Conceptual Design of CFRP Sandwich Structures Interfacing Cryogenic Tankages in Rockets

The study proposes the use of Carbon Fiber Reinforced Plastic (CFRP) sandwich composites configurations for structures interfacing cryogenic tankages. To address the design challenge posed by high thermal contractions in metallic tanks after cryogenic propellant filling, the study incorporates slits near the tank interfaces. Additionally, to minimize the transfer of cryogenic temperatures into these interfacing parts, the sandwich structure features interface end attachment made of thermally insulating Glass Fiber Reinforced Plastic (GFRP) material. Analytical and Finite Element (FE) studies were conducted on a typical cylindrical cryogenic intertank structure to demonstrate the proof of concept. These studies included analytical design using MATLAB based codes, parametric analyses with simplified shell element models and detailed 3D sector models using solid elements. The parametric studies assessed the effects of the number and dimensions of slits to achieve an optimal design, while the detailed 3D sector model provided refined results, validating the adequacy of the proposed concept. Proof-of-concept investigations on the case study sandwich intertank structure demonstrate a notable 30% improvement in mass efficiency compared to the truss configuration and 45% improvement relative to the closed shell metallic configuration, thereby validating the mass efficiency of the proposed design configuration.