BR102019026408B1 - METHOD FOR MANUFACTURING A REINFORCED POLYMER COMPOSITE COMPONENT, AND, REINFORCED POLYMER COMPOSITE COMPONENT - Google Patents

Abstract

METHOD FOR MANUFACTURING A REINFORCED POLYMER COMPOSITE COMPONENT, AND, REINFORCED POLYMER COMPOSITE COMPONENT. A method of manufacturing a monolithic fiber reinforced polymer composite component (228) is provided. The method comprises providing a mold (206) comprising a main cavity (208) and at least one additional cavity (210) extending from the main cavity (208); introduce a polymeric matrix material (222) containing chopped fiber reinforcement into the die (206) to fill the main cavity (208) and the at least one additional cavity (210) to form a monolithic fiber-reinforced polymer composite component (228 ) with a main portion (230) formed in the main cavity (208) and at least one raised feature (232) formed in the additional cavity (210) and extending from a surface plane of said main portion (230). The at least one elevated feature (232) is arranged to incur visually perceptible damage when the component (228) is subjected to an impact with an energy above a predetermined impact energy threshold and to resist an impact with an energy below of the predetermined impact energy threshold

Description

Field of Technique

[001] The present disclosure relates to composite components (e.g., fiber-reinforced polymer) and, in particular, to methods of manufacturing composite components that facilitate the detection of impact damage thereto.

Fundamentals

[002] Composite materials, such as fiber-reinforced polymer, are used in a wide variety of applications, where high strength but low mass parts are required. For example, carbon or glass fiber-reinforced polymer (FRP) composite materials are often used to produce structural components (e.g., struts, connectors), force-transmitting components (e.g., drive shafts, tappets), and conduits. of fluid transfer (e.g. fuel pipes) in the aerospace and automotive industries. Components suitable for these applications must have high strength to handle the large forces involved, but also need to maximize weight for fuel economy and/or performance reasons.

[003] Fiber-reinforced polymer material properties mean that damage (such as delamination or broken fibers) caused by relatively low-energy impacts (e.g., a technician dropping a tool on a part) is often confined to or focused in the internal regions and/or a reverse (i.e., opposite to impact) side of the composite material. Therefore, it can be very difficult to visually detect such damage from the front side of the material. Damage that is detectable by detailed visual inspection is often called Barely Visible Impact Damage (BVID). Impacts to a composite component with sufficient energy to cause BVID are therefore the lowest energy impacts that can be detected. However, impacts that do not cause BVID (i.e., lower energy impacts) can still severely weaken a composite material. With no visible indication from the outside of this weakening on its exterior, these impacts can lead to unexpected failures in components well below a material's rated performance.

[004] In some cases, BVID can be detected by visually inspecting a reverse side or internal surfaces of composite materials, for example, the internal surfaces of a composite tube. However, this may take time and is not always conclusive. Additionally, the geometry of some components (e.g., complex tube geometries) may prevent direct visual inspection of a reverse side or inner surface without inconvenient and time-consuming disassembly or the use of specialist tools (e.g., inspection scopes). ).

[005] As such, composite parts are typically constructed to withstand any impact at an energy below which BVID occurs (i.e., to ensure that impacts that cannot be detected do not decrease the performance of the part). In fact, the identification of BVID and the associated reduction in structural performance at these damage levels is often the primary factor driving the design of composite materials and components. However, this can lead to composite components being reinforced or having increased strength beyond what is necessary for their primary function (for example, a fuel pipe that has thicker walls than necessary to resist fuel pressure). This increases the weight and material cost of components. US 2013/0183087 A1 discloses a molded article comprising a polymeric composite material and surface features created during molding of the polymeric composite material. Document DE 20 2015 006737 U1 discloses a push-pull rod made of fiber composite material having a thin layer of hard plastic foam material on the outward facing surface of the push-pull rod for detecting BVID.

[006] It is important to be able to detect any damage sustained by a composite part to protect against unexpected failures or reduced performance. However, it is also desirable to minimize the weight and material cost of composite parts. As such, means to reduce the energy level at which BVID is established for a composite component and improved methods to effectively and reliably detect BVID are sought.

summary

[007] From a first aspect of the present disclosure there is provided a method of manufacturing a monolithic fiber reinforced polymer component comprising: providing a mold comprising a main cavity and at least one additional cavity extending from the cavity main; introducing a polymeric matrix material containing fiber reinforcement into the mold to fill the main cavity and the at least one additional cavity to form a monolithic fiber reinforced polymer composite component with a main portion formed in the main cavity and at least one raised feature formed in the additional cavity and extending from said main portion; wherein the at least one elevated feature is arranged to incur visually perceptible damage when the component is subjected to an impact with an energy above a predetermined impact energy threshold and to resist an impact with an energy below the threshold energy predetermined impact.

[008] From a second aspect of the present disclosure, there is provided a monolithic fiber-reinforced polymer composite component formed from a polymeric matrix material containing chopped fiber reinforcement, the component comprising: a main portion and at least one raised feature extending from a surface plane of said main portion; wherein the at least one elevated feature is arranged to incur visually perceptible damage when the component is subjected to an impact with an energy above a predetermined impact energy threshold and to resist an impact with an energy below the threshold energy predetermined impact.

[009] The at least one elevated feature thus provides a clear visual aid regarding when a component has suffered an impact with an energy above the predetermined impact energy threshold, even if such damage is not visually perceptible in the main portion . For example, an impact with an energy above the predetermined impact energy threshold may cause damage to the main portion that is not easy to detect, but creates visually noticeable damage to at least one elevated feature. Visually perceptible damage may be visible through inspection from the outside of the component (e.g., by a human inspector or by a detection device such as an automated inspection camera). What is meant by visually perceptible damage is that the damage can be distinguished by an unaided human eye, so that the damage is easily detected when handling the component. Additionally or alternatively, the damage may be visually perceptible to a detection device (e.g., an inspection camera) with a predefined sensitivity (e.g., a predefined imaging resolution).

[0010] It will be understood that a monolithic fiber reinforced polymer component comprises a polymer matrix material that is continuous throughout the main portion and at least one raised feature, with the same cut fiber reinforcement distributed throughout the polymer matrix. However, as will be clear from the discussion below, the distribution of fiber reinforcement may vary between the main portion and at least one elevated feature.

[0011] Because the FRP component is monolithic (i.e., does not comprise separate elements or joined or bonded parts) and is formed in a single molding process, the high capabilities are capable of detecting impacts as soon as the component is produced, without the component having to go through other manufacturing steps (such as a sensing layer being adhered to it). This means that the main portion never exists without the raised feature(s) with impact detection and an inspector can be assured that an undamaged portion visually noticeable to the raised feature(s) ) has never suffered an impact with an energy above the predetermined impact energy threshold.

[0012] Various factors may be considered when selecting the predetermined impact energy threshold, such as likely impact exposures and associated probability. The main portion of the component is preferably that part of the component that activates the function of the component. For example, the component may comprise a fuel pipe and the main portion may be the portion of the component that carries fuel. In another example, the component may comprise a support, and the main portion may be that part of the component that transmits compressive and/or tensile loads.

[0013] In one or more examples, therefore, the predetermined impact energy threshold is selected based on one or more properties (e.g., mechanical or structural properties) of the main portion. Mechanical properties may include, for example, strength, stiffness, toughness, flexural modulus, elastic modulus, etc. The one or more properties can be actual or expected properties.

[0014] In these examples, an impact that would cause significant damage to the main portion (i.e., damage that would threaten the proper functioning of the component) appears on the at least one elevated feature as visually noticeable damage, while impacts that do not threaten the function of the component do not appear.

[0015] For example, the main portion may be designed to have a certain level of resistance to mechanical load, such as a maximum internal pressure (e.g., for a fuel pipe) or a maximum compressive or tensile load (e.g., for a support). In some of these examples, the predetermined impact energy threshold may be selected as an energy at which (or above) impacting the main portion may (or is likely to) compromise the mechanical load resistance of the main portion.

[0016] It will be appreciated that, in one or more examples, the predetermined impact energy threshold may be selected based on the expected use of the component, for example, because significant damage in one application may not be significant in another application (e.g. , load requirements may be different in different applications).

[0017] In some examples, the predetermined impact energy threshold is between 0.5 J and 4 J. This means that at least one elevated feature is sensitive to any impact with an energy above 0.5 J and typically incurs visually noticeable damage whenever there is a risk of damage to the composite component. This may be particularly suitable for applications requiring high strength, for example when the composite component is a tube for transporting fluids at high pressures.

[0018] The at least one high feature preferentially reduces the energy level at which the BVID is established, compared to the main portion alone. Therefore, in some examples, the predetermined impact energy threshold may be selected to be an impact energy below which the main portion would incur visually perceptible impact damage. In at least some examples, in addition or alternatively, the predetermined impact energy threshold may be selected to be less than an impact energy that would cause damage to the main portion. To avoid unnecessary removal of components, the predetermined impact energy threshold can be selected to be close to this impact energy.

[0019] In some examples, the predetermined impact energy threshold is between 2 J and 10 J, for example, about 4 J. This means that at least one elevated feature is sensitive to any impact with an energy above 2 J , whose energy level is close to the 3-5 J (or more) energy level that would cause damage to the main portion.

[0020] The elevated feature may be arranged to provide such clear visual indication of damage that a formal inspection (typically required to identify BVID levels of damage) is not necessary to detect the occurrence of an impact (i.e., sustained damage is more visible than damage BVID levels). Instead, damage can be located during normal handling or maintenance of the component, reducing the time and resources required to maintain confidence in the integrity of the component. This enables impact damage to be detected earlier (i.e. between periodic inspections), reducing the time a potentially compromised component is used.

[0021] Being able to quickly and reliably detect impact damage can lead to significant time and resource savings, as well as increasing the safety and reliability of composite parts, as a damaged component can be immediately identified for repair or replacement before additional use.

[0022] The predetermined impact energy threshold can be measured using standard test methods, for example, ASTM D7136/D7136M-15 “Standard Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a DropWeight Impact Event.” This test method determines the damage resistance of multidirectional polymer matrix composite laminated plates to a drop weight impact event. One or more of impactor shape, impact energy, and support conditions for the sample under test may be selected to represent the expected impact threats that a given component may experience in service.

[0023] In one or more examples, the visually perceptible damage incurred by the at least one elevated feature may comprise at least one minor anomaly of the elevated portion, such as a dent or a chip. In one or more examples, the visually noticeable damage incurred by the at least one elevated feature may comprise a noticeable indentation, knot, fracture or crack. In one or more examples, the visually perceptible damage incurred by the at least one elevated feature may comprise an entire missing section of the at least one elevated portion or certainly a complete absence of the at least one elevated portion. Minor defects to at least one high feature, such as scratches, scrapes or abrasions, may not constitute visually noticeable damage. In at least some examples, the visually perceptible damage may comprise a visible crack (e.g., a crack with a length of at least 10 mm) or a visible notch (e.g., a notch with a depth of at least 0.3 mm or 0. .5mm). Preferably, visually perceptible damage is detectable by a human inspector without the use of tools (e.g., magnifying glass or microscope). A high resource is understood to resist an impact where there is no such visually noticeable damage.

[0024] In addition to providing a visual indicator of impact damage, the at least one elevated feature may additionally provide the component with an increased level of impact resistance. For example, the at least one elevated feature can absorb some impact energy so as to reduce damage transmitted to the main portion. This can mitigate complete failure of a component after an impact has occurred, but before an inspection is performed to determine whether the component needs to be repaired or replaced.

[0025] There may be more than one way in which the at least one elevated feature may be arranged to incur visually perceptible damage for impacts with an energy above the predetermined impact energy threshold. For example, the geometry, e.g., shape and/or size, of at least one raised feature may be adjusted to at least partially control the impact energy to which it is resistant. Such approaches are disclosed in the applicant's pending patent application.

[0026] According to several examples of the present disclosure, the inventors have recognized that the manner in which the composite component is manufactured (e.g., by injection molding) and/or the choice of chopped fiber reinforcement can at least partially control the impact energy to which it is resistant.

[0027] In some examples, the method comprises an injection molding process, wherein introducing the polymer matrix containing chopped fiber reinforcement comprises injecting a molten thermoplastic polymer matrix containing chopped fiber reinforcement into the mold.

[0028] The use of an injection molding process is beneficial as it can manufacture monolithic fiber reinforced components consistently and quickly at relatively low cost. There is little wasted material (for example, compared to subtractive manufacturing processes such as CNC machining) and there are few restrictions on the shape of the component that can be produced.

[0029] The cut fibers of the chopped fiber reinforcement can be substantially the same length. However, in many cases, the cut fibers have a range of lengths that can be characterized by an average fiber length (e.g., mean or median) and/or other parameters of a fiber length distribution. In some preferred examples, the chopped fiber reinforcement has an average fiber length between 50 and 500 microns, for example, 100 microns, 150 microns, 200 microns, 250 microns, 300 microns, 350 microns, 400 microns or 450 microns.

[0030] The chopped fiber reinforcement may comprise one or more carbon fibers, glass fibers, aramid fibers or any other suitable fiber material. Chopped fiber reinforcement may comprise a mixture of two or more types of fiber.

[0031] As mentioned above, the polymer matrix may comprise a thermoplastic polymer matrix, for example, such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyetherketonacetone (PEKK), polyetherketone (PEK) or other polymer that forms part from the polyaryletherketone (PAEK) family. The polymeric matrix may comprise other materials, such as a thermosetting polymer. In a preferred example, the composite component is formed from a PEEK polymeric matrix containing 30% chopped carbon fiber reinforcement.

[0032] The volume fraction of an FRP part that consists of fiber reinforcement is commonly referred to as the fiber volume fraction of the part. Typically, FRP components are manufactured to have a uniform fiber volume fraction, consistency and predictability of mechanical performance, and ease of fabrication. Indeed, in some examples of the present disclosure, the fiber-reinforced polymer component comprises a substantially constant fiber volume fraction throughout (i.e., wherein the fiber volume fraction in the main portion is substantially equal to that of the fur). least one elevated portion).

[0033] However, in some preferred examples, the distribution of chopped fiber reinforcement varies between the main portion and the at least one raised feature, that is, there is a fiber volume fraction gradient or step change between the portion main and at least one high resource. In some such examples, the main portion of the component comprises a first volume fraction of fiber reinforcement and the at least one elevated feature comprises a second volume fraction other than the fiber reinforcement.

[0034] The fiber volume fraction of an FRP material affects the structural properties of the composite component. For example, an FRP part with an increased fiber volume fraction is associated with increased strength but decreased ductility (i.e., greater brittleness) of the part. Likewise, reducing the fiber volume fraction can increase the ductility and/or strength (reduce brittleness) of the part. Thus, different fiber volume fractions in the main portion and the elevated feature(s) can result in the main potion and at least one elevated portion having different structural or mechanical properties. This may facilitate adjustment of the predetermined impact energy threshold and/or the type (and potentially the visibility) of impact damage suffered by at least one elevated feature for impacts above the energy threshold, ideally without altering structural or mechanical properties. of the main portion.

[0035] For example, the second fiber volume fraction of the at least one raised feature may be selected to be greater than the first fiber volume fraction to increase the fragility of the at least one raised feature and reduce the impact energy on the what damage occurs. The type of damage (such as a crack or break) can be more easily seen by the unaided human eye. Preferably, in at least some examples, the second fiber volume fraction of the elevated resource may be selected to be smaller than the first fiber volume fraction. The second fiber volume fraction being smaller, decreases the material strength of the at least one high feature, thus reducing the impact energy at which damage occurs. Additionally, the type of damage may have a different visual appearance, such as warping or denting, due to an increase in ductility and/or strength.

[0036] The at least one elevated feature being more ductile or strong than the main portion (i.e., where the second fiber volume fraction is smaller than the first fiber volume fraction) may be advantageous for one or more reasons. For example, at least one elevated feature can provide a shock absorbing effect. For example, a portion or all of an elevated resource of greater tenacity is less likely to separate from the main portion when damaged. This reduces the likelihood of composite fragments (which can disrupt a fragile elevated feature when subjected to an impact) interfering with component function (e.g., reducing the chance of composite foreign bodies entering a fuel tank where the component is a fuel system component, such as a fuel line).

[0037] The second fiber volume fraction may differ from the first fiber volume fraction by 30% or more. However, a significant change in structural properties can be obtained with smaller differences, and the second fiber volume fraction can differ from the first volume fraction by less than 30%, e.g., 20% or less, 10% or less, 6% or less or up to 1-5%. For example, the first fiber volume fraction may be approximately 30% and the second fiber volume fraction may be approximately 20%.

[0038] Preferably, in at least some examples, the distribution of the chopped fiber reinforcement between the main portion and the at least one elevated feature comprises a binary step change between the first and second volume fractions of the chopped fiber reinforcement . In at least one example, in addition or alternatively, the fiber volume fractions in the main portion and the at least one raised feature are substantially homogeneous (i.e., they contain fiber reinforcement only in the first and second fiber volume fractions, respectively). ). Alternatively, in at least some other examples, there may be a gradual change between the first volume fraction and the second volume fraction, for example, between the main portion and a region (e.g., a tip) of the at least one elevated feature. furthest from the main portion. Obviously, specific geometries of at least one elevated feature may naturally result in a more complex fiber volume fraction gradient (e.g., including inconsequential local minima of fiber volume fraction within parts of the elevated feature), but the general distribution The preferred choice of chopped fiber reinforcement is that of an effective pitch change in the average fiber volume fraction between the main portion and the at least one elevated feature.

[0039] It has been recognized that the use of an injection molding process with a suitably configured mold may be particularly suitable for the production of composite components in which the distribution of chopped fiber reinforcement varies between the main portion and the at least one feature. high.

[0040] Different fiber volume fractions can be produced by controlling various aspects of the injection molding process, such as the shape and/or sizes of the main cavity and/or at least one additional cavity, the overall configuration of the mold (e.g. where and how the polymer is injected), the melting temperature and the length of the cut fiber.

[0041] For example, a molten thermoplastic polymer matrix material containing chopped fiber reinforcement can be injected into the mold so that it follows a primary flow direction in the mold (e.g., in examples where the main portion comprises a shape cylindrical, the primary flow direction may be in a direction parallel to the geometric axis of rotational symmetry, i.e., central geometric axis of the cylinder). In some such examples, the at least one additional cavity may extend at least partially in a direction perpendicular to the primary flow direction (i.e., radially to the main cylindrical portion), such that the polymer matrix material filling the cavity main has the first volume fraction of the chopped fiber reinforcement and the polymeric matrix material that fills the additional cavity has the second volume fraction different from the chopped fiber reinforcement. The inventors have considered that a connection perpendicular to an opening between the main cavity and the at least one additional cavity may hinder the flow of chopped fiber reinforcement into the at least one additional cavity. This effect may depend on the average length of the chopped fiber reinforcement.

[0042] In such examples, the at least one additional cavity may extend from the main cavity into an opening having an opening dimension in a direction parallel to the primary flow direction that is selected to create a desired fiber volume fraction difference. between the main portion and the at least one raised feature (e.g., a small opening may restrict the entry of cut fibers of a comparable length, thereby reducing the volume fraction of fiber within the additional cavity and thus the second fraction of resulting volume in at least one high resource). In some examples, the aperture dimension (corresponding to a width of a base region of the resulting raised feature) is between 500 and 5,000 microns (0.5 - 5 mm), for example, about 1.6 mm. More generally, the opening dimension can be selected not to exceed ten times the average length of the chopped fiber reinforcement.

[0043] The inventors have recognized that the geometry, for example, the shape and/or size, of at least one raised feature can be adjusted to at least partially control the impact energy to which it is resistant. Furthermore, one or more geometric parameters of the at least one raised feature may be selected to at least partially determine the distribution of chopped fiber reinforcement between the main portion and the at least one raised feature.

[0044] In some examples, the at least one raised feature comprises a cross-sectional profile that is selected such that the at least one raised feature resists impacts with an energy below the impact energy threshold while reliably incurring in visually perceptible damage when subjected to an impact with an energy above the impact energy threshold.

[0045] In some examples, in addition or alternatively, the at least one raised feature comprises a cross-sectional profile that is selected so that the main portion comprises a first volume fraction of the chopped fiber reinforcement and the at least one raised feature comprises a second volume fraction different from the chopped fiber reinforcement. Preferably, the second volume fraction is smaller than the first volume fraction, as described above.

[0046] In reality, the distribution of chopped fiber reinforcement between the main portion and at least one elevated feature can be controlled by one or both of manufacturing steps and geometric considerations.

[0047] In at least some examples, the at least one elevated feature has a cross-sectional profile defined in a cross-section made through the surface plane. The cross-section profile can have a curved or curvilinear shape. Examples of some cross-sectional profiles that can be used include triangular, rectangular, polygonal, curved, semicircular, bell-shaped, etc. In at least some examples, the cross-sectional profile is generally triangular. In various examples, the dimensions and/or aspect ratio of a given cross-sectional profile may be adjusted to alter the impact resistance of at least one elevated feature and, therefore, the impact energy threshold above which damage is incurred. visually noticeable.

[0048] The at least one elevated feature may have a single (i.e., constant) cross-sectional profile. However, in some examples, the at least one elevated feature may comprise at least two different cross-section profiles (i.e., at different locations on the component) and/or may comprise a varying cross-section profile. For example, the cross-sectional profile may vary or change along a length of the at least one elevated feature.

[0049] The at least one high resource may cover only a small fraction of the main portion per area, for example, up to 30%, up to 20%, or even 10% or less. For example, the at least one elevated feature may comprise a narrow ridge. However, even in examples where the at least one raised feature does not cover a large fraction of the surface of the main portion by area, effective impact detection can still be achieved as long as the surface areas between the raised feature (or raised features) are small enough. For example, if the component is used in an environment where any impact is likely to be caused by relatively large impact objects (e.g., a wrench), the at least one raised feature need not cover the entire surface of the main portion without interruption. Instead, the at least one high feature need only be present on the surface to the point that an impact on the component from a given impact object would necessarily or very likely hit (and thus damage, if the energy was high enough). ) the high resource. A type and/or source of impact to which a component is likely to be subjected may thus be considered when selecting how the at least one elevated feature is arranged, e.g., its shape, size and/or template in the surface of the main portion. The at least one elevated feature may cover only areas of the main portion that are susceptible to impact damage.

[0050] However, in some examples, at least one high resource may cover a large fraction of the main portion per area (e.g., 70% or more, 80% or more, or even 90% or more). Covering a large fraction of the main portion ensures reliable impact detection no matter where the impact occurs.

[0051] The at least one raised feature may comprise a raised pattern extending across part, most or all of the surface of the main portion. In one or more examples, the main portion comprises a cylindrical surface extending along a central geometric axis and the at least one raised feature comprises a narrow ridge on the cylindrical surface extending in a helix around the central geometric axis. The angle at which the propeller extends can be selected so that the axial spacing between crest passes is less than the smallest dimension of a likely impact object.

[0052] In some examples, the at least one elevated feature provides uniform coverage over the entire surface of the main portion, so that impacts at any location on the surface can be detected.

[0053] The at least one elevated resource may comprise a plurality of elevated resources. In some examples, different elevated features may extend from different areas of the surface of the main portion. In some examples, different raised features may extend from different surfaces of a plurality of surfaces to provide impact resistance to different sections of the main portion. Preferably, the plurality of raised features are disposed across at least one surface of the main portion and are separated by a spacing distance. The spacing distance can be regular or irregular and can be chosen depending on an impact source, as described above. In some examples, the at least one raised feature may comprise a series of circumferential ribs extending from a cylindrical main portion and running around a central geometric axis.

[0054] A plurality of different elevated features (i.e., features sensitive to different impact energy thresholds) may be provided in an area of the at least one surface to provide more information about impact energies. In one or more examples, the plurality of elevated resources comprises at least two different elevated resources. The at least two different raised features may be different types of raised features, for example, one type having a triangular cross-sectional profile and another type having a rounded cross-sectional profile. For example, high sharp peaks (with a low impact energy threshold) can be separated by lower rounded peaks (with a much higher impact energy threshold) to enable impacts to be categorized by energy (i.e., an impact which results in visually noticeable damage to spikes, but not to co-located lower rounded spikes should have an energy between the respective thresholds of the two spike types).

[0055] In one or more examples, the surface plane of the main portion is a cylindrical surface plane extending along a central geometric axis (i.e., the geometric axis of rotation). In at least some examples, the at least one elevated feature comprises one or more ridges extending from the cylindrical surface plane and running in a helix about the central geometric axis. Such an arrangement may contribute to achieving a different volume fraction of cut fiber reinforcement in the ridges compared to the main portion, as the helical ridges do not follow the primary flow direction. The angle at which the propeller runs can be selected so that the axial distance between crest passes is less than the smallest dimension of a likely impact object. In at least some examples, alternatively or in addition, the at least one raised feature comprises a plurality of ridges extending from the cylindrical surface plane and running circumferentially about the central geometric axis. Such an arrangement may contribute to achieving a different volume fraction of cut fiber reinforcement in the ridges compared to the main portion, as the circumferential ridges run perpendicular to the primary flow direction. These circumferential ridges may be axially spaced with a spacing distance as disclosed above, for example, the spacing distance is less than the smallest dimension of a likely impact object.

[0056] In at least some examples, alternatively or in addition, the at least one raised feature comprises a plurality of ridges extending from the cylindrical surface plane and running along the central geometric axis. These circumferential ridges may be spaced circumferentially with a spacing distance as disclosed above, for example, the spacing distance is less than the smallest dimension of a likely impact object. Obviously, a combination of one or more ridge types (helical, circumferential and/or axial) can be provided in any given high feature pattern.

[0057] In at least some examples of the methods disclosed herein, the mold is shaped to form a tubular main portion having a central geometric axis and at least one raised feature extending from a cylindrical surface plane of the main portion and which runs in a helical and/or circumferential manner and/or axial direction in relation to the central geometric axis. The disclosed methods may therefore be particularly suitable for manufacturing tubular components such as fluid transfer conduits, for example a fuel pipe.

[0058] In at least some examples of the present disclosure, the component comprises a tubular main portion that has a central geometric axis and at least one raised feature that extends from an outer surface plane of the main portion and runs in a manner helical and/or circumferential and/or axial direction in relation to the central geometric axis.

[0059] In at least some examples of the present disclosure, the component comprises a tubular main portion with a wall thickness between 0.5 mm and 5 mm. In at least some examples, further or alternatively, the component comprises a tubular main portion having a cylindrical shape with a diameter (internal or external) between 10 mm and 150 mm.

[0060] In some applications of composite materials, such as glass fiber reinforced polymer tubes in aircraft fuel systems, for example, it is important to control the conductivity of the composite component. Ideally, fuel lines are insulating enough to avoid becoming the preferred path for driving lighting, while being conductive enough to avoid static build-up due to fuel flow. Adding a particular amount of a conductive additive (e.g., carbon black) to the polymer during manufacturing allows the desired level of conductivity to be achieved. It is known for tailoring the electrical conductivity of composite fuel pipes by mixing an electrically conductive particulate filler dispersion into a fiber-reinforced polymeric material, for example, as disclosed in WO 2009/087372, the contents of which are incorporated herein by reference. The conductive additive is ideally present throughout the component (i.e., both the main portion and the at least one raised feature).

[0061] In at least some examples of the present disclosure, the composite component is a fluid transfer conduit, such as a fuel pipe.

[0062] In some examples, the at least one raised feature comprises an outer coating with a color that contrasts with a color of the FRP (e.g., the FRP polymer may be black due to the addition of carbon black additive, while the coating is white). This may enable any damage to the at least one raised feature to be more readily identified, since the underlying composite material exposed due to damage incurred by the at least one raised feature would contrast with the intact coating surrounding the damaged area.

[0063] The characteristics of any example described herein may, where appropriate, be applied to any other example described herein. When reference is made to different examples or sets of examples, it should be understood that they are not necessarily distinct, but may overlap.

Detailed Description

[0064] One or more non-limiting examples will now be described, for exemplary purposes only and with reference to the attached figures in which: Figure 1 is a cross-section of a monolithic fiber reinforced polymer composite component according to an example of the present disclosure; Figure 2 is a cross section of the monolithic fiber reinforced polymer composite component along the A-A plane shown in Figure 1; Figure 3 is a perspective view of the monolithic fiber reinforced polymer composite component; Figure 4 is another perspective view of the monolithic fiber reinforced polymer composite component; Figures 5a and 5b are enlarged views of area B shown in Figure 2 according to the first and second examples; Figures 6-8 show the effect of an impact on a monolithic fiber reinforced polymer composite component according to an example of the present disclosure; Figure 9 shows a fiber-reinforced polymer composite tube according to an example of the present disclosure; Figure 10 shows a fiber-reinforced polymer composite tube according to another example of the present disclosure; Figures 11 and 12 schematically illustrate an injection molding process for manufacturing a monolithic fiber-reinforced polymer composite component in accordance with an example of the present disclosure; and Figure 13 is a schematic cross-sectional view of a single raised feature of a monolithic fiber-reinforced polymer composite component in accordance with an example of the present disclosure.

[0065] Figures 1-5 show different views of a monolithic fiber-reinforced polymer composite component 2 (e.g., carbon fiber-reinforced polymer, CFRP). In this example, component 2 comprises a flanged cylindrical connector extending along a central geometric axis C and comprising a pipe section 2a and a flange section 2b. Component 2 comprises a thermoplastic polymer reinforced with chopped fiber reinforcement (fibers are not shown in Figures 1-5). The average (median) length of chopped fiber reinforcement can be between 50 and 500 microns (e.g., 200 microns).

[0066] Component 2 comprises a main portion 4 and a plurality of raised features 6 extending from a surface plane S of the main portion 4. In this example, the plurality of raised features 6 comprises a plurality of ribs with a substantially triangular cross-sectional profile (in section A-A shown in Figure 2). The raised features 6 extend radially away from the surface plane S (relative to the central geometric axis C) and run circumferentially around the pipe section 2a and the flange section 2b of component 2, as seen in Figures 3 and 4 The elevated features 6 are arranged along the entire length of the component 2.

[0067] High features 6 serve to detect potentially damaging impacts to component 2. As explained in more detail below, with reference to Figures 6-8, when component 2 is subjected to an impact with an impact energy above the threshold of predetermined impact energy, at least some of the raised features 6 suffer visually noticeable damage, even when the main portion 4 may not, allowing a human inspecting the part to quickly and easily recognize that the part has been subjected to an impact .

[0068] By appropriate design of the raised features 6, the threshold energy above which the raised features 6 are “sensitive” (i.e., when visually perceptible damage is incurred) can be selected to be an energy at which impacts would cause damage. (i.e., damage that impacts pipe performance) to the main portion 4. Impacts below this energy do not cause visible damage to the elevated features 6, but also do not cause substantial damage to the main portion 4. As such, the external of component 2 may quickly reveal evidence of serious impacts that cause damage, while insignificant impacts (which do not affect the component's ability to function as intended) are not recorded. The presence and magnitude of impact damage to component 2 can therefore be quickly assessed without requiring an in-depth investigation. Visually perceptible damage to raised features 6 may comprise, for example, a portion (or all) of raised feature 6 breaking. They may alternatively comprise a notch or other deformation.

[0069] Figure 5a shows a close-up cross-sectional view of the elevated features 6 in area B indicated in Figure 2 according to a first example. In this example, each elevated feature 6 comprises a profile of generally triangular cross-section (although other profile shapes are possible) extending from a base 6a adjacent to the surface plane S of the main portion 4 to a narrower tip 6b, with a height above the surface plane S (i.e. in a radial direction with respect to the central geometric axis C) by 1.9 mm. The base 6a has a maximum width (in a direction parallel to the central geometric axis C) of 1.60 mm (i.e. less than ten times the average cut fiber length, which in this example is 200 microns). The cross-sectional profile extends away from the base 6a in a converging shape that narrows to a width of 1.30 mm before extending further towards the tip 6b. Tip 6b has a substantially constant width of 0.60 mm and ends with a curve of radius 0.30 mm. The raised features 6 are arranged across the surface plane s of the main portion 4 and the adjacent raised features 6 are connected to each other by a root with a radius of 0.2 mm.

[0070] Figure 5b shows a close-up cross-sectional view of the elevated features 6' in area B indicated in Figure 2 according to a second example. In this example, each elevated feature 6' again comprises a generally triangular cross-sectional profile extending from a base 6'a adjacent to the surface plane S of the main portion 4 to a narrower tip 6'b, with a height above the surface plane S (i.e. in a radial direction with respect to the central geometric axis C) of 1.9 mm. The base 6'a has a maximum width (in a direction parallel to the central geometric axis C) of 1.9 mm (i.e., wider than in the first example, but still less than ten times the average cut fiber length, which in this example it is 200 microns) Tip 6'b has a radius of curvature of 0.5 mm. The 6' raised features being less sharp than those seen in Figure 5a means they are less fragile and can be selected to set a higher value for the predetermined impact energy threshold.

[0071] As seen in Figure 5b, the raised features 6' are arranged across the surface plane s of the main portion 4 and the adjacent raised features 6' are connected to each other by a root with a radius of 0.2 mm. The pitch (or spacing distance) between adjacent raised features 6' may be in the range of 1.5 to 15 mm.

[0072] Also seen in Figure 5b, the raised features 6' have a cross-sectional profile that defines an angle measured from the surface plane s, in this example being about 60°.

[0073] In the examples of Figures 1-5, the plurality of raised features 6, 6' are arranged across the surface plane s of the main portion 4 in a periodic pattern with a regular spacing distance between adjacent raised features 6, 6 '.

[0074] In the examples of Figures 1-5, the main portion 4 in the tube section 2a of the connector 2 is tubular and has a wall thickness T in the range of 0.5-5 mm.

[0075] Figures 6-8 illustrate the effect of an impact with an energy above the predetermined impact energy threshold on a fiber-reinforced polymer composite component 102. The component 102 comprises a main portion 104 and a plurality of raised features 106. The plurality of raised features 106 are arranged (e.g., by virtue of their shape, size, orientation, and/or fiber volume fraction) to incur visually perceptible damage when the component 102 is subjected to an impact with an energy above a predetermined impact energy threshold and resist an impact with an energy below the predetermined impact energy threshold. The predetermined impact energy threshold is selected to correspond to an impact energy that is likely to reduce the mechanical load capacity of the main portion 104.

[0076] Figure 6 shows component 102 immediately prior to impact on component 102 by an impactor 150 (e.g., a discarded maintenance tool). The impact has an energy that is above the predetermined impact energy threshold. Figure 7 shows the moment of impact and Figure 8 shows the consequences of the impact.

[0077] It can be seen from Figures 7 and 8 that the impact causes the main portion 104 to incur significant internal damage 108 that likely negatively affects the mechanical capabilities of the component 102, but may not be easily identified by an external inspection of the component. 102 as the majority of the damage 108 is to an internal wall of the component 102. However, because the impact is above the energy threshold, it causes the elevated features 106 to incur visibly noticeable damage 110 that is easily identifiable by a external inspection, for example, by an unaided human eye. In this case, several of the elevated features 106 have been dented, chipped, broken, or otherwise deformed in a manner that is readily visible.

[0078] The elevated features 106 therefore provide a means of easily detecting and assessing internal damage 108 to component 102.

[0079] Figure 9 shows a side view of a fiber-reinforced polymer composite tube 1202 according to an example of the present disclosure. The tube 1202 comprises a main portion 1204 extending along a central geometric axis C and two raised features 1206 which extend from an outer surface of the tube 1202 and continue in a helix along the outer surface of the tube 1202 around the central geometric axis C. Dashed lines are used to indicate the path of one of the elevated features 1206 on the reverse side of the tube 1202.

[0080] Tube 1202 is constructed from fiber-reinforced polymer composite (e.g., carbon fiber reinforced polymer, CFRP). This endows the main portion 1204 with high strength and resilience, but also means that an impact to the outer surface can cause significant damage to the inner layers of main portion 1204 without leaving a visually noticeable indication on the outer surface of the portion 1204.

[0081] The high features 1206, however, are arranged to incur visually noticeable damage when the composite component is subjected to an impact with an energy above a predetermined impact energy threshold and to resist an impact with an energy below of the predetermined impact energy threshold (e.g. due to a specific geometry and/or fiber volume fraction). As a result, when the tube 1202 is subjected to an impact above a threshold impact energy, the raised features 1206 incur visually noticeable damage even when the main portion 1204 may not occur. By appropriate design of the elevated features 1206, the threshold energy above which the elevated features 1206 are “sensitive” (i.e., when visually perceptible damage is incurred) is selected to be an energy at which impacts would cause severe damage (i.e., , damage that impacts tube performance) to the main portion 1204. Impacts below this energy do not cause visible damage to the elevated features 1206, but also do not cause substantial damage to the main portion 1204. Thus, the exterior of the tube 1202 (any whatever its internal geometry) can quickly reveal evidence of impacts that cause severe damage while significant impacts are not recorded. The presence and magnitude of impact damage to tube 1202 can therefore be quickly assessed without requiring an in-depth investigation. Visually perceptible damage to the raised feature 1206 may comprise, for example, a portion (or all) of the raised feature 1206 breaking. They may alternatively comprise a notch or other significant deformation.

[0082] The shape and/or model of the raised features 1206 are carefully selected to give them the necessary sensitivity. The cross-sectional profile of the features 1206 may be selected to give the features 1206 a certain level of impact resistance. The elevated features 1206 of Figure 9 have a triangular cross-sectional profile.

[0083] Figure 10 shows a side view of a fiber-reinforced polymer composite tube 1302 according to another example of the present disclosure. The tube 1302 comprises a main portion 1304 that extends along a central geometric axis C and raised features 1306 that extend from an outer surface of the tube 1302 and continue in a criss-cross pattern along the tube 1302. The raised features 1306 they run in the circumferential and axial directions in relation to the central geometric axis. Similar to those shown in Figure 9, the elevated features of Figure 10 comprise a triangular cross-section profile. However, as mentioned above, many different high resource profiles can be utilized (and/or fiber volume fractions) to provide the high resources with a desired impact resistance/sensitivity.

[0084] Figures 11 and 12 illustrate an injection molding process for manufacturing a monolithic fiber-reinforced polymer composite component, such as those shown in Figures 1-10.

[0085] As shown in Figure 11, a first mold portion 202 and a second mold portion 204 are brought together to form a complete mold 206. The complete mold 206 comprises a main cavity 208 and a plurality of additional cavities 210 that extend from the main cavity 208. Although not shown in this example, the main cavity 208 and/or additional cavities 210 may comprise additional shapes and/or features to form corresponding features in the resulting component (e.g., a protrusion in the main cavity 208 may be used to form a corresponding through hole in the resulting connector).

[0086] An injection tool 216 comprising a chamber 218 and a screw 220 is used to inject molten thermoplastic polymer 222 containing chopped fiber reinforcement (not shown) into the mold 206. The injection tool 216 is heated to melt the thermoplastic polymer 222 (e.g., supplied as solid pellets) and the screw 220 is turned to force the molten thermoplastic polymer 222 and its chopped fiber reinforcement into the mold 206 so that it fills the main and additional cavities 208, 210.

[0087] As polymer 222 is injected, it fills the main cavity 208, flowing in the primary flow direction 224. Additional cavities 210 extend from the main cavity 208 in a direction perpendicular to the primary flow direction 224 (i.e. , radially), with an opening dimension 226 in a direction parallel to the primary flow direction (i.e., additional cavities extend from the main cavity via an opening with a certain width).

[0088] The opening dimension 226 is selected not to exceed ten times the average length of the chopped fiber reinforcement (e.g., an opening dimension of 1.6 mm for an average fiber length of 200 microns). Because the polymer 222 has to deviate from the primary flow direction 224 and pass through this limited opening to fill the additional cavities 210, it carries less of the chopped fiber reinforcement into the additional cavities 210. As a result, the polymer 222 that fills the Main cavity 208 has a first volume fraction of chopped fiber reinforcement and the polymer 222 that fills additional cavities 210 has a second smaller volume fraction of chopped fiber reinforcement.

[0089] After the cavities 208, 210 have been filled with the chopped fiber reinforced thermoplastic polymer 222, the mold 206 and its contents are allowed to cool (this may in some examples involve active cooling elements that are not shown in Figures 11 or 12) and the injected thermoplastic polymer 222 solidifies to form a fiber-reinforced polymer composite connector 228 (shown in Figure 12). The resulting fiber-reinforced polymer composite connector 228 has a main portion 230, corresponding to the main cavity 208, and a plurality of raised features 232, corresponding to the additional cavities 210.

[0090] The connector 228 can then be easily extracted from the mold 206, for example, by dividing the second mold portion 204 along line 234 and then sliding the connector 228 out of the first mold portion 202.

[0091] Figure 13 shows a close-up cross-sectional view of an FRP composite component 302 (like the components described above) comprising a raised feature 306 with a fiber volume fraction different from that of the main portion 304. The raised feature 306 extends from a surface plane S of the main portion 304, both produced from a thermoplastic polymer 308 reinforced by chopped fibers 310 using an injection molding process as described above with reference to Figures 11 and 12. Elevated feature 306 comprises a substantially triangular cross-sectional profile, extending from a base 306a adjacent to the surface plane S to a narrower tip 306b that defines a maximum height above the surface plane S of the main portion 304.

[0092] Although all of the chopped fiber reinforcement 310 in Figure 13 is schematically shown as fibers of substantially the same length, this is only for ease of illustration and, in reality, the lengths of the chopped fibers 310 may vary.

[0093] The raised feature 306 extends from the surface plane S of the main portion 304 in a direction perpendicular to a primary flow direction 324 of the injection molding process. Due at least partially to the geometry of the raised portion 306 and the average length/fiber length distribution of the chopped fiber reinforcement 310, the injection molding process produces a fiber volume difference between the main portion 304 and the raised feature 306 .

[0094] In this example, the main portion 304 comprises a first fiber volume fraction 312 of approximately 30% (some minor variation may occur across the width of the raised portion 306) and the raised feature 306 comprises a second fiber volume fraction 314 of approximately 20% on average (i.e., less than the first fiber volume fraction 312). The fiber volume fraction at the base 306a of the raised feature 306 may be slightly different from that at the tip 306b, but both are significantly smaller than the first fiber volume fraction 312, so the effective fiber volume fraction difference is a step change between the first volume fraction 312 in the main portion 304 and the second volume fraction 314 in the elevated feature 306.

[0095] Although the present disclosure has been described with reference to several examples, it will be understood by those skilled in the art that various changes in form and details can be made without departing from the scope of the disclosure as set forth in the appended claims.

Claims (15)

1. Method for manufacturing a monolithic fiber reinforced polymer composite component (228), the method comprising: providing a mold (206) comprising a main cavity (208) and at least one additional cavity (210) extending from the main cavity (208); and introducing a polymeric matrix material (222) containing chopped fiber reinforcement into the mold (206) to fill the main cavity (208) and the at least one additional cavity (210) to form a monolithic fiber-reinforced polymer composite component ( 228) with a main portion (230) formed in the main cavity (208) and at least one raised feature (232) formed in the additional cavity (210) and extending from a surface plane of said main portion (230); characterized by the fact that the at least one elevated feature (232) is arranged to incur visually perceptible damage when the component (228) is subjected to an impact with an energy above a predetermined impact energy threshold and to resist a impact with an energy below the predetermined impact energy threshold. 2. The method of claim 1, wherein it comprises an injection molding process, wherein introducing the polymeric matrix material (222) containing chopped fiber reinforcement comprises injecting a molten thermoplastic polymeric matrix material (222) 222) containing mold-cut fiber reinforcement (206). 3. The method of claim 2, wherein the molten thermoplastic polymer matrix material (222) containing chopped fiber reinforcement is injected into the mold (206) so that it follows a primary flow direction (224 ) in the mold (206); and Wherein the at least one additional cavity (210) extends at least partially in a direction perpendicular to the primary flow direction (224), such that the polymeric matrix material (222) filling the main cavity (208) has a first volume fraction of chopped fiber reinforcement and the polymer matrix material (222) filling the additional cavity (210) has a second different volume fraction of chopped fiber reinforcement. 4. Method according to claim 3, characterized by the fact that the first volume fraction is greater than the second volume fraction. 5. Method according to any one of claims 1 to 4, characterized in that the mold (206) comprises a plurality of additional cavities (210) arranged to form a corresponding plurality of raised features (232). 6. Method according to any one of claims 1 to 5, characterized in that the chopped fiber reinforcement has an average fiber length between 50 and 500 microns. 7. Method according to any one of claims 3 to 6, characterized by the fact that: the at least one additional cavity (210) has an opening dimension in a direction parallel to the primary flow direction (224) that is between 500 and 5,000 microns; and/or the at least one additional cavity (210) has an opening dimension in a direction parallel to the flow direction (224) that is not more than 10 times the average fiber length of the chopped fiber reinforcement. 8. Method according to any one of claims 1 to 7, characterized in that the mold (206) is molded to form a tubular main portion (230) having a central geometric axis (C) and at least one raised feature ( 232) which extends from a cylindrical surface plane of the main portion (230) and which runs in a helical and/or circumferential manner and/or axial direction relative to the central geometric axis (C). 9. Monolithic fiber-reinforced polymer composite component (228) formed from a polymer matrix material (222) containing chopped fiber reinforcement, the component (228) comprising: a main portion (230) and at least one raised feature (232) extending from a surface plane of said main portion (230); characterized by the fact that the at least one elevated feature (232) is arranged to incur visually perceptible damage when the component (228) is subjected to an impact with an energy above a predetermined impact energy threshold and to resist a impact with an energy below the predetermined impact energy threshold. 10. Component (228) according to claim 9, characterized in that the main portion (230) comprises a first volume fraction of chopped fiber reinforcement and the at least one raised feature (232) comprises a second fraction of different volume of chopped fiber reinforcement. 11. Component (228) according to claim 10, characterized in that the second volume fraction is smaller than the first volume fraction. 12. Component (228) according to claim 10 or 11, characterized in that it comprises a binary step change between the first and second volume fractions of chopped fiber reinforcement. 13. Component (228) according to any one of claims 10 to 12, characterized in that the predetermined impact energy threshold is selected based on one or more mechanical properties of the main portion (230). 14. Component (228) according to any one of claims 10 to 13, characterized in that it is made by an injection molding process. 15. Component (228) according to any one of claims 10 to 14, characterized in that the component (228) comprises a tubular main portion (230) having a central geometric axis (C) and at least one raised feature (232) which extends from an external surface plane of the main portion (230) and which runs in a helical and/or circumferential and/or axial direction relative to the central geometric axis (C).