K-Calibration of Unidirectional Metal Matrix Composites

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Abstract
Load-displacement curves were obtained for center notch unidirectional boron/aluminum and borsic/titanium composites. Far field displacements, obtained by means of two standard clip gages, 1 and 0.25 inch long, respectively, were used to establish the variation of global compliance with crack length. The local compliance curve was obtained from the crack opening displacement (COD) measured across the crack surfaces by means of the laser interferometric technique. The Interferometric Displacement Gage (IDG), which is more sensitive to the appearance of damage at the crack tip, yielded nonlinear load displacement curves and seemed to better characterize the fracture behavior of composites. The experimental com pliance curves and the K-calibration results were found to be in good agreement with analytical predictions. The K-calibration curves of the com posites studied were found to be almost equal to that of the isotropic materials; both compliances were predictable by using the isotropic K- calibration.