Evaluating the fracture toughness of glass fiber/epoxy interface using slice compression test: Propagation behavior of interfacial debonding

The slice compression test (SCT) is used to evaluate interfacial properties by loading/unloading a specimen of the composite between two plates; one has low modulus and the other has high modulus. The specimenused is an epoxy resin, containing a single SiO₂ glass fiber, with a 200 μm diameter. The interfacial debonding is monitored by using a microscope and a video camera. Then, the energyrelease rate is calculated by finite element analysis. From the in-situ observation, it is found that the interface fracture initiates when the radial stress around the fiber changes from compressionto tension due to the Poisson's effect (applied stress _⩾40 MPa). The length of the crack is proportional to the stress as the load increases. It is also found analytically that the energyrelease rates remain constant once the interface fractures, independent of the initial crack length. It is suggested that the critical energy release rate can be appropriated for the interface fracturecriterion.