## 1 Introduction  
The application of Ni-Ti shape memory alloys has gained considerable interest in the medical field due to the application of the pseudo elastic nature of the material in the medical devices and implants [1]. Ni-Ti shape memory alloys (SMA) are used in medical technology for applications such as stent-grafts and guide wires [2]. However, as this material of Ni-Ti-SMAs has received increased attention in the medical field due to its functional properties, the release of Ni content towards allergy issues raises serious concern for bio medical applications [3]. To avoid Ni release from Ni-Ti- SMAs, the polymer coating is gaining interest in the areas of Ni-Ti alloys. This type of application could benefit from hybrid systems like polymer-coated shape memory composites. Hybrid composites, consisting of binary or more elemental systems involving polymer and Ni-Ti, have been developed in the last 5 years [4]. Some researchers have studied polymer composite actuators with SMA alloys and taking the advantages of the glass transition temperature of the polymer and the phase transition temperature of Ni-Ti alloys [5]. The effect of temperature on the phase transition in the hybrid composite opens up wide potential in shape setting behavior [6; 7; 8; 9] in the field of actuators and in the mechanical response of the composite. However, the mechanical behavior of hybrid composites reveals that the interfacial adhesion between the Ni-Ti ribbon and polymer interface plays a crucial role in adhesion property, thus controlling the thermal and mechanical response of the hybrid composite [10; 11]. Good adhesion between the polymer and the Ni-Ti ribbon on the surface quality holds a crucial step prior to the potential application of hybrid composites. This is because a hybrid composite of the shape memory alloy with polymer provides actuator motion with deflection, and, relying on their mechanical response, these composites of thin films are promising candidates for actuators in MEMs [12]. Ni-Ti shape memory alloys are most successful because of their good structural and functional properties and they can be combined with polymers, forming functional engineering composites (FECs). The growing demand in the sensors and actuators field could be fulfilled by FECs using shape-memory properties, such as bistable behaviour [13]. Ni-Ti shape memory alloys show thermodynamic behavior of three kinds of shape memory effect such as 1-way, 2-way, and pseudo elasticity. All shape memory effects depend on the phase transformation during high and low temperature processes. Polymeric materials are not as strong as alloys but have a number of attractive features, such as low density, good flexibility, good chemical stability, and low electrical conductivity. Poly (methyl methacrylate) (PMMA) was chosen because of its high tensile strength and higher elastic (Young's modulus) and shear modulus of 3.2 and 1.7 GPa, respectively. A number of parameters need to be considered prior to the composites design, including the alloy's surface conditions, the alloy's microstructure, the morphology of the polymer, the build of the metal-polymer interface, the influence of thin layers acting as a coupling agent between Ni-Ti and the polymer, the influence of different processing condition, and the influence of the thermo-mechanical load history. An alloy-polymer composite shows shape memory effect during cooling and heating. On cooling, the polymer acts as a bias spring and leads to shape change. On heating, a shape change occurs against the elastic deformation of the polymer. As a result, the composite as a whole could perform a two-way effect by reinforcing the one-way effect of Ni-Ti ribbon into the polymer matrix. The polymer matrix, in return, could act as a bias force into the material. A strong alloy-polymer interface is required to transfer the stress inside the polymer onto the shape memory alloy on cooling. The deformation of the interface during cyclic shape change in service can lead to delamination, resulting in a loss of memory.