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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]