Department of Engineering Mechanics, Soft Matter Research Center, and Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou 310027, China.
Soft Matter. 2018 Nov 7;14(43):8717-8723. doi: 10.1039/c8sm01654b.
Surface instabilities have been extensively studied for homogeneous materials or film/substrate systems but with less studies on elastic graded materials. This paper studies surface wrinkling of an elastic graded layer theoretically, numerically and experimentally. A theoretical model for the onset of surface wrinkling with a sinusoidal mode is established. The predicted critical wrinkling strain and wavelength agree well with finite element analysis (FEA) for the elastic graded layer with exponentially decaying modulus. The influence of the layer thickness as well as the material properties on the critical conditions for the onset of surface wrinkling is fully investigated. The morphology evolution of surface wrinkling from FEA indicates the transitions of the sinusoidal mode to the arch mode and then to the period-doubling mode with a co-existing crease mode and folding mode, which agree well quantitatively with experimental observations. These results are helpful to provide physical insights into the influence of material inhomogeneity on surface instabilities.
表面不稳定性已经在均质材料或薄膜/基底系统中得到了广泛的研究，但在弹性梯度材料方面的研究较少。本文从理论、数值和实验三个方面研究了弹性梯度层的表面皱缩。建立了一个具有正弦模式的表面皱缩起始的理论模型。预测的临界皱缩应变和波长与指数衰减模量的弹性梯度层的有限元分析（FEA）吻合较好。研究了层厚和材料性质对表面皱缩起始临界条件的影响。从有限元分析中得到的表面皱缩的形态演化表明，正弦模式到拱模式的转变，然后到倍周期模式，并伴有共现的折痕模式和折叠模式，这与实验观察结果在数量上是一致的。这些结果有助于提供对材料非均质性对表面不稳定性影响的物理理解。
