WO2020126771A1

WO2020126771A1 - A method of manufacturing a product by pultrusion,and an apparatus for carrying out such a method

Info

Publication number: WO2020126771A1
Application number: PCT/EP2019/084744
Authority: WO
Inventors: Jeremy Viale; Cyril LE CORRE
Original assignee: Structil S.A.
Priority date: 2018-12-19
Filing date: 2019-12-11
Publication date: 2020-06-25

Abstract

A method of manufacturing a composite product comprises the steps of forming a first layer from a non-crimped fabric material (186;192;208) and forming a second layer from a unidirectional fibre material (124;142;162), wherein the non-crimped fabric material of the first layer comprises fibres at a non-zero angle to the unidirectional fibre material of the second layer, impregnating (106) at least one of the unidirectional fibre material and non-crimped fabric material with an uncured matrix material, assembling the first and second layers, pultruding (108) the first and second layers through a die and curing the matrix material to form the composite product.

Description

A METHOD OF MANUFACTURING A PRODUCT BY PULTRUSION, AND AN APPARATUS FOR

CARRYING OUT SUCH A METHOD

The present invention relates to method of manufacturing a product by pultrusion, an apparatus for carrying out such a method and a product manufactured by such a method. Specifically, the present invention relates to a method of manufacture, apparatus and product involving the use of both unidirectional (UD) and multi-directional non-crimped fibre (NCF) mats in a pultrusion process.

Pultrusion is a well-known process used to manufacture composite materials. In a known pultrusion process, reinforcement material (typically in fibrous or mat form) is provided on a plurality of rolls. The reinforcement is wound off the rolls and combined into a layered reinforcement structure in a continuous manner. The layered reinforcement structure is passed through a bath of liquid matrix material where it becomes impregnated with the matrix (typically resin). The impregnated resin is then passed through a heated die where the matrix is cured to form the pultruded product. The process is defined by the fact that the pultruded product is pulled from the downstream side (e.g. by rollers) through the aforementioned process steps.

Pultrusion is an efficient process, and although generally only able to produce parts with constant cross-section (i.e. prismatic parts), it is generally faster and less costly than other techniques such as resin transfer moulding (RTM). The range of part cross-sections possible is vast, and such cross- sections can be e.g. flat sections, L-sections, etc.

As the benefits of composite materials are being realised, uptake in a wide range of applications is increasing. With this increased uptake, there is a demand for more complex parts, with more bespoke reinforcement configurations. Specifically, it is desirable to provide the reinforcement configurations seen in RTM products in pultruded products.

In the present application, 0 degrees (0°) is defined as the direction parallel to the longitudinal orientation of the product. In other words, it is parallel to the process direction, or the direction in which the material is pulled. 90 degrees (90°) is parallel to the transverse axis of the product.

The traditional pultrusion process generates profiles comprising a majority of fibres at 0 degrees. This facilitates the pultrusion process, as fibres oriented in this direction help to transfer the tension created at the downstream end (i.e. the "pull" through the process) ultimately to the rolls of reinforcement material at the upstream end.

A problem with having the majority of fibres at 0 degrees is that this type of structure leads to weaknesses with regard to torsion and, in particular, transverse traction in the final product. It is therefore desirable to try and orient some reinforcement fibres at a non-zero degree angle. A technique known as "pullwinding" is known and allows fibres to be added at deposition angles other than 0 degrees- typically up to ±20 degrees.

This known technology has three major limitations:

• Firstly, the proportion of oriented fibres is generally very low (around 10%).

• Secondly, as the deposition angle does not exceed 20° (even 45°), optimal properties cannot be obtained on complex parts.

• Thirdly, this technology is aimed at circular cross-section profiles and may be difficult to use for complex forms.

Another prior art solution is proposed in US2015217503. In this document, a pultrusion device is provided which forms a preform by braiding pre-impregnated tape onto a core before curing. A problem with this approach is that braided tape will not produce a product with distinct 0 degree or 90 degree layers, which are desirable for mechanical performance in many applications.

US2017/0137982 provides a nonwoven reinforcement composed of several superposed fibre plies. The invention proposes the use of a binder web between layers of fibre, which purports to hold the layers together without stitching.

US2003/3224141 relates to a reinforcement having two layers of spaced threads, each layer transverse to the other. The threads are coated in a thermoplastic binder powder which joins them at the points where they contact. It is stated that this reinforcement could be used in pultrusion.

Use of the reinforcement in pultrusion is mentioned in these prior art documents, but it is submitted that these products would not be able to properly transfer the tension forces involved in pultrusion without significant distortion during the pultrusion process.

US6572719 describes a technique for guiding components in a pultrusion line. However, this applies to wired components and is generally concerned with UD fibres.

EP1774216 describes a technique for obtaining a multilayer structure with yarns wound at different angles. However, on the one hand this only applies to tubes and cannot be transposed to flat sections, and on the other, the proportion of oriented yarns is too low to provide beneficial mechanical properties in the final product.

It is an aim of the present invention to overcome, or at least mitigate, the above-mentioned problems and/or to provide improvements generally. Specifically, it is an aim of the present invention to provide a pultrusion method and apparatus capable of producing a composite product which is well suited to manufacture by pultrusion (i.e. can support the required tensile force of manufacture) and also has desirable mechanical properties in use (specifically fibres oriented at at least 0°, ±45° and up to and including 90°).

According to the invention there is provided a method and an apparatus as defined in any one of the accompanying claims.

According to a first aspect of the invention there is provided a method of manufacturing a composite product comprising the steps of: forming a first layer from a non-crimped fabric material; forming a second layer from a unidirectional fibre material; wherein the non-crimped fabric material of the first layer comprises fibres at a non-zero angle to the unidirectional fibre material of the second layer; impregnating at least one of the unidirectional fibre material and non-crimped fabric material with an uncured matrix material; assembling the first and second layers; pultruding the first and second layers through a die; and, curing the matrix material to form the composite product.

According to a second aspect of the invention there is provided a manufacturing apparatus for the manufacture of a composite product comprising: a non-crimped fabric material supply apparatus; a unidirectional fibre material supply apparatus; an impregnation station for impregnating at least one of the unidirectional fibre material and non-crimped fabric material with an uncured matrix material; guide apparatus configured to assemble non-crimped fabric material from the non-crimped fabric material supply apparatus and unidirectional fibre material from the unidirectional fibre material supply apparatus into layers; a die for receiving the assembled layers; and, a heater to cure the matrix material to form the product.

According to a third aspect of the invention there is provided a pultruded composite material product obtainable by the method of the present invention, such as a pultruded composite material product comprising at least one layer of unidirectional fibre material; and at least one layer of non-crimped fabric fibre material; which layers are embedded in a cured matrix material.

By "product", we mean either a final product (intended for use with minimal or no modification) or an intermediate product which may undergo further processing to form a final product.

The method and apparatus of the present invention enable continuous or online manufacturing of the product.

Advantageously, by using alternating or interleaved NCF and UD fibres, there is created a balance between the two types of reinforcement. The present invention provides a true multiaxial product which can be manufactured by pultrusion.

The fibres of the non-crimped fabric material and the unidirectional fibre material used in the process of the present invention may be made from any convenient material, such as glass or carbon fibres.

Further, the specific manner in which the present invention is implemented allows the desired material structure to be achieved using a single impregnation bath. Only the unidirectional fibres are directly impregnated and are then interleaved with the NCF layers to impregnate the latter by contact.

In particular embodiments of the method and material of the present invention the method is carried out so that a layer of non-crimped fabric material comprising at least 2 sub-layers (preferably attached to each other by stitching) forms an outermost layer in the assembled layers of the material, and at least the outermost sub-layer of the NCF material comprises fibres at a non-zero angle to the fibres of the unidirectional material. In a particularly preferred embodiment, the fibres of the outermost sub layer are at an angle of approximately 45° to the fibres of the UD material, and this is of particular advantage for aerospace applications as the 45°surface layer will tend to limit crack propagation of the finished part.

An example method and product according to the present invention will now be described with reference to the accompanying figures in which:

Figure 1 is a schematic side view of an apparatus and method in accordance with the present invention;

Figure 2 is a plan view of a first part of the apparatus and method of Figure 1;

Figure 3 is a plan view of a second part of the apparatus and method of Figure 1;

Figure 4 is a plan view of a third part of the apparatus and method of Figure 1; and,

Figure 5 is a side section view of a product resulting from the apparatus and method of Figure 1. Apparatus

Referring to Figure 1, a composite material manufacturing apparatus 100 is provided. The apparatus comprises a first reinforcement fibre supply apparatus 102, a second reinforcement fibre supply apparatus, a resin application assembly 106, a die 108 and a tension assembly 110.

The apparatus has a longitudinal axis X which is the direction in which the material is fed and produced, or "downstream" direction, as will be described below. Y is defined as the transverse axis, i.e. across the "width" of the apparatus 100 and resulting product.

The first reinforcement fibre supply apparatus generally indicated at 102 comprises a first UD feed assembly 114, a second UD feed assembly 116 and a third UD feed assembly 118. The feed assemblies 114, 116, 118 are shown in more detail in Figures 2, 3 and 4 respectively.

Referring to Figure 2, the first UD feed assembly 114 is shown in detail in plan view. The first UD feed assembly comprises a first group of creels 120 and a second group of creels 122. Each group of creels 120, 122 contains five individual creels 123 in this example, but the skilled addressee will understand than many other numbers can be selected based on particular requirements. Each creel comprises a continuous length of unidirectional (UD) reinforcement fibre 124 (carbon fibre in this example) which may be unwound as it is used.

The first UD feed assembly 114 comprises a roller guide arrangement 126 having a first guide roller 128, a second guide roller 130, a third guide roller 132, a fourth guide roller 134 and a tensioning roller 136. The rollers 128, 130, 132, 134, 136 are aligned in the Y direction, but as can be seen in Figure 1, are offset in the X and Z directions to dictate the path of the fibre 124, as will be described below.

The tensioning roller 136 is movable and resiliently biased to apply a tension to the fibre 124.

Referring to Figure 3, the second UD feed assembly 116 is shown in detail in plan view. The second UD feed assembly comprises a group 138 of creels 140. The group 138 contains ten individual creels in this example, but the skilled addressee will understand than another number can be selected based on particular requirements. Each creel 140 comprises a continuous length of unidirectional (UD) reinforcement fibre 142 (carbon fibre in this example) which may be unwound as it is used.

The second UD feed assembly 116 comprises a roller guide arrangement 144 having a first guide roller 128 (common with the first UD feed assembly), a second guide roller 130 (also common with the first UD feed assembly), a third guide roller 132 (also common with the first UD feed assembly), a fourth guide roller 152 and a tensioning roller 154. The rollers 146, 148, 150, 152, 154 are aligned in the Y direction, but as can be seen in Figure 1, are offset in the X and Z directions to dictate the path of the fibre 142, as will be described below.

The tensioning roller 154 is movable and resiliently biased to apply a tension to the fibre 124.

Referring to Figure 4, the third UD feed assembly 118 is shown in detail in plan view. The third UD feed assembly comprises a first group of creels 156 and a second group of creels 158. Each group of creels 156, 158 contains five individual creels 160 in this example, but the skilled addressee will understand than many other numbers can be selected based on particular requirements. Each creel 160 comprises a continuous length of unidirectional (UD) reinforcement fibre 162 (carbon fibre in this example) which may be unwound as it is used.

The third UD feed assembly 118 comprises a roller guide arrangement 164 having a first guide roller 128 (common with the first and second UD feed assemblies), a second guide roller 168, a third guide roller 170, a fourth guide roller 172 and a tensioning roller 174. The rollers 166, 168, 170, 172, 174 are aligned in the Y direction, but as can be seen in Figure 1, are offset in the X and Z directions to dictate the path of the fibre 162, as will be described below.

The tensioning roller 174 is movable and resiliently biased to apply a tension to the fibre 162.

The second reinforcement fibre supply apparatus comprises first, second, third and fourth NCF feed assemblies 176, 178, 180, 182 respectively.

The first NCF feed assembly 176 comprises a reinforcement supply in the form of a first roll 184. The roll 184 comprises a continuous length of multidirectional non-crimped fibre 186. The non-crimped fibre 186 comprises a plurality of fibre sub-layers which are stitch-bonded together. The preferred stitch bond yarn is a polyester yarn using a chain stich to ensure resistance against longitudinal warping. Each layer is oriented in a different direction, but it is preferred that at least one layer is oriented at 0 degrees. Other layers may be oriented at ±45 degrees or 90 degrees, for example. In the present embodiment, the NCF layers comprise fibres at at least 45 degrees. The first NCF feed assembly 176 also comprises a feed roller 188. In the present embodiment, the NCF layers comprise fibres at at least 45 degrees.

The second NCF feed assembly 178 comprises a reinforcement supply in the form of a second roll 190. The roll 192 comprises a continuous length of multidirectional non-crimped fibre 192. The non- crimped fibre 208 comprises a plurality of fibre sub-layers which are stitch-bonded together with polyester thread using a chain stich to ensure resistance against longitudinal warping. Each layer is oriented in a different direction, but it is preferred that at least one layer is oriented at 0 degrees. Other layers may be oriented at ±45 degrees or 90 degrees, for example. In the present embodiment, the NCF layers comprise fibres at at least 45 degrees. The second NCF feed assembly 178 also comprises a first feed roller 194 and second feed roller 196.

The third NCF feed assembly 180 comprises a reinforcement supply in the form of a third roll 198. The roll 198 comprises a continuous length of multidirectional non-crimped fibre 200. The non-crimped fibre 200 comprises a plurality of fibre sub-layers which are stitch-bonded together with polyester thread using a chain stich to ensure resistance against longitudinal warping. Each layer is oriented in a different direction, but it is preferred that at least one layer is oriented at 0 degrees. Other layers may be oriented at ±45 degrees or 90 degrees, for example. In the present embodiment, the NCF layers comprise fibres at at least 45 degrees. The third NCF feed assembly 180 also comprises a first feed roller 202 and second feed roller 204.

The fourth NCF feed assembly 182 comprises a reinforcement supply in the form of a fourth roll 206. The roll 206 comprises a continuous length of multidirectional non-crimped fibre 208. The non- crimped fibre 208 comprises a plurality of fibre sub-layers which are stitch-bonded together. The preferred stitch bond yarn is a polyester yarn using a chain stich to ensure resistance against longitudinal warping. Each layer is oriented in a different direction, but it is preferred that at least one layer is oriented at 0 degrees. Other layers may be oriented at ±45 degrees or 90 degrees, for example. The fourth NCF feed assembly 182 also comprises a feed roller 210.

The resin application assembly 106 comprises a bath 212 containing a liquid resin.

The die 108 is known in the art, but for the purposes of the present invention comprises a heated die aperture through which the material is pulled by the tension assembly 110.

The tension assembly 110 comprises a roller set 216 configured to pull the material in the +X (downstream) direction, through the die 108.

Method

Each creel 123, 140, 160 and roll 184, 190, 198, 206 rotates about its axis, parallel to the Y axis to feed continuous UD tow or NDF mat material predominantly in the +X direction, as shown in Figure 1.

The material fed from the creels 123, 140, 160 and rolls 184, 190, 198, 206 is layered by the apparatus 100 before entering the die 108 in the following manner. Material fed from each of the creels 123, 140, 160 and rolls 184, 190, 198, 206 form individual layers in the product, the layers being described below in the order in which they are stacked (uppermost first in Figure 1, although it will be understood that the product is symmetrical in this embodiment). A first layer comprising a non-crimped fabric material is formed by feeding the NCF material 186 from the roll 184, to contact the roller 188 and towards the die 108. The NCF material 186 forms an outermost layer of the product.

A second layer comprising a unidirectional fibre material is formed as shown in Figure 2. The UD material 124 is fed from each group 120, 122 of creels. It is noted that the groups 120, 122 are spaced- apart so as to form a gap 218 therebetween. The material 124 passes over the first roller 128 (maintaining the gap 218), over the roller 130, into the resin bath 212, under the roller 132 and back out of the resin bath to the roller 134. The material 124 then passes either side of the NCF material 192 (from roll 190). Downstream of the NCF material 192, the gap 218 is closed such that the two groups of UD fibres 124 converge before being fed over the tensioning roller 136. Once the gap 218 is closed, the material 124 forms a consistent layer. The UD material 124 thereby enters the die between the NCF material layers 186, 192.

A third layer comprising a non-crimped fabric material is formed by feeding the NCF material 192 from the roll 190, over the first roller 194, under the second roller 196 and towards the die 108.

A fourth layer comprising a unidirectional fibre material is formed as shown in Figure 3. The UD material 142 is fed from the group 138 of creels 140. The material 142 passes over the first roller 128, over the roller 130, into the resin bath 212, under the roller 132 and back out of the resin bath to the roller 152. The UD material 142 thereby enters the die between the NCF material layers 192, 200. In this configuration, the UD material 142 forms the centre layer in the product.

A fifth layer comprising a non-crimped fabric material is formed by feeding the NCF material 200 from the roll 198, under the first roller 202, over the second roller 204 and towards the die 108.

A sixth layer comprising a unidirectional material is formed as shown in Figure 4. The UD material 162 is fed from each group 156, 158 of creels 160. It is noted that the groups 156, 158 are spaced-apart so as to form a gap 220 therebetween. The material 162 passes over the first roller 128 (maintaining the gap 220), into the resin bath 212, under the roller 168, under the roller 170 and back out of the resin bath to the roller 172. The material 162 then passes either side of the NCF material 200 (from roll 198). Downstream of the NCF material 200, the gap 220 is closed such that the two groups of UD fibres 162 converge before being fed over the tensioning roller 174. Once the gap 220 is closed, the material 162 forms a consistent layer. The UD material 162 thereby enters the die between the NCF material layers 200, 208. A seventh layer comprising a non-crimped fabric material is formed by feeding the NCF material 208 from the roll 206, to contact the roller 210 and towards the die 108. The NCF material 208 forms the opposite outermost layer of the product to the NCF material 186.

It will be noted that only the UD material layers are passed through the resin bath 212. The uptake of resin on the UD material is sufficient to wet out the NCF material layers when the NCF and UD material layers come into contact shortly before the die 108.

The NCF and UD material layers, now assembled and impregnated, pass through the die 108 to the tension assembly 100 where the tension to operate the pultrusion process is maintained. The assembled, cured, composite product 222 is removed from the die 108, as shown in Figure 1.

Product

Referring to Figure 5, the resulting composite product 222 comprises a cured resin matrix 224 containing embedded layers of alternating NCF material 186, 192, 200, 208, and UD material 124, 142, 162.

The ability of the product 222 to withstand the tension applied during the pultrusion process is conferred in the main by the UD fibre layers. The overall mechanical properties of the product 222 are enhanced by the NCF layers.

The pultruded composite material product may comprise at least one layer of unidirectional fibre material and at least one layer of non-crimped fabric fibre material; which layers are embedded in a cured matrix material.

Preferably, the product comprises a plurality of layers of unidirectional fibre material interleaved with a plurality of layers of non-crimped fabric fibre material. Preferably, at least one of the outer layers of the composite product comprises a layer of non-crimped fabric material.

The outermost layers of non-crimped fabric fibre material may comprise a first sub-layer and a second sub-layer, in which the first sub-layer comprises fibres at a zero degree angle to the unidirectional fibre material and the second sub-layer comprises fibres at a non-zero angle to the unidirectional fibre material. Preferably, the second sub-layer is outermost.

In a further embodiment, an interior layer of non-crimped fabric fibre material comprises a first sub layer and a second sub-layer, in which the first and second sub-layers comprise fibres at a non-zero angle to the unidirectional fibre material. Variations

Variations to the above embodiment fall within the scope of the present invention.

More or fewer layers may be provided as desired. The above embodiment provides a structure as follows: NCF-UD-NCF-UD-NCF-UD-NCF Another configuration may be:

NCF-UD-UD-NCF-UD-NCF-UD-UD-NCF or:

NCF-UD-NCF-NCF-UD-NCF-NCF-UD-NCF Therefore, adjacent layers of NCF and / or UD are envisaged. The skilled addressee can envisage other structures.

The NCF material feeds may have the same structure, or different structures depending on the application.

The layers of NCF material within each roll may be stitched (as with the above embodiment) or attached in any other known manner, e.g. by using thermoplastic binder powder or scrim.

For the NCF layers which are not the outermost layers (i.e. layers 192, 200 in the above embodiment), it is possible to use materials with no 0 degree sub-layers at all. The UD layers on either side of the NCF layers support the latter during the pultrusion process, reducing distortion.

In some applications, it is desirable that the outermost layer of fibres is oriented at a specific angle to the longitudinal direction. For example, in some aerospace applications, an outermost layer of 45 degrees is desirable to limit crack propagation. This may be achieved with the present invention by configuring the materials 186 and 208 such that they have an inner sub-layer of 0 degree fibres attached to (e.g. with stitching) an outer sub-layer of 45 degree fibres.

Claims

1. A method of manufacturing a composite product comprising the steps of: forming a first layer from a non-crimped fabric material; forming a second layer from a unidirectional fibre material; wherein the non-crimped fabric material of the first layer comprises fibres at a non-zero angle to the unidirectional fibre material of the second layer; impregnating at least one of the unidirectional fibre material and non-crimped fabric material with an uncured matrix material; assembling the first and second layers; pultruding the first and second layers through a die; and, curing the matrix material to form the composite product.

2. A method of manufacturing a composite product according to claim 1, in which the impregnating step comprises directly impregnating only the unidirectional fibre material, and further comprises transferring some of the uncured resin from the unidirectional fibre material to the non- crimped fabric material by contact between the layers during the assembling step.

3. A method of manufacturing a composite product according to claim 1 or claim 2, comprising the additional steps of: forming a third layer from a non-crimped fabric material; and, forming a fourth layer from a unidirectional fibre material; in which the non-crimped fabric material of the third layer comprises fibres at a non-zero angle to the unidirectional fibre material of the second and fourth layers; and in which the assembling step comprises assembling the four layers in an alternating manner.

4. A method of manufacturing a composite product according to claim 3, comprising the additional step of: forming a fifth layer from a non-crimped fabric material; and in which the assembling step comprises assembling the five layers in an alternating manner such that the first and fifth layers are the outer layers.

5. A method of manufacturing a composite product according to claim 3 or claim 4, in which the impregnating step comprises impregnating the second and fourth layers in a common resin bath.

6. A method of manufacturing a composite product according to any of claims 3 to 5, comprising: providing a gap in at least one of the second and fourth layers before the assembling step; feeding the third layer through the gap before the assembling step; and closing the gap before assembling the layers.

7. A method of manufacturing a composite product according to any preceding claim, in which at least one layer of non-crimped fabric material comprises a first sub-layer and a second sub-layer.

8. A method of manufacturing a composite product according to claim 7, in which the sub-layers are attached to each other by stitching, preferably wherein the stitching is a chain stitch.

9. A method of manufacturing a composite product according to claim 7 or claim 8, wherein the first sub-layer of the at least one layer of non-crimped fabric material comprises 0 degree fibres, and the second sub-layer comprises fibres at a non-zero angle to the 0 degree fibres; and/or wherein the first sub-layer and the second sub-layer both comprise fibres at a non-zero angle to the unidirectional fibre material.

10. A method of manufacturing a composite product according to claim 9, in which the at least one layer of non-crimped fabric material is positioned between two layers of unidirectional fibre material or is an outermost layer.

11. A method of manufacturing a composite product according to claim 10, in which the second sub-layer of the non-crimped fabric material comprising a first sub-layer and a second sub-layer is the outermost.

12. A manufacturing apparatus for the manufacture of a composite product comprising: a non-crimped fabric material supply apparatus; a unidirectional fibre material supply apparatus; an impregnation station for impregnating at least one of the unidirectional fibre material and non-crimped fabric material with an uncured matrix material; guide apparatus configured to assemble non-crimped fabric material from the non-crimped fabric material supply apparatus and unidirectional fibre material from the unidirectional fibre material supply apparatus into layers; a die for receiving the assembled layers; and, a heater to cure the matrix material to form the product.

13. A manufacturing apparatus according to claim 12, in which the guide apparatus is configured to: provide a gap in a layer of unidirectional fibre material; feed a layer of non-crimped fabric material through the gap; and, close the gap before assembling the layers.

14. A manufacturing apparatus according to claim 13, in which the guide apparatus is configured to interleave multiple layers of non-crimped fabric material with multiple layers of unidirectional fibre material, and to guide all of the layers of unidirectional fibre material through the same impregnation station.

15. A manufacturing apparatus according to claim 14, in which the guide apparatus is configured to guide only the layers of unidirectional fibre material through the impregnation station, and to assemble the impregnated layers of unidirectional fibre material with unimpregnated layers of non- crimped fabric material.