Effect of Alignment and Sizing on Mechanical Properties of Discontinuous Recycled Carbon Fiber Composites

Abstract

The exceptional combination of properties offered by carbon fiber composites has propelled their incorporation into high performance markets such as aerospace, wind energy, and luxury cars and sporting goods. However, the high price and energy cost associated with carbon fiber production acts as a significant barrier of entry into larger volume markets, such as the automotive industry. Recycled carbon fiber, reclaimed from carbon fiber composites, can potentially provide comparable mechanical properties to those of virgin carbon fibers at a fraction of the cost. However, the recycling process tends to alter the fiber surface and typically produces discontinuous fibers in loosely packed, fluffy clumps, which require further processing before composite remanufacturing is feasible. In this study, the effect of sizing and alignment on the mechanical properties of recycled carbon fiber composites was investigated. Composites containing Toray T800 carbon fibers were recycled using a wet chemical recycling method (by Adherent Technologies Inc.), and a polymer sizing was applied to a portion of the fibers. The surface of these fibers was characterized with scanning electron microscopy (SEM) and x-ray photoelectron microscopy (XPS) to determine the level of damage and functional groups resulting from the recycling and sizing processes. The mechanical properties of the recycled fibers were measured using single fiber tensile tests, and the interfacial shear strength was found using single fiber fragmentation tests. The fibers were then processed into aligned and randomly oriented mats that were manufactured into composites using either resin transfer molding (RTM) or wet layup. The effect of sizing, alignment, and manufacturing method are then assessed with respect to the composite tensile properties.