Abstract

This international peer reviewed paper was selected for its pioneering approach to developing new natural fibre textile composite materials for future composite markets. Contributors in this issue were selected from high profile experts that tackle issues on ‘Materials for a Low Carbon Future’ presented at the Natural Fibres ‘09 conference in Dec 2009 at The Institute of Materials, London. The author gave a keynote address at this conference. This progressive, hard-hitting paper details the challenges of evolving 3D reinforcements to reach the mechanical properties that established conventional laminates have realised. It highlights technical trade-off’s between old materials that fail in a familiar way and new materials that combat these failure mechanisms but fall slightly short (in certain tests) on enhanced properties. This paper is significant because it showed how much improvement had to be achieved rapidly by natural fibre composites (volume produced) in order to serve the needs of the expanding composites industry. Critical data was released into the public domain for future debate. PUBLISHED ABSTRACT: The cross-discipline research embodied in this paper has been generated from a technical textile design perspective, where the author, as an established technical weave designer, has developed 3D woven natural fibre preforms for composite production and subsequent testing. This research is a comparative study between commercially available 2D bi-axial woven plied composite laminate and 3D reinforced woven multiple layer composites using both flax and naturally derived viscose yarns for natural fibre composite applications. The objective is to determine the initial properties of two natural fibre 3D woven composites with relatively low fibre volume fraction and assess their performance against a standard natural fibre 2D woven fabric lay-up arrangement. In order to achieve this, the textile design and production cycle must be considered. The paper focuses on the design and assemblage of 3D woven textile preforms, discussing the complex design parameters associated with obtaining desired loom state fibre volume fractions within the 3D material. It also highlights the weave production issues that impact on the quality and integrity of 3D woven fabric architectures for flat and tailored reinforcements. Treatment experiments with 4% NaOH on flax yarns were attempted to establish if the woven fabrics would benefit from post-production treatment prior to resin processing to improve interfacial bonds between fibres and matrix. Once woven, it details the Vacuum Assisted Resin Transfer Moulding (VARTM) processing method using epoxy resin and presents initial results from mechanical test programs assessing flexural strength and damage resistance. By selecting a 2D 2/2 woven twill laminate and angle interlock (AI) 3D architecture as baseline control samples, an early assessment will establish the benefits and challenges these materials face, and their future potential. Findings from the research indicated that Alkali treatment of flax yarns was found to decrease the virgin and impregnated yarn tensile properties as well as the flexural strength and stiffness properties of the 3D woven angle interlock composites. 2D twill flax composites achieve a higher fibre volume fraction which, in turn, leads to superior flexural properties with respect to 3D AI composites. 2D 2/2 twill viscose rayon composites flexural strength and modulus were found to be superior to 3D angle interlock structures but inferior in damage resistance. The damage characteristics from impact resistance tests show differences in damage area, impact depths and the dispersal of subsidiary cracking. Test specimens demonstrate that 3D woven viscose rayon composites displayed mostly localized damage around the location and did not allow the damage to radiate out substantially which is in contrast to the delamination damage observed in the 2D material.From this publication the author was invited to be a member of the International Organising Committee for conference “Emerging Green Technologies”, the Annual Environmental Biopolymer Society (BEPS) in USA, held in Toronto, Oct 2010Keywords: WOVEN; PREFORM; NATURAL FIBRE COMPOSITES; VACUUM ASSISTED RESIN TRANSFER MOULDING (VARTM)Document Type: Research article DOI: 10.1166/jbmb.2010.1078