Adhesive joining is the most common and preferred technique when manufacturing complex fiber-reinforced composite structures due to the reduction in stress concentrations and stress cracking introduced by mechanical fasteners. Current adhesive joining technologies often require additional fixtures and assembly steps that introduce defects at the bond line. This results in a labor-intensive process with limitations in quality and cycle time.
A new process has been developed for joining composite members utilizing additive manufacturing and a two-stage (B-stage) curing resin. The resin is additively manufactured using a UV process; resulting in a rigid but only partially cured part. This rigid part is then positioned between pre-impregnated fiber reinforcement and the assembly is heated to activate the second curing reaction and co-cure the two materials. By matching the resin of the printed part with the resin of the pre-impregnated fiber reinforcement, a permanent void-free adhesive bond can be achieved, which not possible with standard methods. Furthermore, the parts can have intricate internal structures, including customized features to improve joint performance and assembly, which can only be produced with additive manufacturing (e.g. honeycomb, lattice, flow channels, etc.). The combination of partially-cured parts and pre-impregnated fibers results in a new family of hybrid high-performance composites.
This study investigates the integration of 3D printed parts produced with Continuous Liquid Interface Production (CLIP) using an epoxy resin system and pre-impregnated carbon fiber fabrics. The adhesive performance of hybrid parts is initially evaluated through single-lap shear joint testing and compared to traditionally manufactured components. Additional optimized geometries are explored utilizing the design flexibility provided by the CLIP process. Benefits are observed in the mechanical performance, assembly time, and repeatability of the hybrid structures.
Epoxy lattice stiffener
Customized epoxy joining element for carbon fiber T-joint