Effects of laser beam scattering on through-transmission welding of polymers

We present here a study of the scattering phenomena in semi-transparent polymers induced by their compositions in the through-transmission laser welding processes. In a 1^st part the scattering of a laser beam into a polymer is explained as well as the mathematical modeling currently used. In a 2^nd part a numerical study of the beam scattering in different inhomogeneous media is realized. We show here that this phenomenon is of prime importance for the welding process and that the simulation allows a good estimation of it. The results are used into a finite elements program, in order to determine the thermal field and the structure behavior under laser excitation and to simulate a through-transmission laser welding process on PMMA polymers and compared with experimental data. We show here the interest of a good understanding of the scattering phenomena and the possibilities to simulate it.