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1

Three-dimensional analysis of a tensile test on a propellant with digital volume correlation

Hild F., Fanget A., Adrien J., Maire E., Roux S.

Archives of Mechanics

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2011

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Vol. 63, nr 5-6

459-478

EN

A full three-dimensional study of a tensile test on a sample made of polymerbonded propellant is presented. The analysis combines different tools, namely, X-ray microtomography of an in situ experiment, image acquisition and treatment, 3D volume correlation to measure three-dimensional displacement fields. It allows for global and local strain analyses prior to and after the peak load. By studying the correlation residuals, it is also possible to analyze the damage activity during the experiment.

2

A multi-scale "morphological approach" for highly-filled participate composites: evaluation in hyperelasticity and first application to viscohyperelasticity

Touboul M., Nadot-Martin C., Dragon A., Fanget A.

Archives of Mechanics

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2007

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Vol. 59, nr 4-5

403-433

EN

This article deals with a non-classical scale transition devoted, in the long-run, to the prediction of the nonlinear mechanical behavior of energetic composites. A geometrical and kinematical schematization of the microstructure is defined as a conspicuous starting point for further localization-homogenization procedure. Thus, salient information on the morphology and some intraphase heterogeneity are taken into account. The first results obtained in a finite strain context for a three-dimensional periodic microstructure are compared to the finite element solution. Furthermore, the ability of the methodology to deal with viscohyperelasticity in a direct manner is illustrated. This is a significant step towards efficient mastery of the scale transition for viscoelastic aggregates, whose inherent characteristic lies in space/time local interactions and relative "long-memory" effect.

3

Damage modelling framework for viscoelastic particulate composites via a scale transition approach

Nadot C., Dragon A., Trumel H., Fanget A.

Journal of Theoretical and Applied Mechanics

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2006

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Vol. 44 nr 3

553-583

EN

The aim of this paper is to pursue, in the wake of the work by Nadot-Martin et al. (2003), a non-classical micromechanical study and scale transition for highly filled particulate composites with viscoelastic matrices. The present extension of a morphology-based approach due to Christoffersen (1983), carried forward to the viscoelastic small strain context by Nadot-Martin et al. (2003), consists here in introducing a supplementary mechanism, namely damage by grain/matrix debonding. Displacement discontinuities (microcracks) on grain/matrix interfaces are first incorporated in a compatible way within geometric and kinematic hypotheses regarding the grains-and-layers assembly of Christoffersen. Then, local field expressions as well as homogenized stresses are established and discussed for a given state of damage (i.e. for a given actual number of open and closed microcracks) and using the hypothesis of no sliding on closed crack lips. A comparison with the results obtained for the sound viscoelastic composite by Nadot-Martin et al. (2003) allows to quantify the damage influence on local and global levels. At last, the basic formulation of the model obtained by scale transition is completed by the second stage leading to a thermodynamically consistent formulation eliminating some superfluous damaged-induced strain-like variables related to open cracks. This second stage is presented here for a simplified system where delayed (viscoelastic) effects are (tentatively) neglected. It appears as a preliminary and crucial step for further generalization in viscoelasticity.

PL

Celem tej publikacji jest sformułowanie wieloskalowego modelu mikromechanicznego dla granulowanych kompozytów o wysokim stopniu upakowania inkluzji w osnowie lepkosprężystej. Przedstawiony model, będący rozwinięciem morfologicznego podejścia Christoffersena (1983) i Nadot-Martin i in. (2003) w zakresie małych odkształceń lepkosprężystych, polega na wprowadzeniu do analizy dodatkowego mechanizmu uszkodzenia - mikropękania na granicy inkluzji i osnowy. Mikroszczeliny na granicy inkluzji i osnowy uwzględniono w hipotezie geometrycznej i kinematycznej metody Christoffersena. Następnie, wyznaczono lokalne oraz uśrednione pola naprężenia dla zadanego stanu uszkodzenia (tzn. dla zadanej liczby otwartych i zamkniętych mikroszczelin przy pominięciu poślizgów na powierzchniach mikroszczelin zamkniętych). Porównanie z wynikami uzyskanymi przez Nadot-Martin i in. (2003) dla nieuszkodzonego kompozytu lepkosprężystego pozwoliło na określenie wpływu uszkodzenia na poziomie lokalnym i globalnym. Na koniec, podstawowy model wieloskalowy uzupełniono o drugą część sformułowania, która pozwoliła usunąć pewne nadmiarowe odkształcenia związane z mikroszczelinami otwartymi, czyniąc cały model termodynamicznie spójnym. Ta druga część modelu wieloskalowego jest przeprowadzona przy założeniu upraszczającym, polegającym na (tymczasowym) pominięciu efektów lepkosprężystych.