Effects of surface treatment and weave structure on interlaminar fracture behaviour of plain glass woven fabric composites: Part II. Report of the 2nd round robin test results

This paper reports the second part of the results from the round robin test program proposed by the Society of Interfacial Materials Science (SIMS) to characterise the interlaminar fracture behaviour of E-glass woven fabric reinforced vinylester composites. Special emphasis was placed on the study of loading direction (i.e. weft and warp directions) effect on interlaminar shear strength and fracture toughness. Ten laboratories worldwide participated in this test (Table 1). Each laboratory was supplied with composite laminates and conducted the tests according to its own procedure. The results showed that although there were large variations in absolute magnitude between laboratories, a general trend was established with higher interlaminar fracture resistance in the weft direction than in the warp direction for a given silane agent. The larger number of strands running in the warp direction with rougher, more undulating areas perpendicular to the direction of crack propagation was mainly responsible for this result. The results also confirmed the previous finding that the mode I interlaminar fracture toughness increased with increasing silane agent concentration.