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In this study, we experimentally and analytically investigated time-dependent deformation of carbon-fiber reinforced plastic sandwich panels with three kinds of polymer foam-core ROHACELL, with the deformation caused by moisture absorption. Tensile tests for the ROHACELLs before and after moisture absorption were performed using the digital image correlation method, and we obtained a stress–strain relationship for each condition. Surface deformations of sandwich panels were calculated using finite element analyses to examine the elasto-plastic deformation of the ROHACELLs based on the tensile test results. Experimentally measured deformation in the sandwich panels varied depending on the cell size of cores, and the largest measured deformation after the moisture absorption was approximately 100 μm. This was much larger than the analytical result. On the basis of this study, we suggest that the main reason for the deformation may be an irreversible shrinkage of the ROHACELLs caused the absorption of moisture during exposure to high-temperature and high-humidity environments. [ABSTRACT FROM PUBLISHER]

The influence of anisotropic thermal diffusivities on non-destructive testing of CFRP laminates using pulse phase thermography (PPT) was studied analytically. The results show that the optimum frequency for maximizing detectable depths of defects increases concomitantly with the increase in the ratio of the thermal diffusivities in the through-thickness direction to that in the in-plane direction. Furthermore, the phase difference between sound and defective areas decreases significantly with decreased. These predicted tendencies were verified through experiments. Experimental results also demonstrated that defects of 10 mm in diameter can be detected up to around 5 mm depth in CFRP with lowerbut only to around 1 mm in CFRP with higher [ABSTRACT FROM PUBLISHER]

Thermal deformation analysis was performed on a carbon fiber reinforced plastic (CFRP) mirror with sandwich structure. To obtain unexpected asymmetry of the surface sheet, we investigated the deformation of a quasi-isotropic laminate under hot and humid conditions. Despite the symmetric lay-up, quasi-isotropic laminate deforms into twisted saddle shape with time, and this deformation could be simulated by assuming ply angle misalignment. Then, the elastic moduli of honeycomb cores were calculated theoretically. A honeycomb sandwich mirror model was constructed by adopting a sheet model and using honeycomb elements. The thermal deformation analysis was performed considering the ply angle misalignment. The test results clarified that the deformation of the surface sheet was a critical factor in the dimensional stability of the CFRP mirror. [ABSTRACT FROM AUTHOR]