Additively Manufactured Hybrid and Hierarchical Auxetic Structures: A Review

Auxetic structures have gained extensive popularity because of their unique mechanical properties such as negative Poisson’s ratio, high strength to weight ratio, energy absorption capabilities, high shear modulus and vibro-acoustic properties. These structures are widely used in automotive shock absorbers, crash box, fasteners, sound absorbers, air seat cushions, and biomedical applications. Over the last few years, additive manufacturing (AM) techniques are widely used for fabrication of these structures. conventional auxetic structures possess limited plateau stress and energy absorption. In order to overcome limitation of conventional auxetic structures, various researchers have proposed hybrid and hierarchical auxetic structures and investigated mechanical properties and energy absorption capacity. The present paper describes a detailed literature review on mechanical properties and energy absorption capacity of additively manufactured hybrid and hierarchical auxetic structures under static and dynamic loading conditions. Further, there is a need of conducting experimental study on these structures for improving mechanical properties such as strength, stiffness and energy absorption capacity. There is enough scope of designing and studying deformation behaviour of hybrid hierarchical structures for maximizing mechanical properties under different static and dynamic loading conditions for specific application.