Composite materials offer superior mechanical performance with lower weight than traditional materials. As a result, they are widely used in various industries, such as aerospace, automotive, construction, and sports. The composite industry is increasingly utilizing natural fibers and developing biodegradable composites in response to environmental sustainability concerns. Natural fibers have comparable physical and mechanical properties to glass fiber, making them suitable for use in the production of bio-composites. Despite this, natural fiber cannot fully replace glass fiber due to a variety of factors that influence the material's variable properties such as the type of fiber used, the conditions in which the fiber grows, the processing methods, and any modification of the fiber. Hence most of the research done on bio-composites has concentrated on using them in non-structural parts.

This project aims to develop and characterize a green and sustainable bio-composite system, to overcome existing application challenges. The constituent materials include a bio-resin extracted from seaweeds and Unidirectional Flax fibers as reinforcements to stiffen and strengthen for semi-structural applications. Although alginates have been studied in-depth for their biomedical applications, their potential as a bio-based matrix for biocomposites has not yet been explored.

In addition to the materials used in the composite preparation, the processing technique significantly impacts the final properties of the composite. Therefore, in the first half of the work, thorough research was conducted to study the constituent properties for their processing. The second half of the work defined a new approach to manufacturing bio-composites from natural constituents. The corresponding analysis useful for product design are thoroughly demonstrated in this thesis.

However, using natural fibers in composites and water alginate soluble matrices has three main concerns: the fiber/matrix interaction and their sensibility to moisture absorption and residual water within the composite structure. Their surfaces can be modified using physical and/or chemical methods to improve the bonding between fibers and matrix. In most studies cited in the literature, the chemical modifications employed are synthetic and toxic. It would be ideal if the chemicals used to modify natural fibers were bio-based and preserved the biodegradable nature of natural fibers.

The development of an optimized seven-step manufacturing approach is a key innovation for water removal, to enhancing fiber reinforcement and boosting overall composite performance, particularly in the use of flax fibers. This approach is notable for its novelty and challenge, as evidenced by the limited literature on the subject. It focuses on achieving sufficient impregnation by utilizing low water percentages in resin, specifically around 7\%, and applying appropriate consolidation pressure and temperatures. The most effective results were observed at 5 MPa and 95°C, which facilitated homogeneous plasticization and mouldability. Additionally, the method of wet/dry cycling, incorporating pre-soaking and heating, has proven beneficial in providing dimensional stability to flax fibers and limiting water absorption, further contributing to the technique's effectiveness.

Analytical techniques like microscopy and SEM reveal promising compatibility between components. No degradation of the bio-resin or the fibers relatable to the heat press was identified.

Finally, the research aimed to establish a meaningful relationship between the critical process variables and the properties of the bio-composite, with the ultimate goal of optimizing the production process and enhancing the quality of the final product by varying the fiber volume fraction within the range of 41-47\%.

The maximum tensile and flexural strengths achieved were 219MPa and 56Mpa, respectively. The elastic tensile and bending moduli in the composites were approximately 6.64GPa and 1.83GPa, respectively.

However, the observed properties fell below the predicted values for the biocomposite system, which were calculated using the rule-of-mixtures and Halpin-Tsai methods. Nonetheless, the experimental data confirm that these biocomposites can be used as secondary structural elements. The observed discrepancy was due to the presence of huge voids further leading to poor adhesion.