Dynamic characterization of interlaminar toughness in carbon fibre epoxy composite laminates

In this work, the influence of the loading rate on the mode I interlaminar fracture toughness of carbon fiber laminates manufactured with prepregs of the second (IM7/8552) and third generation (IM7/M91) was investigated. The study has been carried out using to loading rates ranges, namely, quasi-static between 0.5 and 450mm/min, and dynamic between 100 and 2000mm/s. The latter tests were performed using a Gleeble 3800GTC hydraulic testing system. The dynamic tests were carried out using the WIF methodology (wedge insert fracture) by inserting at high speed a cylinder between the arms of the specimen. Two strain gauges were used to measure the maximum flexural deformation of the loading arms allowing the estimation of the opening force of the specimen to infer the dynamic fracture energy. The results showed that the IM7 / M91 laminate was sensitive to the speed of solicitation presenting a maximum value of the fracture energy for 500mm/s being the toughness more than twice than the one measured under quasi-static conditions.