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Abstract
Optimum stitching for triaxial or multilayered fabric can be determined for the optimum handleability and the extended life service of a composite utilizing this type of reinforcement.
TRIAXIAL FABRIC
ABSTRACT
Optimum stitching for triaxial or multilayered fabric can be
determined for the optimum handleability and the extended life service of a
composite utilizing this type of reinforcement.
The use of non-crimp fabrics (NCF) is well known in both the
fabrics and the composite materials industry.
Such fabrics may be woven or they may be what are commonly referred to
as being “stitched”. Stitching is
usually referred to as the use of tricot or chain stitch patterns. This
stitching, sewing or binding of fibers combines three or more layers of
reinforcement yarns into a unit which is handleable and which may be used as
produced or as an impregnated product. The three dimensional or triaxial fabric thus
can consist of individual layers of single strand reinforcements which can be
placed in different layered orientations to achieve the best drape or
handleability characteristics consistent with the placement of the strength
vectors in the desired orientation. A
typical triaxially stitched fabric may contain a layer of +45° offset to the
parallel direction of the fabric length (linear dimension), a -45° layer offset
to the parallel direction of the fabric length and a 0° layer which is the
pillar or the referenced (linear) parallel direction.
These NCF fabrics
prove to be highly advantageous in that the crimp or waviness of congenitally woven
multiaxial yarns passing over and under one another is eliminated in
comparative fabrics of the same weight. This lack of crimp contributes
significantly to the strength and length of service of the triaxial material. This is primarily due to the reduction of the
number of abrasion areas at yarn cross over points.
Stitching of multiaxial fabrics composed of non-woven layers
of reinforcement is usually accomplished using a tricot, chain stitch or other
configurations known to those skilled in the art. Often, thermoplastic yarns are used as the
stitching materials such as polyethylene, polypropylene, nylon and the like while
the yarn composition is not limited to this class of materials. The number of stitches or gauge required to
bind the layers together is mostly a function of handleability and the number
of stitches necessary to retain the layered components in a uniform
configuration. Cost is also sometimes a
significant factor. Stitching patterns
used to hold fibers together in a triaxi...