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10. Understanding the Damage Mechanisms in Composite Based on Local Deformation Measurements

BEHRAD KOOHBOR, ADDIS TESSEMA, SURAJ RAVINDRAN and ADDIS KIDANE

Abstract


The present work focuses on understanding the damage mechanisms in composites that are responsible for damage initiation and propagation. The local deformation heterogeneity and its influence on the failure response and different failure mechanisms are observed and analyzed through the use of digital image correlation (DIC) at mesoscales. Woven and unidirectional composites are subjected to tensile loading and their local deformation is measured in-situ as a function of fiber orientation angle. In addition the specimens are subjected to fatigue loading and the local damage nucleation and propagation is measured using optical microscope and digital image correlation and the local load transfer mechanisms as a function of fiber orientation is investigated. Finally, an effort is made to link the macroscopic failure mechanisms with damage initiation at a microstructural length scale. It was observed that, locally the deformation is highly heterogeneous, while the level of heterogeneity depends on the fiber orientation angle. The significantly different global mechanical responses and different loadbearing mechanisms observed in the off-axis specimen as a function of fiber orientation is explained.

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