Laser welding of thermoplastic matrix composites

• Autor(a) principal: Almeida, Nuno Miguel Sequeira de
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33712
• topic: Laser transmission welding; Composites; Polymers; Thermoplastics; Parameter optimization; Polyamide; Nd:YAG; Pulsed welding

In recent years, the need for lightweight constructions has increased the demand for polymers and composites, following the design principle known as material substitution. Consequently, new welding methods such as LTW (Laser Transmission Welding) have emerged to overcome the limitations of conventional ones. The aim of this study was to find the best parameters for pulsed Nd:YAG LASER welding of thermoplastic polymers to thermoplastic matrix composites. The effect of laser welding parameters such as peak power, pulse width, overlap, beam diameter and speed on weld strength was investigated. The results obtained were used to infer the process window, which in turn served as a guide to find the optimal parameters. During the experimental procedure, it was observed that it is difficult to achieve consistent results when laser welding dissimilar polymers, even when they are compatible. Laser welding of a polymer to a composite with the same material in the matrix is comparatively easier to weld. From the results obtained, it can be concluded that weld strength (N/mm) increases with Peak Power, Pulse Width, Overlap and beam diameter up to a threshold, decreasing beyond this point. Regarding scan speed, the weld strength achieves higher values at low welding speeds, as the literature suggests. Nevertheless, the highest weld efficiency (95% weld bead efficiency and 35% weld joint efficiency) is obtained at low Peak Powers in combination with high overlap percentages.