Bois composite | EPFL Graph Search

vignette|Aéroport Barcelone : de terrasse en bois composite datant de 2009 (Silvadec) Le bois composite ou wood plastic composite (WPC) est un matériau composite thermoplastique composé de fibres de bois et de résines plastiques. Conçu à l'origine pour se substituer aux essences de bois exotiques menacées, il est aujourd'hui souvent utilisé pour la réalisation de terrasses, plages de piscines, pontons et autres aménagements extérieurs durables, pour l'habillage ou l'isolation de façades ou la création de mobilier urbain et de mobilier intérieur. Fabrication Les profilés en bois composite sont obtenus par extrusion ou parfois par moulage par injection, à partir de matières premières telles que du bois et des résines plastiques souvent issues du recyclage comme le polypropylène, polyéthylène ou polychlorure de vinyle. Ces polymères thermoplastiques constituent la matrice, qu'on associe à du bois ou à une autre fibre cellulosique qui constituent la charge. D'autres types de c

Stiffness of Aligned Wood Fiber Composites: Effect of Microstructure and Phase Properties

Razvan Cristian Neagu

The effect of wood fiber anisotropy and their geometrical features on wood fiber composite stiffness is analyzed. An analytical model for an N-phase composite with orthotropic properties of constituents is developed and used. This model is a straightforward generalization of Hashin’s concentric cylinder assembly model and Christensen’s generalized self-consistent approach. It was found that most macro-properties are governed by only one property of the cell wall which is very important in attempts to back-calculate the fiber properties. The role of lumen (whether it filled by resin or not) has a very large effect on the composite shear properties. It is shown that several of the unknown anisotropic constants characterizing wood fiber are not affecting the stiffness significantly and rough assumptions regarding their value would suffice. The errors introduced by application of the Hashin’s model and neglecting the orthotropic nature of the material behavior in cylindrical axes are evaluated. The effect of geometrical deviations from circular cross-section, representing, for example, collapsed fibers, is analyzed using the finite element method (FEM) and the observed trends are discussed.

2008

Capillary Effects in Fiber Reinforced Polymer Composite Processing: A Review

Baris Çaglar, Véronique Michaud, Jacobus Gerardus Rudolph Staal, Helena Luisa Teixido Pedarros

Capillarity plays a crucial role in many natural and engineered systems, ranging from nutrient delivery in plants to functional textiles for wear comfort or thermal heat pipes for heat dissipation. Unlike nano- or microfluidic systems with well-defined pore network geometries and well-understood capillary flow, fiber textiles or preforms used in composite structures exhibit highly anisotropic pore networks that span from micron scale pores between fibers to millimeter scale pores between fiber yarns that are woven or stitched into a textile preform. Owing to the nature of the composite manufacturing processes, capillary action taking place in the complex network is usually coupled with hydrodynamics as well as the (chemo) rheology of the polymer matrices; these phenomena are known to play a crucial role in producing high quality composites. Despite its importance, the role of capillary effects in composite processing largely remained overlooked. Their magnitude is indeed rather low as compared to hydrodynamic effects, and it is difficult to characterize them due to a lack of adequate monitoring techniques to capture the time and spatial scale on which the capillary effects take place. There is a renewed interest in this topic, due to a combination of increasing demand for high performance composites and recent advances in experimental techniques as well as numerical modeling methods. The present review covers the developments in the identification, measurement and exploitation of capillary effects in composite manufacturing. A special focus is placed on Liquid Composite Molding processes, where a dry stack is impregnated with a low viscosity thermoset resin mainly via in-plane flow, thus exacerbating the capillary effects within the anisotropic pore network of the reinforcements. Experimental techniques to investigate the capillary effects and their evolution from post-mortem analyses to in-situ/rapid techniques compatible with both translucent and non-translucent reinforcements are reviewed. Approaches to control and enhance the capillary effects for improving composite quality are then introduced. This is complemented by a survey of numerical techniques to incorporate capillary effects in process simulation, material characterization and by the remaining challenges in the study of capillary effects in composite manufacturing.

FRONTIERS MEDIA SA2022

Magneto-mechanical actuation of ferromagnetic shape memory alloy/epoxy composites

Luis Pablo Canal Casado, Susanne Glock, Véronique Michaud

Ferromagnetic shape memory alloys (MSMA) exhibit magnetic field- and stress-induced twinning when processed into single crystals, but are brittle and difficult to shape. Embedding slender single crystalline MSMA elements into a polymer matrix can thus provide composites with adjustable magnetic strain actuation behavior. Ni-Mn-Ga single crystalline rods were characterized for their magneto-mechanical behavior and embedded in two different types of epoxy matrices with different volumetric fractions. The magnetic actuation of the composites was measured and shown to depend on the Ni-Mn-Ga volumetric fraction and the matrix stiffness. This behavior was well predicted by finite element simulations of the composite using a simple material model for the strain of the MSMA as a function of the magnetic field and applied stresses. Guidelines for composite behavior prediction could thus be proposed. (C) 2015 Elsevier Ltd. All rights reserved.

2015

Capillary Effects in Fiber Reinforced Polymer Composite Processing: A Review

Baris Çaglar, Véronique Michaud, Jacobus Gerardus Rudolph Staal, Helena Luisa Teixido Pedarros

FRONTIERS MEDIA SA2022