Influence of flax fiber orientation on mechanical, thermo-mechanical and interfacial adhesion properties of epoxidized methyl ricinoleate modified epoxy composite: A sustainable green composite for cleaner production

Renewable natural fibers have been better eco-friendly reinforcing agents for plant oil toughened epoxy composites in order to achieve the desired properties for structural applications. In the current work, epoxy methyl ricinoleate (EMR) synthesized from castor oil was used to modify epoxy to tailor the stiffness-toughness balance. For the first time, an epoxy/EMR blend has been used to fabricate the composite. The fiber pull-out test showed a 17% increment in interfacial shear strength on adding 20% EMR to epoxy and hence this modified epoxy was reinforced with UD (Unidirectional) mat at three different orientations i.e. [0/0], [0/90] and [90/90]. The [0/0] orientation laminates displayed the highest tensile, flexural, and impact strength with an increment of 120%, 151% and 858% respectively as compared to epoxy/EMR copolymer, whereas [0/90] orientation laminates showed superior translaminar fracture toughness and critical strain energy release rate with an increment of 216.5% and 494% respectively. Different theoretical models and a combination of classical lamination theory and modified rules of mixture were adopted to fit with the obtained experimental tensile strength and modulus values of appropriate laminates. Thermogravimetric and dynamic mechanical analysis confirmed the desired thermal stability and damping ability of the composites. Scanning electron microscope (SEM) morphology of the fractured surface and Water Contact Angle (WCA) of the surface of composites were studied to explain the fibermatrix interface mechanism and wettability of the samples respectively. The results demonstrated that the EMR Modified Epoxy Composite can be an alternative to synthetic epoxy composites in automobile and structural applications.