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Lerbet J.,IBISC | Aldowaji M.,IBISC | Challamel N.,Laboratoire Dingenierie Des Materiaux Of Bretagne | Nicot F.,Geomechanics Group | And 2 more authors.
ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik | Year: 2012

The bifurcation problem of constrained non-conservative systems with non symmetric stiffness matrices is investigated. It leads to study the subset D p,n of M n(R) of the so called p-positive definite matrices (1 ≤ p ≤ n). The main result (D 1,n ⊂ D p,n) is proved, the reciprocal result is investigated and the consequences on the stability of elastic nonconservative systems are highlighted. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kuehnert I.,Leibniz Institute of Polymer Research | Fischer M.,Leibniz Institute of Polymer Research | Fischer M.,TU Dresden | Ausias G.,Laboratoire Dingenierie Des Materiaux Of Bretagne
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2014

In this study the correlations between inner properties and fracture behavior were investigated on the "cold" interface that occurs during a multi-shot injection molding process and "hot" interface or well known as weld line, which represents two melt streams meeting. By using Nanoindentation, inner properties, like Young's modulus, were measured through the cross section and had shown similarities to break surfaces. With reference to in-situ SEM tensile test the fracture behavior becomes clearer. Imbalances of mold design, caused by core mechanisms, which are required for multi-shot injections, are reasons for deviation of properties. As basis for complex components, these results provide fundamental approaches. Copyright © (2014) by the Society of Plastics Engineers.

Le Duigou A.,Laboratoire Dingenierie Des Materiaux Of Bretagne | Bourmaud A.,Laboratoire Dingenierie Des Materiaux Of Bretagne | Davies P.,French Research Institute for Exploitation of the Sea | Baley C.,Laboratoire Dingenierie Des Materiaux Of Bretagne
Ocean Engineering | Year: 2014

Innovation in sailing yacht design must include current environmental concerns such as resource depletion and waste management. Indeed most of the materials used today are petro-based and cannot offer viable end of life treatment. Fully biodegradable natural fibre reinforced biopolymers are being increasingly studied as they offer high specific stiffness and low environmental footprint. However, their ageing mechanisms are still not well understood. The present article gives information on 2 years natural seawater aging effect on injection-molded Flax/PLA biocomposite. Biocomposites suffer from relatively high moisture absorption which is controlled by the vegetal fibres. Simple rules of mixtures allow the determination of weight gain for flax fibres which is around 12%. Bundles of fibres and especially middle lamellae influence water uptake. Water alters flax fibres and their biocomposites, since their mechanical properties (Young's modulus and tensile strength) are reduced with aging. A linear relationship is observed between water uptake and loss of mechanical properties. Load-unload cycles highlight damage occuring earlier than unaged biocomposites. This damage can be induced by fibre degradation and washing out of soluble components especially the fibre bundles cement, and by debonding of fibre bundles linked to their swelling. © 2014 Elsevier Ltd. All rights reserved.

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