Grant: Discovery Grants Program - Individual

Laser transmission welding (LTW) involves mating laser-transparent and laser-absorbent parts. Laser energy passes through the transparent component and is absorbed near the interface between the two parts where it melts the polymer, allowing diffusion and ultimately welding to occur. In some cases, the high-temperature polymer melt can flow due to thermal expansion and/or pressure driving forces. However, the flow can also lead to internal stresses and weldline read-through which are often undesirable. High temperatures can also cause material degradation. These high temperatures are often mitigated by the extremely short exposure times generally associated with high-speed LTW. The research on melt flow would develop experimentally validated models for intentional and unintentional melt-flow during 'contour' and quasi-simultaneous welding using Comsol(R) software. This work is important as previous studies have shown that this flow is responsible for residual stresses at the weld interface that can result in visually unacceptable marks on the exterior surface. The degradation work would use techniques such as the Friedman and Flynn-Wall-Ozawa methods to assess the thermal stability of polymers as a function of temperature and time using thermogravimetric analysis. This data would be coupled with simulated temperature-time data from the thermal modelling of various LTW processes in order to predict material degradation at the weld. Exploratory studies in my research group suggest that this work is feasible. These modelling studies would be validated by experimental work that uses a Rofin-Sinar 160W 'contour' welding system and a new Bielomatik 200W 'quasi-simultaneous' welder. Materials such as unreinforced and reinforced polypropylene, polycarbonate and nylon 6 would be used in these studies.