Numerical And Experimental Study Of The Mode. Interlaminar Failure Of Chopped Carbon Fiber Tape Reinforced Thermoplastics

Carbon fiber reinforced plastics (CFRP) are increasingly used in primary structural components of automobile and aircrafts on count of their high specific modulus and strength. For this reason, they have attracted much attention of researchers, industrial manufacturers and even the general public. Randomly oriented carbon fiber reinforced thermoplastics (Randomly oriented CFRTP), in particular chopped carbon fiber tape reinforced thermoplastics (CTT), have been current research focus due to its advantageous properties such as high-productivity and design flexibility that are not attainable from conventional material. Besides, the mass application of randomly oriented CFRTP in automotive industry has been regarded as potential solution to reduce resource shortage and environmental pollution.Interlaminar failure, however, causes significant reduction on the load carrying capacity of fiberreinforced composites, which is a major concern to aerospace and automotive industries. The interlaminar fracture energy release rate of fiber-reinforced composites can be measured for any of the three possible crack propagation modes: opening mode (Mode I), shear mode (Mode II) and tearing mode (Mode III), and Mode I is the most critical crack propagation mode because it has the lowest associated fracture energy release rate. Many researches have focused on interlaminar failure of woven composites and unidirectional carbon fiber epoxy composites by using numerical and experimental analysis, but few studies about interlaminar failure of randomly oriented CFRTP can be found.In the present study, the Mode I interlaminar failure of CTT specimen was investigated during double cantilever beam (DCB) tests in which the crosshead was moved at a constant speed of 1mm/min. In order to measure the compliance of the specimen, it was unloaded after each significant crack propagation during testing. The results show an unstable crack growth resulting in a saw-tooth like force-displacement curve after initial linear stage. The mode. energy release rate was determined by three different analytical calculation methods: modified compliance calibration (MCC), modified beam theory (MBT) and beam theory in reference to JIS K 7086 standard. Furthermore, DCB specimen was modeled to capture the fracture behavior. The numerical results are in good agreement with the experimental results suggesting the finite element model can be used to simulate the delamination process.