FLEXURAL PROPERTIES OF STITCHED GRP LAMINATES

The flexural properties (elastic moduli, yield strength and maximum st rength) and flexural failure processes of GRP laminates reinforced thr ough-the-thickness with Kevlar(R)-49 stitches were studied under four- point bending at strain rates between about 10(-6) and 3 x 10(-2) s(-1 ). The flexural properties of the non-stitched laminate were larger th an the stitched laminates over the range of strain rates studied. Scan ning electron microscopy revealed that some of the failure processes i n the non-stitched laminate differed from those of the stitched lamina tes, which occurred at lower flexural stresses. It appears that the lo wer flexural properties of the stitched laminates result from damage c aused by stitching as well as by the stitches being stress concentrati on sites during bending. (C) 1996 Elsevier Science Limited