FIBRE INTERLAYERS

Abstract

A method of forming a multi-component composite material additive manufacture apparatus is described along with an apparatus therefor. The process involves laying a plurality of materials as part of the same process with a range of continuous and discontinuous fiber reinforcement options designed to optimize the operational capabilities of a component.

Claims

1-25. (canceled)

26. A method of forming a multi-layer thermoplastic component, the method comprising the steps of: (A) laying a first layer of thermoplastic material into a predetermined shape; (B) laying, on top of a previous layer, a second layer of thermoplastic material together compressed onto the first layer of thermoplastic material; and (C) repeating step (B) until a predetermined number of layers have been laid.

27. The method of claim 26, wherein the second layer is in the form of a thermoplastic material containing a fibrous component.

28. The method of claim 27, wherein the fibrous component is selected from (a) a continuous fiber extending through the thermoplastic; or (b) a plurality of discrete discontinuous fibers extending through the thermoplastic.

29. The method of claim 26, wherein each of the first and second layers are laid as a plurality of adjacent strips, each strip abutting with an adjacent strip to form a continuous layer surface extending in multiple directions.

30. The method of claim 26, wherein the fibers within the second layer may be selectively cut or separated at predetermined lengths before being laid upon a preceding layer.

31. The method of claim 30, wherein the fibers within the second layer are cut at lengths according to a predetermined fiber length distribution across each layer and through the thickness of the component.

32. The method of claim 26, wherein the second layer is laid immediately after the respective previous layer.

33. The method of claim 26, wherein the second layer is laid at an angle with respect to the angle at which the first layer has been laid.

34. The method of claim 26, wherein the second layer is laid by means of a feed mechanism and wherein the feed mechanism is selectively controlled so as to selectively start and stop feed of the fibrous containing layer during laying of the first and second layers.

35. The method of claim 26, wherein one or more of the lengths, distribution, and/or relative angle of laying up of the reinforcement fibers with respect to one or more of the previous layers may be changed between different layers of the component being manufactured.

36. The method of claim 35, wherein the laying up of the first and/or second layers is performed according to a predetermined fiber distribution profile corresponding to a predetermined mechanical and/or thermal operating profile of the component.

37. The method of claim 26, wherein an upper surface of the previous layer is heated prior to the second layer being laid upon the previous layer.

38. The method of claim 26, wherein after being laid a compaction force is applied to the upper surface of the second layer.

39. The method of claim 38, wherein the second layer is cooled simultaneously with the compaction force being applied to the upper surface.

40. A multi-component composite material additive manufacture apparatus comprising: a primary layer laying unit arranged in use to lay a layer of primary material onto a substrate or preceding layer of a component; and a secondary layer laying unit arranged to feed a secondary material onto the primary or preceding layer, said secondary material containing a continuous or discontinuous fibrous material content.

41. The apparatus of claim 40, further comprising a heating apparatus arranged to heat an upper surface of a preceding primary layer prior to laying of a secondary layer.

42. The apparatus of claimed in claim 40, further comprising a compression arrangement arranged to compress a laid secondary layer against a preceding primary layer.

43. The apparatus of claimed in claim 42, wherein the compression arrangement is a roller arranged in use to be brought into contact with the upper surface of the secondary layer.

44. The apparatus of claimed in claim 40, wherein the primary layer is laid by an extruder having a discharge nozzle for laying the primary material onto the substrate or preceding layer.

45. The apparatus of claimed in claim 40, wherein the primary material is laid from an extruder mechanism and the secondary material is laid from a supply spool mechanism, wherein the supply spool mechanism comprises a heater mechanism arranged to heat the secondary material in advance of being laid, a drive mechanism to drive the secondary material from a spool and through the heater mechanism and an optional cutting arrangement arranged in use to cut or separate fibers contained within the secondary material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] One or more embodiments of the invention will now be described, by way of example only, and with reference to the following figures in which:

[0049] FIG. 1 shows layers of a component formed according to a manufacturing apparatus and method described herein;

[0050] FIG. 2 shows an alternative prior art arrangement of in-situ impregnation manufacturing;

[0051] FIG. 3 shows an alternative component formed according to the manufacturing apparatus and method described herein;

[0052] FIG. 4 shows a schematic of the primary sub-elements of the manufacturing apparatus and the associated juxtaposition of the sub-elements in the apparatus;

[0053] FIGS. 5 V1, V2, and V3 illustrate alternative reinforcement fiber distribution patterns and types;

[0054] FIG. 6 illustrates a complex/hybrid distribution pattern of reinforcement fibers and associated layers; and

[0055] FIG. 7 illustrates how successive layers may be laid at different angles to preceding layers.

[0056] While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood however that the drawings and detailed description attached hereto are not intended to limit the invention to the particular form disclosed but rather the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the claimed invention.

[0057] Any reference to prior art documents in this specification is not to be considered an admission that such prior art is widely known or forms part of the common general knowledge in the field. As used in this specification, the words “comprises”, “comprising”, and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean “including, but not limited to”. The invention is further described with reference to the following examples. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples. It will also be recognized that the invention covers not only individual embodiments but also a combination of the embodiments described herein.

[0058] The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilized and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc, other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.

[0059] It will be recognized that the features of the aspects described herein can conveniently and interchangeably be used in any suitable combination.

DETAILED DESCRIPTION

[0060] FIG. 1 shows the fundamental layers of a component formed according to a manufacturing apparatus and method described herein.

[0061] As shown in FIG. 1, a composite component 1 is formed of a plurality of layers as described below.

[0062] The term ‘composite’ is a term known in the field of, for example, carbon fiber reinforced plastic (CFRP) components which are common in the aerospace industry owing to their light weight and high strength. Composite components are generally formed of a binding resin which encapsulates stronger fibers such as carbon fiber. Carbon fibers have high tensile strengths and when encapsulated in resin materials and hardened can provide very high strength and lightweight components.

[0063] Conventionally components are formed by laying up woven fabrics made of carbon fibers into a mold of the desired component shape, impregnating them with resin and then curing them (hardening them) in either a vacuum (called out-of-autoclave) or in a heater autoclave (in-autoclave). These processes are time consuming and expensive.

[0064] An alternative process which has been developed, involves simultaneously injecting a polymer into a die which also receives a dry fiber. This is illustrated in FIG. 2. Here, the polymer and fiber are brought together in the die which can then be used to lay down or print part of a component. This arrangement has brought some improvements to manufacturing of composite parts and represents a level of 3D printing to composite components.

[0065] However, there remain barriers to the use of 3DP composite components toolings in many applications. These barriers are two-fold. First, the intense manufacturing costs in terms of time and equipment result in making the large scale production of composite components prohibitive. Secondly, composite components do not allow for close alignment of coefficients of thermal expansion (CTE) of the material with the desired performance of the end product.

[0066] Both of these factors have led to the limited use of 3 dimensional printing (3DP) composites in many applications.

[0067] Specifically it has been noted that in prior art ‘3D printing’ autoclave tooling (which is short fiber reinforced) above 2 m in length brings issues regarding thermal expansion, especially when used in high temperature environments such as in the autoclave which can reach curing temperature of 180° C. To date it has not been possible to provide a 3DP manufacturing method that allows for a CTE value as close as the final product as possible and which allows for competitive production methods.

[0068] There is provided herein a method and apparatus which is capable of placing continuous fibers impregnated with a thermoplastic in a specific predetermined pattern. The method and apparatus can lay or ‘stack’ several patterns in order to create a shape in three dimensions, i.e., x and y and also depth z. In effect the method and apparatus provide a “sandwich” or laminate structure with layers of thermoplastic filled with ‘chopped’ or cut fibers or without fibers and pre-impregnated layers of continuous and/or long fibers in unidirectional or bidirectional direction. The material properties created from the final product are important for the desired application and can be tuned to the application needs.

[0069] Returning to FIG. 1, an example composite component 1 in its simplest form comprises two thermoplastic layers 2a, 2b and an intermediate or interstitial layer 3. In the example shown in FIG. 1 the intermediate layer 3 extends (as a ghost surface in the figure) across the whole area of the component 1. As described below this need not be the case.

[0070] The two opposing thermoplastic layers 2a, 2b are arranged on either side of the intermediate layer and may be formed of any suitable thermoplastic material depending on the chosen application.

[0071] Examples of materials include: [0072] Aerospace: PESU, PPSU, PEI, PEEK, PAEK and other similar materials; [0073] other industries: PP, ABS, PC, and similar thermoplastic resins.

[0074] The intermediate layer 3 acts as the reinforcement layer and comprises reinforcing fibers. These fibers, as described below may be arranged in a number of orientations relative to the thermoplastic layers 2a, 2b. For example, the fibers may be continuous and aligned with one side edge or may be random or aligned at particular angles with respect to the layers 2a, 2b.

[0075] As described above, the fibers may have high strength in a tensile direction meaning that aligning the fibers in particular directions can increase the tensile strength in that direction. In addition, the thermal characteristic of the component can also be adapted by this selective alignment of fibers, and also by providing breaks or discontinuities in the fiber lengths as described below.

[0076] FIG. 3 shows an alternative component according to FIG. 1 illustrating a different and more complex geometry.

[0077] In FIG. 3 a curved component 1 has been formed by laying the first thermoplastic layer 2a over a mold or mandrel (not shown) corresponding to the desired shape of the end component. This laying up may be achieved by mounting the laying up equipment on suitable robotic manipulators or arms as described below.

[0078] Next, the reinforcement or/and fiber-containing layer 3 is then laid on the outside of layer 2a and finally a second layer of thermoplastic is laid on the outside of the reinforcement (fiber) layer 3, again corresponding to the profile of the component. It will be recognized that complex geometries may be followed by a suitably dexterous robotic arm. The process described herein advantageously applies 2 layers at the same time. One thermoplastic layer with/without short fibers and on top a pre-impregnated layer with continuous or long fibers. The process also allows the printing of only one single layer of thermoplastic with/without short fibers. The feeding with continuous or long fibers can be interrupted during the printing process as required according to the desired component.

[0079] The laying up apparatus itself will now be described with reference to FIG. 4. As will be described an apparatus and method described herein involves a separated co-extrusion of pre-impregnated continuous fiber reinforcement with alternating 3D printed layer and continuous fiber reinforcement in one inline step. A continuous process may be realized.

[0080] Referring to FIG. 4 the apparatus comprises, but is not limited to, the following components:

Reference 4 Substrate Support Surface

[0081] FIG. 4 illustrates a flat surface as one example but with reference to FIG. 3 it will be recognized that the surface upon which the composite component is formed may be a mold or other shape corresponding to the desired end product. For example, the profile may correspond to a fan blade in which the mold corresponds to the aerodynamic contours of the blade. Similarly, in an application for a landing flap, other contours and reinforcement structures may be provided to be followed.

[0082] The substrate support surface may be static or may itself be movable relative to the remainder of the apparatus providing an additional degree of freedom of movement.

[0083] The substrate support surface can be pre-heated in order to minimize stresses inside the final part.

Reference 5 Extruder Unit

[0084] The extruder unit 5 is in one example a heated auger arrangement which heats a thermoplastic material and forces the material out of a die and onto the substrate support surface or preceding layer of the component being formed. An example extruder unit is manufactured by CEAD. (www.robotextruder.com)

[0085] The extruder unit is located after the substrate heater described below in a manufacturing flow direction. The speed and flow rate of the extruder unit may be controlled so as to control the thickness of the thermoplastic layer be laid down and can be increased as manufacturing speed increases or as thickness requirements of the component change. As with the other components shown in FIG. 4 the entire assembly may be pivotally mounted so that components such as that shown in FIG. 3 may be manufactured. The entire unit can be mounted on for instance a 6 axis industrial robot or 5 axis machine for increased freedom.

[0086] The extruder unit may eject pure thermoplastic or may alternatively eject a blend of thermoplastic and short fiber reinforcement, i.e., relatively short lengths of reinforcement fibers blended into the thermoplastic. This blend enhances the over strength of each of the thermoplastic layers owing to the tensile strength of the fibers.

Reference 6 Substrate Pre-Heater

[0087] The substrate pre-heater acts to pre-heat the substrate or preceding layer of the component before the subsequent layer is laid on top. Heating the previous layer causes the thermoplastic (the primary layer as well as the thermoplastic impregnated fiber material of the secondary layer) to become tacky and sticky which facilitates bonding (welding) of the subsequent layer to the preceding layer surface. It also encourages air pockets and bubbles to be released that could create discontinuities in the component structure.

[0088] The substrate pre-heater may heat the substrate or preceding layer using a range of heating sources, for example including infrared, laser or other heat source. In effect the heat source ensures adequate layer fusion with the preceding layer.

[0089] The components above refer to the laying up arrangement for preceding layers.

References 7 and 8 Supply Spool & Drive Wheel

[0090] The supply spool contains and releases a continuous supply of pre-impregnated continuous fiber material, i.e., the material comprises one or more continuous reinforcement fibers wrapped around a supply spool. An example of one material may be, for example, continuous carbon fiber uni-directional tape impregnated with PESU.

[0091] The supply spool may be loaded with material of different widths thereby adjusting the number of passes required to form the width of a desired component.

[0092] The material is removed from the spool by the drive wheel or mechanism 8 which is controlled according to the speed of laying of the material. The drive wheel may be in the form of a pair of opposing rollers which pull the pre-impregnated fiber material from the spool and feed the material, through the cutting mechanism to the heaters, described below.

Reference 9 Fiber Cutting Mechanism

[0093] The fiber on the spool may be a continuous length of fiber extending through the reinforcement material on the spool. This fiber may be optionally cut at predetermined positions as the material passes through the cutting mechanism. This thereby creates a discontinuous length of fiber, i.e., a plurality of discrete lengths of fiber as opposed to one continuous length. Interrupting of the continuous fibers may lead to an increase in the CTE value.

[0094] It also allows different fiber distributions to be realized across each layer and through the part on different layers. The cutting may be achieved by a simple knife or blade mechanism arranged to engage against a stationary block or recess. The cutting mechanism is also used when a layer has ended so that the toolhead can move to the next layer.

Reference 10 Fiber Product Pre-Heater

[0095] The drive wheel 8 is activated to drive the reinforcement fiber from the spool through fiber product pre-heater. Here, by means of infrared or other heat source, the continuous or not cut fiber material is heated up to a fusion temperature, i.e., a temperature at which the material is sufficiently melted that it will bond with the preceding layer. In one example, for a material PEI this will be heated to approximately 210 degrees Celsius over a period of approximately 5 seconds. An arrangement of multiple pre-heaters can be used in the toolhead, for which each pre-heater can be set at a different process temperature.

Reference 11 Compaction Roller

[0096] As shown in FIG. 4 the line of movement of the reinforcement fiber from the spool is such that it intersects with the preceding layer at an angle to the horizontal. At this point a roller 11 is located which is controlled to rotate such that the radial speed corresponds to the feed speed of the drive mechanism. The roller 10 acts to compact and consolidate the reinforcement layer with the preceding layer through the application of a small vertical force. The compaction roller can be set in a defined manner in the z-height.

[0097] This ensures secure bonding of the heated reinforcement layer and the preceding layer. It will be recognized that both layers have been heated and are therefore able to fuse together.

[0098] The compaction roller may additionally be cooled, for example through water or other cooling means, to consolidate the bond between the two layers that are being brought together at this point, and it also prevents sticking to the compaction roller. The temperature of the roller can be controlled in order to create the best consolidation and process condition as possible.

Reference 12 Anti Slip Press

[0099] The arrangement may also be provided with an optional anti-slip press which is arranged to prevent the fiber material (secondary layer) from slipping relative to the thermoplastic material (primary layer). This press may be used at the start of the process and optionally through the remainder of the process if the fusion bond is not sufficient to prevent horizontal separation of layer during the forming process.

[0100] Each of the steps above may be advantageously computer controlled in terms of rotational speed of the rollers, flow rate of extruder, temperature of the heaters, and pressure of the consolidation roller and anti-slip press. Thus, a smooth and continuous process may be realized.

[0101] After the first pair of layers, i.e., one thermoplastic layer and one reinforcement layer has been laid, the next pair may be laid on top. The process can be repeated until the desired product thickness/height has been reached.

[0102] As described herein the invention combines two materials in one process. This combination of materials creates a laminate which has better properties than the current materials available for large scale 3D printing. Combining a continuous fiber with an additional thermoplastic material layer has the benefit of reducing cost price and increasing production output in comparison to automatic tape placement technology. Moreover, the reinforcement with continuous and/or long fibers creates a composite material with very low thermal expansion. The use of the invention also ensures a high level of automation, reducing material and labor cost and the need for labor skills.

[0103] The selective distribution of the reinforcement fibers in each layer will now be described.

[0104] There are two aspects to the operability of the apparatus described herein:

[0105] (A) First, the linear distribution of the reinforcement fibers may be selectively controlled. This refers to selectively cutting or separating the fibers so that a layer of reinforcement comprises a series of fibers, all aligned, but with discrete dimension in a lengthwise direction. These may be separated by small or large spaces depending on the thermal and/or mechanical characteristics of the desired components. Each layer of the component may be provided with the same or different distribution or separation.

[0106] (B) The second aspect is the selective angular displacement of fibers in subsequent layers. This refers to the additional functionality of the apparatus that not only allows distribution of fibers between each layer to be modified (as described in paragraph A above) but additionally allows for an angular displacement between one or more subsequent layers making up the sandwich or laminate of the component.

[0107] These two options provide for huge variability in the tensile strength and thermal performance of each layer and thus the resulting component. Modelling allows the optimal distribution across and between layers to be determined and then the apparatus described herein programmed to deposit the reinforcement fibers in the desired profile across and depth-wise through the component.

[0108] FIGS. 5 V1, V2 and V3 illustrate alternative reinforcement fiber distribution patterns and types as will now be described.

[0109] For example, in a basic arrangement alternating 3D printed layers may be provided, each with a reinforced interlayer on top wherein both layers can be printed as part of the same process, i.e., immediately sequentially according to the apparatus described herein.

[0110] In another example, a 3D printed layer may be provided made from thermoplastic or thermoset matrix, with or without short fiber reinforcement may be created.

[0111] In yet another example, a reinforced interlayer may be provided made from pre-impregnated thermoplastic or thermoset in which a matrix with long and/or continuous fiber reinforcement is provided.

[0112] Each arrangement may have its own specific advantages for an application and each can be conveniently manufactured according to the apparatus and method described herein.

[0113] Returning to FIG. 5, the examples shown are in cross-section and illustrate visually the potential distribution of the reinforcement layers across and through the component.

[0114] In example V1 an interlayer reinforcement uni-directional (UD tape) or multi-directional (weaving, NCF) may be used. Here one tape may be used for each interlayer with an arrangement in which there is symmetrical or asymmetrical tape with widths less than, equal to, or greater than the width of the 3D printed layer width.

[0115] In example V2, an interlayer consists of two or more flat tapes in which the arrangement is symmetrical or asymmetrical.

[0116] In example V3 and interlayer consists of one or more profiles with UD fiber reinforcement. The cross-section may be round, square, variable, or another suitable cross-section.

[0117] In each of the examples described herein the continuous fiber material may be selected from any suitable stock of material including, but not limited to, carbon, glass, aramids, ceramic, metallic, optical, and other high performance or technical fibers, e.g., Dyneema.

[0118] Other materials may also be used together with the reinforcement fibers in the intermediate or interlayer such as electric conductive materials or heatable materials. Thus, an arrangement may be provided which can be used to print toolings with integrated heating for curing FRP parts out of autoclave or oven. Furthermore, materials may be introduced which may be used to measure the temperature inside the printed tooling/part

[0119] Furthermore, the following may additionally be adapted: [0120] variable fiber volume fraction [0121] changeable matrix/fiber ratio [0122] combination of short fiber or non-reinforced matrix with continuous or long fibers in uni- or bi-direction

[0123] FIG. 6 illustrates a further more complex/hybrid distribution pattern of reinforcement fibers and associated layers. In the example shown in FIG. 5 a non-linear distribution is shown which may correlate to thermal and/or mechanical requirements for the given application. The apparatus and method advantageously allows for configurations such as that illustrated (for example only) in FIG. 5 to be realized.

[0124] FIG. 7 illustrates the angular control that the apparatus and method additionally provides with the lines indicating different orientations of fibers through the depth of the component.

[0125] As described above the arrangement described herein provides significant flexibility in designing and constructing multi-material, multi-layer additive manufactured composite components. Specifically, the components can be optimized for load carrying properties, stress and fatigue resistance and also thermal performance in terms of controlled CTE values.

[0126] An application of the apparatus and method described herein is the substitution of tooling and intensifiers, which are used for the curing of aircraft composite parts at high temperatures in the autoclave. For example, CFRP intensifiers aerospace components can be replaced using such a technique. Furthermore, large composite tooling which needs geometric accuracy at high temperatures, could also be realized.

[0127] The spools can also be advantageously changed during printing. For example, an automatic spool changer could be used when printing large tooling which requires several 1000 meters of reinforcement. Furthermore, the spool may also be used within a cartridge (housing) to avoid moisture take up. Thus, a more controlled environment is provided for the tape. Humidity and temperature conditions may thereby be controlled. This may also make changeover of the spool faster and more convenient using such an enclosure.