The term “ultimate tensile strength” generally refers to the maximum stress that a material can withstand while being stretched or pulled before necking and is the maximum stress reached on a stress-strain curve produced by a tensile test (such as ASTM D3916-08) at room temperature. The minimum tensile modulus of elasticity may also be about 50 GPa, or in some embodiments the tensile modulus of elasticity may be from about 70 GPa to about 500 GPa, or in some embodiments the tensile modulus of elasticity may be from about 100 GPa to about 300 GPa. The term “tensile modulus of elasticity” generally refers to the ratio of tensile stress over tensile strain and is the slope of a stress-strain curve produced by a tensile test (such as ASTM 3916-08) at room temperature. Notably, the strength properties of the composite rod referenced above may also be maintained over a relatively wide temperature range, such as from about −40° C. to about 300° C., and particularly from about 180° C. to 200° C.
Rods made according to the present disclosure may further have relatively high flexural fatigue life, and may exhibit relatively high residual strength. Flexural fatigue life and residual flexural strength may be determined based on a “three point flexural fatigue” test (such as ASTM D790, typically at room temperature. For example, the rods of the present invention may exhibit residual flexural strength after one million cycles at 160 Newtons (“N”) or 180 N loads of from about 60 kilograms per square inch (“ksi”) to about 115 ksi, in some embodiments about 70 ksi to about 115 ksi, and in some embodiments about 95 ksi to about 115 ksi. Further, the rods may exhibit relatively minimal reductions in flexural strength. For example, rods having void fractions of about 4% or less, in some embodiments about 3% or less, may exhibit reductions in flexural strength after three point flexural fatigue testing of about 1% (for example, from a maximum pristine flexural strength of about 106 ksi to a maximum residual flexural strength of about 105 ksi). Flexural strength may be tested before and after fatigue testing using, for example, a three point flexural test as discussed above.
The linear thermal expansion coefficient of the composite rod may be, on a ppm basis per ° C., less than about 5, less than about 4, less than about 3, or less than about 2. For instance, the coefficient (ppm/° C.) may be in a range from about −0.25 to about 5; alternatively, from about −0.17 to about 4; alternatively, from about −0.17 to about 3; alternatively, from about −0.17 to about 2; or alternatively, from about 0.29 to about 1.18. The temperature range contemplated for this linear thermal expansion coefficient may be generally in the −50° C. to 200° C. range, the 0° C. to 200° C. range, the 0° C. to 175° C. range, or the 25° C. to 150° C. range. The linear thermal expansion coefficient is measured in the longitudinal direction, i.e., along the length of the fibers.
The composite rod may also exhibit a relatively small “bend radius”, which is the minimum radius that the rod can be bent without breaking and is measured to the inside curvature of the rod. A smaller bend radius means that the rod is more flexible and can be spooled onto a smaller diameter bobbin. This property also makes the rod easier to implement in processes that currently use metal rods. Due to the improved process and resulting rod of the present invention, bend radiuses may be achieved that are less than about 40 times the outer diameter of the rod, in some embodiments from about 1 to about 30 times the outer diameter of the rod, and in some embodiments, from about 2 to about 25 times the outer diameter of the rod, determined at a temperature of about 25° C. For instance, the bend radius may be less than about 15 centimeters, in some embodiments from about 0.5 to about 10 centimeters, and in some embodiments, from about 1 to about 6 centimeters, determined at a temperature of about 25° C.
These and other modifications and variations of the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

Claims

What is claimed is:

1. A sucker rod assembly, the sucker rod assembly comprising:

a plurality of continuous fiber reinforced thermoplastic rods arranged in a stranded bundle, each of the plurality of continuous fiber reinforced thermoplastic rods having a core comprising a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin; and

a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the plurality of continuous fiber reinforced thermoplastic rods,

wherein each of the plurality of rods has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, wherein the continuous fibers have a ratio of ultimate tensile strength to mass per unit length of greater than about 1,000 Megapascals per gram per meter, and wherein the continuous fibers constitute from about 25 wt. % to about 80 wt. % of each of the plurality of rods and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of each of the plurality of rods.

2. The sucker rod assembly of claim 1, wherein each of the plurality of rods has an ultimate tensile strength of between approximately 320,000 pounds per square inch and approximately 370,000 pounds per square inch.

3. The sucker rod assembly of claim 1, wherein the continuous fibers have a ratio of ultimate tensile strength to mass per unit length of from about 5,000 to about 20,000 Megapascals per gram per meter.

4. The sucker rod assembly of claim 1, wherein the continuous fibers are carbon fibers.

5. The sucker rod assembly of claim 1, wherein the thermoplastic resin includes a polyarylene sulfide.

6. The sucker rod assembly of claim 5, wherein the polyarylene sulfide is polyphenylene sulfide.

7. The sucker rod assembly of claim 1, wherein the continuous fibers constitute from about 30 wt. % to about 75 wt. % of each of the plurality of rods.

8. The sucker rod assembly of claim 1, wherein the core of each of the plurality of rods has a void fraction of about 3% or less.

9. The sucker rod assembly of claim 1, wherein each of the plurality of rods has a minimum flexural modulus of about 10 Gigapascals.

10. The sucker rod assembly of claim 1, wherein each of the plurality of rods has a minimum tensile modulus of elasticity of about 50 Gigapascals.

11. The sucker rod assembly of claim 1, wherein each of the plurality of rods has a bend radius of from about 0.5 to about 10 centimeters.

12. The sucker rod assembly of claim 1, further comprising a capping layer surrounding the core of each of the plurality of rods.

13. The sucker rod assembly of claim 12, wherein the capping layer includes polyetherether ketone.

14. The sucker rod assembly of claim 12, wherein the capping layer is free from fibers.

15. A sucker rod assembly, the sucker rod assembly comprising:

a single monolithic continuous fiber reinforced thermoplastic rod, the continuous fiber reinforced thermoplastic rod having a core and a capping layer surrounding the core, the core comprising a plurality of generally unidirectionally oriented continuous fibers embedded in a thermoplastic resin, wherein the fibers are carbon fibers and the thermoplastic resin includes a polyarylene sulfide, the capping layer including polyetherether ketone and free from fibers; and

a first end fitting and a second end fitting, at least one of the first and second end fittings connected to the continuous fiber reinforced thermoplastic rod,

wherein the continuous fiber reinforced thermoplastic rod has an ultimate tensile strength of between approximately 280,000 pounds per square inch and approximately 370,000 pounds per square inch, and wherein the continuous fibers constitute from about 25 wt. % to about 80 wt. % of the rod and the thermoplastic resin constitutes from about 20 wt. % to about 75 wt. % of the rod.

16. The sucker rod assembly of claim 15, wherein the continuous fiber reinforced thermoplastic rod has an ultimate tensile strength of between approximately 320,000 pounds per square inch and approximately 370,000 pounds per square inch.

17. The sucker rod assembly of claim 15, wherein the polyarylene sulfide is polyphenylene sulfide.

18. The sucker rod assembly of claim 15, wherein the continuous fibers constitute from about 30 wt. % to about 75 wt. % of the rod.

19. The sucker rod assembly of claim 15, wherein the core of the rod has a void fraction of about 3% or less.

20. The sucker rod assembly of claim 15, wherein the rod has a minimum flexural modulus of about 10 Gigapascals.

21. The sucker rod assembly of claim 15, wherein the rod has a minimum tensile modulus of elasticity of about 50 Gigapascals.

22. The sucker rod assembly of claim 15, wherein the rod has a bend radius of from about 0.5 to about 10 centimeters.