FEATURE / ADDITIVE MANUFACTURED LATTICE Figure 7. Materials coupons and lattice grid representative samples manufactured in the same materials batch, process and equipment type to provide materials strength and stiffness allowables and verify cell design methods. Dimensional Accuracy After AM manufacture and post process cleaning and stress relief heat treatment, sample parts were accurately measured. The geometric characteristics were shown to be accurate Static Strength and Stiffness Static stiffness of sample parts was measured and used to correlate the FEM analysis models, with the results fed back into the detailed design process. Vibration Tests Vibration testing is a standard test approach for spacecraft verification. Tests were performed using a finished component, with added mass dummy simulators representing the mass and inertial properties of the antennae devices (230 g and 120 g). Excitation was performed sequentially in 3 orthogonal axis directions. Swept sine tests were used to characterise the eigenmode frequencies and damping, and validate the FEM mathematical model. High level random vibration tests were used to verify the strength of the antenna mounting component under simulated flight environment loads, including qualification margins. An additional criteria was to detect particles loosened by the vibration and part flexing, which would compromise the stringent spacecraft contamination requirements Modal testing using a modal test hammer was used to check the eigen-mode frequencies and approximate mode shapes before and at stages during the test. The first and second mode frequency measurements were 143.0 and 226.6.5 Hz which was within 3% of predicted values. Random vibration inputs were approximately 8.0 GRMS for X and Y axes and 15.1 GRMS for Z axis, relatively severe loading magnitudes. Figure 8. 3-D precision scanning measurements performed to check the geometric accuracy of the part. Figure 9. Static stiffness and strength measurements performed to check the structural integrity of the part and validate design analyses. 52 | SAMPE JOURNAL | NOVEMBER/DECEMBER 2021 www. sampe.orghttp://www.sampe.org