Mixed mode fracture toughness and mode mixity analysis of face/core debonds in a single-leg sandwich bending specimen

Abstract

Mixed mode fracture, which often occurs during composite materials, can present a safety hazard to the structure. Analytical expressions for the energy release rate (ERR) and mode mixity phase angle are derived for an asymmetric single-leg sandwich bending (SLSB) fracture specimen. Meanwhile, the modified crack surface displacement extrapolation (MCSDE) method is proposed to obtain the numerical solution of ERR and mode mixity. The effects of loading characteristics, core and face sheet geometric parameters and material parameters on ERR and mode mixity are investigated. To solve the problem of excessive deformation of the thin plate specimen during the test, a reinforced single-leg sandwich bending specimen (RSLSB) is proposed, and the detailed derivation process of the RSLSB fracture specimen's analytical solution is given. The results show that loading magnitude greatly affects ERR and mode mixity. The core’s geometric and material parameters have little effect on ERR but have apparent effects on mode mixity. The face sheet's geometric and material parameters have apparent effects on the ERR and mode mixity. The existence of the reinforced layer will increase the mode I fracture component.