Theoretical analysis of the deformation of SMP sandwich beam in flexure

Abstract

Shape memory polymers (SMPs) can have a large frozen strain but with a very small recovery stiffness in comparison with shape memory metals or ceramics. To provide more deployable stresses for the application of actuators, sandwich beams consisting of a SMP core and two thin metallic skins were considered. The packaging behaviors of two types of SMP sandwich beams, aluminum/SMP/aluminum and steel/SMP/steel, were discussed. Due to the high compliance of SMP core on packaging condition that the testing temperature is above the activation temperature of the material, buckling and post-buckling are the essential deformation mechanisms of SMP sandwich beams under bending. Theoretical solutions were derived in studying such non-linear behaviors, including the initiation of critical buckling, post-buckling response, and final failure modes. Systematic parameter's analyses, e.g., buckling half-wavelength, amplitude, location of the neutral-strain surface in different packaging curvatures, were also presented.Keywords Shape memory polymer · Sandwich structure · Shape recovery · Buckling · List of symbols z m thickness of metallic skin z e thickness of SMP epoxy core z t thickness of tensioned SMP core z c thickness of compressed SMP core z t thickness of tensioned metallic skin z c thickness of compressed metallic skin ε eff effective strain E eff effective modulus of buckled skin ε z strain of SMP core γ xoz shear strain of SMP core w buckling displacement of metallic skin w e displacement of SMP core E m Young's modulus of metallic skin E e Young's modulus of SMP epoxy core G m shear modulus of metallic skin G e shear modulus of SMP epoxy core l length of SMP sandwich beam b width of SMP sandwich beam a buckling magnitude of metallic skin λ buckling wavelength of metallic skin m buckling mode number of metallic skin EI flexural stiffness of metallic skin ρ curvature radius M applied bending moment z ns distance from geometric midplane to neutral-strain surface T virtual work applied on the compressed region U m c compressed strain energy in unbuckled metallic skin U m b strain energy in buckled metallic skin U e strain energy in SMP epoxy core U S xoz shear strain energy of SMP core in the x − z plane U T z tensioned/compressed strain energy of SMP core along length direction

A molecular dynamics investigation of the deformation mechanism and shape memory effect of epoxy shape memory polymers

“…Owing to their prominent advantages, e.g., low density, high frozen strain, low manufacturing cost, easy processability, wide shape transition temperature, and partial biocompatibility, SMPs have wide potential applications, such as in actuators, sensors, and smart devices. During the last two decades, extensive attention has been paid to the fabrication and design of new SMPs and their composites, including SMP matrices [9][10][11][12][13], particle-or fiber-reinforced SMP composites [13,14], SMP foams [15,16], and sandwich structures [17,18]. Meanwhile, numerous works have reported the thermomechanical behavior and shape memory effects of SMPs and their composites [19][20][21][22].…”

Investigation of buckling behavior of carbon nanotube/shape memory polymer composite shell

“…Here the material properties of CNT/SMP are above T g (T g is the glass transition temperature) in that case CNT/SMP are in a steady status. The material parameters are listed in Table 1 18,19 . Mises stress distributed in shell structure increases at the same time and lateral sides stress increases rapidly as shown in Fig.3(2).…”

Numerical study of smart honeycomb core using shape memory polymers

“…SMPs have many advantages, including manufacturing simple, low cost, highly dimensional deformability, controlled recovery temperature, biocompatibility, biodegradability, and the like . SMPs are mainly used in power electronics, deployable space structures, self‐assembly robots, biomedical devices, textiles, and national defense industries . Because the polymers show remarkable characteristics caused by interplay at multiple length and time scales, further research depends on an understanding of the principles for the hierarchical structure and behaviors of the polymers.…”