Advanced Strain Energy Accumulator: Materials, Modeling and Manufacturing

Energy efficiency is a prominent target in cost reduction efforts in a variety of machinery including manufacturing equipment and hybrid vehicles. In the course of developing a proof of concept strain energy accumulator on an Ankle Foot Orthosis (AFO) device, several technical barriers have been quantified in this device. Due to the hyperelastic nature of the material, the identification of an appropriate elastomer and the characterization of the strength properties and energy density of this elastomer are challenging tasks. Another technical barrier is the manufacturability of these elastomers including the high cost of fabrication and the limited elastomer formulations with high strength and large energy density. A quantitative analysis of these technical barriers is needed. A comprehensive modeling effort for the strain energy accumulator in 2-D and 3-D using the hyperelastic Mooney-Rivlin model was performed to validate the behavior of the strain energy accumulator. Additionally, various multiscale modeling methods, including the Mori-Tanaka, Hashin-Shtrikman, Lielens, Voigt and Reuss Methods were investigated to estimate the homogenized elastic modulus of carbon nanotube rubber resulting in homogenized modulus estimates ranging anywhere from a few times to almost 80 times the elastic modulus of rubber.