Study Of Mechanical Properties Of Morphing Honeycomb Structures Based On Shape Memory Polymer

Honeycomb structures possess not only a lot of excellent mechanical properties such as lightweight, high specific modulus, high specific strength and outstanding designability, but also some special mechanical properties like achieving negative Poisson’s ratio by designing the configurations of honeycombs, and thus honeycombs have great applicable value because of all these characters. Shape memory polymer is one of the most popular smart materials. The advantages of honeycomb structures and shape memory polymers will be combined if honeycombs are made from shape memory polymers, and the active morphing honeycomb structures will then be realized. Appropriate mechanical properties will be obtained by changing the shape of honeycombs. Consequently, the realization of the morphing honeycomb structures is of great practical significance.This paper mainly discusses double arrowhead honeycombs and hexagonal honeycombs. Since there is less research on the double arrowhead honeycombs, a theoretical model about calculating in-plane elastic constants of double arrowhead honeycombs is presented and validated using the finite element method(FEM). Hexagonal honeycombs specimens with different geometrical parameters are manufactured. The in-plane mechanical properties of hexagonal honeycombs before morphing are studied by experiments and compared with related theory. Experimental results show that the prediction of the elastic constants of hexagonal honeycombs of the three theoretical models is reasonable. Then, the in-plane elastic modulus and Poisson’s ratio of shape memory polymer hexagonal honeycombs are tested after morphing and shape fixing. It proves that the change of angle between walls is the main deformation patterns of shape memory polymer honeycombs after heating. And the in-plane elastic constants of shape memory polymer hexagonal honeycombs after morphing and shape fixing are still consistent with the three theoretical models. Moreover, in order to study the deformation and recovery properties of morphing honeycombs, elastic modulus under different temperature, fixing ratio, recovery ratio are tested and analyzed. Also, morphing and recovery experiments are conducted. All these experiments show that morphing honeycomb structures based on shape memory polymers are reasonable. Finally, vibration mechanical properties of hexagonal honeycomb cantilever are studied through theoretical analysis and FEM. The relationships between the mininum frequency of hexagonal honeycomb cantilever in the height direction and the height of cantilever and the angle between walls are analyzed.