Displacement behaviour in nano-modified epoxy coatings: A Box-Behnken approach

Abstract

The present study focused on the development and balanced in-range displacement optimization of multifunctional epoxy-based hybrid coatings reinforced with graphene, boron carbide, zinc borate, and organic fibers. A Box-Behnken experimental design was applied to evaluate the individual and interactive effects of additive ratios on displacement behaviour under three-point bending. The primary objective was to maintain stable mechanical performance by keeping displacement within an application driven target window rather than maximizing/ minimizing a single metric. A total of 29 experimental runs were conducted with four variables at three levels. The optimum formulation was determined with nano additives as 0.5 wt% graphene, 0.5 wt% B4C, 1.0 wt% zinc borate, and 0.5 wt% organic fiber. The model showed high predictive reliability with R2 = 0.9926, adjusted R2 = 0.9852, and predicted R2 = 0.9685. Thermal analysis via TG-DTA demonstrated that the optimized coating exhibited a main degradation point at 317 degrees C. FT-IR analysis confirmed the chemical integration of the additives through characteristic peaks. SEM images showed a homogeneously dispersed microstructure with minimal agglomeration. These results indicated that the proposed composite system delivers balanced displacement within the target range while preserving load support and structural integrity, together with improved thermal stability, providing an opportunity for high performance engineering applications.