Lightweight laminate composites made from kenaf and polypropylene fibres

Lightweight laminate composites made from kenaf and polypropylene (PP) fibres were fabricated by press forming. The effects of the number of kenaf layers, heating time and kenaf weight fraction on the flexural modulus of the composite specimen were investigated. The flexural modulus increased with increasing number of kenaf layers and heating time. The increase of the number of kenaf layers contributed to homogeneous PP dispersion in the composite board. This is because more kenaf layers caused better contact between kenaf and PP and prevented PP fibres from shrinking by heating. The increase of heating time contributed to better wetting between kenaf and PP. These observations were revealed with SEM microphotographs. Moreover, the flexural modulus difference between experiment and calculation, which was predicted by Cox's model, increased with decrease of the bulk density and PP weight fraction in the composite board. This was attributed to the decrease of the contact area between kenaf and PP decreasing stress transfer efficiency by kenaf in the lightweight laminate composites. Thus, the optimized kenaf weight fraction, which showed maximum flexural modulus of the composite specimen, decreased with decrease of the bulk density. (c) 2005 Elsevier Ltd. All rights reserved.