Comparative experimental study on mechanical properties of CFRP subjected to seawater and hydrostatic pressure

Composite structures used in marine environments experience the erosion of seawater ageing and alternating water pressure during floating and diving. In this paper, the mechanical behavior of CFRP laminates under seawater pressure environment was studied experimentally. The evolution process of moisture absorption behavior and erosion defects in the cross section was monitored. The mechanism of the influence of hydrostatic pressure on the in-plane and interlaminar failure modes of the specimens was revealed. The results demonstrate that the hydrostatic pressure can activate the capillary action at the interface between the fiber and the matrix, and the plasticization of the matrix significantly reduces the in-plane strength of the specimens (the tensile strength decreases by 28.3%). As the pressure increases the specimens are more susceptible to delamination failure in the compression area under bending load. The toughening and embrittlement mechanisms of the specimens were activated simultaneously, with a minor increase in GIC and a slight decrease in GIIC under hydrostatic pressure. A short-term pressure dependent nonlinear model for predicting mechanical degradation was established based on the Arrhenius equation. The fitness of proposed model was compared with other models from the literature to verify the accuracy of the prediction.