Development of an image-based tomographic methodology for the design of jute fibre-reinforced composite materials

This study investigates the influence of fibre dispersion and orientation on the mechanical performance of jute fibre-reinforced polyester compression moulded composites fabricated via the sheet moulding compound route. Fibre assemblies were collected from different stages of industrial yarn preparation viz. spreader, breaker card, finisher card, and successive drawing processes, to evaluate how mechanical processing governs microstructural organisation within composites. A dual-mode optical imaging approach (surface reflection and backlit transmittance) combined with MATLAB-based image analysis was developed to quantify microstructural descriptors, namely the dispersion index ( I d ), orientation index ( I o ), and normalised fibre count per unit area ( N f p 2 ). Among the investigated stages, breaker card sliver exhibited the most homogeneous fibre distribution ( I d = 0.3167) and a multidirectional orientation profile, enabling improved resin infiltration and interfacial stress transfer. Scanning electron microscopy confirmed fibre-dominated fracture behaviour in these composites, whereas poorly dispersed structures exhibited fibre pull-out and void-induced failure. A modified mixture theory model was formulated by incorporating image-derived dispersion and orientation indices into the classical rule of mixtures. Model coefficients were calibrated using experimental tensile and flexural data, and validation was performed through finite element analysis (FEA) to identify stress concentration zones. The model predictions showed close agreement with experimental results, particularly for composites exhibiting uniform microstructural distribution. The study demonstrates that fibre dispersion quality, rather than fibre quantity alone, governs mechanical performance. The proposed image-integrated modelling framework provides a practical methodology for process–structure–property design of sustainable jute-based composite materials.