Characterizing Intralaminar Distal Crack and Delamination in Multidirectional Laminates Under Low Velocity Impact: Modeling Approach With Ultrasound Testing Validation

ABSTRACT Multidirectional laminated composites are essential for load‐bearing structures, especially under frequent impact loading. While existing modeling techniques simulate various impact damage modes, our understanding of the underlying mechanisms, specifically the initiation and progression of intralaminar distal cracks and interlaminar delamination, needs improvement. Validating these mechanisms is crucial for enhancing modeling accuracy and expediting the design process. In this work, we propose a three‐dimensional finite element modeling (3D FEM) approach aimed at elucidating the impact damage mechanisms in multidirectional carbon fiber reinforced polymer (CFRP). Our model incorporates cohesive zone models (CZM) to simulate the behavior of intralaminar cracks at distal points and assess their impact on interlaminar delamination at ply interfaces. Using high‐resolution pulse‐echo ultrasonic testing (UT) and an advanced algorithm, we provide a detailed layer‐by‐layer quantification of impact damage. Our modeling strategy effectively predicts both intralaminar and interlaminar damage modes across various laminate configurations and thicknesses, yielding results that align with experimental data. The strategy can be a significant step forward in understanding the low‐velocity impact damage in composite laminates. By enabling visualization of through‐thickness damage, the strategy may enhance the safety and efficiency of composite structures.