Physical interpretation of the Mullins softening in a carbon-black filled SBR

A 40 phr carbon-black filled styrene butadiene rubber has been submitted to several experiments in order to identify the physical damage responsible for the mechanical softening recorded upon first stretch. Damage in the rubber matrix was determined by swelling. The filler structure alteration was monitored by electrical conductivity measurements. Both damages are shown to be of minor importance compared to the substantial mechanical softening undergone by the material. Degradation at the rubber-filler interface may be recovered by exposing the material at high temperatures in vacuo. The chain mobility in such storage conditions promotes free chain adsorption at the filler surface. The existence of a layer of polymer whose movements are hindered adds to the filler reinforcement and its desorption creates Mullins softening

A statistical theory of polymer network degradation

A statistical theory was proposed for the degradation (random scission of chains) of a network having f-functional nodes in the case where all chains contain equireactive groups and a chain scission event does not create new groups or suppress more than one group. Closedform relations were established between the conversion ratio of the degradation process and the crosslink density. Emphasis was put on the value of the conversion ratio for which the gel disappears. Some limited cases already considered in the literature were recovered, but a general solution was proposed for networks having any number of reactive groups per chain, be it uniform or not, and for conversion ratios up to the degelation point. The results were applied successfully to recent experiments regarding the hydrolysis of a polyester

Direct experimental evidence of time-temperature superposition at finite strain for an amorphous polymer network

The time-temperature superposition property of an amorphous polymer acrylate network is characterized at infinitesimal strain by standard dynamic mechanical analysis tests. Comparison of the shift factors determined in uniaxial tension and in torsion shows that both tests provide equivalent time-temperature superposition properties. More interestingly, finite strain uniaxial tension tests run until break at constant strain rate show that the acrylate network exhibits the same time-temperature superposition property at finite strain as at infinitesimal strain. Such original experimental evidence provides new insight for finite strain constitutive modelling of polymer amorphous networks.ANR REFORM 10-JCJC-091

Les apports de Saint-Simon à une conception de l’entreprise comme passion de l’intérêt général

La pensée de Saint-Simon (1760-1825) montre à quel point au début du XIXème siècle, la nature et les frontières de l'entreprise ainsi que les modalités de sa gouvernance, ont été des questions recouvrant celles sur la nature du régime politique permettant d'achever la Révolution et de mettre un terme aux guerres européennes. A partir d'une apologie du travail et de l'utilité opposés à la force guerrière, Saint-Simon développe une physiologie sociale dans laquelle la société constitue un être unique. Alors que le christianisme se préoccupe du futur dans l'au-delà, Saint-Simon annonce le bonheur ici-bas dans l'association des producteurs visant l'intérêt général et la paix. Les Idéologues, notamment Jean-Baptiste Say, faisaient dériver les principes d'économie politique d'une analyse de la volonté individuelle distincte de la politique d'une part et de la statistique (collection des faits) d'autre part. Saint-Simon dépasse cette épistémè classique logeant le savoir dans l'espace de la représentation, pour développer une visée sociologique positiviste obéissant à la loi supérieure du progrès de l'esprit humain. A partir de cette pensée sociologique, il conçoit une première ébauche des pratiques et des institutions qui régulent le pouvoir des chefs d'industrie et des producteurs. Il annonce le développement des procédures et des techniques de gouvernement qui supplantent la souveraineté des princes et la discipline religieuse

An introduction to the statistical theory of polymer network formation

A short but detailed introduction to the statistical theory of polymer network formation is given, including gel formation, gel structure, and sol fraction. Focus is put on the use of probability generating functions, and results that are of interest for polymer network elasticity are emphasized. Detailed derivations are supplied, and a simple 6-step procedure is provided, so that the reader is able to adapt and apply the theory to his own chemical systems, even if examples are given on polyurethanes essentially

Indian Corporate Social Responsibility : from Philanthropy to Assessing the Sustainability of Business and Society

India Corporate Social Responsibility (CSR) has undergone significant changes in the past three years. Their driving factors are regulations and financial institutions requirements: the National Voluntary Guidelines on Social, Environmental & Economic Responsibilities of Business [2011], the Security Exchange Board of India clause 55 [2012] and the New Company Act section 135 [2013]. Indian CSR appears essentially about what is done with corporation profits. It means engaging directly with local communities, identifying their basic needs and integrating them with business goals. The top major themes area for Indian CSR initiatives are community welfare, education, health care and rural development. This chapter presents the historical tradition of CSR as corporate philanthropy in India. After a presentation of the new legal framework and recent institutional developments, it analyses their implication on CSR reporting and organizational challenges for Indian companies especially SMEsW ostatnich trzech latach Corporate Social Responsibility (CSR) w Indiach podlega ciągłym, znaczącym zmianom. Determinantami tych zmian są przepisy i wymagania dotyczące prowadzenia instytucji finansowych: the National Voluntary Guidelines on Social, Environmental & Economic Responsibilities of Business [2011], the Security Exchange Board of India clause 55 [2012] oraz the New Company Act section 135 [2013]. Indyjski CSR traktuje zasadniczo o przeznaczeniu zysków korporacyjnych. Oznacza to bezpośrednie zaangażowanie się w funkcjonowanie lokalnych społeczności, identyfikację ich podstawowych potrzeb i integrowanie ich z celami biznesowymi. Głównym obszarem zainteresowania dla indyjskich inicjatyw CSR są: dobrobyt społeczności, edukacja, opieka zdrowotna i rozwój obszarów wiejskich. Artykuł przedstawia historyczne uwarunkowania CSR jako filantropii korporacyjnej w Indiach. Po prezentacji nowych ram prawnych i ostatnich zmianach instytucjonalnych, analizuje ich wpływ na sprawozdawczość w zakresie CSR i wyzwań organizacyjnych dla indyjskich przedsiębiorstw, szczególnie MŚ

The effect of moisture-induced swelling on the absorption capacity of transversely isotropic elastic polymer-matrix composites

The interaction between humid air and transversely isotropic fiber-reinforced composites with swelling polymeric matrix is considered. A model is proposed for the water saturation level in a polymer when stresses are applied, that uses directly obtainable material parameters only. In a composite, the reinforcements modify the water uptake of the polymer matrix because of the internal stresses that are induced by its restricted swelling, and this effect is evaluated. As a consequence of the coupling between stresses and absorption capacity, the sorption isotherm of a composite is ruled by the (nonlinear) Langmuir equation when the unreinforced matrix obeys the (linear) Henry’s law

Radiochemical 'degelation' of polymethyl methacrylate networks

Methyl methacrylate-ethylene glycol dimethacrylate networks were synthetized and submitted to radiochemical degradation, with ageing monitored by means of sol-gel analysis. The networks were shown to undergo chain scission predominantly, which leads to their degelation, i.e., the recovery of a thermoplastic-like behavior with loss of all elastically active chains. The degelation dose was shown to increase with crosslink density and the corresponding critical conversion ratio was discussed regarding a recent and general statistical theory that covers radiochemical as well as chemical chain scissions

Multi-scale reliability analysis of composite structures – Application to the Laroin footbridge

This work aims at developing a new methodology for the reliability assessment of composite structures and their design optimization. It relies on the coupling of well established methods: homogenization scheme for the mechanical modelling of composite materials and reliability methods to account for their inherent variability. Moreover, such approach is based on an accurate treatment of inherent uncertainties of these mechanical systems at various scales, including microscopic and macroscopic levels, that provides newperspectives for structural design. As an illustration, we propose to apply the multi-scale reliability analysis on the case of the Laroin footbridge (France) with carbon–epoxy stay cables. Since the reliability assessment of such structure is evaluated through the fibre failure, numerical simulations require the coupling of reliability methods, finite element modelling to derive macroscopic loading within cables and micromechanics to estimate the effective elastic properties of composite and local responses within constituents. Results demonstrate the feasibility of the coupled approach at a structure scale and its main interests for the optimization phase of materials and engineering structures

Homogenization estimates for texture evolution in halite

In this work, the recently developed “second-order” self-consistent method [Liu, Y., Ponte Castaneda, P., 2004a. Second-order estimates for the effective behavior and field fluctuations in viscoplastic polycrystals. J. Mech. Phys. Solids 52 467–495] is used to simulate texture evolution in halite polycrystals. This method makes use of a suitably optimized linear comparison polycrystal and has the distinguishing property of being exact to second order in the heterogeneity contrast. The second-order model takes into consideration the effects of hardening and of the evolution of both crystallographic and morphological texture to yield reliable predictions for the macroscopic behavior of the polycrystal. Comparisons of these predictions with full-field numerical simulations [Lebensohn, R.A., Dawson, P.R., Kern, H.M., Wenk, H.R., 2003. Heterogeneous deformation and texture development in halite polycrystals: comparison of different modeling approaches and experimental data. Tectonophysics 370 287–311], as well as with predictions resulting from the earlier “variational” and “tangent” self-consistent models, included here for comparison purposes, provide insight into how the underlying assumptions of the various models affect slip in the grains, and therefore the texture predictions in highly anisotropic and nonlinear polycrystalline materials. The “second-order” self-consistent method, while giving a softer stress-strain response than the corresponding full-field results, predicts a pattern of texture evolution that is not captured by the other homogenization models and that agrees reasonably well with the full-field predictions and with the experimental measures