Functionally graded materials (FGMs) are widely applied in spacecraft structural design, thermal protection systems, and planetary landing mechanisms, benefiting from their ability to resist large thermal, pressure, and force gradients. To assess structural response behaviors for lander missions, docking maneuvers, and force transfer in layered aerospace structures, analyzing the contacts subjected to heavily stressed areas becomes very important. This article investigates the receding contact between a functionally graded top layer and a uniform substrate lying on a Winkler elastic foundation using the elasticity theory. An analytical approach has been validated using a finite element method (FEM) implemented in ANSYS. Comparison between the analytical solution and the FEM solution has been conducted for different stamp radii, elastic foundation stiffnesses, and ratios of shearing modulus for various realistic materials in the aerospace field. The data indicate very good convergence between the two solutions for both the length of contacts and the normal stress distribution, where differences are always below 3%. An increase in stamp radius leads to an extension of the contacts as well as a reduction in normal stresses and elevated stiffness and shearing modulus ratio contribute to smaller contacts and higher stresses. The validated methodological approach offers a realistic means for predicting force transfer mechanisms in spacecraft landing pads, multi-layer insulation panels, adaptive space structures, and functionally graded parts subjected to localized loads. This work offers predictive capabilities for space material interface design and optimization for harsh mechanical environments.

This study explores the application of FRP strengthening for enhancing the performance and resilience of fire-damaged concrete elements subject to different cooling regimes, with a focus on their effectiveness in restoring structural capacity and durability following fire exposure. To achieve this aim, 90 concrete cylinder specimens were produced and exposed to high temperatures of 200, 400, and 600 °C to induce fire damage. They were then subjected to different cooling methods, including natural cooling in the furnace, natural cooling in air, and fast cooling by water. In the last technique, the specimens were first immersed in water to shock them, and then water spraying was applied for ten minutes. Subsequently, strengthening was applied using two layers of FRP sheets, and compression tests were performed. The investigation is aimed at assessing to what extent the different cooling procedures may impair the effectiveness of FRP wrapping, with specific reference to FRP contribution to the improvement of concrete residual compressive strength. Based on the test results, and as expected, FRP strengthening was found to mitigate the adverse effects of different temperature levels and cooling regimes on the compressive strengths of specimens. Furthermore, the findings indicate that the cooling rate or process does not significantly affect residual strength and that the effectiveness of FRP wrapping should be assessed with reference not only to strength, but also to structural behavior. It is, therefore, necessary to extend the analysis to the structural context.