Modelling laser transmission welding of thermoplastic polymers and composites

激光传输焊接（LTW）涉及到激光透明部件和激光吸收部件的配合。激光能量穿过透明组件，并在两部分之间的界面附近被吸收，在那里它熔化了聚合物，允许扩散并最终发生焊接。在某些情况下，由于热膨胀和/或压力驱动，高温聚合物熔体可以流动。然而，流动也会导致内部应力和焊缝穿透，这通常是不希望看到的。高温还会导致材料降解。这些高温通常通过与高速LTW相关的极短曝光时间来缓解。对熔体流动的研究将利用Comsol(R)软件开发“轮廓”和准同步焊接过程中有意和无意熔体流动的实验验证模型。这项工作很重要，因为先前的研究表明，这种流动是焊接界面残余应力的原因，可能导致外观上无法接受的痕迹。降解工作将使用诸如Friedman和Flynn-Wall-Ozawa方法之类的技术，使用热重分析来评估聚合物的热稳定性作为温度和时间的函数。该数据将与来自各种LTW过程的热建模的模拟温度-时间数据相结合，以预测焊缝处的材料退化。我课题组的探索性研究表明，这项工作是可行的。这些建模研究将通过使用Rofin-Sinar 160W“轮廓”焊接系统和新的Bielomatik 200W“准同步”焊机的实验工作进行验证。这些研究将使用诸如未增强和增强的聚丙烯、聚碳酸酯和尼龙6等材料。

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.