Cactus fibre/polyester biocomposites: Manufacturing, quasi-static mechanical and fatigue characterisation Mustapha Bouakba a , Abderrezak Bezazi b , Katarzyna Boba c , Fabrizio Scarpa c,⇑ , Stuart Bellamy d a Université Kasdi Merbah Ouargla, Route de Ghardaia 30000, Algeria b Laboratoire de Mécanique & Structures (LMS), BP. 401, Université 08, Mai 1945, Guelma 24000, Algeria c Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol, BS8 1TR Bristol, UK d Bristol Centre for Nanoscience and Quantum Information, University of Bristol, BS8 1FD Bristol, UK article info Article history: Received 25 September 2012 Received in revised form 8 October 2012 Accepted 11 October 2012 Available online 31 October 2012 Keywords: A. Structural composites A. Wood B. Mechanical properties B. Fatigue C. Finite element analysis (FEA) D. Infrared (IR) spectroscopy abstract The work describes the fibre extraction, manufacturing and testing of biocomposites made from cactus fibres and polyester matrix. A novel fibre extraction process has been developed, allowing the production of fibres from cactus cladodes with three distinct architectures in terms of microstructure morphology. Biocomposites with polyester matrix have been fabricated, and subjected to tensile and flexural loading. The flexural mechanical properties have been also identified through cyclic (1.5 Hz) 3-point bending tests at different loading ratios (0.60–0.95) and up to 10 6 cycles following the ASTM D790 standard. The cac- tus/polyester composites show a flexural modulus significantly higher compared to their tensile analo- gous, and large energy dissipation per unit volume at low cycles and high loading levels. Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. 1. Introduction The last three decades have seen a rising level of R& D activities connected to the development of composite structure completely or partially obtained from natural materials [1,2]. Natural fibres such as flax, hemp and sisal have been proposed as substitutes for glass fibres also in structural applications [1–6]. From a more general perspective, eco or bio-design is becoming an increasingly popular engineering approach to tackle modern technology, and the possible use of ligno-cellulose based fibres is becoming an interesting sustainable alternative in structural composites rein- forcements [7]. Different techniques have been developed in the past to extract natural fibres in a viable and environmentally sus- tainable process. An approach successfully used to extract dates fi- bres is the water immersion [8], but other extraction techniques involve the use of chemical solutions like the alkalies, which are detrimental from an ecological perspective [9,8]. A wood plant that provides fibres with interesting mechanical properties is the cac- tus, with the Stenocereus Gummosus variety having being investi- gated by Niklas et al. [10]. The present paper describes a novel manufacturing route to produce cactus fibre/polyester composites, and the mechanical properties under tensile and flexural behaviour of the biocomposites specimen produced. The cactus fibres are derived from parts of the Opiuntus ficus-indica, a variety of cactus spread over large parts of Mediterranean and North African coun- tries. To the best of the Author’s knowledge, no previous attempt has been performed at manufacturing fibres for structural rein- forcement from the cladodes of cactus plants. Specific focus is also placed on investigating the fatigue behaviour of these novel cac- tus-based biocomposites subjected to cyclic flexural loading. Three different fibre architectures have been identified from the extrac- tion process, corresponding to different location of the cactus trunk. A quasi-static tensile loading has been initially performed to select the fibre with the highest stiffness and strain to failure, to be then used as standard reinforcement for the composites sub- jected to flexural loading. While tensile fatigue of biocomposites has been investigated extensively by other researchers [11–13], to the best of the Author’s knowledge, this paper describes also the first work dedicated to the flexural fatigue of structural com- posites reinforced with natural fibres. The composite obtained from the cactus reinforcement has an overall in-plane low modulus (only 80% higher than the polyester base matrix), which makes the biocomposite material suitable only for secondary or tertiary struc- tural applications. However, the cactus fibre reinforcement pro- vides a significant bending stiffness, up to 5.3 times the axial one, making therefore the cactus fibre an interesting reinforcement for applications were flexural deformation scale in a more signifi- cant way. 0266-3538/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.compscitech.2012.10.009 ⇑ Corresponding author. E-mail address: f.scarpa@bristol.ac.uk (F. Scarpa). Composites Science and Technology 74 (2013) 150–159 Contents lists available at SciVerse ScienceDirect Composites Science and Technology journal homepage: www.elsevier.com/locate/compscitech