Interfacial zone model

Figure 1 The interface stresses calculated from various adherend and interfacial zone models (a/h2 =...

In bonded materials that are assumed to be piecewise homogeneous, from the viewpoint of mechanical failure,a fundamental problem is that of a crack lying parallel to an interface. This, of course, includes the case of interfacial zones modelled as a homogeneous elastic continuum. Even though for a realistic analysis the particular component geometry and loading conditions may be very important, the characteristic features of the problem may be captured by considering the plane strain problem for two bonded half spaces. 

According to Frumkin and Damaskin, A% at the air/solution interface changes linearly with composition, i.e., the interface behaves as two condensers in series. "" On a molecular basis, this model is tantamount to assuming that an adsorbate and solvent do not interact in the interfacial zone, but create two homogeneous surface layers. 

Journal of the Electrochemical Society Figure 3. Three region structural model for Nafion A, fluorocarbon B, interfacial zone C, ionic clusters (11). 

Neither the duplex film, nor the oriented portlandite crystals in the interfacial zone were found by all the authors [19, 20]. However, there is a common opinion that this area is enriched with calcium hydroxide crystals and exhibits higher porosity. Consequently, it will have a great impact on the corrosion resistance of concrete. The transition zone of high porosity is the weakest micro-area where the corrosion of concrete will begin [21]. For this reason, the interfacial transition zone became a subject of numerous studies [16,17,22-28]. The constitution of this zone can be easily observed on the model proposed by Rooij et al. [28] (Fig. 6.9). 

Lorenzis, L.D. and Zavarise, G. (2009) Cohesive zone modeling of interfacial stresses in plated beams. International Journal of Solids and Structures, 46, 4181—4191. 

The effect of mechanical deformation on a UV-cured urethane-acrylate polymer and on a silicon carbide/ urethane-acrylate model composite was studied by FTIR microspectroscopy. This technique was used for the first time to measure the width of the interfacial zone beyond which the fibre has no influence on the matrix (161). 

It is more complicated to describe the interfacial zone if specific adsorption phenomena are involved. The description often follows a model using several capacitors in series or in parallel. 

This notion is complex and a more detailed presentation would need to go beyond the scope of this document. In particular, in order to describe the thermodynamics of interfaces one would need to refer to the notion of surface excess as defined by the Gibbs model. Ne can still say that TJ is the integral of the volume concentration over a distance equal to the thickness of the interfacial zone... 

On the other hand, the driving force behind the electrochemical reaction occurring in the interfacial zone is related to the double layer voltage (denoted by in figure 4.14). The relationship between the double layer voltage and the current is precisely the subject of studies and models in electrochemical kinetics . 

In this paper the existing interface models are briefly described and the problem of a crack lying parallel to the interface is reconsidered and further examined. Some results obtained from a new model for an interfacial zone with very steep material property... 

If we now assume that the interfacial zone between the membrane and the elastic substrate is modelled by a "shear spring", then the integral equation expressing the displacement continuity becomes [6] (Figure 1)... 

Similarly, if two elastic continua are bonded through an interfacial zone of finite normal and shear stiffness (model c, Eqn. 3), the integral equations may be shown to be of the second kind with log t-xl as the dominant kernel. Thus, the resulting interfacial stresses a(x) and t(x) would be bounded everywhere (see Erdogan [S]). 

The model proposed here deals with the anomalous stress and displacement behavior at the interface crack tips predicted by a piecewise homogeneous material assumption in bonded materials and is based on the observation that, whatever the actual mechanism of binding at the atomic level, in many cases for the sake of thermodynamical consistency the interfacial zone needs to be considered as a distinct phase or chemical species (see Good [l6]), Furthermore, because of the interdiffusion nature of the actual binding process, in many material pairs one may assume that the spatial variation of the thermomechanical material parameters near the nominal interface would be very steep but nevertheless continuous. Tlie... 

The interfacial zone consists of adsorption, diffusion, and charge-transfer processes of oil additives and contaminants. A linear EIS [6] and NLEIS analysis [7] have led to a refinement of this model, taking into consideration the best fit of kinetic parameters to both nonlinear and fundamental-frequency experimental impedance data. The low-frequency impedance data are modeled as a combination of a CPE representing double-layer charging processes, adsorption (Z pj), diffusion (Zp, ), and charge-transfer resistance (R ) impedance segments. 

B. Mobasher and C.Y. Li, Modeling of Stiffness Degradation of the Interfacial Zone During Fiber Debonding , J. Composite Engineering. 5,1995,1349-1365. 

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