Chaudhury M K, Kim K H
Department of Chemical Engineering, Lehigh University, Bethlehem, PA 18015, USA.
Eur Phys J E Soft Matter. 2007 Jun;23(2):175-83. doi: 10.1140/epje/i2007-10171-x.
A rigid-glass prism (square or rectangular base, rectangular cross-section) is sheared off a thin film of silicone elastomer bonded to a glass plate by applying a tangential force at various distances above the prism/elastomer interface. At a given tangential force, the prism starts to slide on the elastomeric film. As the sliding velocity, thus the frictional force, is progressively increased, an elastic instability develops at the interface that results in the formation of numerous bubbles. These bubbles, the lateral dimension of which is comparable to the thickness of the film, move across the interface with speeds 1000 times faster than the overall sliding speed of the glass prism against the PDMS film. It is found that the glass prism continues to slide on the elastomeric film as long as the applied shear stress is less than a critical value. During sliding, however, a normal stress is developed at the interface that decays from the front (i.e. where the force is applied) to the rear end of the prism. When the normal stress reaches a critical value, the prism comes off the film. The critical shear stress of fracture increases with the modulus of the film, but decreases with the thickness following a square root relationship, as is the case with the removal of rigid punches from thin elastomeric films by normal pull-off forces.
通过在棱镜/弹性体界面上方不同距离处施加切向力，将一个刚性玻璃棱镜（方形或矩形底面，矩形横截面）从粘结在玻璃板上的硅橡胶弹性体薄膜上剪切下来。在给定的切向力作用下，棱镜开始在弹性体薄膜上滑动。随着滑动速度进而摩擦力逐渐增加，界面处会出现弹性失稳，导致形成大量气泡。这些气泡的横向尺寸与薄膜厚度相当，其在界面上移动的速度比玻璃棱镜相对于聚二甲基硅氧烷（PDMS）薄膜的整体滑动速度快1000倍。研究发现，只要施加的剪应力小于临界值，玻璃棱镜就会继续在弹性体薄膜上滑动。然而，在滑动过程中，界面处会产生一个法向应力，该应力从棱镜前端（即施加力的位置）向后端逐渐衰减。当法向应力达到临界值时，棱镜会从薄膜上脱落。断裂的临界剪应力随薄膜模量的增加而增大，但随厚度的增加呈平方根关系减小，这与通过法向拉力从薄弹性体薄膜上移除刚性冲头的情况相同。
