Modelling the heating of GFRP by high-energy laser radiation considering the pyrolysis of binder material

Abstract

Composites are subject to a wide variety of physicochemical processes when exposed to laser radiation. Pyrolysis, flow of reaction volatiles and char formation have a considerable influence on the heating process.In this contribution, some of these processes and their impact on the thermal and optical properties of glass-fiber reinforced polymers (GFRP) will be discussed with focus on charring and its impact.Modelling of the thermal and mechanical behavior with all processes occurring will be difficult to realize. With prioritization and concentration on the main processes of pyrolysis, the spatio-temporal thermal evolution was calculated by numerical FEM calculations. Based on the Arrhenius equation, the thermo-dynamical conversion rate was calculated. This transfer from virgin composite to charred material also affects the optical behavior. Absorption and scattering were considered by the photon diffusion equation in the unmodified material, whereas in charred material the laser radiation was assumed to be absorbed already within a small penetration depth.