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Scanning Electron Microscopy Investigation of Deformation in the Vicinity of a Mode II Crack Tip in Unidirectional Toughened Epoxy Composites

Published online by Cambridge University Press:  02 July 2020

E.V. Iarve  and
W. Ragland
E.V. Iarve
Affiliation:
U, University of Dayton Research Institute, Dayton, OH, 45469-0168
W. Ragland
Affiliation:
U, University of Dayton Research Institute, Dayton, OH, 45469-0168
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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.

Type
Advanced Composites
Information
Microscopy and Microanalysis , Volume 7 , Issue S2: Proceedings: Microscopy & Microanalysis 2001, Microscopy Society of America 59th Annual Meeting, Microbeam Analysis Society 35th Annual Meeting, Long Beach, California August 5-9, 2001 , August 2001 , pp. 1122 - 1123
Copyright
Copyright © Microscopy Society of America 2001

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References

references

1.O’Brien, T.K., “Composite Interlaminar Shear Fracture Toughness, Glic: Shear Measurment or Sheer Myth,” Composite Materials Fatigue and Fracture, v. 7, ASTM STP 1330, Bucinell, R.B., Ed. (1998), pp. 3–18Google Scholar
2.’'Brien, T.K., “Interlaminar Fracture toughness: the Long and Winding Road to Standardization,” Composites Part B (1998), pp. 57–62Google Scholar
3.Corleto, C., Bradley, W.and Henricsen, M., “Correspondence between Fields and Damage Zones Ahead of Crack Tip of Composites Under Mode I and Mode II Delamination,“ ICCM-VI Proceedings (1987), V.3, pp. 378–387Google Scholar