APPLICATION OF THE PLATE TWIST TEST TO LAMINATED COMPOSITES.
Technical rept. Jun-Sep 67,
AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OHIO
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The laminated plate theory is used to show that the applicability of the plate twist test for measuring shear modulus of laminated fiber-reinforced composites is limited to cross-ply layups and unsymmetric angle-ply layups. Numerical examples for symmetric plus or minus 45-degree boron-epoxy and glass-epoxy composites are used to illustrate the magnitude of the error generated when this test is used incorrectly. Results show errors of over 100 can occur. It is also concluded from laminated plate theory that the shear modulus for angle-ply composites can be considerably higher than the shear modulus of a unidirectional ply oriented at an angle of zero degrees to the plate axes. For example, the shear modulus of each layer of a plus or minus 45-degree boron-epoxy angle-ply composite containing 70 fiber by volume is approximately 3,500,000 PSI, while the composite shear modulus is 10,500,000 PSI. Author
- Laminates and Composite Materials