THERMO-MECHANICAL ANALYSIS OF COMPOSITES UNDER COMBINED CONDUCTION HEATING AND LARGE DEFLECTION BENDING

摘要

A novel conduction heating apparatus that combines thermal loading with large deflection bending is introduced, and its effectiveness for thermo-mechanical stress analysis was investigated. By clamping composite specimens (M40J/PMR-II-50, [0,90]_s, a uni-tape cross-ply) on the radial sides of half cylinders having two different radii (78.74mm and 37.96mm), three different in-plane strains including a no strain condition were applied to the composites. Three different thermal loading experiments, 1) 23℃ to -196℃ to 250℃, 2) 23℃ to 250℃, and 3) 23℃ to -196℃ were performed as a function of mechanical in-plane strain levels. The apparatus was excellent enough to generate cracks related to the in-plane stresses (or strains) on plies. The quadratic failure criteria solution based on the thermal residual stresses shows a good agreement with the experimental results at low temperatures, but does not supply a good agreement at high temperatures. A weak adhesion of fiber/matrix interface at high temperatures (250℃) might cause the de-bonding at the interface and subsequent exposure to -196℃ caused the intensive crack propagation.