Influence of CO₂ laser surface treatment of basalt fibers on the mechanical properties of epoxy/basalt composites

In fiber reinforced composite materials, the interfacial strength between the fibers and the matrix plays a key role in controlling the stress transfer and damage mechanisms of the composite. In this study, CO₂ laser surface treatment of the fibers was investigated as a potential sustainable substitute for conventional chemical treatments, that can be costly and have negative environmental effects. The influence of the laser treatment on basalt fiber fabric was comprehensively investigated. The fibers were subjected to different laser power levels and characterized from a morphological and mechanical point of view. From optical and scanning electron microscopy, it was observed that the treated fibers manifested increased surface roughness along with spots of fused and bonded fibers. Individual treated fibers exhibited improved tensile properties with increased values of scale parameter (by about 21%) in the case of a laser power equal to 1.04 W/mm², and no substantial changes in Young's modulus. The treated fibers were subsequently used in the preparation of epoxy-based microcomposites, and microdebonding tests revealed an increase in the interfacial shear strength (IFSS) up to 8%. Therefore, this work proved that a laser surface treatment of basalt fibers is a valid alternative to conventional fiber surface modification to enhance the mechanical compatibility between fibers and matrix, and therefore to improve the mechanical performances of basalt fiber composites. Highlights: Failure in composites due to weak interfacial adhesion with epoxy. CO₂ laser treatment of basalt fibers to enhance interfacial adhesion. Treated fibers exhibit improved tensile properties. Treated fibers manifested improved interfacial shear strength (IFSS, +8%).