The present work deals with the characterization of interwoven roselle/sisal fiber fabric reinforced epoxy composites. All the composites are manufactured using the hand layup technique, and the physical (density), mechanical (tensile, flexural, and impact) and dynamic mechanical characteristics are determined as per ASTM standards. The findings reveal that roselle fabric composite has superior mechanical properties than interwoven roselle/sisal fabric composites. The tensile and impact strengths of the sisal fabric composite are lower than those of the roselle fabric composite. However, the roselle fabric composite and sisal fabric composite have similar flexural properties. The sisal fabric composite yields the highest peak value of the loss factor. The loss factor peak height for the roselle/sisal fabric composites increases with increased sisal fiber content. Morphological analysis revealed proof of yarn pullout and matrix damage near the yarn, indicating inadequate stress transfer between the fabric and epoxy. The property map is presented in comparison with available literature.
The influence of weaving architecture on mechanical and dynamic mechanical properties of woven roselle fiber epoxy composite has been investigated. Plain, twill, satin, and basket type weaving patterns are considered for this study.Hand lay-up process is used to produce the woven composites. Mechanical tests (tensile, flexural, and impact test) and dynamic mechanical analysis are conducted according to ASTM standards for material characterization. Results revealed that basket type architecture of woven roselle fiber epoxy composite has better tensile, flexural, and impact strengths. Woven composites have improved storage modulus in comparison with neat epoxy. Woven composites have 3% to 15% lower glass transition temperature than that of neat epoxy.Scanning electron microscopy (SEM) analysis is carried out to correlate the experimental findings. SEM images showed evidence of fiber pullout and cracks near fiber bundle, which indicates non-uniform transfer of stress from fiber to the matrix.
The effect of roselle fabric weave pattern on water absorption and thickness swelling behaviour of woven roselle fibre composites has been investigated. Roselle fabrics with various weaving design such as plain, twill, satin and basket are used in this study. All composites are produced using hand layup process. The water absorption and thickness swelling behaviour of all composites are studied as per ASTM standards. The test samples were immersed in distilled water at room temperature and change in weight and thickness of the test samples recorded at every 24 hour time interval. For all composite samples, saturation in water absorption and thickness swelling was observed after 264 hours of water immersion. Result revealed that the plain-woven composite yields higher resistance to water absorption and thickness swelling than other types of composites.
The influence of fibre orientation on physical, mechanical and dynamic mechanical properties of Hibiscus sabdariffa fibre composites has been studied. The composites with longitudinal (0°), transverse (90°) and inclined (45°) fibre orientation were prepared using the hand layup technique. ASTM standards were used for characterization of continuous Hibiscus sabdariffa fibre composites. The composite with longitudinally placed fibres yields improved mechanical characteristics. The addition of longitudinal (0°) oriented continuous Hibiscus sabdariffa fibres to the epoxy enhances tensile strength by 460%, flexural strength by 160% and impact strength by 603% compared to neat epoxy. The longitudinal (0°) fibre oriented composite offers higher resistance to water absorption and thickness swelling compared to other types of composites. All continuous Hibiscus sabdariffa fibre epoxy composites possess an improved storage modulus than the neat epoxy resin. The glass transition temperature of continuous Hibiscus sabdariffa fibre composites is 8%–31% lower than that of neat epoxy. Scanning electron microscopy (SEM) images confirm the existence of voids in the matrix, fibre pullout and crack propagation near the fibre bundle, which indicates the stress transfer between fibre and matrix is non-uniform.
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