Performance Analysis of CFRP Composite Interface Engineered With Bioactive Polymer‐Supported ZnO Nanoflakes Coating for Improved Bending Strength

ABSTRACT This research explores the integration of ZnO nanoflakes in a dual‐layer format using a bio‐adhesive polymer on carbon fibers to improve the interlocking between the fiber and matrix in carbon fiber‐reinforced polymer (CFRP) composites. A systematic approach to surface preparation was employed, which included the removal of polymer sizing, oxidative treatment, and the preparation of polydopamine (PDA) from dopamine to enhance ZnO adhesion. X‐ray photoelectron spectroscopy indicated improved surface functionalization, while Raman spectroscopy verified the successful deposition of ZnO and structural changes. The innovative two‐step process involving PDA layering followed by ZnO flake deposition led to a significant increase in flexural strength and toughness, with improvements of 48% and 89.4% compared to untreated fibers. Fractography analysis showed that ZnO nanoflakes improved interfacial bonding, minimized fiber pull‐out and delamination, and altered failure modes to matrix cracking and fiber breakage. ZnO nanoflakes functioned as nanoscale bridges, enhancing stress transfer and energy absorption.