This paper presents the findings of an experimental study to investigate the structural behavior of reinforced concrete (RC) beams externally strengthened with various types of kenaf fiber reinforced polymer composite laminates with 50% fiber volume content. The experimental parameters including flexural strength, stress-strain relationship, deflection, tensile stress and young modulus of beams strengthened by different kenaf fiber reinforced polymer composites are discussed. In order to test the flexural strength of the RC beams, a total of eight beams divided into two series were used. In each series, every two of the beams were strengthened with kenaf/epoxy, kenaf/polyester, and kenaf/vinyl ester composite laminates respectively. The remaining two were kept as control specimens. The experimental moment capacity of each beam was calculated using tensile strength and young modulus of the composites. Comparisons were made on the load-deflection, strain behavior and failure mode. Moreover, theoretical moment capacity of each beam was calculated using conventional formulation to verify experimental results. The research findings indicated that all strengthened beams improved structural performance where the maximum flexural strength increase by 40% and maximum deflection reduced by 24%.

Natural fiber is usually used as reinforcement in polymeric materials, and short fibers are commonly used for non-structural applications. However, the lack of studies on long fiber reinforced polymeric materials, especially kenaf fiber, has limited its usage in Malaysia. This paper presents the experimental results of a series of tensile tests conducted on continuous kenaf fibers produced with different types of thermoset resin (epoxy, polyester, and vinyl ester) arranged longitudinally. A total of 75 kenaf fiber reinforced polymer composites containing up to 50% fiber volume fraction including 15 neat samples as control samples were produced. Then, the samples were tested using Universal Testing Machine to obtain their tensile behaviour. Results indicated that the composites’ performance increased gradually with every increment of fiber volume fraction. Factors affecting the tensile behaviour of kenaf fiber reinforced polymers are also explained and discussed. In conclusion, kenaf fiber can be used as reinforcing materials in polymeric materials.