Predicting degradation of composite-titanium adhesively bonded joints exposed to seawater environment

In this paper, focusing on the composite-titanium adhesively bonded structures aging in seawater environment, a prediction method coupling the experiments, theoretical model and numerical simulation for degradation of the tensile behavior of adhesively bonded joint was proposed. Bulk adhesive and fracture specimens were aged in 45 celcius artificial seawater to characterize the adhesive moisture absorption behavior and degraded fracture properties, respectively. Based on the discrete experimental degraded fracture properties, a theoretical continuous water coupled fracture model for the prediction of degraded fracture properties was developed. The theoretical model can predict the degraded fracture toughness based on the moisture. Prediction of the degraded tensile properties of single-lap adhesively bonded joint was conducted. The predicted tensile strength of the aging specimen agreed well with the experimental results, with less than 5 % error. Moreover, spatial variations of the damage and stress of the aging adhesive layer can be predicted by the prediction method coupling the moisture absorption. The predicted results indicated that the damage value and area of the width edge of the adhesive layer were both greater than central region, and the predicted peak stress in the central region was nearly 33.2 MPa while that of the edge decreased to 12.5 MPa.