Abstract
By Tailored Fibre Placement (TFP), a new process based on embroidery technology, it becomes possible to reinforce composite parts very efficiently by stitching additional fibres with defined alignments to a given textile preform locally at highly loaded areas. The attachment of large CFRP aircraft structures is often achieved by shear pin couplings, applying bolt bearing pressure to the composite around the loaded hole. In this study, the potential of TFP to improve material strength of CFRP couplings was investigated by conducting pin loaded bearing tests with samples made of multi-axial warp knitted fabric (MWF) impregnated with Hexcel-RTM6 resin. Samples stitched with different fibre patterns to reinforce the loaded hole were compared to samples with a simple planar thickening in this critical area by additional layers of fabric. TFP was efficient (comparing the additional strength to additional structural mass) regarding bearing strength. However, the best results for the improvement of ultimate bearing strength (failure load) were achieved by increasing the part thickness locally with fabric patches.
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