The Prevention Effect of Seawater Penetration of Gel Coat Applied in Repair of FRP Fishing Vessel

FRP 어선 보수에 적용되는 겔코트의 해수 침투 방지 효과

Abstract

Ships may collide with reefs or other objects during operation, when arriving or departing ports. The hull plate may be damaged due to the contact with other ships. The total number of domestic powered fishing vessels has decreased, but that of FRP fishing vessels has increased by 0.7% and the ratio of FRP fishing vessels to the total fishing vessels increased to 96%. Recently, fishing vessels has been used as fishing boats for income of non-fishermen as well as fishermen. Therefore, safety management for repair and maintenance is necessary. The penetration of moisture and moisture in the composite material such as FRP may deteriorate the mechanical properties and the salt (NaCl) component of the damaged portion may cause a relatively high deterioration in material strength. The gel coat painting is the final stage of repairs ans maintenance of FRP fishing vessels. The thickness criteria in the domestic and foreign gel coat is 0.3~0.762 mm. The joint specimens, which was immersed in seawater for 120 days, were compared with those without seawater immersion. As a result, the tensile strength was 83 ~ 121.8% and the flexural strength was 83 ~ 113% compared with the specimens without seawater immersion. According to the previous study the tensile strength decreased by more than 29% and the flexural strength decreased by more than 50% when the composite material was immersed in seawater for 1,083 hours without coating. As a result, it was found that the gel coat with 0.5 mm thickness is very effective in preventing the strength decrease of the composite material.

Fig. 1. Gel coated tensile & flexural specimen.

Fig. 2. Lamination method of V scarf joint specimen.

Fig. 3. Lamination method of X scarf joint specimen.

Fig. 4. Sea water storage for coated test specimen.

Fig. 5. Measuring the thickness of the gel coating specimen.

Fig. 6. Tensile test.

Fig. 7. Tensile test failure result.

Fig. 8. Flexural test.

Fig. 9. Flexural test failure result.

Table 1. Domestic/Foreign FRP structural strength value^7-11)

Table 2. Domestic/Foreign gel coat thickness standard^7-12)

Table 3. Mat & roving glass content^7,9)

Table 4. V scarf joint lamination length

Table 5. X scarf joint lamination length

Table 6. Number of tensile test specimen

Table 7. Tensile strength test result value

Table 8. Number & Size of flexural test specimen

Table 9. Flexural strength test result value