Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Soft Matter. 2017 Nov 8;13(43):7969-7978. doi: 10.1039/c7sm01828b.
We introduce a new experimental system to study the effects of pre-stretch on the buckling patterns that emerge from the biaxial compression of elastomeric bilayer shells. Upon fabrication of the samples, releasing the pre-stretch in the substrate through deflation places the outer film in a state of biaxial compression and yields a variety of buckling patterns. We systematically explore the parameter space by varying the pre-stretch of the substrate and the ratio between the stiffness of the substrate and film. The phase diagram of the system exhibits a variety of buckling patterns: from the classic periodic wrinkle to creases, folds, and high aspect ratio ridges. Our system is capable of readily transitioning between these buckling patterns, a first for biaxial systems. We focus on the wrinkle to ridge transition. In the latter, we find that pre-stretch plays an essential role and that the ridge geometry (width, height) remains nearly constant throughout their formation process. For the localized ridged patterns, we find that the propagation of the ridge tip depends strongly on both strain and stiffness ratio, in a way that is akin to hierarchical fracture.
我们引入了一个新的实验系统，用于研究预拉伸对双轴压缩下弹性双层壳出现的屈曲模式的影响。在样品制备过程中，通过放气释放基底中的预拉伸，使外膜处于双轴压缩状态，并产生各种屈曲模式。我们通过改变基底的预拉伸和基底与膜的刚度比来系统地探索参数空间。系统的相图显示出各种屈曲模式：从经典的周期性波纹到皱纹、褶皱和高纵横比脊。我们的系统能够在这些屈曲模式之间轻松转换，这在双轴系统中尚属首次。我们专注于波纹到脊的转变。在后一种情况下，我们发现预拉伸起着至关重要的作用，并且脊的几何形状（宽度、高度）在其形成过程中几乎保持不变。对于局部脊状图案，我们发现脊尖端的传播强烈依赖于应变和刚度比，这类似于分级断裂。
