Viscoelastic-damageable behavior of sheet molding compound (SMC) composites

The variability of microstructures in the SMC composite induced by the manufacturing process is very important. The volumetric fraction and reinforcement orientation distribution significantly affect the material’s mechanical properties in both the elastic and nonlinear phases, associated with the development of damage phenomena. The distribution of local stresses between the reinforcements and the matrix is conditioned by the privileged orientation of the reinforcements. This, in turn, influences both the elastic mechanical properties and the degradation mechanisms, resulting in a degree of anisotropy. Additionally, SMC composites typically exhibit viscoelastic-damageable behavior. Therefore, it is necessary to characterize the microstructure accurately and comprehensively to effectively manage the mechanical behavior and damage of SMC structures. The research process involved investigating the viscoelastic behavior of randomly oriented Sheet Molding Compound (SMC) composites using Dynamic Mechanical Analysis (DMA) in the glass transition zone. By conducting a thorough analysis of the frequency and temperature-dependent behavior of the viscoelastic material, the experimental results obtained from the DMA test have been modeled. To demonstrate the effect of the matrix, two types of SMSs were utilized: standard SMC and Advanced SMC (A-SMC). The Cole-Cole experimental results fit well with the Perez model showing deformed semi-circles denoting the heterogeneity of the material system used in this study. The aim of this study is to link the WLF Law to the Perez model near the transition zone. The results demonstrated that dynamic properties can be plotted against temperature due to the strong correlation between the experimental and numerical data. Additionally, an increase in the strain rate results in a shift in the damage threshold and a reduction in damage kinetics. These effects are directly related to the damage thresholds and kinetics at the fiber-matrix interface.