Chapter 8 - Stitched Composites

Abstract

This chapter focuses on the fabrication, mechanical properties, delamination, impact damage performance, and joining performance of stitched composites. Stitching can be preformed on both dry fabric and uncured prepreg tape. Stitching most types of fabric is relatively easy because the needle tip can push aside the dry fibers as it pierces the preform. Sewing prepreg tape can be more difficult because the inherent tackiness of the uncured resin matrix impedes the needle action. The materials most often used as the reinforcing threads for stitching are carbon, glass, and Kevlar yarns, although it is possible to sew with other types of fibrous materials. The tension, compression, bending modulus, and strength are material properties of great engineering importance in load-bearing structures, and therefore, these properties have been measured for many types of stitched composites, including carbon-, glass-, and Kevlar- fiber laminates. The experimental data indicates that most stitched composites have slightly lower tension, compression, and flexural properties than their equivalent unstitched laminate; although some stitched materials exhibit no change or a modest improvement to their mechanical properties.