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Abstract Recently laterally pre-stretched pure shear deformation is considered as the most compatible and easier way of achieving higher actuation performances of dielectric elastomer actuator due to improvement of its dielectric strength and pull-in stability. However, an accurate experimental investigation and modelling criteria of dielectric elastomer under various lateral pre-stretches up to failure have still not been reported in details. In the present work, different pre-stretch levels are incorporated in commonly used material, VHB 4910 under pure shear loading at sufficiently slow strain rate to obtain stress-stretch curves up to failure. It has been also established that Ogden model parameters obtained by fitting pure shear test data are more accurate for pre-stretched pure shear modelling than those obtained from commonly used uniaxial pull test. Highlights • Laterally pre-stretched pure shear experiments are performed till failure. • Failure stretch keeps on decreasing with increasing lateral pre-stretch. • Reduction of stiffness in the transverse direction is obtained due to lateral pre-stretching. • Ogden model fitting parameters are obtained from pure shear experimental data. • Model using parameters from pure shear data provides better accuracy compared to that obtained from uniaxial data. [ABSTRACT FROM AUTHOR]

Aponeuroses are stiff sheath-like components of the muscle-tendon unit that play a vital role in force transmission and thus locomotion. There is clear importance of the aponeurosis in musculoskeletal function, but there have been relatively few studies of aponeurosis material properties to date. The goals of this work were to: 1) perform tensile stress-relaxation tests, 2) perform planar biaxial tests, 3) employ computational modeling to the data from 1 to 2, and 4) perform scanning electron microscopy to determine collagen fibril organization for aponeurosis tissue. Viscoelastic modeling and statistical analysis of stress-relaxation data showed that while relaxation rate differed statistically between strain levels (p = 0.044), functionally the relaxation behavior was nearly the same. Biaxial testing and associated modeling highlighted the nonlinear (toe region of ~2–3% strain) and anisotropic (longitudinal direction linear modulus ~50 MPa, transverse ~2.5 MPa) tensile mechanical behavior of aponeurosis tissue. Comparisons of various constitutive formulations showed that a transversely isotropic Ogden approach balanced strong fitting (goodness of fit 0.984) with a limited number of parameters (five), while damage modeling parameters were also provided. Scanning electron microscopy showed a composite structure of highly aligned, partially wavy collagen fibrils with more random collagen cables for aponeurosis microstructure. Future work to expand microstructural analysis and use these data to inform computational modeling would benefit this work and the field. Image 1 [ABSTRACT FROM AUTHOR]