Mode II interlaminar fracture toughness of woven E-glass/epoxy composites in the presence of mat interleaves

Composite laminates are widely used as primary load bearing structures in various industries. Using a thin layer of chopped strand mat between sub-laminates of a thick structural composite laminate would prevent crack development across the whole laminate thickness and reduce the risk of catastrophic failure in the structure. In this research, end-notched flexure (ENF) specimens were used to examine the impact of the mat layer between woven layers on the mode II interlaminar fracture toughness of glass/epoxy composites. ENF specimens are fabricated using hand lay-up method assisted by vacuum bagging technique. Experimental results revealed that the existence of a mat interlayer resulted in a reduction of interlaminar fracture toughness of the delamination initiation and propagation by 59% and 35%, respectively, compared to one without mat interlayer. Moreover, results showed that in the ENF specimens without interleaving of the mat, the dominant mechanism of increased fracture toughness is not fiber bridging and delamination propagates in fiber-matrix interface in these specimens.