采用Z-Pin增强体的3D炭/炭复合材料层间断裂行为

采用炭纤维平纹织物和精细Z-pin制备了新型3D炭纤维预制件。炭基体采用等温化学气相沉积和高温煤沥青高压浸渍炭化制备。短梁剪切试验和开口拉剪试验用来表征Z-pin增强体对剪切破坏模式的影响。短梁剪切失效模式为似塑性，而拉剪失效模式为非似塑性破坏。分析了产生此现象的机制，短梁剪切假塑性失效由炭／炭复合材料叠层中纤维束内、纤维束间和叠层间微裂纹扩展形成，而产生拉剪失效的单一层间裂纹扩展不引起宏观假塑性现象。采用Z-pin作为提高层间剪切强度的增强体间隔1．5mm比间隔2，5mm可提高剪切强度40％～50％，陔技术将成为3D炭／炭复合材料预制体制备更为先进的技术．

Interlaminar fracture behavior of 3D C/C composites using z-pins as through-thickness reinforcements

A novel form of preform consisting of plain weave fabric and z-pin through-thickness reinforcements was prepared. The carbon matrix was derived from a combination of isothermal chemical vapor infiltration and high pressure impregnation-carbonization of coal tar pitch. The interlaminar shear strength of the composites was characterized by a short beam interlaminar shear test and a double edge-notched tensile shear test. Hyper pseudoplastic fracture behavior of short beam interlaminar shear of 3D C/C composites was found, which is ascribed to the propagation of microcracks formed between laminations within and between bundles. Z-pins can have effective control over the progress of pseudoplastic fracture. True shear failure, which is characterized by the double edge-notched tensile test, shows non-pseudoplastic fracture progress that is ascribed to shear sliding occurring only within one interlamination. Both short beam interlaminar strength and double edge-notched tensile strength is 40～50 % higher for a z-pin density of 1.5 mm interval than for a z-pin density of 2.5 mm interval. Employing z-pins as through-thickness reinforcements has advantages over a 3D weave.