SEDL / STP / STP1230-EB / STP14029S

Fracture of Glass-Epoxy Laminates Under Torsion and Combined Tension-Torsion Loads

Sen, JK
Senior R&E technical leader, McDonnell Douglas Helicopter System, Mesa, AZ

Fish, JC
Senior design specialist, Lockheed Martin Skunk Works, Palmdale, CA

Pages: 27    Published: Jan 1995

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Abstract

An experimental program and a finite element stress analysis were conducted to study delamination failures in glass-epoxy laminates subjected to torsion and combined tension-torsion loads. Nine laminate configurations with three ply orientations and three stacking sequences were evaluated. The failures consisted of through-the-thickness shear cracks in off-axis plies, which promoted delaminations at adjacent 0° interfaces. The predominant stress in all cases is the interlaminar shear stress, σxz. Dispersing off-axis plies away from the laminate midplane increased the torsion load-carrying capability but did not significantly increase twist capability. The failure torque and twist angles were higher under combined tension-torsion loads than under torsion load alone due to the increased torsional rigidity and the compressive interlaminar normal stress induced by the tension load.