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The COHMAS team imagines, develops and validates new strategies for identification, modeling and numerical design of composite materials and structures.

Since a few years, tremendous new challenges emerged for composite materials and their applications. From classical mechanical loading to long-term aggressive environments, these new frameworks involves multiple scales, both in time and in space, due to the diversity of involved phenomena.

To achieve these goals, classical numerical and modeling strategies are useless. We have to achieve high predictive simulations while saving reasonable computation times. The COHMAS team is specialized in numerical strategies and material models, from the low scale to the one of the structure. The key characteristic of COHMAS is the strong will to fuse hill-level theoretical research and practical applications. Based on close relationships with industrial partners, we identify underlying key scientific challenges for in depth research. Then, these core developments are adapted or simplified to fit the industrial standards and requirements. 

The unique and integrated environment of COHMAS supports this duality. You will find there state of the art both experimental and computational facilities. 

Welcome in our group's website!

  
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Pr. Gilles Lubineau

Principal Investigator Associate Professor in Mechanical Engineering
  
 

• Lubineau G., (2009).
A goal-oriented filtering technique of field measurements for parameters identification of material model.

Computational Mechanics, accepted, to appear.


Abstract: The post-processing of experiments with nonuniform fields is still a challenge: the information is often much richer, but its interpretation for identification purposes is not straightforward. However, this is a very promising field of development because it would pave the way for the robust identification of multiple material parameters using only a small number of experiments.
This paper presents a goal-oriented filtering technique in which data are combined into new output fields which are strongly correlated with specific quantities of interest (the material parameters to be identified). Thus, this combination, which is nonuniform in space, constitutes a filter of the experimental outputs, whose relevance is quantified by a quality function based on global variance analysis. Then, this filter is optimized using genetic algorithms.
 
 

• Lubineau G. (2008).
Estimation of residual stresses in laminated composites using field measurements on a cracked sample.


Composites Science and Technology, v. 68(13), pp. 2761-2769.


Abstract: Today, advanced damage models taking into account residual stresses are available. In particular, microcracking as a degradation mechanism in laminates is very sensitive to manufacturing-induced stresses. However, these stresses are often introduced through a model parameter whose identification remains difficult or requires time-consuming and costly additional tests. Here, we propose a relatively simple method based on the observation of the displacement field associated with the creation of a transverse crack in a crosswise laminate. Subsequently, this displacement field can be reinterpreted according to the model being used in order to build the quantity required by the model.
 
 

• Lubineau G. & al. (2008).
Construction of a micromechanics-based intralaminar mesomodel, and illustrations in ABAQUS/Standard.


Computational Materials Science, v. 43(1), pp. 137-145.

Abstract: The recent advances in the modeling of degradations in stratified composites have led to improved models on all scales. In particular, today, micromechanics derived in a generic framework enables one to define a reference virtual material which integrates most of the knowledge of a material. Thus, a model using damage mechanics on the mesoscale and usable for structural analysis can be built as a homogenized version of this reference model through previously-developed bridges. The objective is to derive a refined model worthy of micromechanics confidence, but transposable into a commercial code (here, ABAQUS/Standard).