Numerical and experimental investigation of transverse low-velocity impact on thick-ply and thin-ply CFRP composite laminates

Date

2023-12-05

Author

Batmaz, Onur Ali

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The objective of this thesis is to investigate the low-velocity impact induced damage mechanisms observed within the cross-ply composite laminates with different ply-group thicknesses. This thesis is divided into two independent yet connected parts: In the first part, the objective is to model the in situ observations of low-velocity line impact experiments conducted by Bozkurt and Coker (2021) on [05/903]s CFRP laminates by constructing a high-fidelity finite element model that accurately captures the matrix cracking using a continuum damage model with LaRC05 initiation criterion, delaminations utilizing the cohesive zone model, and experimental boundary conditions by proposing a heuristic modeling approach that replicates the experiment boundaries through the assembly of spring elements. The simulations successfully replicated the in situ observations on the composite failure patterns and sequences and provided insights into underlying damage mechanisms, validating the capabilities of the numerical model. In the second part, the effect of ply-group thickness on damage mechanisms under low-velocity line impact is investigated by conducting in situ experiments on [04/904/02]s and [02/902/02/902/02]s CFRP laminates, and performing high-fidelity numerical simulations employing the finite element model constructed in the first part. Our experiments and simulations revealed that the damage mechanisms differ for different ply thicknesses, with the failure mechanism changing from only matrix cracking induced delamination to matrix cracking induced delamination with fiber breakage. The comparison between numerical simulations and experimental observations provides evidence supporting the so-called in-situ strength concept, where employing it played a very important role not only in global response but also in failure mechanism choice. This thesis demonstrates the necessity of high-fidelity modeling to accurately capture the high-fidelity in situ observations of dynamic failure mechanisms.

Subject Keywords

Low-velocity impact, Polymer-matrix composites, High-fidelity finite element analysis, In situ experiments, Damage mechanics

URI

https://hdl.handle.net/11511/107645

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Graduate School of Natural and Applied Sciences, Thesis