18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS 1 Introduction SustainComp, a project sponsored by the Seventh Research Framework Programme (FP7) of the European Union (EU), has as one of its main goals to develop advanced cellular composites based on renewable resources, for application in the fields of packaging, display and core materials [1,2]. Fibre reinforced foams have the potential of being lighter, stiffer and stronger than conventional foams. Until now wood fibre reinforced polylactic acid (PLA) composite foams have been successfully produced using supercritical carbon dioxide. Upon addition of wood fibres the stiffness properties of the foams in compression improve. A significant increase of specific stiffness was achieved by adding 5-10 wt% wood fibres [1]. The aim of this particular work has been to develop a process to produce sandwich materials where the faces are composites of PLA and wood fibres and the core is a foam structure of PLA, which might also be reinforced with wood fibres. Sandwich structures represent a key component of composites structural design technology. They provide the structural efficiency of very lightweight material (core) “sandwiched” between higher stiffness and strength laminates (skins) in order to carry tension, compression and shear loads imposed upon the resultant structure. The primary properties of interest for the core material are typically low density and high compression and shear stiffness and strength as well as good bonding with the skins. PLA foams, both neat and reinforced with wood fibres, are investigated as a core material for sandwich structures intended for packaging applications. 2 Materials and Methods 2.1 Preform Manufacturing Stratified preforms of PLA fibres (PLA01, N.I. Teijin Shoji Co. Ltd., Japan) and wood fibres (fully bleached birch, Innventia AB, Sweden) were manufactured using a wet commingling technique similar to slurry processing in papermaking [1]. A black colouring agent (Cartasol, Sandoz AG, Switzerland) was used to dye the wood fibres. The colouring reduces the dewatering time during preform fabrication [3]. Only wood fibres used to reinforce the core material were died since preliminary results showed a very poor adhesion between the PLA and coloured wood fibre skins. It has been shown in another work that treatment of the wood fibres with a surfactant can contribute to increase the foam expansion attributable to reduced wood fibre network forming ability [4]. However, due to worse fibre-matrix adhesion of treated fibres, foams with inferior strength properties were obtained. Each preform weighed 2 g and consisted of a fibre mat composed of three layers, i.e. the two wood fibre skins and the PLA core in between. The wood fibre content in the core was changed from 0 to 10 wt%. The preforms were dried in a ventilated oven at 55°C for more than 24 hours before being consolidated by compression moulding at 120°C and 200 bar for 10 min. Additional drying before any NOVEL BIODEGRADABLE WOOD FIBRE POLYLACTIC ACID FOAM SANDWICH COMPOSITES R.C. Neagu 1* , L. Bertolla 2 , C.I.R. Boissard 1 , F. Berthold 2 , P.-E. Bourban 1 , E.K. Gamstedt 3 , J.-A.E. Månson 1 1 Laboratoire de Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, 2 New Materials and Composites, Innventia AB, Stockholm, Sweden 3 Applied Mechanics, Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Uppsala, Sweden * Corresponding author (cristian.neagu@epfl.ch ) Keywords: cellular materials, foams, wood fiber, polylactic acid, sandwich material