ANALYSING THE EFFECT OF SPATIAL VARIABILITY OF MATERIAL PROPERTIES ON LVI DAMAGE IN COMPOSITES – A STOCHASTIC FINITE ELEMENT ANALYSIS

Kurzfassung

"The numerical simulation of low-velocity impact (LVI) damage in fiber-reinforced composites remains a challenging task. Numerous modeling approaches have been developed to simulate the damage modes matrix cracking, delamination and fiber breakage. Despite significant progress, discrepancies between numerically predicted and experimentally observed damage are still encountered in practice and the models remain computationally demanding. This underlines the need for more accurate and efficient modeling strategies. One aspect that is often neglected in the simulation of LVI damage is the spatial variability of material properties. Uncertainties in material parameters may arise from local variations in ply thickness, fiber volume fraction or porosity, potentially causing spatial variability in material properties. Although the importance of spatial variability in composites has been generally highlighted in the literature \cite{Sriramula2009} , it has not yet been addressed enough in the context of LVI. Most models assume constant material properties across the impact domain, either globally or ply-wise. This is somewhat questionable, given the highly localized and nonlinear nature of LVI – suggesting that even small uncertainties in local material properties could significantly influence impact damage. A study by \cite{Bogenfeld&Gorsky2021} further emphasized that scatter effects in LVI may arise from spatial variability. Therefore, the consideration of spatially varying material properties appears both reasonable and necessary. This work investigates the influence of spatial variability on LVI damage with a particular focus on delamination. A non-intrusive stochastic finite element approach is employed, incorporating spatially distributed uncertainties in relevant material properties within the critical impact region. The underlying meso-scale FE model combines well-established methods of continuum damage mechanics (CDM) and cohesive zone modeling (CZM). Using Monte Carlo simulations and surrogate models, a large number of realizations are evaluated to assess the sensitivity. The results demonstrate a significant influence on the delamination behavior."