Rubber Impact on 3D Textile Composites

A low velocity impact study of aircraft tire rubber on 3D textile-reinforced composite plates was performed experimentally and numerically. In contrast to regular unidirectional composite laminates, no delaminations occur in such a 3D textile composite. Yarn decohesions, matrix cracks and yarn ruptures have been identified as the major damage mechanisms under impact load. An increase in the number of 3D warp yarns is proposed to improve the impact damage resistance. The characteristic of a rubber impact is the high amount of elastic energy stored in the impactor during impact, which was more than 90% of the initial kinetic energy. This large geometrical deformation of the rubber during impact leads to a less localised loading of the target structure and poses great challenges for the numerical modelling. A hyperelastic Mooney-Rivlin constitutive law was used in Abaqus/Explicit based on a step-by-step validation with static rubber compression tests and low velocity impact tests on aluminium plates. Simulation models of the textile weave were developed on the meso- and macro-scale. The final correlation between impact simulation results on 3D textile-reinforced composite plates and impact test data was promising, highlighting the potential of such numerical simulation tools

Rubber Impact on 3D Textile Composites

A low velocity impact study of aircraft tire rubber on 3D textile-reinforced composite plates was performed experimentally and numerically. In contrast to regular unidirectional composite laminates, no delaminations occur in such a 3D textile composite. Yarn decohesions, matrix cracks and yarn ruptures have been identified as the major damage mechanisms under impact load. An increase in the number of 3D warp yarns is proposed to improve the impact damage resistance. The characteristic of a rubber impact is the high amount of elastic energy stored in the impactor during impact, which was more than 90% of the initial kinetic energy. This large geometrical deformation of the rubber during impact leads to a less localised loading of the target structure and poses great challenges for the numerical modelling. A hyperelastic Mooney-Rivlin constitutive law was used in Abaqus/Explicit based on a step-by-step validation with static rubber compression tests and low velocity impact tests on aluminium plates. Simulation models of the textile weave were developed on the meso- and macro-scale. The final correlation between impact simulation results on 3D textile-reinforced composite plates and impact test data was promising, highlighting the potential of such numerical simulation tools

Des affections viscérales dans la goutte et le rhumatisme chronique

SudocFranceF

Ostéosynthèse des fractures de la palette humérale chez le sujet âgé de plus de 65 ans (pronostic fonctionnel à moyen terme)

CAEN-BU Médecine pharmacie (141182102) / SudocSudocFranceF

Space-time Local/adaptive - Global/fixed coupling strategy for simulation of impact on composite structures.

International audienceCurrent design tools allow to avoid failure of composite structures under dynamic loads using appropriate safety margins. On the other hand, the same tools do not allow to predict residual stiffness of a structure after damaging impacts. In the case of unidirectional multi-layered composites, this damage can specify important delamination in many zones through the thickness, an effect not easily detectable on the external surface. The non-linear context of crack propagation and the multi-scale aspects in space and in time increase the complexity of the problem. Furthermore, a methodology able to run accurate simulations of this phenomenon in large structures and with large delaminated zones is not available today with the computing time required by the industry. This work is a contribution to the development of such methods, that must be implemented in commercial software for the operational design. The starting point of our work is the coupling method between subdomains with incompatible time steps developed and improved by the team of Combescure at INSA de Lyon. Parameters, mesh refinement, local time step, space-time coupling method between global and local models have been adapted for the delamination case. The obtained results show a nearly perfect agreement with a fine 3D analysis applied on the entire structure. A disadvantage of the method based on domain decomposition approaches is that different subdomain meshes involve different time steps. In particular, this method obliges to define a shell structure domain and a 3D finer domain and to couple themselves. This feature of the method is suitable for cases in which domains can be predefined and fixed a priori. In addition, subdomains definitions (as shell model or as 3D model) change in function of delamination propagation and size. As well, we have tried to develop a superposition multi-scale strategy by analogies with nonintrusive methods proposed in non-linear statics. The goal is to use a global shell model on the entire structure and to activate or deactivate 3D patches with a finer model only on limited zones of the same structure. The method is necessarily iterative and needs data transfers form global to local and from local to global. When delamination is well defined on a zone of the structure, the 3D finer model can be deactivated and a new penalised constitutive law can be applied on the interested structural finite elements

Towards a weakly intrusive space-time multi-scale strategy for the prediction of delamination under impact.

International audienceComposite laminated materials are increasingly employed in aeronautics but can be prone to extensive delamination when submitted to impact loads such as from bird strikes. For most practical purposes, current analysis tools allow to determine whether a given structure can sustain given impact loads while appropriate safety margins are considered. In order to improve a given design, further insight needs to be gained into the complex interactions associated with impact on composites. The need to be able to perform virtual delamination testing, that is to be able to predict the extension of damage under impact, becomes essential to engineering workflows. In that case the use of a meso-scale modeling scheme for laminates, where individual modeling of the plies and interfaces are introduced, seems desirable. However, the computational cost associated with such modeling schemes for large structures would be prohibitively high for the engineering practice, as the precise study of the damage and failure response requires the consideration of phenomena encompassing multiple spatial scales and temporal scales. In order to construct an efficient numerical scheme, the basic idea is that while a rather detailed mesoscale model could be used to simulate delamination where needed, the rest of the structure could be described by a less detailed more economical macroscale model. The paper will first discuss in broad terms the possibility to adapt a commercial software package (such as Abaqus) to deal as efficiently as possible with such a multi-scale scheme. Estimates of potential advantages of multi-scale strategies compared to monolithic solutions for industrial applications are also given. In order to efficiently follow the delamination front propagation, the classical Domain Decomposition would have to be coupled with a re-meshing technique, which is costly and complex to implement. The paper will present the basis of a proposed less intrusive approach, called the Substitution method. The method is designed in such a way that is possible to make use of an unchanged coarse macro model for the whole structure and to couple it with an evolutive meso-scale analysis where needed. The computational price to pay is that the method is "locally" iterative. Two versions of the Substitution method have been developed, based on two different formulations on how to couple the macro and meso models. A weakly intrusive version of the method developed in has first been obtained. It leads to satisfying results but with a level of dissipated energy difficult to control. Therefore a second formulation based on has been developed which avoids the precedent drawback. First simple applications of this method in the case of the propagation of delamination under impact should be presented during the conference

A weakly-intrusive coupling scheme in space and time for localized effects in explicit dynamics.

International audienceComposite materials are increasingly employed in aeronautics but can be prone to extensive delamination when submitted to impact loads and the necessity to perform virtual delamination testing under impact becomes essential to engineering workflows. The use of a refined but expensive model for laminates seems desirable. The purpose of the present work consists in reducing the computational costs using a refi ned model only in a limited zone of the domain. To date, many methodologies are available for coupling di fferent models, but they require a re-meshing strategy in order to follow the evolution of the local phenomena. In this work, the basis of a weakly-intrusive approach for dynamics adaptivity, called Substitution method, are presented

A Space-Time Multiscale Coupling Strategy for Predicting Delamination Due to Impacts.

International audienceComposite laminates are increasingly employed in aeronautics but can be prone to extensive delamination when submitted to impact loads such as from bird strikes or tire failures. Current analysis tools allow to determine whether a given structure can sustain given impact loads, while appropriate safety margins are considered. In order to enhance the industrial design, more advanced numerical techniques are necessary to gain accuracy for complex materials. In the case of laminates, meso-scale schemes, in which plies and cohesive interfaces are modeled in detail, are necessary to provide robust analysis tools. However, the computational costs associated with such fine modeling would be excessively high for the engineering practice. So, macro-scale schemes, e.g. shell models, are usually employed but are not able to represent complex mechanisms like the delamination propagation. Our aim is to develop a bridging coupling between a macro-scale, applied to large structures, and a meso-scale, applied only to the front of delamination for predicting its propagation. The transient nature of the impact problems leads to explicit schemes and, because of the stability condition, the spatial multiscale coupling involves a temporal multiscale coupling too. The classical application of a Domain Decomposition approach would require to re-mesh the global model in order to follow the delamination propagation, which would be costly and complex to implement. In this paper, we present the basis for a less intrusive approach, called the Substitution method. This latter is developed in order to leave unchanged the structural macro-scale analysis, coupling it with an iterative adaptive finer meso-scale analysis. Two versions of the Substitution method have been developed, based on different bridging formulations. The first one, inspired by the multi-timestep method developed for Domain Decomposition, and the second one, inspired by the enhancements, based to numerical energy considerations. Two-dimensional applications of this method will be presented

The production of reduced-alcohol wines using Gluzyme Mono® 10.000 BG-treated grape juice

The original publication is available at http://www.sasev.org/.High alcohol wines have become a major challenge in the international wine trade. Several physical processes are used to produce wines with reduced-alcohol content, all of which involve the selective extraction of ethanol based on volatility or diffusion. In this study, the possibility of Gluzyme Mono® 10.000 BG (Gluzyme) (Novozymes, South Africa) to reduce the glucose content of synthetic grape juice before fermentation was investigated in order to produce wine with reduced-alcohol content. Gluzyme is a glucose oxidase preparation from Aspergillus oryzae, currently used in the baking industry. Glucose oxidase catalyses the oxidation of glucose to gluconic acid and hydrogen peroxide(H2O2) in the presence of molecular oxygen. Gluzyme was initially used in synthetic grape juice, where different enzyme concentrations and factors influencing its efficiency were investigated under winemaking conditions. The results showed up to 0.5% v/v less alcohol at an enzyme concentration of 20 kU compared to the control samples. This reduction in alcohol was increased to 1 and 1.3% v/v alcohol at pH 3.5 and pH 5.5 respectively in aerated (8 mg/L O2) synthetic grape juice using 30 kU enzyme. Secondly, Gluzyme was used to treat Pinotage grape must before fermentation. Gluzyme-treated wines at 30 kU enzyme concentration after fermentation contained 0.68% v/v less alcohol than the control wines. A decrease in acetic acid concentration of the treated compared to control wines was also observed.Publishers' versio