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 na tural-fibre-reinforced thermosets, as a result of optimization of the prope rties of tossa jute fibres by the use of an NaOH treatment process. By this process shrinkage of the fibres during treatment had significant effects o n fibre structure and, as a result, an the mechanical properties of the fib res. The highest fibre strength and stiffness were reached by using isometr ic conditions (shrinkage = 0%). The fracture mechanism of the fibre was als o affected by the shrinkage state. Regarding fibre/matrix adhesion, the rou gher surface morphology after NaOH treatment did not lead to any improvemen t. Composite strength and stiffness generally increased as a consequence of the improved mechanical properties of the fibres by NaOH treatment under i sometric conditions. The Young's modulus of the composites was linearly dep endent on fibre content for both untreated and treated fibre composites. Th e Young's moduli of composites with treated and untreated fibres were appro ximately 30% and 50%, respectively, lower than for comparable glass-fibre/e poxy composites. The improvement in dynamic modulus (measured in an increas ing-load test) of the composites as a result of the use of treated fibres w as similar to that observed for Young's modulus. Furthermore, the use of tr eated fibres and of higher fibre contents, both led to a decrease in fatigu e behaviour and progress in damage in the composites. Impact damping was di stinctly affected by the shrinkage state of the fibres during the NaOH trea tment because of its influence on yarn toughness. A good correlation was fo und between composite impact damping and yarn toughness for the jute/epoxy composites investigated. (C) 1999 Elsevier Science Ltd. All rights reserved .