A solid-shell based finite element model for thin-walled soft structures with a growing mass

This paper presents a solid-shell based nonlinear finite element model for the numerical analysis of the growth of thin-walled soft structures. A multiplicative decomposition of the deformation gradient tensor is employed to describe the total shape change induced by the mass growth and the elastic deformation. Then a solid-shell model with only displacement degree of freedom is developed and the shell kinematics of deformation considering the growth effect are constructed. The enhanced assumed strain and assumed natural strain methods are employed in the finite element algorithm, so that numerical difficulties arising from the Poisson-thickness locking, volumetric locking and shearing locking phenomena can be avoided. In the finite element formula, an additional term related to the growth in the tangent modulus emerges and an equivalent body force that acts as an additional driving force for the deformation of the materials from the numerical aspect arises. Several representative two- and three-dimensional examples with inplane and volumetric growth modes are presented to demonstrate the efficiency and accuracy of the proposed model. The model is also proved to be a versatile tool for the modeling of many fascinating growth-induced shape changes and actuating behaviors observed in nature and engineering. (C) 2018 Elsevier Ltd. All rights reserved.