Optimisation of laser welding process for thermoplastic composite materials with regard to component quality and cost

Abstract

The laser transmission welding (LTW) process is optimised with regard to quality and cost for welded thermoplastic stiffeners on aircraft's fuselage skin. A generic optimisation concept developed in previous author's work is applied. Quality and cost sensitivity analyses were performed to derive material dependent quality function and process dependent cost estimation relationships. Quality function and cost estimation relationships are exploited to derive iteratively the optimal welding parameters. The derivation of the important heating process parameters arises from the numerical simulation of the process thermal cycle by means of finite element method. To optimise the LTW process with respect to quality and cost, a software tool, namely the LTSM-OPT tool, is extended to the LTW process. The optimal process parameters of the LTW system along with the optimal heating cycle for welding thermoplastic lap joints are obtained, in the form of a reference welding temperature along with an allowable process window, which meets the minimum quality requirements. The results of the study were successfully exploited by an aeronautic industry to weld stiffeners on aircraft's fuselage panel.