Determination of fibre tension fracture toughness of composite laminates at high loading rate

The dynamic fracture toughness of composite laminates in fibre tension failure mode is characterized here with compact tension (CT) sample, at loading rate of 25 m/s using bi-directional electromagnetic Hopkinson bars. Digital image correlation (DIC) with high-speed imaging is employed for obtaining the full-field strain fields. A dynamic J-integral method is proposed to analyse the dynamic fracture toughness, the kinetic energy and inertia effects involved in dynamic loading and crack propagation process has been analysed and calibrated. The fracture toughness of fibre tension failure at high loading rate is found to be about 25% lower than that in quasi -static load regime, and the R-curve effect under high loading rate is not significant than that in quasi-static load regime. It is suggested from X-ray CT and SEM images that the fibre pull-out length and size of failure process zone is reduced with increase in loading rate.

Automated summary

The dynamic fracture toughness of composite laminates in fibre tension failure mode was characterized using compact tension (CT) samples with a loading rate of 25 m/s. Digital image correlation (DIC) with high-speed imaging was used to obtain full-field strain fields. A dynamic J-integral method was proposed to analyze the fracture toughness, taking into account the kinetic energy and inertia effects in the dynamic loading and crack propagation process. It was found that the fracture toughness of fibre tension failure at high loading rates was about 25% lower than that in quasi-static load regime. The R-curve effect was not significant under high loading rates compared to quasi-static load regime. X-ray CT and SEM images suggested that the fibre pull-out length and size of the failure process zone were reduced with an increase in loading rate.