A Study of the Fracture Behavior of Unindirectional Fiber- Reinforced Composite Using Coherent Gradient Sensing (CGS) Interferometry |
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Authors: | C Liu AJ Rosakis RW Ellis MG Stout |
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Affiliation: | (1) MST-8, Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, U.S.A.;(2) Graduate Aeronautical Laboratories, California Institute of Technology, Pasadena, California, 91125, U.S.A |
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Abstract: | The feasibility of using Coherent Gradient Sensing (CGS) interferometry for studying the fracture behavior of unidirectional
fiber-reinforced composites is investigated in this paper. First, the solution for the deformation field surrounding the tip
of a crack in an orthotropic material is summarized. Specifically, the most singular term in the asymptotic expansion is explicitly
presented. Then, the quantities that relate to the CGS measurements are derived in terms of the spatial position, stress intensity
factors, and material constants. Based on these results, synthetic CGS fringe patterns are plotted numerically, and the effects
of material anisotropy and crack-tip mixity on the shape of CGS fringe pattern are investigated. In addition, a finite difference
interpretation of CGS fringes caused by the finite spacing of the CGS diffraction gratings is taken into account in the simulation.
Finally, the initiation fracture toughness and the subsequent resistance curve behavior of a particular unidirectional graphite/epoxy
composite are measured using the CGS method. The optically measured stress intensity factors compare successfully to values
obtained from the load measurements and the available analytical solutions.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | Composite fracture optical method stress intensity factors fracture toughness |
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