The effect of contact on the decohesion of laminated beams with multiple microcracks

Abstract

The problem of interface decohesion in laminated beams is addressed with reference to the debonding double cantilever beam test geometry (DCB). The paper deals with the analysis of the influence of nonuniform bonding properties or interfacial defects on the crack propagation process and its stability. To this aim, the classical analytical approach based on the Euler-Bernoulli beam on an elastic foundation is extended to the presence of a general distribution of microcracks ahead of the macrocrack tip. The main features and limitations of this approach are carefully analyzed. In particular, it is shown that this simplified approach does not consider the unilateral contact condition along the interface, thus admitting a penetration between the two arms of the beam. A comparison with a finite element formulation is proposed to assess if this violation of the constraints inequalities, usually adopted in the case of uniform bonding, is still acceptable when interfacial defects are present. In order to fully describe the whole nonlinear behavior of the interface, a generalized interface constitutive law is used. The models comparison shows that, in the presence of interfacial defects, the effect of contact plays a crucial role in the description of the mechanical response of the joint.

An integrated cohesive/overlapping crack model for the analysis of flexural cracking and crushing in RC beams

“…As a general remark, it is possible to state that the effect of the shape of the cohesive crack law is not of primary importance when the stress field is characterized by a strong gradient, as analytically and numerically shown in (Williams and Hadavinia 2002;Carpinteri et al 2008) for double cantilever beam tests. Moreover, the examples proposed in this section focus on the evaluation of the post-peak branch of the momentrotation curve, where the nonlinearity due to crushing and steel yielding or slippage are highly prevailing.…”

A Thermo-mechanical cohesive zone model

“…In case of repeated loadings, the interfacial response weakens as the number of unloading-reloading cycles increases. The traction-opening relations used in the present work can not capture such effects and in case of repeated loadings, dedicated models such as the one presented in [21,22] should be used. In case of crack closure and contact, the normal traction takes the following form, (25) based on the fractal models of contact.…”

A cohesive crack model coupled with damage for interface fatigue problems

“…Since then, several alternative methods have been proposed in terms of J -integral range, J , crack tip opening displacement variation, CTOD, or strain energy release rate range, G, (Dowling and Begley 1976;Neumann 1974;Mostovoy and Ripling 1975;Hertzberg 1995) to extend the application of Paris' law. It is worth noting that the latter has been frequently employed by several authors to investigate the problem of interface crack growth (Roe and Siegmund 2003;Pirondi and Nicoletto 2004;Geubelle 2005, 2006;Carpinteri et al 2008).…”

“…We focus our attention on a double cantilever beam (DCB), where two metallic substrates are bonded together by a polymeric adhesive. Furthermore, an analytical approach based on a beam on an elastic foundation, as formerly proposed by Williams and Hadavinia (2002) for monotonic loading and subsequently generalized by Carpinteri et al (2008) in case of a periodic distribution of microdefects along the interface, is here extended to cyclic loading. The evolution of fatigue damage is taken into account by considering an average opening displacement of the cohesive zone length.…”