Environmental aging and its influence on mechanical integrity and interface of bio-filled E-glass/epoxy composites

The present research analyzes the impact of accelerated aging on the mechanical characteristics and environmental stability of E-glass fiber-reinforced epoxy composites containing Moringa Oleifera Seed Powder (MOSP) and Tamarind Shell Powder (TSP) in both acidic (acetic acid, CH₃COOH) and basic (ammonium hydroxide, NH₄OH) environments. The accelerated aging study was conducted over a period of 10 weeks, during which the tensile, flexural, and compressive properties of the composites were evaluated. The tensile strength of 3 wt% MOSP composites decreased by 56.5%, from an initial value of 395 MPa to 172 MPa after aging, while 3 wt% TSP composites exhibited a similar reduction of 55.6%, decreasing from 423 MPa to 188 MPa. Both 3 wt% MOSP and 3 wt% TSP composites showed significant reductions in flexural strength under acidic conditions, with decreases of 56.2% and 54.8%, respectively. Similarly, the compressive strength decreased by 60.8% for MOSP composites and 58% for TSP composites. In contrast, aging in a basic medium resulted in lower reductions in mechanical properties, with decreases limited to 26.6% for MOSP and 22.5% for TSP at their optimum filler concentrations. NH₄OH interacts less aggressively with the composite materials, primarily affecting the surface regions while preserving the fiber-matrix interfacial bonding. Microstructural analysis supported these findings by revealing significant matrix degradation and interfacial debonding in acidic-aged specimens, whereas the basic-aged samples largely retained their original morphological features. In the MOSP- and TSP-filled E-glass/epoxy hybrid composites, the evaluation of energy dispersive spectroscopy (EDS) further established that acidic aging resulted in significant elemental and interfacial deterioration as opposed to alkaline aging. The experimental results demonstrate the potential of natural fillers to enhance composite sustainability and longevity, while also emphasizing the importance of environmental stability for practical engineering applications.