DE19932842B4 - Carbon fiber sewing thread for fiber-plastic composite components - Google Patents

Abstract

Multi-filament carbon fiber sewing thread for processing on loop-forming machines, as a loop-forming thread, in particular lockstitch sewing machines, characterized in that the carbon fibers in the core (2) are in multi-filament shape (rovings) and by a crocheted stitch jacket (4) consisting of a further material (1) are covered.

Description

The ending concerns a yarn class according to the preamble of claim 1.

For the production of reinforcing fiber preforms for the Resin injection technology for the production of fiber-plastic composites (FKV) becomes sewing technology used. It is known that carbon fiber sewing threads are optimal Offer properties in the fiber-plastic composite. A sewing thread from the company Toray, which is available in double and triple twisted form available on the market. Furthermore, different versions of carbon staple fiber yarns are which are further processed into a thread available (Toray Industries, Inc., Tokyo, Japan: Product Overview / Blantyre-Schappe Carbon Products SA, Charnoz, France: product overview). Both described sewing threads are on an industrial scale on sewing systems (or loop-forming machines) can only be processed insufficiently. About that in addition there is a drop in the static strength values for both determined by the manufacturing process used (twisting, tearing) (Morales, A .: Structural Stitching of textile Preforms. 22nd Int. SAMPE Technical Conference, Nov. 6-8, 1990). Abrasion occurs (on sewing thread) while of the various thread deflections on the processing machine continues to lead to increased Wear on the Machine parts, as well as to lower the fiber properties increased Fiber abrasion (e.g. sewing machine gripper). The use of previous reinforcement sewing threads various sewing machine types is only very limited possible. So could such threads So far only on thread-saving chain stitch machines where the takeover of the needle thread by the hook is not critical, successfully processed become. Rovings (multi-filament yarns) are because of their openness Cannot be sewn on lockstitch machines. The takeover of the complete needle thread due to the gripper tip, this cannot be done safely.

It is known from textile technology elastic threads to crochet to limit their stretchability (Strauss, T .: Elastane combination yarns. Warp knitting practice 2/98, Obersthausen) and therefore processable on textile machines close. The elasticity For example, a Bayer Dorlastan yarn can have over 200 % are reduced to 50% (Strauss, T .: Elastane combination yarns. Warp knitting practice 2/99, Obertshausen).

In US 48 38 043 discloses an embodiment showing a knitted sheath of a carbon fiber core. The in US 48 38 043 The mesh jacket described is used to generate a longitudinal extensibility setting, which is used in particular to limit the extensibility of elastic goods. On the other hand, it is not possible to produce a highly compacted sewing thread, which is necessary for use as a loop-forming upper thread when producing a lockstitch. In view of the use of core materials with very low stretch (e.g. carbon fiber multifilament yarn with ε _max = approx. 1.8%), the knitting process cannot be used to compact the yarn over its length. This is due to the characteristic of stitch formation during knitting, which primarily produces rows of stitches in the circumferential direction. The in US 48 38 043 In addition, the knitted coat disclosed applies a lot to the surface of the multi-filament core, which is why it is displaced by the thread deflections of a sewing machine. This can be seen in particular in the sense of the yarn being able to be taken over by the hook tip in the needle groove. A yarn after US 48 38 043 Furthermore, it does not offer the flexibility and delicacy required at the time the thread is transferred from needle to hook.

The invention has for its object carbon fiber rovings (Multi-filament yarn) sewable, this means Can be processed on a standard sewing machine close. As well as compatible on the manufacture of fiber matrix composite Sewing threads. The Task is characterized by the characteristic features of the claim 1 solved.

High-strength multi-filament cores (carbon fiber rovings) offer the best compared to twisted or staple fiber yarns mechanical properties. Such yarns offer for the sewing of textile reinforcement structures considerable potential for plastic reinforcement. These requirements will be by using a yarn with the features of the claim 1 solved.

The multi-filament core is on a crochet machine crochet with another thread, whereby the roving is still stretched after this process. This makes it possible to get high brittle Materials a certain elasticity to rent. This is the main difference from today's Use of this technique because the crochet is not for fixation an elastic core, but used to protect a rigid bundle of filaments becomes. The previous effect of the crochet process is therefore reversed.

By using a yarn according to the invention can the introduction of a Z-reinforcement, in Shape of a multi-filament roving into an essentially two-dimensional one textile structure, by a lockstitch sewing machine or other textile techniques respectively. When using such a yarn, it is also possible to use the Sewing speed due to the increased abrasion resistance.

Abrasion on a brittle carbon fiber twist due to the thread-guiding elements is considerably reduced, which on the one hand leads to sewability itself and on the other hand leads to increased fiber properties of the sewn yarn. The strength of the resulting fiber-plastic composite is also improved. The mesh structure protecting the core, the crochet, enables a continuous sewing process, even if the core material is damaged. The monitoring of seam parameters can thus be used to check the mechanical properties of the fiber-plastic composite (FKV) to be expected.

The crochet of the multi-filament core is compacted and closes the yarn in one for the processing necessary so that the loop formation, especially on lockstitch sewing machines through the takeover of the needle thread through the hook tip.

By choosing the crochet material Is it possible, To produce 1- or 2-material systems. For example, water-soluble polymers are used, which only provide temporary protection until the end of the Offer processing or the processing operation at all enable first. Other advantages are associated with 3-dimensional thermoplastic fiber plastic to find. There you can the stitch threads from the matrix polymer of the FKV and therefore part of the consolidation after the consolidation of the matrix. The viscosity of the Thermoplastics during of the impregnation process also the placement of the matrix threads in the immediate vicinity of the impregnated Fiber, which is achieved or supported with the yarn construction.

The yarns of the invention can be loop-forming on all Machines are used. So this technology also makes it possible the extended use of further textile technologies for FKV applications (Knitting, knitting, 3D techniques, fleeces, ...).

The process of crocheting enables production of very thin Blended threads, what specifically with regard to the in-plain properties, i.e. the mechanical characteristics in the laminate level is an advantage.

Hybrid multi-filament threads can also be made without a twisting process sutured be made.

A carbon fiber mulit filament roving ( 2 ) is achieved by using another thread used to crochet the multi-filament core ( 1 ) made sewable, ie essentially increased the compactness of the yarn for sewing to a sufficient extent. The carbon fiber mulit filament roving is fed to a crochet system on which a strand of mesh is produced around the mulit filament core. The number of entanglements is varied and adapted to the requirements of the following textile or material-specific processing process.

For an optimal frictional connection between several flat reinforcement textiles to produce, the use of carbon fiber rovings is required. The introduction of the reinforcement threads by means of sewing, especially lockstitch, is by using the here described yarn possible. The roving is stretched in the direction of the thickness of the laminate in front. Losses due to twisting or twisting of the rovings are thus avoided. Due to the mesh structure of the crochet, fibers with a extensibility sewable by approx. 1%. The crochet described protects and compacting the yarn at the same time, resulting in undisturbed pulling off of threads contributes and also ensures that partially damaged Rovings sewn on will be able because the overall structure remains intact and therefore the process is not   interrupted. The Making a very thin crocheted Yarns (approx. 5 - 10 tex) could be here also a FKV-compatible alternative to the annoying polyester threads in multi-axial fabrics (manufactured on machines from Liba Maschinenfabrik GmbH or Karl-Mayer Malimo machines) represent.

The sheathing can be with the yarn are available in several variations. For example, a single-substance system generated, it is possible the protective To produce a jacket with a thread of water-soluble polymer. This polymer can be removed by washing in a subsequent process. The stitched After washing, textile exists as a single-substance system, which is one high quality of the FKV.

The crochet can also be made from the matrix polymer consist. This case is particularly used for the production of thermoplastic Fiber composite materials interesting. The use of multi-axial fabrics for the Semi-finished product manufacture can be optimized through the use of sewing threads, on the one hand consist of the matrix polymer and therefore compatible with the matrix and secondly by carbon roving the fixation of consolidation situations. The impregnation this roving in the thickness direction is made with the crocheted matrix thread, whose proportion is adjustable with the number of crochet. The Carbon fiber roving in the thickness direction also offers an improvement in damage tolerance to impact loads (impact properties).

The invention is based on two forms of representation explains:

1 shows a section of the carbon fiber sewing thread, consisting of carbon fiber roving core ( 2 ) and a mesh coat ( 4 ).

2 shows the thread in cross section. you recognizes the aligned filaments ( 3 ) of multi-filament roving ( 2 ), as well as the looping stitch-forming thread ( 1 ).

1

stitch-forming thread

2

core

3

filament

4

mesh jacket

Claims (6)

Multi-filament carbon fiber sewing thread for processing on loop-forming machines, as a loop-forming thread, in particular lockstitch sewing machines, characterized in that the carbon fibers in the core ( 2 ) in multi-filament form (rovings) and through a crocheted mesh jacket ( 4 ), consisting of another material ( 1 ) are enveloped. Carbon fiber sewing thread according to claim 1, characterized in that in the core ( 2 ) Hybrid threads are introduced. Carbon fiber sewing thread according to claim 1 or 2, characterized in that the stitch jacket ( 4 ) consists of a water-soluble polymer. Carbon fiber sewing thread according to claim 1 or 2, characterized in that the matrix portion of the later fiber-plastic composite ^{is adjustable} via the number of loops (stitches) ^. Carbon fiber sewing thread according to claim 1 or 2, characterized in that the stitch jacket ( 4 ) is formed from multi-filament threads. Carbon fiber sewing thread according to claim 1 or 2, characterized in that the stitch jacket made of ( 4 ) textured threads is formed.