Green hybrid composites for automotive roof applications: experimental study and design optimization using reused PET and jute fiber reinforcements

This study explores the development, experimental evaluation, and optimization of a hybrid jute/PET fiber-reinforced polyester composite for lightweight automotive applications, particularly bus roof panels. 10 laminates were prepared by varying the weight fractions of Jute and PET fibers and their stacking sequences. These laminates were grouped into four categories: (1) pure Jute/Polyester laminates, (2) hybrid Jute-PET configurations with alternating layers of Jute and PET (J-P-J-P), (3) hybrid configurations with a PET-dominated outer layer (P-J-J-P), and (4) hybrid configurations with a Jute-dominated outer layer (J-P-P-J). The weight fractions of Jute and PET fibers ranged from 10% to 40%, with the remaining content being polyester resin. Mechanical testing, including tensile, compressive, flexural, and impact tests, showed that hybridizing with PET slightly reduced tensile and compressive strengths but significantly improved flexural strength, impact resistance, and reduced water absorption. The stacking sequence influenced performance, with the P-J-J-P configuration identified as optimal through the TOPSIS multi-criteria decision-making method. Optimization using HyperWorks-OptiStruct resulted in a 34.58% mass reduction in the bus roof panel, leading to an estimated fuel saving of 0.146 L per 100 km. Finite element analysis (FEA) with Abaqus validated the results, showing minimal displacement (3.88 mm) and a safety factor aligned with failure criteria. These findings demonstrate the potential of hybrid Jute/PET composites as a sustainable, high-performance alternative to steel in automotive applications.