Surface modification of basalt fibers and its effect on the mechanical properties of basalt fiber/epoxy composite laminates

Basalt fibers (BFs) are being explored due to their excellent thermo-mechanical properties and commercial value. However, additional surface modifications are needed to improve the interfacial adhesion of the fibers with the matrix. Therefore, the present work explored the applicability of nitric acid, oxalic acid, and silane reagents as surface modification agents. The fibers were subjected to immersion in the chemicals for a varied length of time. The laminates were fabricated using a wet layup process and compression-cured. The developed composites were subjected to mechanical testing to ascertain the effect of the selected surface treatment acids and the treatment duration on the tensile, impact, and flexural strength. Acid treatment was found to be beneficial for improving the mechanical properties of the laminates due to the generation of several functional groups on the surface of the acid-treated fibers. The mechanical properties of the laminate improved for nitric acid treatment in comparison to oxalic acid treatment. With respect to time, the mechanical properties of the laminate improved when nitric acid treatment time was increased to 30 min from 15 min. However, when oxalic acid treatment was performed for 180 min instead of 90 min, there was an observed reduction in the mechanical properties of the laminates. The highest increase in the tensile strength was noted in composites manufactured using fibers subjected to primary acid treatment and secondary silane treatment. Conclusively, nitric acid treatment was most beneficial as it helped improve the tensile, impact, and flexural strength of the BF/epoxy composites.