Experimental investigation of dynamic delamination in curved composite laminates

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2014
Uyar, İmren
In the aerospace industry, high demand for lightweight structures is fostering the use of composite laminates in a wide variety of shapes, as primary load carrying elements. However, once a composite laminate takes a highly curved shape, such as an L-shape, high interlaminar stresses induced in the curved region causes dynamic delamination formation. This thesis discusses the experimental investigation of delamination in L-shaped CFRP composite laminates under quasi-static shear loading. An experimental setup is designed to apply pure quasi-static shear loading. Three lay-up configurations are investigated: [0/90] fabric, uni-directional [0] and cross-ply [90/0] CFRP composite laminates. The effect of material lay-up, inner radius and thickness on the failure process is studied. The load displacement curves are recorded and the subsequent dynamic delamination is captured with a million fps high-speed camera. The failed specimens are analyzed under a microscope. A single delamination is found to grow in a single load drop for [0/90] fabric laminate. Multiple delaminations in a single load drop are observed in the failure of the unidirectional laminate whereas a sequential delamination at each discrete load drop is seen in the cross-ply laminate. The geometrical constraints such as the thickness and the inner radius are also found to be affecting the failure process. Delamination in all cases is observed to be propagating in the arms at the intersonic speed of 2200 m/s. This study presents the first known experimental evidence of intersonic delamination in composite laminates.

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Citation Formats
İ. Uyar, “Experimental investigation of dynamic delamination in curved composite laminates,” M.S. - Master of Science, Middle East Technical University, 2014.