Flaw analysis on glass fiber reinforced plastic inshore petrol craft hull using pulse echo technique

Abstract

The Glass fiber Reinforced Plastic (GRP) material is considered as the most prominent material for small boat industry due to the convenience of workmanship and light weight. Although the technology of GRP boat construction has been developed immensely for the last three decades, the technology related to the periodic assessment of GRP hull has not been developed in the same way compared to the steel and aluminum boat construction industry due to the inhomogeneous nature of the GRP structure. At the designing stage of GRP boat, number of factors such as compressive modulus, tensile modulus, ultimate flexural strength, ultimate compressive strength and ultimate tensile strength will be considered in order to meet the level of performance expected by the end user. However the deterioration of the boat structure with the age, reduces the level of confidence to deploy the boat under same role. In general flexural strength of GRP is measured destructively. However the destructive tests make the structure unusable, as such this study focuses on estimating flexural strength through nondestructive method with the aid of ultrasound technology. The objective of this study; is to develop two independent relationships such as “Number of repeated blows Vs. Percentage Echo height” and “Number of repeated blows Vs. Flexural strength” using the data obtained from selected specimens. These specimens were obtained from the most prominent areas of damages expected on a GRP hull. These were then narrowed down to a single relationship; that is “Percentage Echo height Vs. Flexural strength”.