Gilles Robert

Micromechanical modeling of short glass-fiber reinforced thermoplastics-Isotropic damage of pseudograins

A micromechanical damage modeling approach is presented to predict the overall elasto‐plastic behavior and damage evolution in short fiber reinforced composite materials. The practical use of the approach is for injection molded thermoplastic parts reinforced with short glass fibers. The modeling is proceeded as follows. The representative volume element is decomposed into a set of pseudograins, the damage of which affects progressively the overall stiffness and strength up to total failure. Each pseudograin is a two‐phase composite with aligned inclusions having same aspect ratio. A two‐step mean‐field homogenization procedure is adopted. In the first step, the pseudograins are homogenized individually according to the Mori‐Tanaka scheme. The second step consists in a self‐consistent homogenization of homogenized pseudograins. An isotropic damage model is applied at the pseudograin level. The model is implemented as a UMAT in the finite element code ABAQUS. Model is shown to reproduce the strength and th...

Multiscale Modeling of the Orthotropic Behaviour of PA6-6 overmoulded Composites using MMI Approach

In this study the MMI ConfidentDesign™ multiscale approach (consisting in a non‐linear multiscale simulation based on DIGIMAT® including the injection modeling of the filled polymer and a multiscale mechanical model using the fiber orientation tensor resulting from the injection) has been combined with an orthotropic damageable elastic simulation. The anisotropic properties (including rupture criterion) are estimated and a multiscale simulation including the heterogeneous material properties issued from injection process is done. The impact of fiber ratios is then investigated. The structural simulation predicts stresses localized close to the punch, as well in injected PA66 than in composite part. Greater the fiber volume ratio, greater the modulus and more brittle the composite.