Ablation behaviour and HAZ prediction in laser cutting of GFRP: experiments and conical Gaussian heat source modelling

Laser cutting of glass fibre reinforced polymer (GFRP) faces a critical challenge. The formation of a heat-affected zone (HAZ) degrades machining quality and compromises mechanical performance. To address this, the present study develops a predictive methodology for HAZ formation during laser cutting of GFRP. The approach integrates numerical simulation with experimental validation, with particular emphasis on accurately capturing the energy distribution of the laser beam. A conical Gaussian heat source model was established to represent the converging beam geometry and the corresponding energy density distribution along the thickness direction. This model overcomes limitations of conventional surface or cylindrical heat sources, which inadequately describe the tapered cut kerf morphology. The model was implemented in ANSYS using a transient thermal analysis framework. Element birth-and-death and restart techniques were incorporated. These enable dynamic simulation of material removal and temperature field evolution throughout the cutting process. Systematic parametric investigations were conducted to evaluate the effects of laser power, cutting speed, and focal position on HAZ width and ablation behaviour. Laser cutting experiments were performed using a high-power fibre laser system. The simulated HAZ widths showed agreement with experimental measurements. Relative errors ranged from 3.52% to 8.33% across all parameter combinations. The validated model indicates a positive correlation between HAZ width and laser power, cutting speed, as well as focal position. Furthermore, the simulation elucidates a mechanism whereby spot size modulates the entry gap geometry at the cut front, thereby influencing ablation efficiency and the extent of thermal damage. The proposed methodology is physically accurate and computationally efficient. It offers a robust numerical tool for predicting HAZ formation in laser-cut GFRP. This supports process parameter optimisation and quality control in high-precision manufacturing of lightweight composite structures.