FATIGUE BEHAVIOR OF STITCHED GRP LAMINATES

This paper examines the effect of through-thickness stitching on the i n-plane fatigue performance and fatigue damage mechanisms of a glass-r einforced polymer (GRP) laminate under zero-to-tension cyclic loading The influence of stitching orientation and stitching density on the S- N curve of the laminate has also been investigated. The fatigue resist ance was reduced considerably by stitching, particularly at relatively low fatigue stresses. Both the non-stitched and stitched laminates ex perienced similar types of fatigue damage, i.e. cracking of the vinyl ester resin matrix and glass fibres, and debonding between the matrix and fibres. However, the stitched laminates also suffered fatigue fail ure between the stitches and surrounding laminate, which contributed t o the reduction in the fatigue lives of these materials. Their fatigue resistance was also reduced by damage to the glass fibres caused when the laminates were stitched. It was concluded that while stitching im proved the interlaminar fracture properties of the GRP, it seriously d egraded the fatigue performance. (C) 1996 Published by Elsevier Scienc e Limited