Mechanics Behavioranalysis Of Multi-stable Shape-shifting Lattice Structure

A multi-stable structure is a structure which has numbers of load bearable stable configurations, with the help of external energy each stable configuration can deform greatly and snap to another stable configuration, namely the snap-through phenomenon. The characteristic of multi-stable structure makes it good prospects in the application on the morphing aircraft in the future.The cross-ply unsymmetric composite laminate will be bi-stable after cooling down from curing temperature and the bi-stable composite laminate (BCL) can curl along two perpendicular directions. A tri-stable lattice structure (TLS) is assembled by 4 rectangular bi-stable composite laminate (RBCL), and a multi-stable structure is structured when numbers of lattice structures are assembled together.This paper first investigates the mechanics prosperities of RBCL and TLC. The finite element model of RBCL is built, then the snap-through process of RBCL under center load is simulated and analysised, from the simulation it is discovered that the RBCL will go through two critical statuses before totally snaps. The predicted curvature of RBCL and corresponding critical snap-through load are compared with experiments and the effects of moisture absorption and laminate depth variation on them are analysised. After the study on RBCL, the finite element model of TLC is built, the deformation and snap-through of TLC under different loads and boundary conditions are analysised to evaluate the overall mechanics prosperities of TLC and the compatibility of deformation of its components. Based on the analysis of mechanics prosperities, two kinds of snap-through actuation methods with Macro-Fiber Composite (MFC) actuator and Shape memory alloy (SMA) actuator are simulated. A new actuation method which snaps the RBCL by changing the distribution of internal residual thermal stress of RBCL through heating local region of it is proposed in this paper, and the details are discussed and analysised. The effectiveness of this new snap actuation method is then verified in experiments; also this method is applied on the actuation of lattice structure in experiments and the compatibility of components'deformation is analysised.