Structural Integrity Evaluation of Plastic Welding (Heat Stake) Tower in Door Trim Panels of Vehicles Using Finite Element Method

Structural integrity is a characteristic that must be evaluated during development of plastic parts as door trim panels. One of the critical areas in door trims is the interface between different parts that often use heat stakes due to process capacity and low costs. To predict issue on those interfaces, a methodology combining finite element analysis (FEA) and physical test results was applied to drive design in two door trim designs, with different material combinations. Aiming to support FEA conclusions, physical tests were performed to determine the maximum retention force that a heat stake withstands, indicating values about 168N for heat stakes of medium impact polypropylene blend >PP+EP(D)M-T<. and 216N for stakes of unfilled polypropylene copolymer >PP<. These values were used as upper limits for reaction forces provided by FEA in each heat stake under a load of 600 N at Pull Handle. The results for first door trim design indicated no structural issue in any heat stake, what generated a weld process investigation. Its conclusion indicated as root cause the weld quality. The results for second door trim design indicated an issue in one heat stake that required a relocation to redistribute the load. After including a new heat stake and redistributing their position, simulation indicated lower efforts, meeting the requirements. This methodology proved to be efficient to evaluate heat stakes performance during door trim development process.