ヘリカル繊維強化Cu/W複合材料の破壊靭性

Abstract

The fracture toughness of copper matrix composites reinforced with helical tungsten fibers has been investigated. Tungsten fibers 15 μm in diameter were formed into helices, whose helical radius and angle were 75 μm and 78.4°, respectively. They were embedded in a copper matrix by means of electrodeposition and vacuum hot-pressing techniques. The volume fraction of the fiber was 0.072. Single edge notched (SEN) type specimens with various notch depths were tensile tested, and their fracture behaviors were examined. The process of fracture, the appearance of fracture surface and the behavior of fiber-matrix interface were observed macroscopically as well as microscopically. The results were compared with those for the straight fiber reinforced composites.When tensile tested, the helical fiber reinforced composites showed loss notch-sensitivity than the straight fiber reinforced composites. A much larger plastic deformation zone was observed in front of the notch root for the former type of composite than for the latter type. Thus, the difference in the notch sensitivity between the two types of composites was attributable to the difference in the work of fracture, that is, the difference between the work done in plastic deformation of the matrix and that in breaking the fibers during the process of crack propagation. As a trial, the difference in fracture toughness between the two types of composites was represented quantitatively by using the nonlinear energy fracture toughness \ ildeGc or \ ildeKc.