Constitutive modeling for the tear fracture of artificial tissues in human-like soft robots

Abstract

Artificial tissues made of fiber-reinforced polymeric materials typically show biological tissue-like mechanical properties, which motivates its usage in designing and constructing human-like soft robots. Inspired by nature, soft robots aimed to perform a wide range of human-like motions and work cordially with the human environment effectively. In some applications, soft robots may be torn or damaged for unknown reasons. In this regard, this work presents the constitutive modeling for the tear fracture and its impact on the mechanical behavior of artificial tissues used in the novel field of soft robotics. Firstly, a continuum mechanics-based deformation model for artificial tissue is developed and experimentally validated to justify that tissues have inherent anisotropic behavior, which cannot be neglected while modeling such materials. Secondly, the tear fracture model is derived to investigate the effect of concerning physical parameters linked with the tearing phenomenon of artificial tissues. A well-known Griffith criterion is adopted to investigate a particular fracture test of mode-III, namely the trousers test, where two legs of a cut specimen are pulled horizontally apart. The findings of the proposed model solution indicate that a significant impact on the cut position due to the stretch gradient arises during the gradual transition through one leg to another. Additionally, the fracture toughness of artificial tissue increases with increasing fiber inclination and limiting chain extensibility, corresponding to a given critical driving force.