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Combination of thermoforming process of thermoplastic laminates reinforced with continuous fibers associated with injection molding of discontinuous reinforced thermoplastic in order to add stiffeners or specific functions at precisely defined locations is increasingly used for applications which require structural lightweight parts. This technique is well suitable to use in substituting metals and thermosetting composite materials by thermoplastics based composites particularly in automotive industries allowing to the various advantages which can offer thermoplastics composites like: lightness (compared to metals), toughness and recyclability (compared to thermosets).
In this study which is made in the framework of FUI project ARIZONA, complex shaped components were fabricated from thermoplastic prepreg combined with injected composite based on PA6 matrix. The prepreg lay-up was consolidated as a plate, pre-heated with an IR heating system, and put inside the mold. The plate was then thermoformed by closing the mold and over-molded in one step.
The objective of this study was to characterize the thermal-mechanical and mechanical properties of the laminate, injected and over-molded zones in relation with the processing parameters for different environments use (temperature and moisture). Thermal-mechanical properties were investigated by the Mechanical Dynamical Analysis (DMA) in range of temperature between -130°C to 200°C and dynamical frequency was varied from 0.1 to 30 [Hz]. Three-point bending and tensile tests were used to investigate the mechanical properties. Micro-tomography was realized to investigate in 3D reinforcement architecture and failure scenarii. The results show clearly the influence of the moisture absorption on the mechanical properties of each composite.
