Effect of post-cure duration on the mode I interlaminar fracture toughness of glass-fibre reinforced vinylester

The effect of different post-cure conditions on the mode I fracture toughness of a vinylester resin and its glass-fibre reinforced composite counterpart has been studied. Two sets of parameters were investigated. The first was the post-cure duration at constant temperature; 90 °C for 1, 4 and 24 h. The second, for resin toughness only, was a combination of post-cure temperature and duration; 90 °C/4 h, 80 °C/8 h and 70 °C/16 h. The results show that the post-cure increases toughness. This trend is consistent between the pure resin and the fibre composite for all treatments, except at 90 °C/24 h. It is believed that the prolonged post-cure duration of 24 h has weakened the bond strength at the fibre-matrix interface, thus reducing the effectiveness of toughness transfer from the matrix to the composite. The study concludes that the post-cure enhances the toughness of the glass-fibre/vinylester composite, mainly due to the increase of resin toughness.