单向碳纤维增强碳化硅基复合材料的拉伸试验

采用手工精细加工板状双哑呤拉伸试件，并配以恰当的加强块，避免了因试件较短和加工等引起的夹持段压环，从夹持段拔出及试件在试验段根部破坏等问题，成功地实施了短试件（热压法制备的单向碳纤维增强碳化硅基体复合材料）的拉伸试验，微实时观察表明，由于界面强度非常弱，试件中首先出现因界面破坏而形成的沿纤维方向的裂纹，随着载荷的增加，裂纹数量迅速增多且裂纹均平行于纤维方向，最终，这些平行裂纹横向连接使试件被拉断，因此，对于界面强度过弱的单向纤维增强陶瓷基复合材料不可能产生横向的饱和裂纹。

Tensile test of unidirectional Cf/SiC composites

The tensile specimens are elaborated into bi-dumb-bell shape. By using a skillful reinforce, although the specimen is very short, the tensile test of unidirectional carbon fiber reinforced silicon carbide matrix composite (C f/SiC) made by hot-press method (HP) is conducted successfully, and the problems caused by shortness of the specimens and the limit of processing technique such as compression failure and pulling out in the gripped region, and failure near can be avoided. It is testified by real-time observation with micro-telescope that micro-cracks in direction of fiber, which are formed because of the weakness of interfacial strength, appear first in the specimens. Such cracks are all parallel to the fibers and get more and more with the increment of load. At last, the parallel cracks are connected and cut through in the transverse direction, making the specimen broken. It is proved that the saturated parallel cracks in the transverse direction do not appear in the unidirectional carbon fiber reinforced silicon carbide matrix composite with too weak interfacial strength.