Effect of a surface coating on flexural performance of thermally aged hybrid glass/carbon epoxy composite rods

Polymer Core Composite Conductors (PCCCs) are subjected in-service to thermal aging which in some cases can be severe. To reduce aging a proprietary fluorinated ethylene propylene (FEP) based surface coating was applied to a hybrid glass/carbon epoxy composite rod used in Aluminum Core Composite Conductors (ACCC®), one type of PCCC. The rods were aged in air at 180 °C for up to 12 months. Surface damage was evaluated using optical and scanning electron microscopes and compared to uncoated rods previously subjected to the same conditions. Subsequently the rods were tested under four point bending to determine their flexural performances as a function of aging time. It was found that the uncoated rods lost significantly more flexural stiffness and strength than the coated rods. To explain the experimental mechanical data a Finite Elements Modeling (FEM) was performed. A new hypothesis is offered to explain the strongly beneficial effect of the coating in maintaining mechanical properties after thermal aging. Thus it appears that FEP or other coatings could be used to significantly reduce thermal aging of glass/carbon epoxy composites and in particular extend the life of PCCCs in service.