The Advanced Manufacturing Lab at Lawrence Livermore National Laboratory (LLNL) is continuing to make progress in the field of material design for 3D printing. In January, we covered the lab’s research into 3D printing microscopic trusses that resulted in a lightweight object with extreme rigidity. The 3D printing scientists and engineers at LLNL have now released a new study, titled “Three-Dimensional Printing of Elastomeric, Cellular Architectures with Negative Stiffness“, that delves into controlling the properties of foam materials.
Padding materials, like foams and gels, have their advantages and disadvantages. Gels, on the one hand, cushion well, but have added weight and poor compression properties. Foams, on the other hand, are lightweight, compressible alternatives that suffer the shortcoming of inconsistent performance, as controlling the characteristics and locations of air pockets in the material are difficult to control when manufacturing the stuff. The team at LLNL’s Advanced Manufacturing Lab, however, are beginning to develop the ability to control the physical properties of materials through digital design and 3D printing.
As with their previous work, LLNL’s researchers are able to program the material properties of a 3D printed object at the microscopic level, this time creating new cushioning materials that may overcome the limitations of foams and gels. Using a silicone-based ink, engineer Eric Duoss and scientist Tom Wilson, have 3D printed horizontally oriented rows of filaments, as fine as a human hair. On top of that layer, the researchers 3D printed filaments oriented in the vertical direction. They then continue to alternate each layer of filaments until they’ve created an object with the size and pore structure that they wish. The material is then cured to form a rubber-like substance.
In their experiments, Duoss and Wilson altered the alignment of these layers, printing each layer in an inline formation and printing them in a staggered formation. Doing so proved to yield objects that, though they were made from the same substance with the same porosity, would demonstrate markedly different physical characteristics. The stacked structure, for instance, was stiffer while under pressure, as each printed filament was able to support the filament immediately above. As that compression increased, the stacked structure would finally buckle. In the case of the staggered alignment, the material, softer when compressed, would bend, due the voids under each line of filament.
The researchers continue to model their materials, enabling them to accurately predict the behaviors of various structures before 3D printing them, something that would be almost impossible to do when manufacturing foams, with their unpredictable architectures. Duoss said of the research’s implications, “The ability to dial in a predetermined set of behaviors across a material at this resolution is unique, and it offers industry a level of customization that has not been seen before.”
In the future, LLNL’s researchers plan to explore the use of these padding materials to create inserts for shoes and helmets, cushioning materials for sensitive instruments, and to control temperature fluctuation and vibrations in aerospace parts.
