Mechanical testing of threaded inserts for additively manufactured sandwich panels with Gyroid core structures

Additively manufactured sheet networks with low relative density show significant load-bearing capabilities while fulfilling additional requirements such as conducting gases. Introducing sheet networks as a core structure in sandwich panels requires fastening points for panel installation. This study develops, manufactures and mechanically investigates fastening points for triply periodic minimal surface sheet networks. While two concepts for Gyroid sheet networks are derived from an existing Honeycomb concept, a third concept improves the load-to-weight ratio by functionally grading the Gyroid's relative density. Pull-out tests were conducted to compare the performance of the insert concepts integrated into the Honeycomb and Gyroid sandwich specimens. The tests showed that only the functionally graded Gyroid concept reaches a significantly higher load-to-weight ratio than the Honeycomb concept, suggesting that its modified structure is effective. A numerical comparison of the Honeycomb's and Gyroid's unit cells shows equal moments of area for equal relative densities, thereby underlining the same load-bearing capabilities for similar insert concepts. In contrast to the Honeycomb fastening points, the Gyroid fastening points show a significant load-bearing capacity after the initial failure, which results in a residual load-bearing capability and, therefore, increased system robustness.