Exploring the influence of stacking sequence on the mechanical properties of flax-ramie bi-quadratic layered hybrid epoxy composites

Abstract Over the past two decades, there has been a remarkable surge in the utilization of composites, with fiber-reinforced polymer composites gaining significant traction owing to their commendable structural performance. Concurrently, extensive research has been conducted to assess the behavior of composite materials, focusing on various parameters such as fiber type, lamination order, matrix type, and the inclusion of filler materials. In this study, we investigated the mechanical properties of flax (F)/ramie (R) epoxy hybrid composites, specifically exploring the effects of different lamination sequences. Four distinct lamination sequences were chosen: FFRR, FRFR, FRRF, and RFFR. The composites were fabricated using compression molding techniques, adhering to ASTM standards for the evaluation of mechanical properties including tensile strength, flexural strength, impact strength, and interlaminar shear strength. Among the laminate sequences studied, FRFR exhibited the lowest void content at 4.76%, while RFFR composites showed the highest void content at 16.67%. The most favorable results were observed with FRFR composites, boasting a tensile strength of 77.06 MPa, impact strength of 13.36 kJ m⁻², and interlaminar shear strength of 8.13 MPa. Notably, the FFRR composite exhibited the highest flexural strength at 118.09 MPa. Additionally, scanning electron microscopy (SEM) analysis was conducted to investigate surface morphology and identify reasons for failure.