论文和技术资料

The modelling of the optical and thermal response of translucent composite materials submitted to a high-energy laser irradiation is very complex, as glass fibers-reinforced polymers are highly heat-sensitive and their physical behavior dramatically changes at high temperatures. All begins with the travelling of the laser beam within the material. Part of the light energy is absorbed, but the presence of a polymer and fibers, both transparent but of different refractive indexes, also generates light scattering. The volume absorption of those collimated and diffused laser fluxes leads to a fast heating of the material, which quickly results in the degradation of the polymer phase and drastically changes its optical properties. The material is now opaque and most of the laser energy is absorbed on the surface, inducing a much faster heating rate of the irradiated area. The material soon reaches a thermal equilibrium due to thermal losses, and drilling can occur. This dynamic process has been simulated in 3D with the Heat Transfer module of COMSOL Multiphysics, based on material inputs identified at room-temperature by standard optical and thermodynamical methods, or chosen arbitrarily. Heat release due to the phase change of the polymer is also taken into account, as well as convective and radiative losses on both sides of the sample. Numerical results are in agreement with experimental observations, the irradiated surface of the material reaching more than 1000 °C in a few seconds. The temperature of the specimen also quickly drops down when the laser irradiation stops, leaving an irreversible degradation of the composite material onto the irradiated area but also a few millimeters within the volume, a consequence which can threaten the overall integrity of the sample for its initial purpose.