Properties of stitched composite laminates - The principal properties of general laminates

The experiments were carried out on tensile and compressive properties of the ordinary laminates made of uniweave T300/QY9512. The effects were investigated of stitching directions, layup sequences and environmental factors on tensile and compressive properties. Tensile and compressive strength and modulus were measured for three kinds of un-notched laminates and laminates with a hole. It is shown that stitching and stitching directions have little effect on the strength and modulus of ordinary laminates, and the effects were different on the laminates with different layup sequences. Stitching and layup sequences have influence on stitching effectiveness of laminates with a hole. The best stitching direction is varied with the laminate layup sequence. The effect of stitching on the laminate compressive properties in hygrothermal environment is greatly related to layup sequences. Stitching makes compressive strength of laminates with a hole increase obviously under normal environmental condition, but decrease under hygrothermal environmental condition.