摘要：In this study, control factors which included aspect ratio of fibres, volume fraction of fibres and fibres orientation were the focus for determining the optimum tensile strengths of coir fibres reinforced polyester resin composites. After using Archimedes principle to determine the volume fraction of fibres, tensile test was conducted on the samples of treated and untreated coir fibres reinforced polyester resin composites, respectively. For the optimum properties to be obtained, a Universal Testing Machine-TUE-C-100 was used for the conducted tensile tests which established the levels of control factors settings for quality characteristics needed to optimize the mechanical properties being investigated. Applying Taguchi robust design technique for the greater-the-better, the highest signal-to-noise ratio (S/N ratio) for the quality characteristics being investigated was obtained employing Minitab 16 software. The optimum values of the control factors were established for treated coir fibres reinforced polyester resin composites and untreated coir fibres reinforced polyester resin composites. The treated coir fibres reinforced polyester matrix composite has the optimum tensile strength of 42.7 N/mm2 while the untreated coir fibres reinforced matrix composite has the optimum tensile strength of 21.9 N/mm2. The reinforcement combinations of control factors contribute greatly to the tensile properties, and the treated coir fibres reinforced polyester composites are stronger in tension than the untreated coir fibres reinforced polyester composites.