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Space and time homogenization of viscoelastic-viscoplastic composites under large numbers of cycles

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Conférencier : Issam DOGHRI, Université catholique de Louvain
Date de l'événement : mardi 26 avril 2016 13:00 - 14:00
Lieu : Campus Kirchberg, room A02

Recent developments in the modeling of homogeneous or short fiber reinforced thermoplastic polymers are presented. 

About the topic

Spatial scale transition is based on nonlinear mean-field homogenization (MFH). The polymer matrix’s response is described by a multiaxial constitutive model coupling viscoelasticity (VE), viscoplasticity (VP) and ductile damage (D). Two multiscale modeling approaches are proposed to predict the high cycle fatigue (HCF) failure of neat thermoplastic polymers and of short glass fiber reinforced thermoplastics.The modeling is based on the concept of so-called weak spots within the polymer matrix, whose behavior is VE-VP-D. Predictions are compared to experimental data. In order to reduce drastically the computational cost of simulations under large numbers of cycles, a modeling strategy combining space and time homogenization is proposed. The latter is based on the definition of micro- and macro-chronological time scales, and on asymptotic expansions of the unknown variables. The original anisotropic VE-VP initial-boundary value problem of the composite material is decomposed into coupled micro-chronological (fast time scale) and macro-chronological (slow time-scale) problems. The former corresponds to a VE composite, and is solved once for each macro time step, whereas the latter problem is a nonlinear composite and solved iteratively using fully implicit time integration. Numerical simulations are shown.

About the speaker

Issam Doghri is a tenured full professor at Université catholique de Louvain. He holds a Master in Civil Engineering from Ecole Nationale d’Ingénieurs de Tunis (Tunisia), a Master in Applied Mechanics from Ecole Normale Supérieure de Cachan (France) and a Ph.D. in Mechanics from Université Pierre et Marie Curie (Paris 6). Issam was also a post-doc at University of California at Santa Barbara. He is the author of a book and about 100 scientific papers, the advisor of several Ph.D. theses and the principal investigator of a number of funded research projects. He is regularly invited to give talks at various conferences and teach graduate-level courses in different countries. 

Issam’s expertise is on nonlinear mechanics of solid materials and structures, and his research activities are in computational mechanics of materials, with a special focus on multiscale modeling of heterogeneous materials in a broad sense (e.g., composites with a polymer matrix reinforced with short, long or continuous fibers).

Issam’s professional experience is both in academia and industry. Indeed, he has consulted for several companies and was a member of technical staff in a finite element company in Palo Alto, California. Based on his DIGIMAT software for multiscale modeling of composites, in May 2003 Issam co-founded e-Xstream engineering with Dr. Roger Assaker. The company was acquired by MSC Software in September 2012.

Fichier : Flyer Conference Issam Doghri.pdf 1,03 MB