Effect of interlayer carbon nanotube films on the quasi-static and dynamic mode I fracture behavior of laminated composites-An experimental and numerical investigation

A combined experimental and numerical study was conducted to investigate the quasi-static and dynamic mode I fracture behavior of laminated composites toughened by carbon nanotube (CNT) films. Fracture tests under quasi-static and dynamic loading conditions were carried out by using electronic universal testing machine and electromagnetic Hopkinson bar device respectively. It's illustrated that the CNT films can suppress the propa-gation of interlayer cracks effectively. Dynamic strengthening effect was also observed for CNT toughened composites during tests. For numerical simulations, the three-linear cohesive zone model (CZM) was proposed to simulate the Mode I delamination of CNT films toughened composites under quasi-static loading condition. Furthermore, rate-dependent parameters were introduced into this model by user-defined subroutine to describe the dynamic fracture behavior of toughened composites. This developed numerical model was validated by comparing with dynamic crack propagating speeds obtained from experimental tests. During the dynamic delaminating process, the average crack propagation rate of toughened composites decreased while the energy release rate increased, indicating that the interlayer CNT films can hinder the dynamic delamination effectively.