Experimental and computational investigation of crack growth along curved interfaces

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2013

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Yavaş, Denizhan

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In this study, crack growth along curved weak interfaces is investigated experimentally and computationally. First, delamination of curved composite laminates subjected to axial load is studied computationally. Delamination in curved laminates is modeled using explicit finite element analysis in conjunction with cohesive zone method. It is observed that delamination is highly dynamic and that as the initial crack grows, the crack tip speed reaches the Rayleigh wave speed of the composite material with increasing laminate thickness and decreasing initial crack length. A second observation is that a secondary delamination in the arm region nucleates depending on the initial crack length and laminate thickness. Second, delamination of curved composite laminates subjected to shear loading is studied experimentally. Dynamic delamination growth is captured using high speed camera. It is observed that crack growth speed reachs the shear wave speed and an increase in the length of initial crack changes the crack growth from unstable to stable. Finally, crack growth along curved interface in polycarbonate beams subjected to shear loading is studied experimentally and computationally. In experiments, the full-field technique of photoelasticity is used in order to visualize isochromatic fringe pattern around the crack tip. In computational study, debonding at the curved interface is modeled using dynamic (explicit) finite element analysis in conjunction with cohesive zone methods. Stable and unstable crack growth regimes, depending on the initial crack length, are identified in agreement with energy release rate calculations. It is also observed that crack propagation speed can reach the shear wave speed.

Subject Keywords

Composite materials, Fracture mechanics., Photoelasticity., Surfaces (Physics).

URI

http://etd.lib.metu.edu.tr/upload/12616090/index.pdf
https://hdl.handle.net/11511/22707

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

D. Yavaş, “Experimental and computational investigation of crack growth along curved interfaces,” M.S. - Master of Science, Middle East Technical University, 2013.