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Szczurek A.,CNRS Jean Lamour Institute | Fierro V.,CNRS Jean Lamour Institute | Pizzi A.,CNRS Jean Lamour Institute | Pizzi A.,CNRS Wood Materials Research Laboratory | And 2 more authors.
Carbon | Year: 2014

Tannin-based, carbonised, polymerised High Internal Phase Emulsions (polyHIPEs) are described in detail for the first time. Such highly porous materials were prepared by emulsion-templating, using an aqueous phase made of tannin and a low amount of hexamine dissolved in water, sunflower oil, and ethoxylated castor oil. After hardening of the tannin-based resin, the oil was leached out and the resultant monoliths were pyrolysed. The porous structure of carbon polyHIPEs prepared with an initial oil fraction ranging from 43 to 80 vol.% has been investigated, as well as their mechanical and thermal properties. We show that the most homogeneous materials, having the smallest pores, the narrowest pore size distributions and also the highest mechanical properties, are those made with an initial oil fraction around 70 vol.%. Such value is close to random and hexagonal close packing fractions: 64% and 74%, respectively. © 2014 Elsevier Ltd. All rights reserved.


Garcia D.E.,Albert Ludwigs University of Freiburg | Glasser W.G.,Albert Ludwigs University of Freiburg | Pizzi A.,CNRS Wood Materials Research Laboratory | Osorio-Madrazo A.,Albert Ludwigs University of Freiburg | Laborie M.-P.,Albert Ludwigs University of Freiburg
Industrial Crops and Products | Year: 2013

Tannins from Pinus pinaster bark were modified with propylene oxide (PO) in aqueous alkali at room temperature (~22°C) for the first time. The hydroxypropylation to four different degrees of substitution (DS) produced derivatives (HPT) with monosubstituted phenolic functionalities in yields in excess of 80%. The isolated HPTs were characterized by FT-IR, UV-vis, 1H NMR and bidimensional spectroscopies (HMBC, HSQC and COSY). The integration of the aromatic proton signals in the 1H NMR spectra of acetylated HPT allowed for an easy quantitative determination of DS. HPTs possess properties that are expected to enhance their role in new oligomeric building-blocks for the synthesis of engineered plastics and tannin-based bio-foams. © 2013 Elsevier B.V.


Oudjene M.,CNRS Wood Materials Research Laboratory | Meghlat E.-M.,Mouloud Mammeri University | Ait-Aider H.,Mouloud Mammeri University | Batoz J.-L.,Center Pierre Guillaumat 2
Composite Structures | Year: 2013

This paper discusses a numerical approach, based on beam-to-solid modelling, for the simulation of the nonlinear structural behaviour of timber-to-concrete composite beams made with screws. The present contribution is an alternative to the detailed 3D modelling of the screws using solid elements and simplified approaches which use spring elements at each screw location. The screws were modelled using one-dimensional beam element, while the timber and concrete members were modelled, in detail, using 3D solid elements. To deal with the coupling between the common nodes, the 4-node beam element with only translational degrees of freedom (d.o.f.) per node, recently developed by the authors [1,2], has been extended to nonlinear analysis and employed to model the screws, since the existing 2-node beam element is obviously not fulfilled for screws in timber [2]. The effectiveness of the numerical model developed was verified experimentally showing several advantages by comparison to the existing models in the literature. © 2013 Elsevier Ltd.


Meghlat E.-M.,Mouloud Mammeri University | Oudjene M.,CNRS Wood Materials Research Laboratory | Ait-Aider H.,Mouloud Mammeri University | Batoz J.-L.,Center Pierre Guillaumat 2
Construction and Building Materials | Year: 2013

This paper presents a novel way to simulate the behaviour of nailed and screwed timber joints, using the finite element method. In order to avoid the detailed 3D modelling of nails (or screws) using solid elements, which is costly ineffective, the authors proposed and developed an approach based on beam-to-solid coupling where the nails (or screws) were modelled using one-dimensional beam element, while the assembled timber members were modelled using solid elements. To deal with the coupling between the degrees of freedom (d.o.f.) belonging to the screws and those belonging to the timber, the existing 2-node beam element has been modified involving in a 4-node beam element with only translational d.o.f. per node, leading in fact to a full compatibility with solid elements. Using the numerical approach developed, the linear elastic behaviour of a push-out shear test of a single shear timber-to-timber connection was successfully simulated.©2012 Elsevier Ltd. All rights reserved.


Abdallah R.,University of Aleppo | Auchet S.,CNRS Wood Materials Research Laboratory | Meausoone P.J.,CNRS Wood Materials Research Laboratory
Biomass and Bioenergy | Year: 2014

Nowadays wood chips produced from raw material of inferior quality are mainly used to feed domestic and industrial boilers. For this use, a good chip size distribution and low manufacturing energy consumption are required. Cutting forces are still inaccurately measured during the wood chipping process, which implies the use of oversized chippers' motors. A test bench for chipping wood under reasonably realistic conditions of industrial production is improved by adding an indirect force measurement system with high bandwidth of 3KHz. The dynamic experimentations give the data needed to compute the curve presenting the vertical component of the cutting force, which is composed of three sections; the first one presents the values of the impact force; the second one is relatively straight and it refers to shear stress in wood; the third section corresponds to the period between two crosscuts. © 2014 Elsevier Ltd.

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