Research engineer, NASA Langley Research Center, Hampton, VA
The current work formulated a micromechanical analysis of a cross-ply laminate and calculated the thermal residual stress in a very thick [0/90]ns silicon-carbide/titanium laminate. Results were also shown for a unidirectional laminate of the same material. Discrete fiber-matrix models assuming a rectangular array of fibers with a fiber volume fraction of 32.5% and a three-dimensional, finite element analysis were used. Significant differences in the trends and magnitudes for the fiber, matrix, and interface stresses were calculated for the unidirectional and [0/90] models. Larger hoop stresses calculated for the [0/90] model indicate that it may be more susceptible to radial cracking when subjected to mechanical loading than the unidirectional model. The axial stresses in the matrix were calculated to be slightly larger for the [0/90] model. The compressive axial stresses in the fiber were significantly larger in the [0/90] model. The presence of the cross-ply in the [0/90] model reduced the constraint on the fiber, producing radial interface stresses that were less compressive, which could lead to earlier failure of the fiber-matrix interface.
Paper ID: CTR10383J