Analyzing and testing bimetallic additively manufactured structures for tailored thermal expansion

Purpose Designing structures with low thermal expansion is critical in aerospace and space applications, especially for optical instruments that require support structures capable of withstanding extreme thermal conditions with minimal displacement. Conventionally, supports are fabricated from materials like Invar or composites that are expensive and have limited operating temperature ranges. This research aims to explore the use of multi-material (bimetallic) additive manufacturing (AM) to produce structures with controllable thermal expansion by combining materials with different coefficients of thermal expansion (CTEs). Design/methodology/approach Triangular structures were designed and printed using directed energy deposition with IN625 and SS316L metals. These bimetallic structures underwent thermal expansion testing and numerical models were developed for validation. Findings Experimental results closely matched numerical simulations with an average error of approximately 5%. This validated the use of AM for bimetallic structures and the capability of bimetallic triangular designs to control thermal expansion. Originality/value Researchers have previously developed geometric designs and material combinations with low CTEs; however, a significant CTE differential between materials is needed to achieve dissimilar thermal expansion. This allows for the structures to have controllable effective CTEs. Generally, adhesives, snap-fit joints or welds are used to combine different materials. However, limited research exists on using AM to design bimetallic structures for controllable thermal expansion. This study demonstrates the feasibility and effectiveness of this approach, leading to the development of a bimetallic support structure for an optical instrument that meets critical requirements.