DESIGN OF INTELLIGENT MATERIAL SYSTEM BY COMBINING THE CONTROL WITH EVALUATION OF SHAPE MEMORY ALLOY

为了提高TiNi纤维增强金属（Al）或聚合物（环氧树脂）基复合材料的力学性能，阐明其增强机理，特别是抗拉强度和抗疲劳性能，研究了TiNi纤维增强金属（Al）或聚合物（环氧树脂）基复合材料的形状记忆效应。在高于奥氏体终止温度的温度下，TiNi形状记忆纤维增强体的屈服应力和疲劳抗力随预应变的增加而增加。通过TiNi/环氧复合材料模型裂纹尖端光弹性条纹图的变化，对断裂韧性K值提高的机理进行了实验探讨。这些增强效应是由于预应变TiNi纤维在加热到A_f以上时收缩到其初始长度而在基体中产生的压应力场所致。基于分析模型的预测结果与实验结果吻合较好。其次，作为本研究在主动裂缝控制中的扩展应用，具有SMA驱动器和声发射（AE）的智能复合材料系统研制了一种声发射传感器，该传感器利用典型的声发射爆发作为触发器，在指令下开始控制TiNi纤维的形状记忆收缩增强块体复合材料与AE传感器相连的微电脑加热。

The shape memory effects of TiNi fiber reinforced metal (Al) or polymer (epoxy) matrix composites were developed for enhancing their mechanical properties as well as for clarifying the strengthening mechanisms, especially, of tensile strength and fatigue resistance. The yield stress and fatigue resistance were observed to increase with prestrain at temperatures above austenitic finish temperature of shape memory TiNi fiber (A_f) as a reinforcement. The increasing mechanism of fracture toughness K value was also discussed experimentally by the changes of photoelastic fringe pattern at a crack-tip of TiNi/epoxy composite model. These sttengthening effects were found to be atrributed to the compressive stress field in the matrix which is induced when the prestrained TiNi fibers shrink to its initial length upon heating above A_f. The predictions based on the analytical model agree reasonably well with the experiments.Next, as an expanded application of this study for active fracture control, a smart composite material system with SMA actuator as well as acoustic emission (AE) sensor was developed in which a typical AE outbreaks was utilized as a trigger to start to control the strengthening the bulk composite by shape memory shrinkages of TiNi fibers under the commands of heating from amicrocomputer linked with AE sensor.