Simulation of the thermoforming process of glass fiber-reinforced polymeric components: investigation of the combined effect of the crosshead speed and material temperature

Thermoplastic-based composite materials are increasingly gaining the interest of many engineering sectors, among them the automotive. Their unique features, resulted from the thermoplastic matrix characteristics, such as their recyclability and their formability have given new perspectives in their use. Among the most promising fabrication methods of thermoplastic composite components is the thermoforming process, the press forming of a heated semi-finalized composite plate. This method, although requires a quite simple working station and can be implemented in mass production, demonstrates a series of disadvantages on the quality of the product. Among them, the variation of the thickness, formation of wrinkles, and overall undesired deformations are considered as defects that decrease the quality not only from the esthetical but also from the structural point of view. In the present work, a numerical analysis of the thermoforming process is conducted when applied to a box-shaped geometry. As an input for the material behavior during the process, mechanical tests are conducted at elevated temperatures. The flat and curved critical zones of the component are identified, and an analysis of the effect of the temperature and the crosshead speed of the molds on the thickness distribution are examined as well as the overall residual stress field. The results indicate a strong dependency on the quality of the product by these parameters of the process.