Possibilities for improving the mechanical properties of jute epoxy composites by alkali treatment of fibres

The aim of this paper is the improvement of the mechanical properties of natural-fibre-reinforced thermosets, as a result of optimization of the properties of tossa jute fibres by the use of an NaOH treatment process. By this process shrinkage of the fibres during treatment had significant effects on fibre structure and, as a result, an the mechanical properties of the fibres. The highest fibre strength and stiffness were reached by using isometric conditions (shrinkage = 0%). The fracture mechanism of the fibre was also affected by the shrinkage state. Regarding fibre/matrix adhesion, the rougher surface morphology after NaOH treatment did not lead to any improvement. Composite strength and stiffness generally increased as a consequence of the improved mechanical properties of the fibres by NaOH treatment under isometric conditions. The Young's modulus of the composites was linearly dependent on fibre content for both untreated and treated fibre composites. The Young's moduli of composites with treated and untreated fibres were approximately 30% and 50%, respectively, lower than for comparable glass-fibre/epoxy composites. The improvement in dynamic modulus (measured in an increasing-load test) of the composites as a result of the use of treated fibres was similar to that observed for Young's modulus. Furthermore, the use of treated fibres and of higher fibre contents, both led to a decrease in fatigue behaviour and progress in damage in the composites. Impact damping was distinctly affected by the shrinkage state of the fibres during the NaOH treatment because of its influence on yarn toughness. A good correlation was found between composite impact damping and yarn toughness for the jute/epoxy composites investigated. (C) 1999 Elsevier Science Ltd. All rights reserved.