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The development of additive manufacturing processes (3D printing), applied to metal alloys, is in line with the industry's current need for optimization, cost and development time reduction, allowing the construction of representative prototypes with equivalent materials / mechanical characteristics and customized end products, such as prostheses and brake system calipers, for which Ti6Al4V alloy has wide application due to biocompatibility and resistance. In addition, the need for more resilient materials is becoming ever greater at same time that failures need to be avoided. The occurrence of failures in structural components generates consumer dissatisfaction, which can result in serious accidents and the use of numerical tools during the project contributes to its prediction. For this, it is necessary to know the structural characteristics of the material resulting from the printing processes to guarantee robust designs.

Among the most important finishing structures of a vehicle interior, the door trim panels reduce external noises, present ergonomic concepts generating comfort, improve appearance, and provide objects storage, knobs and buttons. The panels usually composed of several molded parts (trim, armrest, etc.) connected to each other also have structural function as support closing loads, protect occupants of door internal mechanisms, energy absorption in side impacts and resist misuse conditions. Therefore, these trims usually made of polymeric materials must to present good structural integrity, demanding appropriate connections between components to have good load distribution. The connections between parts can be made using bolts, interference fits (like self-locking), welding tubular plastic towers (heat stakes), or clips (such as snap fits) and last two are the most common due to be cheap and with good retention.

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.