The paper presents an investigation into the thermomechanical performance of complex composite sandwich structures with adhesively bonded metallic fittings when exposed to extreme temperature ranges. A detailed finite element analysis is conducted by explicitly modeling the honeycomb core geometry with a cup metallic fitting. The material properties for the core sheet are identified from the experimental load-displacement curves of the test coupons. The identified properties are implemented in a finite element model of a sandwich cylindrical panel section of a spacecraft’s thrust tube subjected to thermal cycles. The critical stresses and potential failure modes of the sandwich panel section with the cup bonded fitting are correlated with experimental observations. The developed methodology for the analysis of composite sandwich structures is intended to investigate thrust tubes with other configurations of bonded joints and fittings.