We peel a highly stretchable silicone (Ecoflex), thickness H and width B, sandwiched between two inextensible films. When the peel front advances steadily in the elastomer, the peel force reaches a plateau ${\mathit{F}}_{ss}$, and the ratio 2${\mathit{F}}_{ss}$/B is commonly reported as the toughness of the elastomer. Our data show that this “peel toughness” is not always a material constant, but can depend on the thickness H and width B. We interpret the data in terms of two fundamental ideas in fracture mechanics. First, as the ratio B/H increases, the deformation in the elastomer changes from the plane stress to the plane strain conditions, so that the stress state ahead the peel front changes from biaxial to triaxial tension. We show that the elastomer under triaxial tension reaches higher stress and damages more than the elastomer under biaxial tension. Second, when the inelastic zone around a peel front is not much smaller than H, peel is under large-scale inelasticity conditions, and the material ahead the peel front deforms in nearly a homogeneous state. We show our data measured using various thicknesses collapse into a single curve on the plane with axes $\Gamma ∕H$ and B/H.

我们将高度可拉伸的有机硅（Ecoflex）剥离，厚度为H，宽度为B，夹在两个不可拉伸的薄膜之间。当剥离前沿在弹性体中稳定前进时，剥离力达到平稳状态${\mathit{F}}_{ss}$，比率2${\mathit{F}}_{ss}$/ B通常被报告为弹性体的韧性。我们的数据表明，这种“剥离韧性”并不总是材料常数，但是可以依赖于厚度ħ和宽度乙。我们根据断裂力学中的两个基本思想来解释数据。首先，随着比率B / H的增加，弹性体的变形从平面应力变为平面应变条件，因此剥离前沿前方的应力状态从双轴张力变为三轴张力。我们表明，三轴张力下的弹性体比双轴张力下的弹性体达到更高的应力和更大的损伤。其次，当剥离前缘周围的非弹性区域不小于H时，剥离处于大规模的非弹性条件下，剥离前沿前方的材料几乎以均质状态变形。我们显示了使用各种厚度测量的数据，这些数据在带有轴的平面上塌陷成一条曲线$\Gamma ∕H$和B / H。