Effect of temperature and clearance on shear cutting behaviors in CFRP laminates

The purpose of the present study is to optimize the shear cutting conditions of CFRP laminates. First, specimens of thermosetting (epoxy) and thermoplastic (polyamide 6) CFRP cross-ply laminates 1.2 mm thick were cut by shearing using lower and upper blades. The shear cutting tests were performed at various temperatures ranging from a room temperature (RT) to temperatures higher than the glass transition temperature T_g. The effect of clearance between the upper and lower blades was investigated only for thermosetting CFRP specimens. Next, cross-sectional and internal damages adjacent to the cutting planes were observed using optical microscopy together with soft X-ray analysis to quantitatively measure the size of burrs, removal parts (lost from the workpiece due to cracking) and delamination area. Finally, double cantilever beam (DCB) and end-notched flexural (ENF) tests were performed to measure the modes I and II interlaminar fracture toughness of the thermosetting CFRP at various temperatures. It was proved from the experiment that the best machining quality, namely, the least delamination area, length of burrs and removal parts, was obtained at a temperature of 70^oC and 45^oC for the thermosetting and thermoplastic CFRP laminates, respectively. These optimum temperatures are lower than T_g, where the interlaminar fracture toughness becomes higher than that at RT while the rigidity is lower than that at RT. The optimum clearance was found to be around 0.05 mm for the thermosetting CFRP laminate. In addition, the maximum shear stress becomes almost constant when the clearance exceeds the optimum one.