Creep and Aging Evaluation of Phenol–Formaldehyde Carbon Fiber Composites in Overhead Transmission Lines

Abstract

The use of reinforced polymers as cores of transmission cables can provide significant advantages compared to traditional steel cores, such as high tensile strength, low thermal expansion coefficients, and low sag between towers. This work evaluates the applicability of pultruded rods consisting of phenol–formaldehyde resin reinforced with carbon fiber as cores of transmission cables. In this work, the samples were divided into three groups: samples without aging, and samples UV and thermally aged. At first, a dynamic mechanical analysis was performed on samples without aging in order to determine the viscoelastic properties of the material based on the application to see if it would be compatible. In addition to this test, tensile strength and Young's modulus were determined for the three groups. Since the composite cores are susceptible to creep in high temperatures, the applicability must be below the glass transition temperature. Regarding creep behavior, results showed that at a reference temperature of 100 °C, the stress level necessary to cause failure after 50 years was 89% of the ultimate strength. The results of tensile tests were favorable for application of the pultruded system as transmission cables cores and the accelerated aging affected positively in these composites.