Development of single-layer 3D ‘T’ profile with fillet for composite ‘T’ joints

Abstract

This paper details about weaving of single-layer 3D ‘T’ profile with fillet for use as insert in composite ‘T’ joints and ‘T’ stiffeners. The ‘T’ insert with fillet was woven using 3 K carbon tows on a narrow width multi-beam automatic loom. Weaving was carried out based on the double-cloth weaving principle. Novelty of the work lied in the approach adopted for designing of the weave architecture in developing 3D ‘T’ profile with fillet portion, arriving at the pick cycle diagram for weave design development which has been detailed in this paper. Test results of composite ‘T’ joints fabricated incorporating the insert showed strength improvement as well as change in crack propagation mode as compared to conventional ‘T’ joint. The continuous insert with fillet acted as a bridging member among the three sections of the ‘T’ joint, thus contributing to performance improvement.

Integral weaving of orthogonal 3D ‘T’ stiffeners based on pleat weaving concept

“…Manufacturing information in literature based on 3D orthogonal technologies include woven ‘Pi’ joint element for wind mill blade’s shear web and spar cap [6], simple noobed woven preform based on the conventional weaving approach [7], formability studies on complex moulds [8], studies of adhesive bonded joints of composites panel reinforced with non-crimp 3D orthogonal woven E glass fibre fabrics [9], design and manufacture of 3D flat woven fabric on an ordinary loom [10], effect of wire space and weaving pattern on performance of microstrip antennas [11] varied weave architectures [12], weaving of 3D orthogonal ramie fabric [13], development of UHMWPE/vinyl ester composites [14], PMR type polyimide composites using glass fibre preforms [15] and such others. Continuing on the approaches adopted for the manufacturing of the ‘T’ stiffener element in particular, attempts have been made to combine orthogonal flat preforms with stitching [16], design of a light weight ‘T’ joint [17], ‘flattening-weaving-unfurling approach [18], use of transverse stitching, z-Pinning and tufting technologies [19–23], use of PP layers [24], use of inserts [25], self-healing concepts [26] and others. With this backdrop, this paper adopts yet another approach for manufacturing the ‘T’ stiffener using orthogonal weaving approach based on the existing pleat concept [27].…”

Effect of crossing warp architecture on tear strength of 3D orthogonal woven T-shaped reinforcements

“…4 Hence, the transfer of tensile and flexural loads from the web to the flange of a T-joint occurs in an out-of-plane direction and that from one flange to another flange takes place in an in-plane direction. [4][5][6] Under such load conditions, composite T-joints are prone to delamination because of stress concentration at the junction. In the case where a composite T-joint is made from two-dimensional (2D) laminates, there will be a triangular void at the junction due to the bending of 2D laminate in order to form the three-dimensional (3D) joint, [7][8][9] forming a resin-rich region in the composite T-joint.…”

“…However, the 2D weaving loom with some modifications was also used to weave 3D woven reinforcement for composites, including composite T-joints. 24 The use of conventional weaving illustrated, through various research studies, 6,8,18,21,[25][26][27][28][29] that the profiled reinforcements were able to be fabricated by the folding method where the reinforcements were woven in a flat configuration with pre-positioned bifurcations. After weaving, the reinforcements could be opened up into the desired 3D shapes.…”

“…4 Hence, the transfer of tensile and flexural loads from the web to the flange of a T-joint occurs in an out-of-plane direction and that from one flange to another flange takes place in an in-plane direction. 4 –6…”