Properties of stitched composite laminates-the principal properties of simple laminates

For the application of stitched composites in aircraft structures, experimental studies were carried out on the effect of stitching and stitching directions on tensile and compressive properties of unidirectional laminates and cross-ply symmetric laminates made of uniweave T300/QY9512. Some principal properties of uniweave T300/QY9512 were measured. It shows that stitching and stitching directions have little effect on the moduli of these two kinds of laminates, while the effect is great on the Possion ratio of unidirectional laminates. The transform of off-axial modulus is not fit for the Poisson ratio of off-axial stitched unidirectional laminates. Stitching and its directions have great effect on the tensile strength of unidirectional laminates, but have no obvious effect on the compressive strength. Because the tension failure mechanisms of stitched cross-ply symmetric laminates are different from that of stitched unidirectional laminates, the strength of stitched unidirectional laminates cannot be used as the laminar strength of stitched cross-ply symmetric laminates.