Active fracture control of a composite material system with SMA actuator and AE sensor

An Active control of the material degradation (i.e. damage accumulation, crack, delamination etc.) in service time and furthermore, an active prevention system of final sudden failure of machinery components and structures are studied by using shape memory TiNi fiber reinforced epoxy matrix composite model. First, the basic experimental study on active suppression of stress intensity (K value) at the crack-tip is performed by using photoelastic material. This is because the compressive stress effect is induced by means of direct current joule heating of the prestrained TiNi fibers embedded in epoxy matrix. Next, as an expansion of this study, another composite material system with SMA actuator as well as acoustic emission (AE) sensor is fabricated in which a typical AE outbreaks is utilized as a trigger to control the strengthening the bulk composite. The shape memory shrinkage of TiNi fibers is controlled under the commands from a microcomputer linked with AE sensor. This type of SMA intelligent (smart) material systems will be applicable for the elongation of the lives of material components, prevention of the sudden failure and maintaining the safety of the machinery devices, vehicles and building structures.