Multiple layer article with interactive reinforcements linear ribbon fiber reinforcement for composite forms

Abstract

A form for a thin reinforced composite material includes a plurality of separate linear fiber strips, each having a rectangular cross section composed of reinforcement fibers. The linear fiber strips laid out in a two-dimensional base layer defining a shape of the form. A first successive layer formed with the plurality of separate linear fiber strips contacting the base layer, the linear fiber strips laid out in the first successive layer interspersed from the separate linear fiber strips in the two-dimensional base layer. A method of forming the form includes arranging the plurality of separate linear fiber strips on a substrate and tacking the plurality of separate linear fiber strips to the substrate with a plurality of stitches. A method of forming a unitary reinforced composite component from the form is further provided. The resulting component having high strength and light weight and being efficient to manufacture.

Claims

1. A form for a component comprising: a plurality of separate linear fiber strips, each of said plurality of linear fiber strips having a rectangular cross section with a width and a thickness, each of said plurality of linear fiber strips being composed of reinforcement fibers, said reinforcement fibers being glass fibers, aramid fibers, carbon fibers, or a combination thereof, said plurality of linear fiber strips sewn to a two-dimensional base layer that defines a shape of the form, said plurality of linear fiber strips provided in a pattern; and a first successive layer of a successive layer plurality of separate linear fiber strips sewn to a first successive layer two-dimensional base layer, said first successive layer adapted to overlay said two-dimensional base layer; wherein the successive layer plurality of separate linear fiber strips are provided in the same pattern as said linear fiber strips, but the successive layer plurality of separate linear fiber strips are offset from said linear fiber strips.

2. The form of claim 1 further comprising one to eighteen additional successive layers placed on said first successive layer, where the plurality of said separate linear fiber strips are interspersed in said one to eighteen additional layers.

3. The form of claim 2 wherein said two-dimensional base layer, said first successive layer, and each of said one to eighteen additional successive layers have a mixture of commingled fiber strips and strips made up of a single fiber, or different fiber.

4. The form of claim 1 wherein the reinforcement fibers are exclusively only the glass fibers in at least one of said two-dimensional base layer or said first successive layer.

5. The form of claim 1 wherein the reinforcement fibers are exclusively only the carbon fibers in at least one of said two-dimensional base layer or said first successive layer.

6. The form of claim 1 wherein said plurality of separate linear fiber strips in said first successive layer is angularly displaced relative to said plurality of separate linear fiber strips in said two-dimensional base layer.

7. The form of claim 1 wherein the form is formed using selective comingled fiber bundle positioning (SCFBP), where the form is held together with a thermoplastic stitching.

8. The form of claim 1 wherein said plurality of separate linear fiber strips includes recycled fibers.

9. A method of forming a unitary reinforced composite component comprising: placing the form of claim 1 onto a mold platen, heating the form to promote fusion of a plurality of thermoplastic fibers therein; cooling the form until solidified with contours of the component; and removing the vehicle component from the mold platen.

10. The method of claim 9 further comprising applying a thermoplastic skin intermediate between the form and the mold platen.

11. The method of claim 9 further comprising applying a second opposing platen to apply pressure and sandwich the form.

12. The method of claim 9 wherein the unitary reinforced composite component is a vehicle component.

13. A method of forming the form of claim 1, comprising: arranging the plurality of separate linear fiber strips on a substrate; and tacking the plurality of separate linear fiber strips to the substrate with a plurality of stitches.

14. The method of claim 13 further comprising conveying the plurality of separate linear fibers strips to the substrate using a guide pipe.

15. The method of claim 13 wherein the plurality of stitches are of a thermoplastic thread.

16. The method of claim 13 wherein the plurality of stitches are formed by a sewing machine and needle.

17. The method of claim 13 wherein the plurality of stitches are present in an amount of 0.1 to 7 weight percent of the plurality of separate linear fiber strips.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

(2) FIG. 1 is a photograph of an example of a non-crimp fabric (NCF);

(3) FIG. 2 is a prior art schematic view of a fiber bundle stitched to a substrate forming a fiber preform;

(4) FIG. 3 is a perspective prior art view of a woven carbon and soluble fiber configuration with soluble stitching formed using selective comingled fiber bundle positioning (SCFBP);

(5) FIG. 4 illustrates a cross sectional view of a commingled ribbon or strip of reinforcing fibers in accordance with embodiments of the invention;

(6) FIGS. 5A-5C illustrate varying cross-sectional aspect ratios of a ribbon or strip of reinforcing fibers in accordance with embodiments of the invention;

(7) FIGS. 6A-6H illustrate interspersed patterns of eight layers of reinforcing ribbons or strips in accordance with embodiments of the invention;

(8) FIG. 7 illustrates an exploded view of an eight-layer reinforced composite structure using the layers of interspersed patterns of reinforcing ribbons or strips shown in FIGS. 6A-6H in accordance with embodiments of the invention;

(9) FIG. 8 is a side view of a prior art apparatus for manufacturing strips or ribbons of reinforcing fibers;

(10) FIG. 9 is a perspective view of a detail of the prior art apparatus of FIG. 8 for spreading the fibers;

(11) FIG. 10 is a perspective view of a further detail of the prior art apparatus of FIG. 8 for spreading the fiber;

(12) FIG. 11 is a schematic illustrating the application and stitching of ribbons or strips of reinforcing fibers to a substrate in accordance with embodiments of the invention; and

(13) FIGS. 12A-C are a sequence of schematic steps of processing an inventive SCFBP form into a vehicle component by melting thermoplastic content of the SCFBP form.

DESCRIPTION OF THE INVENTION

(14) The present invention has utility for the formation of thin composites formed with linear strips or ribbons of fiber for reinforcement that are of high strength and light weight, and that are also efficient to manufacture. In inventive embodiments the position of reinforcement strips between adjacent layers are interspersed from each other. Unlike existing woven reinforcement fibers with a circular or oval cross section, the individual fibers of a fiber bundle are spread to form a rectangular cross section with a lower thickness (height above a substrate) as compared to circular or oval cross sections. This allows for the formation of composites with a thickness and structural performance on par with prepreg and composites using non-crimp fabrics (NCF). For example, currently NCF and prepreg are able to yield 1.3 mm thickness parts while using 8 layers of fiber with orientations of 45/−45/90/0/0/90/−45/45° using 50K tow carbon fiber (CF). However, a similar design using woven 50K CF with a circular cross section yields a composite structure of approximately 4 mm, and only a four-layer construction would have a thickness on par with NCF but would lack quasi-isotropic properties. Alternatively, a 12K or less CF tow may be used but this would increase the cost of the preform by at least 30%.

(15) It is to be understood that in instances where a range of values are provided that the range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the range. By way of example, a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4.

(16) As used herein, the term melting as used with respect to thermoplastic fibers or thread is intended to encompass both thermofusion of fibers such that a vestigial core structure of separate fibers is retained, as well as a complete melting of the fibers to obtain a homogenous thermoplastic matrix.

(17) Embodiments of the invention utilize staggered fiber paths and employ a fiber laying technique that increases the width of the 50K tow during a stitching process to a substrate layer. Currently, pending in an application entitled “Thread” filed on or about 9 Mar. 2017, the contents of which are hereby incorporated by reference. In an inventive embodiment a pneumatic device may be used to open up the fiber being feed to a stitching mechanism. Using these techniques an eight-layer configuration using ribbons or strips of fiber, yields a molded panel thickness of 1.35 mm or less. Furthermore, the use of ribbons or strips of fiber results in lower fiber wastage and lower direct labor in preparation of a preform or charge pattern as compared to NCF. For example, for a lattice based on strips or ribbon of CF a preform is 100 parts by weight, while NCF is 150 parts by weight, and prepreg is 225 parts by weight.

(18) FIG. 4 illustrates a fiber strip or ribbon formed with strands of carbon and strands of glass. It is appreciated that the reinforcing fiber strips or ribbons may be made of a single fiber type or may be a collection of commingled fibers as shown in FIG. 4. The thickness T of the reinforcement fiber strips may be varied by changing the cross-sectional aspect ratio with respect to thickness T and width W as shown in FIGS. 5A-5C while maintaining a constant cross-sectional area (W times T).

(19) FIGS. 6A-6H illustrate an inventive embodiment of interspersed patterns of eight layers of reinforcing ribbons or strips of rectangular cross section that form a composite sheet. Each of the individual layers 6A-6H may have a single type of reinforcing strips on a layer surface such as strips made of commingled fibers or strips made up of a single fiber type. In specific inventive embodiments, each of the individual layers may have a mixture of commingled fiber strips and strips made up of a single fiber type, or different fiber types in separate strips on the layer. FIG. 7 illustrates an exploded view of an eight-layer reinforced composite structure using the interspersed patterns of reinforcing ribbons or strips as shown in FIGS. 6A-6H. As may be seen in FIGS. 6A-6H and in FIG. 7 the interspersed patterns of eight layers of reinforcing ribbons or strips of rectangular cross section that form a composite sheet in the layers are offset from each other in pairs. For example, the horizontal stripe pattern in layer 3 (L3) and layer 6 (L6) are offset from each other; the vertical stripe pattern in adjacent layer 4 (L4) and layer 5 (L5) are offset from each other; and the diagonal stripe pattern in adjacent layer 1 (L1) and layer 2 (L2) are offset from each other, as are the diagonal stripe pattern in adjacent layer 7 (L7) and layer 8 (L8) are offset from each other.

(20) A co-pending application to the same applicant discloses an apparatus that is shown in FIG. 8 for manufacturing commingled fibers or a single fiber types as a strip or ribbon 60 made up of reinforcing fibers, illustratively including those made of carbon, glass, or aramid fibers, recycled, and thermofusible fibers which serve to provide a matrix in a composite material made of both reinforcing and matrix fibers. The matrix fibers, being of a thermofusible nature may be formed from material such as, for example, polyamide, polypropylene, polyester, polyether ether ketone, polybenzobisoxazole, or liquid crystal polymer. The reinforcing fibers may also be of a material that is meltable with the proviso that melting occurs at a temperature which is higher than the matrix fibers so that, when both fibers are used to create a composite, at the temperature point at which melting of the matrix fibers occurs, the state of the reinforcing fibers is unaffected.

(21) The thermoplastic and reinforcing carbon fibers are each fed from individual tows 30, 40 of pure thermoplastic fibers 30 and carbon fibers 40 and combined to form the roving 60 at a blending roller 50. The thermoplastic fibers are first drawn off a spool 32 to form the tow 30. Subsequently, the thermoplastic fibers of the tow 30 pass over and under a sequence of guide rollers 70 during which time the fibers are spread. The carbon fibers of the tow 40 are drawn off spool 42 and guided by guide rollers 70. Referring additionally to FIG. 9, the spreading of the thermoplastic fibers is created by the use of static electricity. Accordingly, as the thermoplastic tow 30 is drawn over and under the guide rollers 70 it passes over a charged plate 100. The electrostatic charge on the plate 100 causes mutual dispersal of the fibers due to electrostatic repulsion between them as a consequence of the charge acquired during their passage over the plate 100.

(22) Referring additionally to FIG. 10, the carbon fibers of tow 40 are spread by the use of a flow of air passing over the tow 40 which has the action of dispersing the fibers. The air flow passes transverse, and preferably substantially orthogonally to the length of the fibers of the tow 40. The air flow has the action of urging the tow 40 against a supporting surface and, as a consequence, of dispersing the fibers of the tow across that surface. The supporting surface extends transversely, and preferably substantially orthogonally to the length of the fibers (and therefore the motion of the tow) and a supporting surface is provided by a cylindrical mandrel 80. A further supporting surface, provided by a further mandrel 82 is provided upstream of the mandrel 80 and the action of the air flow in combination with the surfaces have, as a consequence of the fibers of the tow being urged against them by the air flow, a dispersing effect upon the fibers of the tow. The air flow is created by an air pressure differential across the movement of the tow 40 and the extent of the dispersal of the fibers on the supporting surface or surfaces is related to the air pressure gradient in the region of the tow 40 and supporting surfaces (80, 82). The spread fibers are subsequently formed to a ribbon or strip.

(23) FIG. 11 is a schematic illustrating the application and stitching of ribbons or strips of reinforcing fibers 112 to a substrate 114. The comingled fiber or single type fiber bundle 112 is conveyed to a substrate 114 by a guide pipe 116 to lay out the comingled fiber bundle or single type fiber 112 in predetermined pattern on the substrate 114. A conventional sewing machine head operating a needle 118 with a top thread 120 tacks the fiber bundle 112 with stitches 122. A bobbin below the substrate 114, including a bobbin with a lower thread are not shown, and are conventional to sewing machines. The top thread 120 and the bottom thread are thermoplastic threads. In certain inventive embodiments, the comingled fiber bundle 112 is laid out in a base layer 124 in generally parallels lines with a given orientation. In addition to the substantially linear pattern of fiber bundles positioned as depicted in FIG. 11, it is appreciated that other patterns operative herein illustratively include spirals, and any space filling curve such as a Peano curve, dragon curve, or Sierpinksi curve.

(24) If zero degrees is defined as the long axis of the base layer 124, the subsequent layers are overlaid at angles of 0-90°. For example, an angular displacement between adjacent layers is 45° resulting in a 0-45-90-45-0 pattern of layers. Further specific patterns illustratively include 0-45-90-45-0, 0-45-60-60-45-0, 0-0-45-60-45-0-0, 0-15-30-45-60-45-30-15-0, and 0-90-45-45-60-60-45-45-90-0. While these exemplary patterns are for from 5 to 10 layers of directional SCFBP, it is appreciated that the form 110 may include from 3 to 20 layers. It is appreciated that the form layers may be symmetrical about a central layer, in the case of an odd number of layers, or about a central latitudinal plane parallel to the players.

(25) The stitching 122 is applied with a preselected tension, stitching diameter, stitch spacing. The stitching 122 is typically present in an amount of from 0.1 to 7 weight percent of the fiber bundle 112.

(26) While FIG. 11 only shows a single layer, it is appreciated that a form 110 is readily formed with up to 20 layers with the only technical limit being the length of the travel of the needle 118.

(27) It is appreciated that while only linear patterns for the reinforcement strips or ribbons have been shown that additional patterns may be formed with reinforce strips with rectangular cross sections. In specific inventive embodiments Moire patterns may be used to provide localized reinforcement through the use of overlap of reinforcement strips between layers. Various overlapping reinforcement regions may be produced by offsetting layered patterns of the reinforcement strips.

(28) FIG. 12A-C are a series of schematics showing a melt formation of a vehicle component 400. In FIG. 12A a form 200 such as that shown in FIG. 7 is brought into simultaneous contact with opposing mold platens 410 and 412 that define a cavity volume, V. The volume V corresponding in shape to the desired vehicle component. By selectively heating one or both of the platens 410 or 412 to a temperature sufficient to melt the thermoplastic content of the form 200 or a combination thereof, a vehicle component is formed upon cooling the mass compressed within the platens 410 and 412 by temperature and pressure, as shown in FIG. 12B. In a specific inventive embodiment, a thermoplastic veil 414 is in contact one or both platens 410 and 412 to create a skin on the resulting vehicle component. Upon opening the volume V, a completed vehicle component 400 is removed.

(29) The foregoing description is illustrative of particular embodiments of the invention but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention.