Sandwich structures with advanced facings
"The purpose of this research is to investigate potential advantages of two innovative designs of sandwich panels. The first design involves sandwich panels with a piece-wise thickness of the facings aiming at two possible outcomes: (I) improved the structural response, i.e. strength and stiffness, without increasing the weight of the structure or (2) reduction in the weight of the structure without a detriment to its structural response. The analysis is conducted analytically using the first-order shear deformation theory and numerically by the finite element analysis of conventional and stepped-wise sandwich panels. The applicability of the first-order shear deformation theory to the analysis of typical panels employed in aerospace applications is validated as a part of this research. This theory is considered since it may provide benchmark analytical solutions necessary to confirm the validity of FEA. The conclusions from this phase of the study are that piece-wise (stepped) facings can result in a significant improvement of the strength of the panel subject to either static or dynamic loads and an increase of the buckling load, with a minimal change in weight. On the other hand, fundamental frequencies of the panels decreased (a higher frequency is sometimes desirable to avoid an overlap between natural and driving frequencies spectra). The second design is concerned with the effectiveness of multifunctional thermal barrier coatings employed in sandwich panels with a dual objective, i.e. slowing heat transfer from the surface exposed to thermal load to the opposite surface and improvements in the thermo-mechanical response, including higher strength and stiffness. The solution is obtained for a typical aerospace panel mimicking thermal loading at a supersonic high-altitude flight. The analysis is conducted numerically as dictated by the necessity to account for temperature-dependent material properties. The results illustrate that the introduction of thermal barrier coatings between the facings and core of a panel may result in a significant reduction of temperature at the inner (colder) surface of the panel in both transient and steady-state phases. It has also been demonstrated that besides an improved heat conduction behavior, modified panels with thermal barrier coatings have lower stresses (higher strength) and higher stiffness (higher stability and fundamental frequencies). The objectives considered in the paper were achieved with the minimum weight penalty"--Abstract, page iii.
Missouri University of Science and Technology
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