Additively Manufactured Titanium Alloy Sandwich Structures for Thermal Protection

Abstract

The launch of the first 3D-printed rocket in March 2023 has shown the value of additive manufacturing for the space industry. Successful applications include the areas of lightweight structures and propulsion. However, additively manufactured thermal protection systems are in their infancy. This research investigates additively manufactured sandwich structures for use in metallic thermal protection systems. The heat transfer in sandwich structures with low-density cores has been modelled and optimised using existing relations for metal foams. Cylindrical sandwich samples with open-cell lattice cores were then designed and manufactured in Ti-6Al-4V using Electron Beam Melting. The samples were exposed to transient heating experiments at low temperatures as well as wind tunnel tests in the arc-heated facility L2K at the German Aerospace Center. The performance of these various lattice designs was assessed experimentally, and a survivability threshold was determined. Optimised Ti-6Al-4V sandwich structures were shown to survive maximum cold-wall heat fluxes of 550 kWm−2 and Pitot pressures of 47 hPa for 3 min. However, a liquid oxide film on the front surface was observed to form under these conditions. At higher heat loads, the displacement of this film led to the disintegration of these samples. Additively manufactured Ti-6Al-4V sandwiches may be utilised for single-use load cases within the determined threshold. Sandwich designs and modelling could be applied to other material classes available for additive manufacturing.