Multi-scale experimental investigation of the viscous nature of damage in Advanced Sheet Molding Compound (A-SMC) submitted to high strain rates

Abstract This paper aims to present an experimental multi-scale analysis of quasi-static and high strain rate damage behavior of a new formulation of SMC composite (Advanced SMC). In order to study its capability to absorb energy through damage accumulation, Randomly Oriented (RO) and High oriented (HO) A-SMC composites damage has been investigated at both microscopic and macroscopic scales. A specific device has been developed in order to perform Interrupted Dynamic Tensile Tests (IDTT) which allows analyzing the evolution of the microscopic damage mechanisms occurring during rapid tensile tests. Several damage micro-mechanisms have been pointed out. The relative influences of these micro-damage events and their interactions have been related to the macroscopic damage behavior through the definition of microscopic and macroscopic damage indicators. Damage threshold and kinetic have been quantified at various strain rate for different microstructures and loading cases (RO, HO-0° and HO-90°). It has been shown at both scales that increasing strain rate leads to an onset of damage initiation together with a reduction of the damage accumulation kinetic. Moreover, the influence of the fiber orientation has been studied in order to emphasize the anisotropic strain rate effect at the fiber-matrix interface scale. The latter was related to the influence of the microstructure of A-SMC composites. Finally, on the basis of the whole experimental results, the microscopic origin of the viscous nature of the damage behavior of A-SMCs composites have been discussed and related to the influence of the strain rate and microstructure.