Thermodynamic Framework of Multiscale Homogenization Schemes for Dissipative Materials

The prediction of failure processes in composite, heterogeneous materials require multiscale analysis to account for the complex mechanisms and features taking place. Between the different multiscale schemes the more commonly used are those based on homogenization procedures, due to their versatility. In this work a thermodynamically consistent homogenisation based multiscale approach is formulated for modelling thermo-plastic materials. The proposal is valid for arbitrary multiscale procedures, including local or nonlocal methods, and continuum or discontinuum methods in either scale. The necessary and sufficient conditions for fulfilling the thermodynamic consistency are defined. It is demonstrated that the Hill-Mandel variational criterion for homogenization scheme is a necessary, but not a sufficient condition when dissipative material responses are involved at any scale. On this point, the additional condition that needs to be fulfilled is established. The general case of temperature-dependent, higher order elastoplasticity is considered as theoretical framework to account for the material dissipation at micro and macro scales of observation. Additionally, it is shown that the thermodynamic consistency enforces the homogenization of the nonlocal terms of the micro scale’s free energy density; however, this does not necessarily lead to nonlocal effects on the macro scale. Finally, the particular cases of local isothermal elastoplasticity and continuum damage are considered for the purpose of the proposed approach for multiscale homogenizations.Publicado en: Mecánica Computacional vol. XXXV, no. 23Facultad de Ingenierí

Thermodynamic Framework of Multiscale Homogenization Schemes for Dissipative Materials

The prediction of failure processes in composite, heterogeneous materials require multiscale analysis to account for the complex mechanisms and features taking place. Between the different multiscale schemes the more commonly used are those based on homogenization procedures, due to their versatility. In this work a thermodynamically consistent homogenisation based multiscale approach is formulated for modelling thermo-plastic materials. The proposal is valid for arbitrary multiscale procedures, including local or nonlocal methods, and continuum or discontinuum methods in either scale. The necessary and sufficient conditions for fulfilling the thermodynamic consistency are defined. It is demonstrated that the Hill-Mandel variational criterion for homogenization scheme is a necessary, but not a sufficient condition when dissipative material responses are involved at any scale. On this point, the additional condition that needs to be fulfilled is established. The general case of temperature-dependent, higher order elastoplasticity is considered as theoretical framework to account for the material dissipation at micro and macro scales of observation. Additionally, it is shown that the thermodynamic consistency enforces the homogenization of the nonlocal terms of the micro scale’s free energy density; however, this does not necessarily lead to nonlocal effects on the macro scale. Finally, the particular cases of local isothermal elastoplasticity and continuum damage are considered for the purpose of the proposed approach for multiscale homogenizations.Publicado en: Mecánica Computacional vol. XXXV, no. 23Facultad de Ingenierí

The Encore Project: Sustainable Solutions For Cementitious Materials

Since concrete is the most widely utilized construction material, several solutions are currently being developed and investigated for enhancing the sustainability of cementitious materials. One of these solutions is based on producing Recycled Concrete Aggregates (RCA) from existing concrete members resulting by either industrial processes or demolitions of existing structures as a whole. Moreover, waste resulting from industrial processes other than the building construction (i.e., tire recycling, production of steel, powders resulting from other depuration processes) are also being considered as possible low-impact constituents for producing structural concrete and Fiber-Reinforced Cementitious Composites (FRCC). Furthermore, the use of natural fibers is another option for producing environmentally-friendly and cost-effective materials, depending on the local availability of raw materials. To promote the use of concretes partially composed of recycled constituents, their influence on the mechanical and durability performance of these concretes have to be deeply investigated and correlated. This was the main goal of the EnCoRe Project (www.encore-fp7.unisa.it), a EU-funded initiative, whose activities and main findings are summarized in this paper