THE EFFECT OF FIBER ORIENTATION ON MATRIX PLASTICITY AND FRACTURE-BEHAVIOR OF SIC FIBER-REINFORCED TITANIUM MATRIX COMPOSITES

The effect of fiber orientation on the matrix plasticity and fracture behavior of SCS-6 fiber-reinforced Ti-15V-3Al-3Cr-3Sn composites was studied. The laminates used in this study were [0]6, [0/+/-45]s, and [90/-/+45]s. Three-point bending tests were conducted on chevron-notched specimens to determine the crack initiation energy, fracture toughness, and fracture strength as a function of notch length. The critical energy release rate was determined from the slope of the crack initiation energy versus notch length curve. The damage evolution and development of the matrix plastic deformation zone at the notch tip during the crack initiation and propagation as a function of fiber orientation were also determined. The relationships among the crack-tip matrix plastic deformation zone size, the critical energy release rate, and notch strength of the composites were discussed.