The effect of weave pattern on the mode-I interlaminar fracture energy of E-glass vinyl ester composites

In this work, the effect of weave structure on the mode-I interlaminar fracture energy (G(Ic)) of glass/toughened vinyl ester laminates has been investigated. The matrix material used was commercially available rubber-modified vinyl ester resin, DERAKANE 8084. The glass fibres used were E-glass plain weave, twill weave, quadran 4-harness satin weave, and 8-harness satin weave with weave index of 2, 3, 4 and 8 respectively. The specimens were prepared by a vacuum bagging technique. The mode-I delamination tests have been done at a constant displacement rate of 2 mm/min in an Instron testing machine, using specimens machined in accordance with ASTM D5528-94a. By using a HITACHI S-4500 scanning electron microscope, microscopic details of crack growth in the interply region were examined after fracture testing. The twill-weave laminate with weave index n(g) = 3 yielded the highest value of fracture energy for critical crack propagation (G(Ic)). Whilst the 8-harness satin-weave laminate gave the highest value of initial fracture energy (G(Ii)). Partial debonding of transversely oriented yarns results in the delamination resistance for twill-weave, quadran 4-harness satin-weave, and 8-harness satin-weave laminates. Fracture of debonded fibres ascribed to as 'fibre bridging' was observed in the twill-weave, quadran 4-harness satin-weave and 8-harness satin-weave laminates. No indications of fibre bridging were observed in the plain-weave laminate. (C) 2002 Elsevier Science Ltd. All rights reserved.