Date of Award


Publication Type

Master Thesis

Degree Name



Civil and Environmental Engineering


Amorphous, Plastic Welding, Thermoplastic, Vibration Welding, Weld Factor, Weldability


Rajeev Ruparathna




This research paper analyzes the material compatibility, in terms of weld strength, of thermoplastics currently in use for external lighting applications. Signal lamps typically consist of a transparent lens welded to an opaque housing. The different types of polymers used in housing materials are polycarbonate (PC), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), and blends thereof. The different types of transparent lens materials are polymethyl methacrylate (PMMA) and PC. The specific thermoplastic material grades in this document are kept confidential. The scope of the work is to determine plaque-level compatibility of materials as a function of weld strength performance and to create material-level weld strength guidelines regarding optimal welding parameters for component level design/development and quality. This is achieved through a parametric study, strength testing welds with dissimilar (chemically different) materials through a varying set of welding parameters. Material combinations are found which can reach the weaker material’s bulk strength and other combinations are found which have very poor compatibility, as confirmed by the weld factor. A great majority of the weld combinations’ strengths increase with weld depth, and most dissimilar material welds continue to increase in strength with even further weld penetration. Optimal weld parameters are determined for each material combination.