WO2012149490A1

WO2012149490A1 - Improved composite member and method of making

Info

Publication number: WO2012149490A1
Application number: PCT/US2012/035686
Authority: WO
Inventors: Xu JIANSHENG
Original assignee: Xene Corporation
Priority date: 2011-04-29
Filing date: 2012-04-27
Publication date: 2012-11-01
Also published as: CN202052290U

Abstract

A method of forming a composite member comprises placing a heat formable resin adjacent fibers to form a fiber member or members and forming the same into a plurality of, for example tubular members. The fiber member is placed against a first mold part. An expandable material is distributed into a distributed configuration and expands under the application of heat. The distributed material is optionally stabilized in the distributed configuration to form an expandable member, which is placed said expandable member adjacent said fiber member. A second mold parts seals the mold forming a closed cavity containing the fiber member and the expandable member. The mold parts are heated, causing the expandable material to expand and form a pressure, which drives the fiber member against one of the mold parts, the mold parts also heating the resin adjacent the fibers. The resin then hardens to form the composite member.

Description

IMPROVED COMPOSITE MEMBER AND METHOD OF MAKING

CRO S S REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Chinese Utility Model Patent Application No. 201120133323.X, filed on April 29, 2011.

TECHNICAL FIELD

The invention related to apparatus and methods for fiberglass and graphite resin composite members, such as sports racquet frames, golf club shafts, bicycle frames, wind and other turbine blades, airplane wings, high-impact strength containers, and luggage.

BACKGROUND OF THE INVENTION

For many years, graphite and fiber composite sports racquet frames and other structural parts, such as automobile body parts, have been produced by manual labor in molds using air injection in the case or tennis racquets, suction in the case of turbines and other techniques. This description is specific to tennis racquets as the applicant's current work has been focused in that area and the techniques described herein are applicable to a range of products. In a typical process, a "layup," sometimes taking the form of a bladder, is created by manually rolling multiple sheets or laminations (which take the form of strips of planar material), commonly formed of fibrous material, such as carbon or graphite fiber or fiberglass. The bladder is formed, for example, using a number of "sheets" of graphite fiber, permeated, for example saturated, with an uncured thermoplastic or thermo-setting resin. Generally, the sheets are wrapped by hand around a rigid mandrel or rod to control the desired layup tubular shape.The layup shapes are then assembled and cured to form a conventional racket.

More particularly, before the graphite is wound on the mandrel, the mandrel is wrapped with a layer of material meant to form the internal surface of a layup bladder to be inflated during the manufacturing process. Next the sheets are made of carbon fibers, and as alluded to above, permeated with an uncured plastic resin. These carbon fibers/resin sheets are manually cut into strips or ribbons, with various fiber orientations, prior to their assembly into a layup, typically by being wound around a mandrel to form a tube. After being wound, the layup (which, after winding, may take the form of a bladder) is manually formed into a desired racquet shape, reinforced with additional patches of the planar strips of carbon fiber material, and placed in a mold. By resinous material is meant any material which can be used in graphite or fiberglass composite to bind the fibers into a substantially rigid structure.

The mold is then manually closed. The bladder is subjected to heat by the mold, causing the thermoplastic resin to cure. The result in the finished racquet is a hardening of the material of the layup. Alternatively, thermosetting resins may be used.

SUMMARY OF THE INVENTION

Quite apart from the strength of the material of which the tennis racquet is made, in accordance with the invention it is also believed that the hollow nature of present state-of-the-art graphite racquets, in comparison to earlier generation solid wooden racquets, have increased injury to shoulders and elbows due to vibration and shock, particularly from off-center shots. This is because the hollow frame and open- ended shaft at the handle is coupled, during play, to the hand and then to the arm.

In accordance with the invention, the opening for air injection at the bottom of the shaft is believed to worsen the shock that resonated at the handle of the racquet and propagates to and through the hand, arm, and shoulder of the player.

Years of industry development have been invested to address the minimization of these propagated vibrations and shock, by implementing various methods of dampening the transmission of vibration from the handle of the racquet to the hand of the player.

The invention addresses these issues by providing a carbon composite frame structure of increased strength and reliability, providing the frame head, throat portion, and handle with an inner core of foam plastic as described in U.S. Pub. No. 2011/0136602, with the additional benefit of constructing the head frame, throat portion, and handle from multiple layups, which, when cured, fuse together to form reinforcing walls.

In accordance with the invention, it is believed that providing a carbon composite frame structure with multiple reinforcing walls and optionally different graphite fiber orientation directions in the frame head, throat portion, and handle will further improve the performance of a sports racquet and other products, such as ladders, golf clubs, boat hulls, automobile parts and building construction members.

The invention allows for different users' requirements for strength, weight, and shock resistance of the various racquet parts to besatisfied.

The process of making the racquet in accordance with the invention uses a micro encapsulated plastic material, including a foaming agent in the form of a powdered material, to form the foam plastic. This material is put into the tubular layup bladder, which is sealed at both ends. The bladder is then put into an iron mold, which is optionally and preferably closed in configuration and then heated. This results in the material being heated, causing it to melt and expand under the pressure of a foaming agent contained therein. This process is disclosed in more detail in U.S. Pub. No. 2011/0136602.

In accordance with the invention, it is noted that the foaming of the plastic which forms the foam plastic inner core of the racquet occurs at a temperature roughly about the temperature required for the curing and fusing of layers of the carbon/thermoplastic resin sheets which form the layup bladder, although somewhat higher temperatures can be tolerated. The particular temperatures are a function of the material being used to form the foam plastic and may be obtained by routine trial of the same and checking the final product to verify that the temperature has not been excessive.

In accordance with the invention, one fills up the layup with the powder microcapsule foaming plastic material, which does not begin to expand, in the examples set forth below, until the temperature reaches 120-130 degrees Centigrade, for example 130 degrees centigrade. At the same time, the gas generates pressure inside the layup bladder, which is sealed at both ends, due to the foaming action of the micro encapsulated material inside the bladder. This makes the fiber layer laminations, which form the racquet frame in the finished product, press up against the inside surface of the mold to take shape of the mold cavity.

It is understood that when heat is applied, the micro encapsulated foaming agent expands and deforms the capsules enclosing it, thus forming a foam plastic under pressure. This results in creating enough pressure to press the layers of the graphite carbon fiber against the mold walls to form the carbon fiber into the shape of the cavity of the mold. The combination of heat and pressure results in fusing of the layers and the formation of the composite material of which the racquet frame is made. This occurs at the temperature of about 120-130 degrees Centigrade. This temperature range may vary depending upon the characteristics of the thermoplastic material forming the carbon fiber sheet.

Preferably, the head and throat portions of the racquet comprise a plurality of reinforcing walls, made of fibers whose direction and quantity may be different from each other. The direction of fibers in the reinforcing walls in the head and throat portions in a given local position.

In accordance with the invention, the layups are formed with an expandable microcapsule such as Expancel™ which provides extremely high pressure during heat curing. The uncured, un-expanded layups filled with Expancel microcapsules are assembled as described herein and then heat cured in a closed clamshell mold. It is also possible to have the same quantity of reinforcing walls in the head and throat portions of the racquet, but with the reinforcing walls formed of fibers oriented in opposite directions. In the preferred embodiments, all tubular layups are made of fibers oriented in a plurality of directions. For example, the head portion of the frame may be formed by three tubular layups positioned beside and in contact with each other. The largest layup would extend around the next largest medium sized one, which, in turn, would extend around the smallest layup, but the layups would all be in the same plane. Thiswould definetwo reinforcing walls, formed between the largest and medium sized layup and another formed between the medium and smallest layup, with the reinforcing wallsperpendicular to the plane of the racquet. Alternatively, the layups may be of similar diameter andlaid on top of each other with the result that the walls are parallel to the face plane of the racquet. In the last case, the throat portion may also have two reinforcing walls, running perpendicular to the face plane of the racquet.

In a preferred embodiment, there are two reinforcing walls in the head frame that parallel the face plane of the racquet formed by an oval layup and two wraparound layups that start at the base of the handle and extend from there around the oval layup in the head, and then return to the base of the handle, separating the head portion of the frame into three cavities, the upper (or outer), middle, and lower (or outer) cavities. There are also two reinforcing walls in the throat portion of the racquet that run parallel to the face plane of the racquet, separating the throat portion into three cavities, the left, middle, and right cavities. These are formed by, for example, a single tubular layup extending from the base of the handle, up, then across one side of the throat, across the bottom of the head portion, down across the other side of the throat and down back to the base.

In one preferred embodiment, the quantity of the reinforcing walls in the head frame and throat portion may be the same ordifferent, but the direction of the walls may be the same. For example, there may beone reinforcing wall in the head frame that runs parallel to the face plane of the racquet, separating the head frame into symmetrical cavities. There may bethree reinforcing walls in the throat portion that run parallel to the face plane of the racquet, separating the throat portion into four cavities.

In another preferred embodiment, both the quantity and direction of the reinforcing walls in the head frame and throat portion are different. For example, there are three reinforcing walls in the head frame that run perpendicular to the face plane, separating the head frame into four cavities, and one reinforcing wall in the throat portion that runs parallel to the face plane, separating the throat portion into two symmetrical cavities.

In a preferred embodiment, the reinforcing walls in the upper part and lower part of the head frame are different in either direction or quantity. For example, there may be one reinforcing wall in the upper part of the head frame that is perpendicular to the face plane, separating the upper part of the head frame into two symmetrical cavities. There may be two reinforcing walls in the lower part of the head frame that run parallel to the face plane, separating the lower portion of the head frame into three cavities.

In a preferred embodiment, the reinforcing walls in the upper, middle, and lower parts of the head frame are different at least in direction or quantity or both.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Fig. 1 shows front view of the inventive tennis racket;

Fig. 2 shows the tennis racket of Figure 1 in cross section along lines 2-2 of Fig. 1.

Fig. 3 illustrates the tennis racket of Figure 1 in a cross section taken along lines 3-3 of Fig. 1.

Fig. 4 is a cross section taken along lines 4-4 of Fig. 1. Fig. 5 shows an alternative embodiment, illustrated in a cross section, with a view similar to that of Figure 2.

Fig. 6 is a cross section of the embodiment of Figure 5, with a view similar to that in Fig. 3.

Fig. 7 is a cross section of the embodiment of Figure 5, with a view similar to that of Fig. 4.

Fig. 8 illustrates an alternative embodiment of the inventive racquet frame.

Fig. 9 shows cross section view along lines 9-9 of Fig. 8.

Fig. 10 shows cross section diagram along lines 10-10 of Fig. 8.

Fig. 11 shows cross section diagram along lines 11-11 Fig. 8.

Fig. 12 is a cross-sectional view, similar to that of Figure 9, of an alternative embodiment of the invention.

Fig. 13 is a cross-sectional view, similar to the view of Figure 10, of the embodiment of Figure 12.

Fig. 14 is a cross-sectional view, similar to the view of Figure 11, of the embodiment of Figure 12.

Fig. 15 is a cross-sectional view, similar to that of Figure 9, of another alternative embodiment of the invention.

Fig. 16 is a cross-sectional view, similar to the view of Figure 10, of the embodiment of Figure 15.

Fig. 17 is a cross-sectional view, similar to the view of Figure 11, of the embodiment of Figure 15.

Fig. 18 shows overall structural diagram of the racket frame in the yet another embodiment of the invention.

Fig. 19 is a cross-section of view along lines 19-19 of Figure 18.

Fig. 20 is a cross-section of view along lines 20-20 of Figure 18.

Fig. 21 is an exploded perspective illustrating the formation of a planar member.

Fig. 22 illustrates a member formed by the process of Figure 21.

Fig. 23 illustrates a layup for a fiberglass ladder.

Fig. 24 illustrates a layup for a planar member suitable for use in a mold such as that illustrated in Figure 21.

Figures 25 and 26 illustrate a composite graphite member with a plurality of layups formed in a braided configuration.

Figures 27-42 illustrate the manufacturing method of the present invention for making composite members.

Fig. 43 is an exploded perspective illustrating the manufacture of a flat graphite member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a graphite racquet frame 40 with a common racquet shape. When fabricated using air injection graphite manufacturing techniques, it has an advantage in strength to weight ratio over the predecessor wooden racquet. In accordance with the invention still better characteristics are achieved. The racquet frame 40 has a head portion 10, a throat portion 20, and a handle or shaft portion 30. These portions of racquet frame 40 are formed as a single, integral and continuous member. Bifurcated throat portion 20 is continuous with the head portion 10 and with shaft portion 30. A crosspiece or yoke portionl3 is provided between both sides of throat portion 20. Yoke portion 13 and head portion 10 form a roughly oval-stretching portion 14 surrounding a ball-hitting face IS. A string groove 16 is concavely formed on the outer surface of the head portion 10.

Figure 2 shows a structure of the inventive product with the reinforcing wall 11 and hollow tubes 12 of the head frame 10. Figure 3 shows a cross section of the throat section 20 of a tennis racquet at a perpendicular angle to the plane of the face of the racquet with reinforcing wall 21 and hollow tubes 22.

The quantity of the reinforcing walls 11 and 21 is one. Reinforcing walls 11 and 21 separate the cross section of the head frame and triangular throat into cavity 12 and cavity 22 in a bilateral direction. Figure 4 shows a cross section of the handle portion of a racquet at the same angle as the head frames and throat portion, with three walls 31 running perpendicular the plane of the face of the racquet separating the handle into four hollow tubes 32.

Figures 5, 6 and 7 show an alternativestructure for the inventive products. The reinforcing walls 11 , 21 and 31 run parallel to the face plane of the racquet. There is one reinforcing wall 11 and one reinforcing wall 12 at the head frame 10 and the triangular throat 20 from the angle of cross section. The reinforcing walls separate the cross section of the head frame 10 and triangular throat 20 into two symmetrical cavities 12 and 22. There are three reinforcing walls 31 in handle 30 from the angle of cross section. The reinforcing walls separate the cross section of handle 30 into four cavities 32.

Although these two structures can improve impact and compression resistance of the racket, the reinforcing walls on the cross section of the head frame and throat section of the whole racket frame are most easily made in the same in direction and quantity due to restriction of processing technologies. in accordance with still another embodiment, the reinforcing walls of the cross section of the head frame may bemade parallel the plane of the face of the racquet, the reinforcing walls of the cross section of the throat section may bemade perpendicular to the face plane of the racquet and that the quantity of reinforcing walls of the cross section of the head frame may be different from that of reinforcing walls of the cross section of the throat section. This may be done by placing an inner oval head member inside a handle base to head to handle base member and placing an oval head member on top of this assembly, all within the clamshell mold. Alternatively, a small amount of layup displacement may be implemented at the juncture of the head and throat.

FIG. 2illustrates a structure of the inventiveproduct with the reinforcing wall 11 and hollow tubes 12 of the head frame 10. FIG. 3 shows a cross section of the throat section 20 of a tennis racquet at a perpendicular angle to the plane of the face of the racquet with reinforcing wall 21 and hollow tubes 22. The quantity of the said reinforcing walls 11 and 21 is one. Reinforcing walls 11 and 21 separate the cross section of the head frame and triangular throat into cavity 12 and cavity 22 in a bilateral direction. FIG. 4 shows a cross section of the handle portion of a racquet at the same angle as the head frames and throat portion, with three walls 31 run perpendicular to the plane of the face of the racquet separating the handle into four hollow tubes 32.

The prevailing tennis racquet making technique today is the uses air-pressure. The carbon fiber used to make the layup takes the form of a graphite sheet. Graphite sheets are wrapped around a seamless sleeve to produce the layup.

Air pressure is forced through an inflation assembly comprising a valve coupled to a nozzle for receiving a source of air pressure. The inflation assembly is coupled at one end to a source of compressed air and to the sleeveless tube of the layup at the other end. The layup, formed of an inner tubular member and layers of graphite material impregnated with resin, is placed in the cavity defined by mold halves for heating and curing of the layup, under the application of air pressure, in order ultimately to form the molded and cured frame.

The present invention is made of layup 70, which is formed by adhering one side of resin impregnated carbon fiber sheets 60, 62are, for example, the same as those used in the racquet described in US published application 201 1 /01 36602, except that the pieces used in that patent are distributed among the two layups forming the racquet, for example, distributed evenly, but modification as necessary to insure that each of the two graphite tubes are made of fiber ribbons with a diversity of fiber orientations . The sheets are positioned next to one another on a table. An aluminum rod 66 is then inserted into a seamless plastic tube 68 measuring, for example, about (two centimeters in diameter and having a length typical of graphite fiber manufactured tennis racket component part elements. FIG. 27 illustrates carbon fiber sheets 60, 62, 64, rod 66, and seamless plastic tube 68. FIG. 28 illustrates rod 66 with seamless plastic tube 68; this assembly is placed in the middle of carbon fiber sheet 60. Carbon fiber sheet 60is then wrapped around rod 66 with seamless plastic tube 68 inside of it. Next, rod 66 with seamless plastic tube 68 wrapped in carbon fiber sheet 60 is placed in the middle of carbon fiber sheet 62. Carbon fiber sheet 62 is then wrapped around rod 66 and seamless plastic tube 68 in the same way as carbon sheet 60 forming a two-layer carbon fiber shell 69 as shown in FIG. 29.

A second layup 72 may be made using the same process. Layups 70 and 72 may be used to form composite elements which extend, for example, from the base of the butt of the handle around the head and back to the base of the handle. A third layup 74 is formed from resin impregnated carbon fiber sheets like sheets 60, 62, and 64, which are placed next to one another on a table. Rod 66 is then inserted into seamless plastic tube 68. Then rod 66 with seamless plastic tube 68 is placed in the middle of carbon fiber sheet 60 and carbon fiber sheet 60 is wrapped around rod 66 and seamless plastic tube 68. The carbon wrapped rod 66 and seamless plastic tube 68 is then placed in the middle of carbon fiber sheet 62, which is also wrapped around rod 66 and seamless plastic tube 68. This process is repeated with carbon fiber sheet 64 forming a three-layer carbon fiber shell 71 as shown in FIG. 30. Layup 74 is substantially similar to layups 70 and 72, but wrapped in three carbon fiber sheets instead of two. Layup 74 may comprise the head portion of the racquet. Layups 76, 78, 80, and 82, which maycomprise the throat and handle portions of the racquet are formed by adhering one side of two resin impregnated carbon fiber sheets 84 and 86 next to one another on a table as shown in FIG. 31. A rod 88 is then inserted into seamless plastic tube 90 as illustrated separately in FIG. 31. Rod 88 with seamless plastic tube 90 is then placed in the middle of carbon fiber sheet 84, and carbon fiber sheet 84 is then wrapped around rod 88 and seamless plastic tube 90. Then rod 88 with seamless plastic tube 90 is wrapped in carbon fiber sheet 84andthen placed in the middle to carbon fiber sheet 86. Carbon fiber sheet 86 is then wrapped around rod 88 and seamless plastic tube 90 in the same way as carbon sheet 84 forming a two-layer carbon fiber shell 85 as shown in FIG. 32.

FIG. 33 shows a metal wire 92 bent to form a loop94 that is inserted into a layup, such as layup 70 as shown in FIG. 34. FIG. 34 also shows wire 92 is then attached to a plastic film expansion sheet 96, which contains a foaming plastic material (of the type disclosed inUnited States Published Application Number 20 1 1 /0 1 36602), by tying sheet 96 around loop 94 of metal wire 92.wire92 is then pulled back through layup 70, thereby inserting sheet 96 into the cavity of layup 70 as shown in FIG. 35. Care should be taken to make sure sheet 96remains flat and smooth while being pulled into the cavity of the layup 70. This may be done by smoothing sheet 96 with a finger as it is being pulled through layup 70. Sheet 96is then cut to length such that it is contained within the seamless plastic tube. Then the portion of seamless plastic tube 66 that remains outside on both ends of layup 70 is tied off at both ends, forming closed ends such as closed end 97 shown in FIG. 38. This process is repeated for layups 72 and 74

Sheet 96 is formed by taking a transparent plastic tube (preferably having a flat configuration), inserting a quantity of expansion microcapsule material in an amount such as that taught inUnited States Published Application Number 20 1 1 /0 136602, and then sealing one end. The microcapsule material may be inserted with an elongated curved metal blade, as shown in said published application. The micro capsule material is then distributed evenly by pressing with the fingers. Air is then evacuated from the tube. Further steps may then be taken to more evenly distribute the material, if necessary, for example by pressing against a table. After the air is evacuated, the other end of the tube is also sealed, thus forming a stable distribution of micro encapsulated material within the transparent plastic tube. The method has the advantage of allowing the inspection visually of distribution material, as opposed to putting microcapsule material into a black layup tube and not seeing the quality of distribution.

FIG. 36 shows a rod 98 which may be made of wood because it is less likely to damage the layup) inserted into layup 76. Alternatively, a bent wire 92 may be used. A piece of tape 102 is then wound around the end of rod 98 and used to secure a sheet 104similar to sheet 96with a foaming plastic material contained within it to the end of rod 98 with the tape as shown in FIG. 36. Sheet 104 is then pulled through the cavity of layup 76, shown in FIG. 37, and then detached from rod 98. This process is repeated for layups 78, 80, and 82.

Both ends of the seamless plastic to 68 are tied closed. Layups 70, 72, and 74 are then laid out next to one another with layups 76, and 78 lined up at one end of layups 70, 72, and 74 and layups 80, and 82 at the opposite end as shown in FIG. 39. The ends of layups 70, 72, and 74 are then attached to the ends of layups 80, and 82 by wrapping them in several carbon fiber sheets 108as shown in FIG. 40. The same process is repeated atthe opposite ends with layups 76, and 78. Next, the layups are further wrapped in two carbon fiber sheets 110 which cover a portion of carbon fiber sheet 108 and a portion of exposed layups 70, 72, and 74. The layupsare then centered over carbon fiber sheetsl 12 and 1 14 as illustrated in FIG 41.

Carbon fiber sheet 120 is then placed on the top side of the layups, shown in FIG. 41.

The layups are then centered over carbon fiber sheet 122and extending in both directions from centerline 126. Carbon fiber sheet 122 is then wrapped around the layups, shown in FIG.42.

Finally, three carbon fiber sheets 124 are placed on top of one another and are wrapped around centerline 126, shown in FIG. 42.

The number of carbon fiber sheets, their size, and the amount of microcapsules in the finished tennis racket (including all of the component layups thereof) are, in total, he substantially the same as inUnited States Published Application Number 201 1 /0136602.

In the preferred embodiment, a material understood to comprise plastic hollow microspheres is used to form the foam plastic. The microspheres are spherically formed particles with a thermoplastic shell encapsulating a gas. When the microspheres are heated the thermoplastic shell softens and the gas increases in pressure, resulting in an expansion of the spheres. The microspheres or microcapsules including the foaming agent are about 10-30 microns in diameter, with a thickness of 5-15 microns and a density of 1.03g per cubic centimeter.

In accordance with the preferred embodiment, curing temperature for the resin is about 140-150 degrees Centigrade. The racquet frame or other composite part should be held at this temperature for about 20 to 35 minutes. The expansion ratio of the foam plastic foaming material selected in accordance with the invention (Expancel 152) is believed to be about sixty to one. In accordance with the invention, microcapsule foam forming material used starts to expand from around 105-115 degrees Centigrade and higher. It can continue to expand significantly until the temperature drops to under around 105 degrees Centigrade. However, the above temperature may vary depending on the particular foaming plastic product used. Significant factors in this may be the resin used, the foaming agent, and the nature of the microcapsule.

Thus, the microcapsules substantially do not begin to expand until the temperature is close to the temperature needed to cure and fuse the graphite fiber composite material. The shell of the capsule is understood to be made of an acrylic copolymer resin. The shell material, after expansion, can form the material of the final foam core of the graphite racquet. The foaming agent may be a pentane or any other foaming agent suitable for the material of which the microcapsule is made and for the application, for example tennis racquet frames.

In accordance with the invention, the particular foam plastic material that is deposited in the layup is Expancel 152, available commercially from Akzo Noble.

The layup is then finished as indicated in United States Published Application Number

20 1 1 /0136602 and put in a closed mold having the shape of the part being formed. The mold is then heated. As in all of the embodiments described herein, heating of the mold results in curing the resin and securing the various layups into a single rigid unitary structure after the same have been cooled. Once the desired temperature is reached, as understood, the microcapsules will soften and the foaming agent associated with the Expancel 152 expands in size. When cooled, the expanded

microcapsules, which form a foam plastic core, will substantially hold their volume.

FIG. 8 shows tennis racquet frame 100 made of carbon fiber materials, comprising head portion 10, throat portion 20, and handle portion 30. Head frame 10 is bent into a closed oval shape. A set of thread holes 16 are set along the perimeter of head frame 10. The tennis racquet threads cross through the holes longitudinally and transversely to form ball-hitting face 15. The lower end of head frame 10 is linked up with the upper end of the throat portion 20 and the lower end of throat portion 20 is connected to handle portion 30 in a single, integral, and contiguous member.

FIG. 9 shows a cross section of head frame 10 with reinforcing walls 11. In this embodiment, there are two reinforcing walls 11 in head frame 10 that run parallel to the plane of ball-hitting face 15. However, the reinforcing walls in the head frame are not restricted to two, there may be less than or more than two reinforcing walls. The two reinforcing walls 11 in head frame 10 separate head frame 10 into three cavities 12, i.e. the upper cavity, the middle cavity and the lower cavity. Each cavity 12 is filled with expansible fillers 40. FIG. 10 shows a cross section of throat portion 20 with reinforcing walls 21. In this embodiment, there are also two reinforcing walls 21 in throat portion 20 that run perpendicular to the plane of ball- hitting face 15. However, the reinforcing walls in the throat portion are not restricted to two, there may be less than or more than two reinforcing walls. The two reinforcing walls 21 in throat portion 20 separate throat portion 20 into three cavities 22, i.e., the left cavity, the middle cavity, and the right cavity. Each cavity 22 is filled with expansible fillers 40.

FIG. 11 shows a cross section of handle portion 30 with reinforcing walls 31. In this embodiment, there are two reinforcing walls 31 in handle portion 30 that run parallel to the plane of ball-hitting face 15. However, the reinforcing walls in the handle portion are not restricted to two, there may be less than or more than two reinforcing walls. The two reinforcing walls 31 in handle portion 30 separate handle portion 30 into three cavities 32, i.e., the upper cavity, the middle cavity, and the lower cavity. Each cavity 32 is filled with expansible fillers 40.

In accordance with the preferred embodiment, the reinforcing walls 1 1 of head portion 10 and reinforcing walls 21 of throat portion 20 are the same in quantity, for example two, but run in different directions.

In accordance with the preferred embodiment, as illustrated in figure 9 through 11 , during the processing and molding of the racquet frame three carbon fiber made hollow tubes filled with expansible filler 40 are laid up to form the internal structure. Laying three carbon fiber made hollow tubes filled with expansible filler 40 on top of one another makes the internal structure of head frame 10. Laying three carbon fiber made hollow tubes side-by-side makes the internal structure of throat portion 20. Laying three carbon fiber made hollow tubes filled with expansible filler 40 on top of one another makes the internal structure of handle portion 30. Finally, a piece of carbon fiber cloth is used to wrap the head portion 10, throat portion 20, and handle portion 30.

In accordance with the invention, the final wrapping of the carbon fiber made hollow tubes may be done as much or as little as desired depending on the object being made. On one hand, it may be desirable to leave the covering layer very thin, so as to create a thinner, more lightweight product. On the other hand, it may be desirable to build up the final covering to make a stronger, more durable product.

In a second embodiment, the reinforcing walls in head frame 10 and throat section 20 run in the same direction but are different in quantity.

FIG. 12 shows one reinforcing wall 11 in head frame 10 that runs parallel to the plane of the ball- hitting face. Reinforcing wall 11 in head frame 10 divides the head frame into two symmetrical cavities, i.e., the upper cavity, and lower cavity.

FIG. 13 shows three reinforcing walls 21 in throat portion 20 that run parallel to the plane of ball- hitting face 15. Reinforcing walls 21 separate throat section 20 into four cavities 22. FIG. 14 shows two reinforcing walls 31 in handle portion 30, one running parallel to the plane of the ball-hitting face, and one running perpendicular to the plane of the ball-hitting face. Reinforcing walls 31 separate handle portion 30 into four cavities, i.e., an upper and lower right cavity, and an upper and lower left cavity.

In a third embodiment, the reinforcing walls in head frame 10 and throat section 20 run in different directions and in different quantities.

FIG. 15 shows three reinforcing walls 11 in head frame 10 that run perpendicular to the plane of the ball-hitting face. Reinforcing walls 11 separate head frame 10 into four cavities 12 from left to right.

FIG. 16 shows one reinforcing wall 21 in throat portion 20 that runs parallel to the plane of the ball-hitting face. Reinforcing wall 21 separates throat section 20 into two symmetrical cavities 22, i.e., the left cavity, and the right cavity.

FIG. 17 shows three reinforcing walls 31 in handle portion 30 that run perpendicular to the plane of the ball-hitting face. Reinforcing ribs 31 separate handle portion 30 into four cavities 32 from left to right.

In a fourth embodiment, the reinforcing walls in the upper and lower parts of the head frame are different in direction and/or quantity. FIG. 18 illustrates tennis racquet 100, with upper part T and lower part K of head frame 10.

FIG. 19 shows a cross section of tennis racquet 100 at upper part T of head frame 10. There is one reinforcing wall 11 that runs perpendicular to the plane of the ball-hitting face. Reinforcing wall 11 separates upper part T of head frame 10 into two symmetrical cavities 12 from left to right.

FIG. 20 shows a cross section of tennis racquet 100 at lower part K of head frame 10. There are two reinforcing walls 11 that run parallel to the plane of the ball-hitting face. Reinforcing walls 11 separates lower part K of head frame 10 into three cavities 12, i.e., the lower cavity, the middle cavity, and the upper cavity.

In a fifth embodiment, the reinforcing walls in the upper, middle, and lower parts of the head frame may be different in at least direction or quantity. For example, a tennis racquet, with upper part, middle part, and lower part of head frame.

A cross-section of such a tennis racquet at the upper part of head frame includes one reinforcing wall that runs parallel to the plane of the ball-hitting face. That reinforcing wall separates the upper part of the head frame into two symmetrical cavities, i.e., the upper cavity, and the lower cavity.

The cross section of such a tennis racquet at middle part of the head frame includes three reinforcing walls that run perpendicular to the plane of the ball-hitting face. Those reinforcing walls separate the middle part of head frame into four cavities from left to right.

The cross section of the tennis racquet at the lower part of the head frame has two reinforcing walls that run parallel to the plane of the ball-hitting face. The reinforcing walls separate me lower part of head frame into three cavities, i.e., the lower cavity, the middle cavity, and the upper cavity.

In a sixth embodiment, the layups of the different portions of the tennis racquet are braided together. The number of layups may be varied in the different portions of the racquet depending on the desired dimensions and strength of the racquet frame. FIG. 25 show a schematic view of three layups 50, 52, and 54 braided together. FIG. 26 shows a cross section of FIG. 25 of three braided layups 50, 52, and 54.

In accordance with the invention it is also possible to manufacture planar members, for example by forming a layup comprised of a number of layup tubes 312. Layup tubes 312 each include a preferably sealed micro capsule member. They are put in a clamshell mold comprising mold halves 314 and 316. After heating and expansion of the microcapsules, and cooling of the same, a black member 316 results, as illustrated in Figure 22.

Referring to Figure 23, layup tubes 412 may be put in different configurations, such as the matrix illustrated, and put in a clamshell mold similar to the mold illustrated in Figure 21. After manufacture, the material may be sewn into any desired shape, which may be molded into its final shape.

In accordance with the invention a ladder may be manufactured. A layup for a ladder 510 as illustrated in Figure 24a. It includes two vertical supports 512, and a plurality of rungs 514. As illustrated in Figure 24b, each of the lungs has a binding portion 516, which is bound by a graphite or fiberglass ribbon 518 with longitudinally extending fibers wrapped around its respective vertical support 512.

After assembly of the layup illustrated in Figure 24a, the same is put in a clamshell mold formed in the shape of the finished ladder. The mold is heated and the microcapsule material expands forming a finished fiberglass ladder of exceptional strength and lightness of weight.

Figure 43 illustrates the manufacture of a flat graphite member. More particularly, such a flat member is manufactured by first taking a flat transparent plastic envelope and filling it with expandable microcapsule material. The envelope is then evacuated of air by, for example, placing the envelope on a table and sliding the edge of a ruler over the top of the envelope to make it almost completely flat and contain only microcapsules. Drawing the air out using a vacuum pump would even be a more effective technique and will better stabilize the microcapsules within the envelope. The filled envelope is then sealed, for example heat sealed at its open edge, thus resulting in maintaining a substantial vacuum or a very low volume of air within the envelope, as in the other embodiments. The microcapsules may be smoothed out using a ruler edge to press the top of the envelope on the table.

Alternative to a vacuum, the microcapsules may be stabilized in position by adhering to a sheet of material using a glue or adhesive.

As shown in Figure 43, sealed envelope 508 is placed on a lower mold 512, thus placing a uniform layer of expandable microcapsules in position. A first layer 518 of graphite or fiberglass saturated with curable resin is then placed over envelope 508.A second layer 520 of graphite or fiberglass saturated with curable resin is then placed over first layer 518. Upper mold member 514 is then placed over the assembly and the same is heated causing the microcapsules to expand, and drive layer 518 into layer 520 to intimately bind the two layers to each other and cure the plastic resin. During the application of heat, means are used to secure lower bold portion 512 to upper mold portion 514 so that the same are closed. Such means may be clamps or bolts or any other artifice.

While illustrative embodiments of the invention have been disclosed, it is understood that various modifications of the inventive method and the materials used will be obvious to those of ordinary skill in the art in view of the above description and specification. In addition to these obvious modifications, the invention may be applied in other areas. For example, the inventive technique may be used to for a bicycle frame in which different orientations are applied to different parts of the frame to address the stresses formed at those parts of the frame during use. Similarly, the inventive technique may be used for wind turbines, airplane bodies, boat hulls, automobile parts, high-impact strength containers, and luggage just to name a few. Such variations are within the spirit and scope of the invention, which is limited and defined only by the appended claims.

Claims

1. A method of forming a composite member, comprising:

(a) placing a heat formable resin adjacent fibers to form a fiber member,

(b) placing said fiber member, comprising a plurality of fibers against a first mold part;

wherein the improvement comprises

(c) distributing into a distributed configuration an expandable material which expands under the application of heat;

(d) stabilizing said distributed material in said distributed configuration to form an expandable member;

(e) placing said expandable member adjacent said fiber member;

(f) placing a second mold part over said first mold part;

(g) sealing a closed cavity e defined between said first and second mold parts, said closed cavity containing said fiber member and said expandable member;

(h) heating said first and second mold parts, causing said expandable material to expand and form a pressure, said pressure driving said fiber member against one of said mold parts, said mold parts also heating the resin adjacent the fibers; and

(i) hardening said resin to form said composite member.

2. A method as in claim 1, wherein said first and second mold parts are sealed to each other.

3. A method as in claim 1, wherein said distributed material is distributed between two planar members and said to plan our members define a substantially closed volume between said two when our members.

4. A method as in claim 3, wherein said two planarr members are transparent.

5. A method as in claim 1, wherein said expendable material is made by encapsulating a heat expandable material in resin to form microcapsules made of resin and containing said heat expandable material.

6. A method as in claim 1, wherein said fiber member includes multiple layers of fibers in different orientations.

7. A method as in claim 1, wherein said fibers are made of graphite or fiberglass.

8. A method as in claim 1, wherein said heat formable resin is selected from the group consisting of thermoplastic, thermosetting and two part epoxy plastics.

9. A method as in claim 1 wherein said distributed configuration is stabilized by gluing said heat expandable material in position.

10. A method as in claim 1, wherein said distributed configuration is stabilized by maintaining said heat expendable material in position between a pair of film members.

11. A method as in claim 1 , wherein said expendable material is contained within a substantially closed film member.

12. A method as in claim 1, wherein said fiber member is a tube and said expendable material is contained within said tube.

13. A method as in claim 12, wherein a plurality of tubular fiber members are placed adjacent each other and cured in a single mold.

14. A method of forming a composite member, comprising:

(a) placing a heat formable resin adjacent fibers to form a plurality of tubular fiber members;

(b) placing said tubular fiber members against a first mold part;

wherein the improvement comprises

(c) distributing, within said tubular members, an expandable material which expands under the application of heat;

(d) placing a second mold part over said first mold part;

(g) sealing a closed cavity defined between said first and second mold parts, said closed cavity containing said fiber member and said expandable member;

(i) hardening said resin to form said composite member.

15. A method of forming a composite member as in claim 14, wherein said tubular members are twisted or braided with respect to each other before being placed in said mold.