Evaluation of thermally conditioned LID-bonded and Al-brazed titanium sandwich structure for RLV main propellant tanks

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Evaluation of thermally conditioned LID-bonded and Al-brazed titanium sandwich structure for RLV main propellant tanks

Stickler, P.B.

Reusable launch vehicles (RLV's) require lightweight durable structure to meet stringent mass fraction requirements and to achieve reduced operating costs. Titanium honeycomb, with its high specific strength and stiffness and inherent insulative properties is a viable option for RLV liquid hydrogen (LH2) propellant tanks. In order to evaluate the potential use of titanium honeycomb, room temperature flat wise tension (FWT) tests were conducted on conditioned and unconditioned specimens with two types of core-to-facesheet bonding methods: liquid interface diffusion (LID) bonding and aluminum brazing. Conditioned specimens were thermally cycled from -253 degree C to 315 degree C for 100 cycles representing one life time of a RLV LH2 main propellant tank. Results indicated that only a slight reduction (approximately = 7%) in FWT strength occurred due to thermal conditioning for both LID-bonded and Al-brazed specimens. Microscopic examination of conditioned specimen bond lines did not indicate appreciable thermal-induced microcracking.