Patent Description:
For the avoidance of doubt, the term "reinforcement assembly" refers to a material having a first, reinforcement portion and a second portion (in this invention, a binder portion).

Composite materials in general comprise two primary phases- the reinforcement and the matrix. The present invention is concerned with reinforcements which are constructed from a fibre / fibrous material.

Fibre reinforcements contain multiple filaments and come in a variety of forms. The most common form is as a tow containing a plurality of individual filaments. When the filaments are co-linear but warped or twisted around into a bundle the tow is of an essentially circular cross section. When the filaments are collected into a single strip which is essentially flat, this is called a tape (in which the filaments are parallel and co-planar).

In a yarn, the filaments are also collected into a bundle, in which although they may not be strictly parallel, they extend in the same general direction along the main axis of the yarn. Yarns typically have fewer filaments then tows and they are therefore of a smaller thickness than a tow.

Tows, tapes and yarns are all types of "long-fibre" or elongate fibre reinforcements in which the fibres extend along a main, longitudinal reinforcement axis.

The tows or tapes may be woven to form a fabric or non-woven.

Elongate fibre reinforcements are used to form both woven and non-woven fabric reinforcements for the preparation of preforms which will eventually be infused with resin to form a composite component. As elongate fibre reinforcement consist of many filaments (typically thousands) which are in very close proximity, infusing these materials with a resin matrix is difficult and can result in uninfused (dry) areas in the fibre reinforcements.

Document <CIT> discloses, according to its abstract, a method for manufacturing a reinforcing sheet containing at least one sheet made of a plurality of high tensile modulus fiber monofilaments. The sheet defines a first surface and a second surface. A first scrim is bonded to the first surface of the sheet and a second scrim is bonded to the second surface of the sheet.

Many fibrous materials are used in composite manufacture, such as carbon, glass and aramid. The present invention is applicable to carbon fibres and the preparation of carbon fibre reinforced polymers (CFRPs).

The invention aims to obviate and/or mitigate the above described problems and/or to provide improvements generally.

A further object of the present invention is to provide a fibre reinforcement assembly which enhances infusion of resin during composite manufacture.

According to a first aspect of the invention there is provided a reinforcement assembly according to claim <NUM>. According to the second aspect there is provided a method of forming a composite component according to claim <NUM>.

Advantageously, once the reinforcement assembly is formed into a layered material in a preform the projecting portions form voids in the preform material which encourage better infusion of the resin matrix.

The binder comprises a length of fibrous thermoplastic polymer.

Preferably the binder becomes tacky at a predetermined temperature. The binder material may be selected from the following list:.

Preferably the second portion extends at an angle to the longitudinal axis, the angle being between <NUM> and <NUM> degrees.

The first portion is at least partially constructed from carbon fibres.

Preferably the first portion is in the form of a tape.

The first portion comprises a plurality of adjacent unidirectional fibres extending along the longitudinal axis.

Preferably the tape has a width at least <NUM> times greater than its thickness.

Preferably the tape has a width which is in the range of from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM> and even more preferably from <NUM> to <NUM> and/or combinations of the aforesaid ranges. The width of the tape may also range between <NUM> to <NUM>, preferably from <NUM> to <NUM> or from <NUM> to <NUM> and/or combinations of the aforesaid ranges. In another embodiment the width of the tape is <NUM>/N inch (<NUM>/N x <NUM>) with N being selected from <NUM>, <NUM>,<NUM>,<NUM>,<NUM>, or <NUM>. The width of the tape is a constant and shows a variation in the range of from +/-<NUM>%, preferably from +/-<NUM>% and more preferably from +/-<NUM> % or from +/- <NUM>% per linear metre. The variation is measured by sampling the width of the tape over <NUM> equidistance positions along <NUM> length of the tape and calculating the average width and the deviation in relation to this average width.

According to the invention there is provided a method of forming a composite component, comprising the steps of providing an elongate reinforcement assembly; building up a multiaxial preform from the elongate reinforcement assembly by laying down at least four laminae of the assembly at angles between -<NUM> and +<NUM>° from the longitudinal direction of the multiaxial fabric; infusing a liquid matrix material into the layers; and curing the matrix material to form a product.

Preferably the laminae are interconnected by the binder. The individual elongate assemblies may also be interconnected by the binder. Preferably, they are interconnected by melt bonding.

The present invention will now be described with reference to the accompanying Figures in which:.

Referring to <FIG>, a section of elongate reinforcement assembly <NUM> is shown in plan view. The elongate reinforcement assembly <NUM> is generally planar having a first edge <NUM> and a second edge <NUM> (the edges running along the length of the elongate reinforcement assembly <NUM>). A very short section of elongate reinforcement assembly <NUM> is shown having length L along a longitudinal axis X, but it will be understood that the elongate reinforcement assembly <NUM> is manufactured as a continuous strip of material, and thus L may vary significantly. The width of the elongate reinforcement assembly W along a transverse axis Y (that is the perpendicular distance between the edges <NUM>, <NUM>) is substantially constant along the length L. The elongate reinforcement assembly <NUM> has a length L and width W which significantly exceeds its thickness (by at least a factor of <NUM>).

The elongate reinforcement assembly <NUM> is constructed from a first, reinforcement portion <NUM> and a second binder portion <NUM>.

The reinforcement portion <NUM> comprises a plurality of individual fibres <NUM> which are constructed (in this embodiment) from carbon, and manufactured in a manner known in the art. The fibres of the reinforcement portion <NUM> run in parallel in the direction of the length L of the elongate reinforcement assembly <NUM>, and as such the reinforcement portion <NUM> can be described as a "unidirectional" fibre tow or tape. Ordinarily, the fibres <NUM> of the reinforcement portion <NUM> do not adhere to each other.

The binder portion <NUM> comprises a plurality of individual binder sub-portions <NUM> which are discrete, and spaced-apart along the reinforcement portion <NUM>. In this embodiment, the binder sub-portions <NUM> are equally spaced along the length L of the elongate reinforcement assembly <NUM>.

Each binder sub-portion <NUM> extends at an angle A to the direction of the fibres <NUM> of the reinforcement portion <NUM>. The angle A is <NUM> degrees in this embodiment- i.e. the sub-portions <NUM> generally extend in the width direction W of the elongate reinforcement assembly <NUM>.

Each binder sub-portion <NUM> is constructed from a strip of fibrous thermoplastic material (known in the art as "scrim") which extends across the width W of the elongate reinforcement assembly <NUM> and extends past each edge <NUM>, <NUM> to form two individual projecting regions <NUM>, <NUM> respectively. The sub-portions are attached to alternating sides <NUM>, <NUM> of the elongate reinforcement assembly <NUM>.

The resulting elongate reinforcement assembly <NUM> has the appearance of a strip or tape of reinforcement material with spaced apart "hairs" projecting from each edge. It will be noted that because the thermoplastic scrim material is deformable, the projecting regions <NUM>, <NUM> are also deformable.

The binder used in this embodiment has the following characteristics:.

Turning to <FIG>, a method for the manufacture of the elongate reinforcement assembly <NUM> is shown.

At step A, the reinforcement portion <NUM> is provided in a continuous length (only a small portion of which is shown for clarity). Three such portions <NUM>, <NUM>', <NUM>" are provided, each being spaced apart by gaps having gap distances 2D.

At step B, a plurality of binder strips <NUM> are provided which span each of the plurality of reinforcement portions <NUM>, <NUM>', <NUM>" and the gaps therebetween. The strips are adhered to the reinforcement portions <NUM> by the application of heat to partially melt and thereby tackify them. The strips <NUM> on the first side <NUM> are applied before the reinforcement portion <NUM> is turned over and the strips applied to the second side <NUM>. Each strip <NUM> overhangs the outermost reinforcement portions <NUM>', <NUM>" to provide the projecting region <NUM> for the first reinforcement portion <NUM> and the projection region <NUM> for the third reinforcement portion <NUM>".

At step C, the binder strips <NUM> are cut along cut lines <NUM>, <NUM>' at the midpoint between adjacent reinforcement portions <NUM>. This creates the further projecting region <NUM>, <NUM> as shown.

The elongate reinforcement assembly <NUM> of <FIG> is the resulting product.

The elongate reinforcement assembly <NUM> is then used in a composite manufacturing process. For example, the elongate reinforcement assembly <NUM> may be used to create a preform in which the reinforcement portions of adjacent elongate reinforcement assembly <NUM> are placed next to each other. The projecting regions <NUM>, <NUM> then overlap the adjacent tows. The preform is formed of multiple layers of elongate reinforcement assembly <NUM>, preferably in different directions.

The projecting regions <NUM>, <NUM> force the adjacent layers to be spaced-apart, thus creating voids within the preform which encourages infiltration of resin in a resin transfer moulding process. This is advantageous.

It will be noted that the example may be adapted to other types of elongate reinforcement portions. For example, the first portion <NUM> may be a yarn or other type of elongate reinforcement.

Referring to <FIG>, a section of known elongate reinforcement assembly <NUM> is shown in plan. The elongate reinforcement assembly <NUM> is generally planar having a first edge <NUM> and a second edge <NUM> (the edges running along the length of the elongate reinforcement assembly <NUM>). A very short section of elongate reinforcement assembly <NUM> is shown having length L, but it will be understood that the elongate reinforcement assembly <NUM> is manufactured as a continuous strip of material, and thus L may vary significantly. The width of the the elongate reinforcement assembly W (that is the perpendicular distance between the edges <NUM>, <NUM>) is substantially constant along the length L. The elongate reinforcement assembly <NUM> is constructed from a reinforcement portion <NUM> and a binder portion <NUM>.

The reinforcement portion <NUM> comprises a plurality of individual fibres <NUM> which are constructed from carbon, and manufactured in a manner known in the art. The reinforcement portion <NUM> has a length L and width W which significantly exceed its thickness (by at least a factor of <NUM>) and as such the elongate reinforcement portion <NUM> can be referred to as a "tape" having a first side <NUM> and a second side <NUM>. The fibres of the reinforcement portion <NUM> run in parallel in the direction of the length L of the elongate reinforcement assembly <NUM>, and as such the reinforcement portion <NUM> can be described as a "unidirectional" fibre tow. Ordinarily, the fibres <NUM> of the reinforcement portion <NUM> do not adhere to each other.

The binder portion <NUM> comprises a strip of fibrous thermoplastic material (known in the art as "yarn") which wraps around the reinforcement portion <NUM> in a helical manner. In other words, the binder portion <NUM> is helically wound around the reinforcement portion <NUM>. The winding angle B is shown as <NUM> degrees in this embodiment.

Referring to <FIG>, a section of elongate reinforcement assembly <NUM> in accordance with the invention is shown. It is similar to the section of elongate reinforcement assembly <NUM> with the exception of the configuration of the second, binder portion <NUM>. Reference numerals for common features are shown <NUM> greater. The binder portion <NUM> of the elongate reinforcement assembly <NUM>, instead of changing direction to wrap around the width W of the reinforcement portion <NUM> extends past the respective edges <NUM>, <NUM> to form respective projecting regions <NUM>, <NUM>. In other words, the binder portion <NUM> forms a helix having a width X which is larger than W. The resulting projection portions <NUM>, <NUM> are in the form of spaced-apart deformable loops.

The binder portion <NUM>, <NUM> is created by wrapping the yarn around the reinforcement portion <NUM>, <NUM> of the elongate reinforcement assembly <NUM>.

Variations fall within the present invention.

The thermoplastic yarn for the embodiment of <FIG> could be added by an automated fibre placement (AFP) head during the process of forming a preform. The yarn would be adhered to the reinforcement material before deposition. A multiaxial preform is formed from the reinforcement assembly by laying down at least four laminae of the assembly at angles between -<NUM> and +<NUM>° from the longitudinal direction of the multiaxial fabric and this is followed by the step of infusing a liquid matrix material into the layers; and curing the matrix material to form a composite product.

Claim 1:
An elongate reinforcement assembly (<NUM>) comprising:
a first portion (<NUM>) comprising a composite reinforcement material, the first portion being elongate having a first edge (<NUM>) and a second edge (<NUM>) each extending along a longitudinal axis (L) said first portion (<NUM>) comprising a plurality of adjacent unidirectional carbon fibres (<NUM>) extending along the longitudinal axis (L); and,
a second portion (<NUM>) comprising a binder, the second portion comprising a plurality of spaced-apart projecting regions (<NUM>, <NUM>) extending past at least one of the edges (<NUM>, <NUM>) of the first portion (<NUM>), wherein the binder extends into the projecting regions (<NUM>, <NUM>);
and wherein the binder comprises a length of fibrous thermoplastic polymer characterized in that the length of thermoplastic polymer wraps around the first portion (<NUM>), extends along the longitudinal axis (L) and zigzags between the first (<NUM>) and second (<NUM>) edge forming at least three projecting regions (<NUM>, <NUM>) in the form of loops.