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

研究了TiNi纤维增强金属(Al)或聚合物(环氧基)复合材料的形状记忆效应，以提高其力学性能，并阐明其增强机理，特别是拉伸强度和抗疲劳性能。以形状记忆TiNi纤维(Af)为增强体，在高于奥氏体终温度的温度下，随着预应变的增加，其屈服应力和疲劳抗力均有所提高。通过TiNi/环氧复合材料模型裂纹尖端光弹条纹的变化，从实验上探讨了断裂韧性K值的提高机理。这些强化效应是由于预应变TiNi纤维在A_f以上加热收缩到其初始长度时在基体中产生的压应力场所致。基于分析模型的预测与实验符合得很好。其次，作为本研究在主动断裂控制方面的扩展应用，开发了一种带有SMA致动器和声发射(AE)传感器的智能复合材料系统，该系统以典型的声发射(AE)爆发为触发器，在与声发射传感器相连的微型计算机的加热指令下，通过TiNi纤维的形状记忆收缩来控制块体复合材料的增强。

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.