UTTFRWORTH EINEMANN Construction and Building Materials. Vol. 9, No. 1, pp. 3944, 1995 Copyright 8 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 095CUl618/95 %10.00+0.00 Mechanical behaviour of particulate hybrid composite laminates as potential building materials B. Singh*, Manorama Gupta and Anchal Verma Central Building Research Institute, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Roorkee-247 667, India Received 10 January 1994; revised 20 June 1994; accepted 7 July 1994 Sisal fibres and red mud were treated with different hydrophobic chelates based on titanium and silicon. The effect of the addition of treated red-mud loading on the mechanical properties of poly- ester resin has been investigated. Composite laminates have been prepared and their physico- mechanical properties were evaluated as a function of fibre length, fibre content, sisal/glass fibres and sisal/glass/red mud combinations. It was found that particulate hybrid composites had superior physico-mechanical properties than those of sisal/polyester, neat and filled unsaturated polyester resin. The suitability of particulate composites was also assessed in relation to medium-density fibreboard/high-density particleboard. Keywords: hybrid composite laminates; building materials; fibre reinforcement The use of natural-fibre-reinforced polymeric building materials has been strongly favoured .to promote the utilization of indigenous materials in the developing countries in view of their low cost, easy availability, saving in energy and pollution-free production. Natural fibres are much cheaper than glass fibres and could replace them in applications where cost consideration outweighs strength requirements. However, natural fibres have not been widely used commercially to rein- force more modern resins such as unsaturated polyester, epoxy, etc., despite extensive research. The major prob- lems associated with the applications of natural fibres in the composite industry are poor wettability, high mois- ture absorption and susceptibility to environmental degradation. In such composites, delamination due to moisture absorption leads to weakening of the inter- facial bond, thus causing a reduction in the mechanical properties of the composites. In an effort to overcome some of these disadvantages, several attempts have been made to modify the surface of these fibres either by imparting hydrophobicityi-5 or by applying a gelcoat/ glass fibres as a surfacing layeti to the composites. The work carried out by Winfield in India and Bangladesh on jute-reinforced polyester systems for the construction of cheap primary school buildings has been considered to be a major breakthrough in this field. Considerable work*-‘4 has also been attempted to develop plastic composite products based on natural fibres for various applications such as roofings, panellings, food grain silos and other low-cost housing units. Work on *Correspondence to Dr B. Singh natural-fibre-reinforced polymer composites was initi- ated at the Central Building Research Institute (CBRI), Roorkee, with the main objectives of finding costeffec- tive applications for use in different Indian climatic conditions. This paper describes the systematic work carried out so far on particulate hybrid composites based on glass/sisal fibres, red-mud filler, and unsatu- rated polyester resin. Experimental M aterials Sisal fibres were obtained from a local market (Roorkee), and their physicochemical, mechanical and surface topographic characteristics are as given in Table 2 and Figure I respectively. Glass mat (E. glass, weigh- ing 450 g m-2) was supplied by Pilkington Fibre Glass Ltd, India. The sample of red mud (industrial by- product) used in the experiments was collected from the Indian Aluminium Company (Indalco, India). Its chem- ical analysis is given in Table 2. Unsaturated polyester resin (HSR 8131) was received from Bakelite Hylam Ltd, India. Coupling agents such as gamma-Methacryl- oxypropyltrimethoxy silane, A-174 (Union Carbide, USA), and neopentyl (diallyl)oxy, tri (dioctyl) pyro- phosphatotitanate, LICA-38 (Kenrich, USA), were used as supplied. FibreBiller coating procedure Red- mud coating Red mud was first calcined at 200 “C for 24 hours and washed with distilled water. The sample was dried at Construction and Building Materials 1995 Volume 9 Number 1 39