Measurement of the mode II intralaminar fracture toughness and R-curve of polymer composites using a modified Iosipescu specimen and the size effect law

•A test method to obtain the mode II intralaminar R-curve of FRP is investigated.•A modified Iosipescu specimen is proposed to measure the fracture toughness.•A new technique based on a variation of the size effect method is developed.•FEA are performed to obtain the correction factor for the energy release rate.•Intralaminar fracture toughness in mode II is obtained for IM7/8552.

A modified Iosipescu specimen is proposed to measure the mode II intralaminar fracture toughness and the corresponding crack resistance curve of fibre reinforced composites. Due to the impossibility of scaling the specimen, a modification of the classical size effect method is proposed. The calculation of the crack driving force curves is performed using the Finite Element Method. The classical Iosipescu shear feature was used and tests were coupled with digital image correlation to support the proposed approach. Experiments were performed on IM7/8552 material system and the R-curve was obtained. The steady-state value of the fracture toughness of the ply is found to be equal to R0ss=34.4R0ss=34.4 kJ/m2.