PSI - Issue 61

Onur Ali Batmaz et al. / Procedia Structural Integrity 61 (2024) 305–314 Onur Ali Batmaz et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The model with proposed BCs yields better displacement values at failure than the fixed BCs, but slightly overpredicts the experimental results. However, this overprediction in the simulation correlates with the delay in the failure initiation time, which is deduced to result from the deviation of tested speci men’s reduced strength from the nominal values provided in Table 1. Despite the changes in the stiffness of the system, the maximum failure load level is found to be an ineffective metric for validating the FE model's global response as it yields similar values for fixed (10801 N) and proposed BCs models (10036 N), with a difference of less than 8%. It is worth noting that the critical load levels have been found to be approximately the same for impacts occurring at locations offset from the symmetry axes of the specimens and hence different BCs (Sun and Hallett, 2017), and even for different types of BCs of clamped and supported (Minak and Ghelli, 2008) under LVI loading in literature. 5. Conclusions In this study, we conducted a finite element simulation of the low-velocity impact experiment on the [0 5 /90 3 ] s CFRP beams from Bozkurt and Coker (2021). The simulation was carried out using ABAQUS/Explicit and includes a user implemented ply damage model with LaRC05 criterion for matrix cracking, and the built-in cohesive zone method for delamination. A heuristic approach for modeling BCs that involves replicating the experiment's boundaries by incorporating spring elements, which are tuned using deformation and strain data obtained from digital image correlation analyses, is proposed. The validity and influence of the proposed BCs modeling approach are assessed through detailed comparisons between numerical and experimental results. Comparing the displacement and strain data between the experiment and FE simulation with fixed supports revealed that constraining the displacement degrees of freedom by idealizing the clamped boundaries as fixed supports led to poor representation of deformation and overpredictions in strain fields. By employing the proposed BCs modeling approach, we achieved improved agreement with experimental findings in terms of deformation, strain fields, and delamination initiation time and displacement. While the global stiffness response decreased, the maximum failure load level remained consistent, aligning with findings in the existing literature. The accurate modeling of the experimental boundary conditions can also influence the dynamic damage characteristics including matrix cracking patterns, matrix cracking-induced delamination sequences, delamination growth mechanisms, large-scale contact and friction between crack surfaces, and these results are presented in Batmaz et al. (2024). Acknowledgements The authors acknowledge RÜZGEM (METU Center for Wind Energy Research) for the use of the facilities. References Adams, R.D., Cawley, P., 1988. A review of defect types and nondestructive testing techniques for composites and bonded joints. NDT International 21, 208 – 222. Batmaz, O.A., 2023. Numerical and experimental investigation of transverse low-velocity impact on thick-ply and thin-ply CFRP composite laminates (Master Thesis). Middle East Technical University. Batmaz, O.A., Bozkurt, M.O., Gurses, E., Coker, D., 2024. High-fidelity simulations of low-velocity impact induced matrix cracking and dynamic delamination progression in CFRP beams. Composites Part A: Applied Science and Manufacturing 177, 107960. 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. Camanho, P.P., Dávila, C.G., Pinho, S.T., Iannucci, L., Robinson, P., 2006. Prediction of in situ strengths and matrix cracking in composites under transverse tension and in-plane shear. Composites Part A: Applied Science and Manufacturing, CompTest 2004 37, 165 – 176. Cantwell, W.J., Morton, J., 1991. The impact resistance of composite materials — a review. Composites 22, 347 – 362. Catalanotti, G., 2019. Prediction of in situ strengths in composites: Some considerations. Composite Structures 207, 889 – 893. Chang, F.-K., Springer, G.S., 1986. The Strengths of Fiber Reinforced Composite Bends. Journal of Composite Materials 20, 30 – 45. Hibbitt, H., Karlsson, B., Sorensen, P., 2016. Abaqus analysis user’s manual version 6.10. Lopes, C.S., Camanho, P.P., Gürdal, Z., Maimí, P., González, E.V., 2009a. Low-velocity impact damage on dispersed stacking sequence laminates. Part II: Numerical simulations. Composites Science and Technology 69, 937 – 947. Lopes, C.S., Seresta, O., Coquet, Y., Gürdal, Z., Camanho, P.P., Thuis, B., 2009b. Low-velocity impact damage on dispersed stacking sequence laminates. Part I: Experiments. Composites Science and Technology 69, 926 – 936.