The influence of high-temperature sulfuric acid solution ageing on the properties of laminated vinyl-ester joints

A carbon fiber powder doped corrosion layer is used as an inner layer in large composite tanks to improve their chemical and wear resistance. In joints fabricated on site, this layer is embedded into the structure. This study evaluates the lap shear strength of specimens, simulating a laminated joint in between the corrosion layer and the inner joint laminate. Lap-shear tests were carried out for as-fabricated and aged laminates at room temperature and at elevated temperature. Ageing was carried out for half a year in a 95 °C pressurized sulfuric acid solution. The tests showed that, after ageing, the room temperature shear strength remained unaltered but high-temperature shear strength was lowered. When the temperature increased, the failure location shifted from the interface between the doped layer and the joint laminate to the doped layer. Thermal analysis and microscopy were employed to clarify the reasons for the observed behavior.