Strength Characteristics and Fracture Mechanism of Advanced Continuous Ceramic-Fiber Reinforced Ceramic-Composite

研究了连续碳化硅纤维增强碳化硅基体的强度特性和断裂机理。在材料中，将碳包覆纤维缎面织物浸渍在基体粘结剂中，然后经过反复的成型、固化和燃烧过程。将垂直于堆垛层和平行于堆垛层的试件分别命名为v形试件和p形试件。两种类型的试样均未观察到不稳定断裂，这是由于碳纤维涂层改善了界面性能。p型试样的表观断裂韧性和抗弯强度大于v型试样。这是由于不同的堆叠方向导致了断裂形态的不同。在v型试样中，纤维断裂过程以拉拔和拉伸断裂为主，导致纤维分离成两部分。另一方面，在p -试样中，在最终断裂之前观察到层间层的分离。宏观断裂模式的差异应体现在抗断裂性能上。通过对比基体材料的强度特性，研究了纤维在复合材料中的增强效果。在这种情况下，基体材料的强度特性是通过考虑其体积密度来估计的。通过比较，发现每种试样的表观断裂韧性和弯曲强度都大于基体的估计值。只要将块状材料的强度与基体强度进行比较，就可以肯定纤维增强的效果。

Strength characteristics and frature mechanim of a silicon carbide matrix reinforced by continuous silicon carbide fiber were investigated. In the material, satin woven cloths with carbon-coated fiber were impregnated in matrix binder, followed by repeated process of molding, cure and burning. Specimens subjected to loading vertically to stacking layrs and those pallarel to stacking layrs were designated as V-specimen and P-specimen, respectively. Unstable fracture was not observed for both types of specimen, because of interface property refined by carbon coating on fiber. Apparent fracture toughness and bending strength in P-specimen were found to be larger than those in V-specimen. This was resulted from difference in the fracture morphology depending on stacking direction. In V-specimen, pull-out and tensile rapture of fibers were dominant in fracture process, and resulted in separation into two parts. On the other hand, in P-specimen, separation in interlaminate was obserbed before final frature. The differnce in macroscopic fracture pattern was supposed to appear in the fracture resistance. The reinforcement effect by fiber in the present material was investigated by ccmlparison with strength characteristics of the matrix material. In this case, the strength characteristics of the matrix material were estimated by taking account of its bulk density. By the comparison, apparent fracture toughness and bending strength of each type of specimen were found to be larger than those estimated for the matrix. The effect of fiber reinforcement was concluded to be affirmed as long as strength of the bulk material was compared with that of matrix strength.