Design and Validation of Material Properties of Additively Manufactured Latticed Materials

Additive Manufacturing (AM), or 3D printing, has gathered increased interest for radio frequency (RF) applications in recent years due to its ability to easily fabricate complex shapes at a low cost. One such application of interest is additive manufacturing of dielectric materials. Through varying the percent fill volume of a print, the bulk material properties can be changed. One method of altering the percent fill volume is through the use of lattice structures, or repeating geometric patterns, through a volume. The lattice is appropriately designed to result in a sample with a specific percent fill volume. This percent fill volume defines the ratio of material to air which in turn defines the bulk dielectric constant of the sample. This paper demonstrates the use of AM and lattice structures to alter the bulk material properties. The latticed material designs are validated through simulated and measured samples. These results are compared to common dielectric mixing approximations to gauge the accuracy of these approximations for latticed AM materials. Included is a parametric study of commonly used lattice structures at different percent fill volumes which is analyzed for variations on bulk dielectric constant due to geometry variations. Theoretically, the bulk dielectric constant should not change so long as the lattice unit cells are sufficiently smaller than the wavelength of the frequency of operation. Additionally, since many 3D printing materials are not well characterized, or do not provide, the necessary material properties critical for RF design, like dielectric constant and losses through the material, a free space lens system is utilized to initially characterize and compare some common 3D printing materials.