Fracture characteristics of short fiber‐toughened matrix laminates

Abstract Interlaminar fracture properties of glass‐fabric laminates are enhanced by reinforcing the matrix with up to 4% short glass fibers. The toughened matrix laminates are subjected to double cantilever beam (DCB) and end‐notched flexure (ENF) tests. In the case of mode‐I loading, the crack initiation toughness is not influenced by the reinforcement, but it increases with increasing filler content in the mode‐II case. While the maximum energy release rate increases with increasing fillers in both loading cases, the maximum enhancement in mode‐I critical energy release rate (G Ic ) is noted for the 2% filler case. Further increase in filler content instigates unstable crack growth. While short fiber‐induced bridging is evident during mode‐I loading, excessive filler/matrix debonding along with fiber and matrix fracture is noted in the mode‐II case. Fracture surface micrographs reveal the influence of interlaminar matrix layer (IML) on fracture mechanisms. During stable crack growth, the crack propagates along the IML/lamina interface as well as through the IML. At low volume fraction, the matrix toughening fillers enhance the interlaminar fracture characteristics by increasing the resistance to crack propagation. On the contrary, at high volume fraction, the fillers effectively keep the IML intact; thus, virtually guiding the crack to propagate along the IML/lamina interface, which leads to unstable crack growth. Besides short fiber concentration, the mode‐II fracture behavior also depends upon the fiber orientations in the adjacent laminae. Highlights Interlaminar matrix layer (IML) governs the fracture characteristics in a laminate. Limited matrix toughening by fillers enhances interlaminar fracture properties. Excessive fillers lead to unstable crack growth along IML/lamina interface. Mode‐I crack initiation toughness ( G Ii ) remains unaffected by matrix toughening fillers. Increasing filler content increases interlayer shear strength as well as G IIi .