Experimental and numerical analysis of laser beam transmission in continuous fiber thermoplastic composites

Thermoplastics composites offer the possibility to use welding techniques for joining, due to the ability of the polymer constituting the matrix to melt when exposed to sufficient thermal energy. Laser technology is a good alternative for continuous joining of thermoplastics composites structures. However, presence of continuous fibers at a high fiber volume fraction generates laser beam diffusion. Optimization of the process requires understanding of the physics involved during laser propagation through continuous fibres composite media. Therefore laser beam diffusion and absorption at the substrate interface is modelled using ray tracing technique. Variability of simulated weld seam can be studied by a close enough representation of the composite microstructure. This variability can also be reproduced using experimental techniques. The knowledge of material properties constituting the composite and on the fibrous architecture are then sufficient to demonstrate the limits of the laser welding process without using trial and error developments. This approach can thus be broadened to any other laser application on semi-transparent and non-homogeneous structures.