Effect of hygrothermal environment on mechanical properties and damage mechanism of CFRP

The moisture absorption properties of carbon fiber reinforced plastics (CFRP) laminates treated with three kinds of hygrothermal environments (relative humidity 85% RH, temperature 25, 70, 85℃ respectively) were investigated by accelerated moisture absorption method. Tensile, compressive and shear tests were carried out to study the effect of hygrothermal conditions on the mechanical behavior of CFRP laminates. Meanwhile, the damage mechanism of CFRP laminates in hygrothermal environment was analyzed by scanning electron microscopy and infrared spectroscopy. Finally, a formula which could predict the mechanical properties of CFRP laminates in hygrothermal environments was proposed by least square method. The results show that the moisture absorption characteristics of CFRP laminates in preliminary stage accords with Fick's law well. At the same humidity, the CFRP's moisture absorption speeds, the moisture saturation contents and times are increased with the increment of the environmental temperature. The mechanical properties of CFRP laminates in 90°tensile test and shear test are decreased most obviously. Water molecules are associated with epoxy resin through hydrogen bonds after the treatment in hygrothermal environment, however, there is no chemical structure change in the components of the CFRP laminate. The formula of mechanical performance degradation under different hygrothermal conditions is basically consistent with the experimental results