NOVEL GRADED HONEYCOMBS FABRICATED BY MATERIAL EXTRUSION ADDITIVE MANUFACTURING

摘要

Cellular materials offer unique combinations of strength, stiffness, and low density that are unattainable in traditional engineering materials. Natural materials utilize graded cellular architectures to access superior combinations of static strength and stiffness, dynamic properties, and functional properties (e.g. fluid flow) over uniform cellular materials while maintaining low density. Graded structures have been studied analytically in the past, but few experimental studies exist due to the difficulty in fabricating cellular materials with well-defined gradients. However, material extrusion additive manufacturing offers an ideal route to design, fabricate, and study the mechanical and functional properties of graded cellular materials. This talk will outline a novel method for fabricating graded honeycomb structures tailored for material extrusion AM, including both commercial fused filament fabrication (FFF) for thermoplastic materials (ABS and PLA) and custom direct ink writing for fiber- and nanoclay-reinforced epoxy composites. The talk will include characterization of different grading schemes and a discussion of their effects on stiffness, strength, and programmed collapse behavior using finite element analysis, experimental mechanical characterization, and analytical modeling. Results suggest that classical honeycomb mechanics models can be adapted to accurately predict the properties of graded honeycombs, and that gradients can be effectively utilized to "program" the post-yield behavior of graded structures. Potential applications of such structures will also be discussed.