Abstract
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.
Highlights
Nowadays, all the industrial sectors are oriented towards the implementation of advanced materials in several engineering applications aiming to exploit at maximum their potentials
Considering the geometrical complexity of the component studied in the present work, it was divided into these 3 zones of interest that consist of 1 zone at the center (Zone 1) with 2 irregularities, 1 zone without any geometrical interference (Zone 2) and 1 zone with an elongated geometrical oval-shaped bulge (Zone 3)
A finite element simulation campaign was conducted based on a viscoelastic approach that aimed to predict the outcome of the thermoforming of a single plied box-shaped component, using both a woven textile E glass/PP and a UD E glass/PA6 material
Summary
All the industrial sectors are oriented towards the implementation of advanced materials in several engineering applications aiming to exploit at maximum their potentials. This fact requires complex experimental characterization of the tensile, shear and bending mechanical behaviour or the GFRTPs in temperatures which are, most of the time, near the melting point of them as well as the friction interaction characterization between the composite material and the stamping tools These tests are widely investigated and implemented in a significant number of works. Among these works mentioned should be those of Chen et al [18] and Hamila et al [19] where the objective is the accurate simulation of the deformation of the reinforcing constituent while being formed, Haanappel et al [20] where the torsion test in elevated temperatures is proposed for characterizing the shear behaviour of thermoplastic composites and Harrison et al [21,22], as well as Boisse et al [23], where the efficiency of the bias extension and the picture frame tests is assessed. The results of reveal a strong dependency of the output of the process on the material temperature and the stamping speed both for the case of the woven textile and the UD thermoplastic composite part
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