Effect of plasma surface activation on bond strength and mechanical performance of flax/epoxy composites

Atmospheric pressure plasma (APP) is a sustainable surface treatment technique that has gained traction for its ability to activate and coat various materials. This research focuses on the treatment of flax fabrics using both dry air and argon APP, investigating the resultant effects on their wettability and physical and chemical structures. The evaluation methods employed include contact angle measurements, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and Energy-dispersive X-ray spectroscopy (EDX). Following the treatment, flax/epoxy composites were fabricated utilizing the vacuum-assisted resin infusion method, a process known for its efficiency in composite manufacturing. To assess the mechanical properties of the composite samples, comprehensive tensile and interlaminar shear strength (ILSS) tests were conducted. The results from the contact angle tests indicated a significant improvement in the wettability of all APP-treated fibers compared to their untreated counterparts, attributed to alterations in surface morphology on the fiber surfaces and the formation of oxygen functional bonding. EDX analysis revealed an increase in oxygen content on the treated fibers, enhancing the fiber-resin interfacial bonding. By comparing the Young’s modulus of untreated flax fiber composite (0.89 GPa), it significantly increases by 121.29% for dry air APP-treated fiber and 96.58% for argon APP-treated fiber. For the shear modulus of flax fiber composite, it increases 41.97% for argon gas APP-treated fiber (9.37 MPa), and 15.45% for APP with argon treated fiber (7.62 MPa). The tensile and ILSS test outcomes demonstrated that APP treatment enhances both the tensile properties and bond strength of the flax/epoxy composites, suggesting its potential for advancing composite material performance in various applications. This study highlights the efficacy of APP as a transformative approach in material science.