Filamentary Composite Laminates Subjected to Biaxial Stress Fields.
Final technical rept. 3 Mar 70-31 Aug 73,
IIT RESEARCH INST CHICAGO ILL
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A study is presented in which four biaxial test specimens suitable for composite materials are evaluated -the off-axis coupon, the bulge plate, the tubular specimen and the crossbeam. The off-axis coupon and the tubular specimen were selected as having the greatest potential for biaxial characterization of composites, and further development work is presented for these two specimens. Improved specimen design and data reduction techniques are presented for the off-axis coupon. Also, a novel technique for testing tubes without mechanical attachment is presented. End constraints are virtually eliminated from the tubular specimen by introducing tractions through the use of hydraulic pressures. Torque is applied through a non- constraining end spline coupling. Feasibility tests were conducted with both test methods, primarily on the Narmco 5505 boron-epoxy system, both in laminate and unidirectional form. The biaxial data is presented and the results are discussed. The maximum strain, Hill and Tsai-Wu failure criteria are used to predict biaxial behavior of composite materials. Hypothetical design allowable interaction diagrams are presented and compared to the biaxial data. Author-PL
- Laminates and Composite Materials
- Test Facilities, Equipment and Methods