Influence of the specimen thickness on low velocity impact behavior of composites

In this work, the influence of specimen thickness on low velocity impact behavior of carbon-epoxy composite laminates is studied. Plates with different thicknesses were tested under low velocity impact using a hemispherical impactor. The internal damage was mainly constituted by delaminations which were evaluated through the inspection of the impacted plates by the ultrasonic C-scan technique. It was observed that delaminations increase with plate thickness. In order to better understand the physical phenomenon explaining this result, a progressive damage model was used to simulate composites behavior under low velocity impact. In this context, a three-dimensional numerical analysis considering interface finite elements, including a cohesive mixed-mode damage model, which allows simulating delaminations onset and growth between layers, was performed. Good agreement was obtained between experimental and numerical analysis, which validated the proposed procedure. In addition, the proposed numerical methodology allowed identification of physical phenomena related to the influence of plate thickness on delamination size.