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复合材料的强度特性和断裂机理。在该材料中，将涂碳纤维的缎子机织物浸渍在基质粘结剂中，然后进行反复的成型、固化和燃烧过程。垂直加载到堆积层的试件和垂直加载到堆积层的试件分别称为V型试件和P型试件。两种试件都没有观察到不稳定的断裂，这是由于碳涂层改善了纤维的界面性质。P型试件的表观断裂韧性和抗弯强度均大于V型试件。这是由于不同堆积方向的断口形态不同造成的。在V型试件中，纤维的拔出和拉伸断裂在断裂过程中占主导地位，导致断裂分为两部分。另一方面，在P-试件中，在最终断口之前观察到层间的分离。宏观断裂模式的不同应表现在断裂抗力上。结合基体材料的强度特性，研究了纤维在现有材料中的增强效果。在这种情况下，通过考虑其体积密度来估计基质材料的强度特性。通过比较发现，每种类型的试件的表观断裂韧性和弯曲强度都大于对母材的估计值。只要将块体材料的强度与母材的强度进行比较，纤维增强的效果是肯定的。

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.