Abstract
A comparative study of glass fiber content (Gc) measurement methods was conducted using actual glass fiber reinforced plastic laminates from the hull plate of a 26-ton yacht. Two prototype side hull plates with the design Gc (40 wt.%) and higher Gc (64 wt.%) were prepared. Four methods were used to study the samples: the calculation method suggested by classification societies’ rules; two direct measurement methods using either calipers and scales or a hydrometer; and the burn-off method, wherein the resin matrix is combusted from the laminates. The results were compared and analyzed to identify the accuracy and benefits of each method. The rule calculation method was found to be effective if the quality of the manufacturing process is known. However, fabrication errors in the laminate structures cannot be detected. Additionally, while direct methods are used to measure the density of glass fibers using measurements of the densities of raw materials and laminates, the volume of inner defects occurring during the fabrication of laminates could not be considered. Finally, it was found that the burn-off method measures Gc and considers the defect volume (voids) inside laminates as well as the non-uniformity of the external shape.
Highlights
Glass fiber reinforced plastics (GFRPs) have been widely used for decades for building small ships, such as fishing boats and yachts [1,2], as they exhibit good specific strength, corrosion resistance, and excellent workability
The higher-glass fiber content (Gc) laminate structure was designed according to the ISO 12215-15 and Registro Italiano Navale (RINA) design rules; by intentionally increasing the design Gc to 64 wt.%, the number of plies of cloth was increased while the amount of resin was reduced to fabricate a composite hull structure with a higher Gc and smaller thickness
The Gc values of two hull plates of composite ships with different glass fiber weight fractions were measured using rule calculation, simple direct measurement, hydrometer, and burn-off fractions were measured using rule calculation, simple direct measurement, hydrometer, and burnmethods, with the aim of identifying the change in fabrication quality resulting from quantitative off methods, with the aim of identifying the change in fabrication quality resulting from quantitative changes in Gc
Summary
Glass fiber reinforced plastics (GFRPs) have been widely used for decades for building small ships, such as fishing boats and yachts [1,2], as they exhibit good specific strength, corrosion resistance, and excellent workability. The mechanical properties are often verified by fracture testing according to the ASTM standards [3,7,11,17], while experimental methods (e.g., resin burn-off) or theoretical calculations are recommended to determine Gc. the classification rules do not provide detailed specifications on determining Gc. In addition, because of the flexible fabrication characteristics and different types and combinations of materials, it is difficult to verify that laminates are fabricated according to the designed Gc. To aid the design and manufacture of GFRP laminates for shipbuilding, it is critical to identify an accurate and consistent method of determining Gc. The method should measure the size and volume of voids inside the laminate structure, as well as the measurement error of the outer shape. We expect that this comparative study on methods for assessing laminate structures of actual GFRP ship components will provide a good reference for GFRP ship design
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