Co-authors​ :

 Mohammadali SHIRINBAYAN (FRANCE), Joseph FITOUSSI  

The automotive industry prioritizes Zero- and Low-Emission Vehicles (ZLEV). The European Commission regularly sets targets to enhance service life and reduce greenhouse gas emissions in new vehicle generations. Sheet Molding Compounds (SMCs) emerge as an alternative to metal parts due to their lightweight nature, exceptional chemical resistance, and long-lasting service, particularly in structural components for automobiles. Advanced sheet molding compounds (A-SMC) are a new generation of alternative materials to steels for applying in automotive structures. It contains a vinyl ester matrix involving mineral charge (CaCO3) reinforced with around 50% (in mass) of discontinuous bundles of glass fibers. It is crucial to assess the crashworthiness and conduct multi-scale mechanical characterizations of this automotive material. In this paper, the microstructure of A-SMC composite was analysed by different methods. The influence of fiber orientation in two configurations plates of Randomly Oriented (RO) and Highly Oriented (HO) was investigated under quasi-static shear loading. For HO plate, two tensile directions were chosen: HO-0° (parallel to the Mold Flow Direction (MFD)) and HO-90° (perpendicular to the MFD). A novel shear testing setup was designed after optimization via ABAQUS FE code to achieve constant strain rate. Consequently, the effects of strain rate (from quasi-static to 10 s-1) on shear properties and visco-damage behavior of A-SMC composite has been studied. The findings indicated that HO-0° samples exhibited lower strength in shear loading. The investigation into strain rate effects on shear tests confirmed the correlation between mechanical properties, such as ultimate strength and ultimate strain. The Shear modulus remained constant regardless of the strain rate until around 5 s-1, after which it showed a significant increase. Finally, a multi-scale damage study confirmed that predominant damage mechanism is decohesion at fiber/matrix interface under shear loading. Initially, crack propagation mainly occurred along the circumferential surface of fibers, particularly those oriented at 0° to the load direction. The cracks then begin to grow perpendicular to the load direction through the matrix until final failure occurs with a pseudo-delamination mechanism.