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Assemblies of many materials, especially composites, laminates, interlayers, and assemblies of composites with metals are made preferentially with a structural adhesive. The mechanical behavior of an adhesive thin film, 100 to 500 micrometers of thickness, embedded by adjacent stiff surfaces, is not the behavior of the same free massive material. The plasticity and the rupture of those adhesive films subjected to complex state of stresses can be studied to get the intrinsic properties of the adhesives. Plasticity and rupture criteria depend on the stress invariants I1 (hydrostatic pressure) and J2 (Von Mises equivalent stress). The Arcan-Mines test gives those plasticity and rupture criteria of thin adhesive films when submitted to complex loading. Those criteria are modified Drucker-Prager criteria. The rupture criterion obtained with Arcan-Mines test is compared with results obtained with linear fracture mechanic applied to the fracture of the adhesive film. [ABSTRACT FROM AUTHOR]

In the frame of the European project PMJoin, researches lead to the development of a new manufacturing laser process in order to assemble metal and glass fibber reinforced polyamide 6-6 composite, without extra filler. Knowledge on the mechanical behaviour and characterization data for both material components, and evaluation of the assembly performances, (Arcan-Mines tests), permit the strength calculation and the numerical simulation of the impact failure of a hybrid assembly. [ABSTRACT FROM AUTHOR]

For different welded plastics assemblies by laser TWIST® we experimentally establish a plastic and breaking intrinsic stress criterion. Lot of plastic materials has been studied. We present here, the characterization of ABS assemblies and PA66 assemblies. The yield surfaces which characterize the limit of elasticity and the rupture, have been described by a modified Drucker-Prager criterion identified in the case of complex mixed modes state of stresses coupling tensile and shear stresses. For design purpose of welded zones, the proposed Drucker-Prager criterion has been used for the calculation and the simulation of breaking welded ABS plates and welded PA66 stepped plates. The comparison between experimental and numerical simulation values shows a relatively good agreement. [ABSTRACT FROM AUTHOR]

We propose a non-local failure criterion to predict the failure of composite laminated structures submitted to local stress concentration. The twill glass/polyamide 6 composite specimens with an open-hole as well as a bolted joint have been investigated. Material behavior was modeled using Hill's yield criterion to describe its anisotropic non-linearity. To determine a structure failure, based on the classical characteristic distance approach, the proposed method predicts the structure failure using the characteristic volume identified by experimental testing and numerical simulations. The average values of failure criteria indices over this characteristic volume were used to determine the failure. The damage initiations were predicted and showed a good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This study deals with the characterization of two adhesive joints under quasi static and fatigue loading. Different testing systems were involved. For quasi static loading, the complex behaviour model based on modified Drucker-Prager criterion taken into account hydrostatic stress and rate dependence was proposed to describe the elasto-visco-plastic experiments with the aid of finite element simulations (FEM). For fatigue loading, the lifetime of adhesives was studied. S-N curves was established and extended a failure criterion for any number of cycles. Endurance limit was determined for any combination of applied load for one adhesive, while another adhesive showed the endurance limit only in shear loading. [ABSTRACT FROM AUTHOR]