Modeling of intersonic delamination in curved and thick composite laminates under quasi-static loading

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2014
Gözlüklü, Burak
One of the widely used geometrically complex parts in advanced commercial aircraft is L-shaped composite laminates in which mixed-mode delamination failure is reported. Dynamic delamination under quasi-static loading is studied using explicit finite element method in conjunction with Cohesive Zone Modeling (CZM). A 4-noded interface element working with Bilinear (BL), Xu-Needleman (XN) and ratedependent bilinear (RD) CZMs are implemented in ABAQUS/Explicit. The interface elements are validated with benchmark tests from literature for each fracture mode subjected to static and dynamic loading. A 12-ply woven-fabric Graphite/Epoxy Lshaped composite laminate is modeled with BL cohesive layers placed in all interfaces. Macromechanical and micromechanical behaviors are compared to experiments and are found to be in good agreement. Single delamination initiates in mode-I and smoothly transitions to mode-II during propagation at intersonic crack tip speeds reaching 3500 m/s. Shear Mach waves fronts, follower reflecting waves, train of pulses in normal stresses and vortex like particle velocity patterns are observed. The analysis is repeated using XN and RD CZMs. XN CZM exhibited early slippage of plies due to low initial stiffness, whereas RD CZM provided the best agreement with experiments. This thesis reports the intersonic crack propagation in engineering parts for the first time, which was previously observed in earthquakes.

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Citation Formats
B. Gözlüklü, “Modeling of intersonic delamination in curved and thick composite laminates under quasi-static loading,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.