Whole-field strain analysis and strength prediction of fiber laser machined CFRP laminate at elevated temperature

High power fiber laser was proved to be feasible to cut carbon fiber reinforced plastic (CFRP) laminate with high efficiency, while the machined quality on mechanical performance was not fully understood. This paper studied the effect of high temperature up to 220 degrees C on tensile strength degradation and strain distribution of unidirectional CFRP laminate with open hole machined with fiber laser. Differential scanning calorimetry (DSC) was firstly employed to determine the glass transition temperature (T-g) of polymer-matrix composite. Digital image correlation technique was applied to evaluate whole-field strain distribution and crack propagation/evolution of CFRP laminate featured with open hole under tensile loading. Results showed that the tensile strength of laser machined CFRP laminate degraded significantly during working in high temperature above 100 degrees C. The value of strains distributed around center hole was highly related to the elevated temperature and applied load levels. Splitting was the prevalent failure mode of CFRP laminate under elevated temperature up to 180 degrees C. Finally, semi-empirical model was developed for evaluating tensile performance of laser machined CFRP laminate at elevated temperature based on regression analysis.