Abstract
Delamination related research in fiber-reinforced composites has attracted considerable interest due to its significant practical importance. Significant difference in deformation patterns in the crack tip vicinity were observed for Mode I and Mode II delaminations and reported by several authors including [1-3]. A sequence of 45° (with respect to the crack plane) microcracks is believed to form beyond the Mode II crack tip in polymer composites. The propagation of a Mode II crack is believed to be a result of rupture and coalescence of these tension microcracks.A Philips XL30 ESEM scanning electron microscope was used for testing. A three-point bend stage was designed to perform in situ end notch flexure tests on a pre-cracked miniature (1.4” long and 0.25” wide) 24-ply unidirectional specimen. The material system utilized in the experiment was a toughened carbon epoxy unidirectional composite, IM7/977-3. The miniature specimen was cut out of a standard size (8” long, 1” wide) specimen after a shear crack formed in the course of ENF testing.
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