Interfacial properties of Shape Memory Alloy (SMA) reinforced polymer matrix composites can be enhanced by improving the interfacial bonding. This paper focuses on studying the interfacial stresses developed in the SMAepoxy interface due to various laser shot penning conditions. Fiber-pull test-setup is designed to understand the role of mechanical bias stress cycling and thermal actuation cycling. Phase transformation is tracked over mechanical and thermal fatigue cycles. A micromechanics based model developed earlier based on shear lag in SMA and energy based consistent homogenization is extended here to incorporate the stress-temperature phase diagram parameters for modeling fatigue.
Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is
an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential
application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness
as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the
structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present
paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors
like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in
composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing
in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied
for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A
comparison of the performance of these three types of embedded sensors is made to study their suitability in various
applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in
embedded sensor based SHM of composite structures.
Debonding of Shape Memory Alloy (SMA) wires in SMA reinforced polymer matrix composites is a complex phenomenon compared to other fabric fiber debonding in similar matrix composites. This paper focuses on experimental study and analytical correlation of stress required for debonding of thermal SMA actuator wire reinforced composites. Fiber pull-out tests are carried out on thermal SMA actuator at parent state to understand the effect of stress induced detwinned martensites. An ASTM standard is followed as benchmark method for fiber pull-out test. Debonding stress is derived with the help of non-local shear-lag theory applied to elasto-plastic interface. Furthermore, experimental investigations are carried out to study the effect of Laser shot peening on SMA surface to improve the interfacial strength. Variation in debonding stress due to length of SMA wire reinforced in epoxy are investigated for non-peened and peened SMA wires. Experimental results of interfacial strength variation due to various L/d ratio for non-peened and peened SMA actuator wires in epoxy matrix are discussed.