Experimental study on hole quality and tensile progressive failure following fiber laser cutting of multidirectional carbon fiber reinforced plastic laminates

Fiber laser was feasible to cut carbon fiber reinforced plastic (CFRP) laminate with high efficiency and particularly meet short cycle time in large-volume vehicle production. Large differences in physical and thermal properties between fiber and resin, however, have been prohibiting the application of fiber laser cutting on CFRP composites. Joining of CFRP parts is mainly dependent on mechanical bolting/riveting, which depends critically on the quality of processed holes. In this study, CFRP laminates used for manufacturing new energy vehicles were employed to investigate the hole quality during fiber laser cutting in continuous wave and pulse modes. Statistical analysis was performed to optimize process parameters to minimize heat affected zone (HAZ) levels. Results indicated that thermal defects including matrix recessing/decomposition and protruding and uncut fibers were prevalent at hole entry and exit irrespective of processing parameters. Low level of laser power (800 W) and linear energy (50 J/mm) together with the pulse mode were preferred to minimize HAZ during fiber laser cutting of CFRP laminates, while the effect of a laser mode was negligible. Tensile strength of samples with open hole (6.0 mm diameter) cut by a fiber laser varied from 131 to 143 MPa, which depended to some extent on HAZ levels. Massive delamination, fiber breakage, and splitting bounds were the main damage/failure modes.