Issue 30

C. Putignano et alii, Frattura ed Integrità Strutturale, 30 (2014) 237-243; DOI: 10.3221/IGF-ESIS.30.30 238 F ORMULATION iven an adhesive tape going to be peeled from a flat rigid substrate, the non-contact area can be studied as an interfacial crack, which, during the detachment process, propagates determining the advance of the peeling process. As a matter of fact, by recalling the Griffith criterion, we can observe that, in equilibrium conditions, the total free energy U tot has to be stationary: G    (1) where   is the work of adhesion and G is the energy release rate at the crack tip and, for fixed load P , is equal to: p el P U U G S S              (2) with el U and p U respectively equal to the elastic energy stored in the system and the potential energy associated with the external load P ; S is the size of the detached area. Now, let us focus on the peeling tape. In Ref. [6], it has been shown that, given a symmetric tape loaded with a normal load 2P , it is possible to study just an half of the tape loaded with a force equal to P. As matter of fact, in the following, we study the reduced system in Fig. 1. More in details, the problem is formulated considering two different initial configurations of the elastic tape having cross section t A bt  (Fig. 1). In the first configuration (Fig. 1a), a length h of the tape is not attached to the substrate and, before applying the external force P , it is rotated. In the latter (Fig. 1b), the tape is stretched of the quantity h before loading. In both cases, a pre-tension P 0 can be applied to the tape before it is attached to the substrate. (a) (b) Figure 1 : Peeling of a load. Initial configuration (a) : a length h of the tape is not attached to the substrate and it is rotated before applying the external force P; initial configuration (b) : the tape is stretched of a quantity h before loading. Now, given the system in Fig. 1, elastic and potential contributions will be respectably equal to:   2 2 0 2 1 2 sin el a h P U P Ebt           (3)   0 1 sin 1 sin P P U P a h P Ebt                    (4) By recalling Eq. (1) and introducing the following dimensionless quantities G