Quantitative study on the interfacial performance of micron-fiber cord/elastomer

Abstract

Fiber-reinforced rubber composites (FRRC) are extensively utilized owing to their superior performances, which stems from the efficient load transfer between the rubber matrix and reinforcing fibers through complex interfacial stress transfer mechanisms. In 1952, Cox's interfacial stress transfer model underscored the critical roles of interfacial thickness and modulus in determining interfacial debonding stress. Although the model remains foundational in understanding stress transfer mechanisms in FRRC, its application has been limited by the challenges in quantitatively measuring these interfacial parameters. This study addresses this gap by developing a polishing technique that integrates mechanical and ion beam polishing, specifically tailored for FRRC. By optimizing key parameters, including rubber thickness on fiber surface, ion beam polishing voltage and temperature, and fiber monofilament density, ultra-flat surfaces on micron-fiber cord/elastomer composites have been achieved. This enabled the successful visualization of the intricate tri-phase, two-interface structure using the quantitative nanomechanical mapping technique of atomic force microscopy (AFM-QNM). The interfacial thickness and modulus were then quantitatively characterized using AFM-QNM and nanoindentation techniques. Thus, the interfacial shear strength and debonding stress were successfully calculated using the KT and COX models. Using RFL-treated nylon 66 fiber/rubber composites as a case study, based on the quantitative characterization of interfacial thickness and modulus, the interfacial shear strength and interfacial debonding stress were quantified as 5.63 MPa and 112.14 MPa, respectively. By using such a method, a critical link between fiber surface treatment, interfacial performance, and macroscopic adhesion properties can be established, thereby facilitating the design and performance optimization of FRRC materials.