Printable epoxy core for hybrid manufacturing of composite sandwich structures

Composite sandwich structure cores are used for weight reduction without sacrificing stiffness, but their design is not engineered to optimize performance under given in-service loading conditions. In order to realize optimal performance, an engineer needs customizability, geometric complexity, and manufacturing process flexibility - all attributes of additive manufacturing. Another benefit of additive manufacturing is the potential to reduce the number of sandwich composite manufacturing steps by printing a core directly onto prepreg preforms with a material of similar chemistry and co-curing the structure. To this end, honeycomb cores are printed with a chopped fiber reinforced epoxy ink onto carbon fiber epoxy prepreg. As a comparison, sandwich composites are also fabricated by adhesively bonding printed and cured honeycombs onto composite laminates and tested in 3-point flexure. Progress and challenges with these processes are discussed.