Experimental investigation of mode I delamination growth in unidirectional E-glass/ vinyl ester composites on acid aging

In the present investigation, the mode I fracture toughness of unidirectional E-glass/vinyl ester composites subjected to sulfuric acid was studied. Specimens were manufactured using the hand lay-up method with the [0]_18 stacking sequence according to standard size. Specimens were exposed to 20 wt.% sulfuric acid (with 98% purity) at the laboratory temperature for 0, 1, 2, 5 and 10 weeks. Subsequent to conditioning for the aforesaid period of times, samples were dried and according to the standard, the double cantilever beam tests were performed to study variations of the initiation and propagation fracture toughness. Results show a reduction in the propagation fracture toughness after conditioning, although the variation of the initiation fracture toughness at the first 5 weeks was increasingly and after that at the 10th week had a significant reduction. Moreover, it was observed that the amount of the crack initiation force of samples was decreased after the conditioning.