This work proposes new interface conditions between the layers of a three-dimensional composite structure in the framework of coupled thermoelasticity. More precisely, the mechanical behavior of two linear isotropic thermoelastic solids, bonded together by a thin layer, constituted of a linear isotropic thermoelastic material, is studied by means of an asymptotic analysis. After defining a small parameter $\epsilon$, which tends to zero, associated with the thickness and constitutive coefficients of the intermediate layer, two different limit models and their associated limit problems, the so-called soft and hard thermoelastic interface models, are characterized. The asymptotic expansion method is reviewed by taking into account the effect of higher-order terms and defining a generalized thermoelastic interface law which comprises the above aforementioned models, as presented previously. A numerical example is presented to show the efficiency of the proposed methodology, based on a finite element approach developed previously.

In this paper a composite body is considered. This body is made of three solids: two linear elastic adherents and a piecewise linear thin adhesive. The composite occupies a bounded domain depending naturally on a small parameter $\epsilon$ , which is the thickness, assumed constant, of the adhesive. Classically, it is possible to derive an interface imperfect law using asymptotic expansions as the thickness $\epsilon$ tends to zero. In this work, the material in the interphase is assumed to be graded, i.e. its elasticity properties vary along the thickness. Moreover, an unilateral condition is considered to avoid penetrations. A first result of the paper is that it is possible to apply the above methodology based on asymptotic expansions to this kind of material. Then, a finite element method is introduced to solve the initial problem (with three layers) and the limit problem (with two layers in imperfect contact). Various types of graded materials are numerically analyzed. In particular, different types of stiffness distributions are studied in detail.

In this paper a study on double lap joints made of glass fibre-reinforced polymer (GFRP) adherents and an epoxy resin as a glue is performed. Both an experimental procedure and a theoretical model with an associated numerical discretization are presented. Experimental and numerical results are discussed and compared. They indicate the possibility of performing an advanced mechanical analysis of adhesive joints based on a preliminary characterization of a few mechanical parameters.