Micromechanics Analysis of Space Simulated Thermal Stresses in Composites. Part II: Multidirectional Laminates and Failure Predictions

• Published in: Journal of reinforced plastics and composites 1991-09, Vol.10 (5), p.522-539
• Main Authors: Bowles, David E., Griffin, O.H.
• Format: Article
• Language: English
• Subjects: failure; finite element method; spacecraft; thermal stress
• ISSN: 0731-6844; 1530-7964
• DOI: 10.1177/073168449101000507

A finite element micromechanics approach was used to predict thermally induced stresses in fiber reinforced polymer matrix composites at temperatures typical of spacecraft operating environments. The influence of laminate orientation was investigated with a simple global/local formulation. Thermal stress calculations were used to predict probable damage initiation locations, and the results were compared to experimentally observed damage in several epoxy matrix composites. Multidirectional [O2/ ±θ]s laminates had larger predicted matrix stresses than unidirectional [0] laminates. The stresses in creased with increasing lamination angle θ, and resulted in large tensile radial stresses at the fiber/matrix interface, that were not present in unidirectional laminates. Thermally in duced matrix failure predictions, using a failure criterion based on the maximum radial in terfacial stress and the ultimate radial interfacial strength, were in excellent agreement with experimental data. This criterion was able to accurately account for the influence of both laminate configuration and constituent properties. Predictions based on the bulk matrix tensile strength or on lamina stresses (computed from laminated plate theory) and strengths were in poor agreement with experimental data.