Category: All posts

Together with my student Damien Ollion, we have converted the finite-strain viscoelastic UMAT originally developed with Florian Gouhier into a VUMAT for Abaqus/Explicit. The implementation reproduces the constitutive model of Reese and Govindjee (1998) for a generalized Maxwell model and includes the following features: A comprehensive How-to-use.pdf document is provided. It presents the constitutive equations, illustrates the...

Following our previous investigation of the beahvior of hyperelastic classic Voronoi closed-cell foams submitted to severe compression, we have extended the study to assess the influence of microstructure on the mechanical response of highly porous foams. To this end, two additional classes of microstructures were generated: mechanically grown Voronoi (M-Voro) closed-cell foams and open-cell foams...

The mechanical response of isotropic elastomeric closed-cell foams with Classical Voronoi microstructures is examined through three-dimensional finite element simulations. The study focuses on finite-strain uniaxial compression, complemented by infinitesimal-strain shear and hydrostatic loading. Random foam geometries with porosities between 77% and 95% and narrow pore-size distributions were generated by subtracting irregular Voronoi polyhedra, constructed from...

During the 2020 confinement as I was writting papers, I thought about making a 10 minutes black board video to explain my writting process to help students of our LMS lab to write their first paper. It seems to appeal students, so I give it a little bit more exposure here by sharing the link...

During the COVID period, I supervised two Master’s students for three months, tasking them with developing an educational Jupyter notebook on homogenization. The notebook implements classic mean-field models, including Mori-Tanaka, self-consistent, generalized self-consistent, the four-phase model, Voigt, Reuss, and Hashin-Shtrikman bounds. Although I haven’t promoted it yet, I believe it could be highly beneficial to...

We have been developping stamps to apply precise patterns on sample surfaces for local strain measurements using digital image correlation (DIC) during mechanical and thermal testing. Typically, when local strain measurements are needed in mechanical tests, sample surfaces are marked with spray paint or an airbrush to create a speckle pattern with good gray-level contrast....

When highly reinforced a soft matrix, like an elastomer matrix, undergoes incredibly localized high strain where particles nearly touch. Therefore, it requires extensive remeshing efforts in an order to estimate numerically the equivalent homogeneous behavior of such a composite. We did that, using Abaqus *MAP SOLUTION option. This allowed to provide original numerical stress-strain responses...

When dealing with isotropic polymer, it is easy to characterize the linear viscoelasticity in the lab via dynamic mechanic analysis in tension, torsion. What about for a transversely isotropic material such as a carbon fibers reinforced polymer? Actually, one may find out that it is not possible to directly assert any of the five parameters...

In an effort to bring some clarification on the vast literature on finite strain viscoelastic models, initially defined for elastomers, a review of the pioneering models on finite strain viscoelastic from Le Tallec et al. (1993), Lion (1997) and Reese and Govindjee (1998) has shown that these models are totally equivalent [1]. It is not...

We have compared the mode I opening critical energy release rate (GIc) measured using the single edge notch bending test and double cleavage drilled compression test on an elastic fragile PMMA and a bulk viscoplastic acrylate used as a glue for wind turbine blades. The study details the experimental procedure, for the crack initiation and...