Study On Preparation Method Of SMA Fiber Composites Specimen With Strength Control Function

Shape memory alloy (SMA) as a kind of intelligent materials has a shape memory effect and super elasticity. It can be used as a sensor and driver to use. With the SMA fiber compounded in metal or epoxy matrix the intelligent composite material formed. The material properties such as modulus, strength and damping can be changed when the temperature of SMA fiber in intelligent composite material changed.This paper studied the preparation process in order to make out the SMA composites whose strength can be controlled by SMA. The composites have the actical value of engineering. Combining with the heat conduction and heat convection of theory, this paper deduced the relationship between fiber surface temperature and the SMA electricity current in the SMA epoxy resin composite material column model. We successfully solve the problem that temperature of SMA fiber is not easily measured in SMA epoxy composite in the heating process. Then, this paper studied the recovering characteristics of SMA fiber by using dc power heating. At last we found that maximal recovering stress of NiTi shape memory alloy fiber is as high as 747 MPa.This paper studied handmade preparation process. We used PVC plastic mold to ensure specimen surface is smooth. The ends of the bulkhead was used to fix the fiber and prevent the resin leaking out along the fiber. We determined the best curing conditions to improve the high temperature resistant performance of specimens. We designed fiber fixed devices that can guarantee the prestrain of the SMA fiber not recover in high temperature curing process. The specimens have reliable quality and stable mechanical performance.The high prestrain SMA fiber can provide larger recovering force, however, high prestrain SMA fiber produce large shearing force around fiber and matrix in the recovering process. The large shearing force will damage the interfacial property of SMA fiber epoxy composite. Therefore, this paper got the tensile strength of different prestrain SMA fiber composites which are tested by the tensile test. The experimental results show that the tensile strength of the composite specimens increase with the prestrain of SMA fiber and the debond strain decrease with the prestrain of SMA fiber.(?) order to improve interfacial property of SMA fiber epoxy composites, this paper compared the tensile curves of the knot SMA fiber and straight SMA fiber composites specimens that have the same prestrain SMA fiber and finally found that the fracture strain was much larger than the straight. The knot of SMA fiber was very good to overcome the debonding of SMA fiber and epoxy matrix.