Moisture absorption characteristics and mechanical degradation of composite lattice truss core sandwich panel in a hygrothermal environment

This paper investigates the impact of hygrothermal aging upon the compressive mechanical properties of carbon fiber reinforced plastics (CFRP) composite sandwich panels with a tetrahedral truss core. Gravimetric absorption data, through accelerated moisture absorption tests, were presented for three different temperatures of 30 degrees C, 55 degrees C and 80 degrees C. Predictions by Fickian and Langmuir-type diffusion models were compared to evaluate which one best describe the moisture diffusion process in the sandwich panels. A subroutine implementing the Langmuir-type diffusion model in ABAQUS was developed to simulate the variations of moisture concentration. The compressive properties of composite strut and tetrahedral truss cores sandwich panel after hygrothermal aging at different temperatures were tested, respectively. The experimental results indicated that the degradation of compressive properties of composite sandwich panel was induced by the combined effect of temperature and moisture absorption. Analytical expressions were developed to predict the compressive strength and stiffness of the sandwich panel following hygrothermal aging. A good agreement was found between the predictions by finite element, analytical model and experimental results.