The effect of loading rate on the mode I interlaminar fracture toughness

Abstract

This paper studies the effect of loading rate on mode I interlaminar fracture of unidirectional carbon/epoxy laminates. Double cantilever beam (DCB) test geometry was used to test quasi-static and dynamic fracture toughness. The DCB specimens were loaded symmetrically by a novel electromagnetic Hopkinson bar system at the maximum loading rate 30 m/s. The crack initiation is monitored by a pair of strain gage mounted on the surface of DCB arms. The hybrid experiment-numerical methods was used to calculate the fracture toughness by employing J-integral technique for quasi-static and dynamic tests. The finite element model takes use of incident stress wave as the boundary conditions for dynamic tests. It shows that the fracture toughness is rate positive at high loading rates, and rate insensitive at low loading rates.