Analysis and optimisation of soft electroactive laminated composites

The aim of this study was to improve the overall electromechanical response of dielectric composite actuators. The microstructures of rank-1 and rank-2 laminates, composed of two materials of varying dielectric and shear moduli, were optimised for four types of actuation due to an applied nominal electric field. A homogenization theory, established in the literature in finite electroelasticity for rank-1 layered composites, was specialized to the actuation types to develop a closed-form solution. A similar lamination methodology was then derived for rank-2 laminates to obtain a numerical solution. Expressions for specific sequentially laminated microstructures of rank-1 and rank-2 type were obtained so as to determine optimum microstructural configurations for maximum longitudinal stretch. These results were obtained iteratively using the Newton-Raphson method for a set of simultaneous equations. Results for rank-1 laminates obtained in finite strain were found to produce actuation strains higher than those obtained by previous authors in small strain. Rank-2 laminates then presented an improvement in actuation strain compared to those obtained in small strain by the same authors. Ratios of shear and dielectric moduli were varied to obtain different contrasts and four parameters were defined to contribute to rank-2 laminate performance, namely two lamination angles and two volume fractions. For all actuation types, rank-2 longitudinal stretch presented strong improvement from rank-1 laminates. Electromechanical instability was observed in rank-2 laminates for two of the four actuation types and a trade-off requirement was demonstrated between applied nominal electric field, shear and laminate microstructure for optimum performance. At least a tenfold enhancement of phase electric fields was obtained for rank-2 laminates and the current configuration of lamination angles highlighted differences to the reference configuration. The ratios of shear and dielectric moduli were lastly perturbed and further enhancement of maximum longitudinal stretch obtained as a foundation for future work