Laser Three-Dimensional incremental Multi-Routine interval scanning for quantitative removal of CFRP: Defect Analysis, ablation mechanism and strategy optimization

Abstract

Deliberating on the necessity for precise removal of impaired sectors within the realm of aerospace industry's composite material rehabilitation, a novel method is proposed using a nanosecond laser to achieve quantitative removal of carbon fiber reinforced polymers (CFRP) via the three-dimensional incremental multi-routine interval scanning (3D-IMRIS). This study for the first time establishes a finite element simulation of multi-routine laser machining CFRP considering anisotropy, which aims at combining experiments and numerical simulation to analyze the ablation mechanism of CFRP in different modes, and optimize the removal strategy. The results reveal that the processing defects mainly consist of fiber expansion and thermal damage. This expansion can be attributed to the reconfiguration of carbon atoms in the fibers exhibiting a low level of graphitization, induced by transient heating and high-temperature gradients caused by laser interaction. In addition, the primary removal mechanisms for CFRP composites are photothermal ablation and thermo-mechanical peeling effect. The 3D-IMRIS mode effectively addresses the challenge of heat accumulation during laser processing by redirecting it towards heat utilization, resulting in a remarkable 94.2% reduction in the overall back Heat-Affected Zone (HAZ). Furthermore, the optimized scanning strategy increased material removal efficiency by 308.7% during 32 repeated scans, while the micro surface defects are also less.