Effect of loading rate on the delamination behavior of carbon/epoxy laminated composites

Abstract

Previous studies show that fracture toughness of carbon/epoxy composite is affected by hydrostatic pressure. The fracture toughness of carbon/epoxy composite is also affected by strain rate. To date, no study has been made on the combined effects of hydrostatic pressure and strain rate on the fracture toughness of carbon/epoxy composite. This work investigates the compressive fracture behavior of carbon/epoxy composite subjected to low and high strain rates in the hydrostatic pressure environment. Compressive fracture tests were performed in the atmospheric pressure and hydrostatic pressure environment of 270MPa. The compliance and fracture load were determined from load-displacement curves as a function of applied strain rate. Fracture toughness was determined from the elastic work factor approach. The results showed that the compliance decreased as the applied strain rate increased. However, the fracture load is less affected by the strain rate. The toughness decreased with increasing strain rate. Specifically, for 270 MPa hydrostatic pressure environment, fracture toughness decreased from 4.64 kJ/m2 to 4.05 kJ/m2 (12.7% decrease) as the strain rate increased from 0.05% to 0.55%. The decrease of fracture toughness with an increase in the strain rate is due to the epoxy becoming brittle as there is not sufficient time for the stress to be relieved.