SEDL / STP / STP1003-EB / STP10028S

Use of Torsion Tubes to Measure In-Plane Shear Properties of Filament-Wound Composites

Foley, GE
Mechanical engineer and research materials engineer, U.S. Army Materials Technology Laboratory, Watertown, MA

Roylance, ME
Mechanical engineer and research materials engineer, U.S. Army Materials Technology Laboratory, Watertown, MA

Houghton, WW
Director, Advanced Composites Laboratories, West Newton, MA

Pages: 16    Published: Jan 1989

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Abstract

This paper discusses an investigation into the applicability of torsion of filament-wound tubes to determine the in-plane shear properties of ±45° Kevlar and S-glass/epoxy com-posites. Results show that this test method can be used to determine in-plane shear properties of these materials, although failure by buckling must be prevented if valid in-plane shear strength values are to be obtained. The Kevlar/epoxy fails under in-plane shear by compressive microfrac-ture of the compressively loaded -45° regions of the tube at about half the strength of the S-glass/ epoxy. This failure appears as a yield point in the stress-strain curve of the Kevlar/epoxy, and is accompanied by a largely irrecoverable drop of more than an order of magnitude in the shear moedulus. The results also indicate that the in-plane shear strength of a filament-wound composite depends upon its winding pattern, with the use of tighter crossover spacing producing a lower strength composite.