Metacomposite structure with sign-changing coefficients of hygrothermal expansions inspired by Islamic motif

摘要

A composite metamaterial honeycomb that exhibits sign-switching expansion coefficients has been introduced herein, in which at certain conditions the microstructures display resemblances of an ancient Islamic art. This is achieved by the use of two types of materials within each unit cell: a cross rod of very high expansivity and a frame linkage of insignificant expansivity. When the frame linkage material is of zero expansivity, sign-toggling of the thermal and moisture expansions occurs at the original state such that any deviation from the original environmental condition always result in overall shrinkage of the metacomposite. The capability of this meta-composite to exhibit sign-flipping of expansion coefficients not only demonstrates the tunability of composite properties in situ, but also to do so across opposing signs without any active control. In addition, the currently introduced metamaterial design pays homage to an ancient Islamic pattern.