Abstract
This study investigated damage condition of a large GFRP tank used to dilute caustic soda. The tank was continuously used in a chemical factory for 13 years and finally scrapped. Samples for the investigation were obtained from four typical positions of the tank. For the samples, optical observation was conducted on the inside surface of the tank and on its cross-section in detail. The results showed that alkaline solution penetrated from fishnet-like cracks formed on the surface to the inside of GFRP. Formation of the cracks was thought to be caused by both deterioration of surfacing mats and cyclic stress due to change in temperature. The penetrated solution damaged chopped strand mats existing under the surfacing mats. Such damage condition was adequately predicted using ultrasonic echo data. Although the damage condition was different at each position of the tank, the bending strength was almost the same. That was because no damage reached to the filament winding layer to maintain the strength. The above results suggested that the investigated tank was suitably scrapped before a severe incident.
