SYMPOSIA PAPER Published: 01 January 1997

Determination of Transverse Shear Strength Through Torsion Testing


The in-plane characterization of composite materials is, in general, well understood and widely utilized throughout the aerospace industry. However, the use of composites in structural elements such as fuselage frames and rotorcraft flexbeams place large out-of-plane or through-the-thickness stresses for which there is little data. Efforts to determine the interlaminar shear strength of laminated composites have been hampered due to the nonlinear behavior of test specimens and the limitations of current analysis tools.

An inexpensive rectangular torsion test specimen was designed to determine the interlaminar shear strength, s23, of composite materials. Six different layups were fabricated of AS4/2220-3 carbon/epoxy unidirectional tape and tested in pure torsion. All of the specimens failed abruptly with well-defined shear cracks and exhibited linear load-deflection behavior. A quasi-three-dimensional (Q-3-D) finite element analysis was conducted on each of the specimen configurations to determine the interlaminar shear stress at failure. From this analysis, s23 was found to be 107 MPa for this material.

Author Information

Marcucelli, KT
Lockheed Martin Skunk Works, Palmdale, CA
Fish, JC
Lockheed Martin Skunk Works, Palmdale, CA
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Developed by Committee: D30
Pages: 85–100
DOI: 10.1520/STP19923S
ISBN-EB: 978-0-8031-5353-0
ISBN-13: 978-0-8031-2411-0