Numerical Simulation of Low-Velocity Impact on [05/903]s CFRP BeamConsidering Accurate Experimental Conditions O. A. Batmaz∗, M. O. Bozkurt, E. Gurses, D. Coker Department of Aerospace Engineering, Middle East Technical University, Ankara 06800, Turkey ∗ onur.batmaz@metu.edu.tr Keywords: Polymer-matrix composites, Low-velocity impact, Finite element method Composite materials are extensively employed in aerospace, renewable energy, and transportation industries due to their exceptional strength-to-weight ratios. However, their weak interfacial characteristics make them vulnerable to out-of-plane loadings, including lowvelocity impact (LVI) events, which can result in internal failures like matrix cracking and delamination. While experiments can determine the failure behaviour and resistance of composites to LVI, there is a growing interest in replacing a significant portion of experimental efforts with physically accurate numerical simulations. To validate these simulations and their associated damage models, direct observation of the dynamic evolution of damage becomes important. In a recent experimental study by Bozkurt and Coker [1], [05/903]s CFRP beam specimens subjected to transverse impact loadings were analysed with full-field digital image correlation method, and in-situ progression of matrix cracking followed by dynamic progression of delamination were captured. In this study, we constructed the finite element (FE) model of the LVI experiments presented in [1]. Our objectives are to reproduce the observed damage accurately and to investigate its dynamic progression beyond the limitations of experimental observations. The numerical model is constructed in the commercial FE package ABAQUS/Explicit and incorporates the following features. For modeling ply damage, we employed a three-dimensional continuum damage mechanics approach, utilizing the LaRC05 damage initiation criterion implemented through a user-defined subroutine (VUMAT) with an explicit integration scheme. To simulate delamination damage, we employed the cohesive zone method and inserted built-in cohesive elements at the 0◦/90◦ interfaces. To replicate the experimental boundaries, we proposed a heuristic approach for modeling boundary conditions (BCs) by assembling spring elements at the corresponding boundary nodes. The stiffness of these springs was determined based on minimizing the differences between the full-field displacements and strains obtained from both the experiment and simulation. The numerical simulations showed good agreement with the experimental results in terms of failure load, sequence, and initiation location. The influence of experimental boundaries on the dynamic damage characteristics is illuminated by utilizing the proposed BCs approach. By comparing the numerical findings with the experiments, we gained further insights into the damage growth in composite beams under LVI loading. References [1] Bozkurt, M.O., Coker, D., (2021). In-situ investigation of dynamic failure in [05/903]s CFRP beams under quasi-static and low-velocity impact loadings. International Journal of Solids and Structures, 217–218, 134–154. 130
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