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Abstract
Ship structures made of glass fiber-reinforced polymer (GFRP) composite laminates are considerably thicker than aircraft and automobile structures and more likely to contain voids. The production characteristics of such composite laminates were investigated in this study by ultrasonic nondestructive evaluation (NDE). The laminate samples were produced from E-glass chopped strand mat (CSM) and woven roving (WR) fabrics with different glass fiber contents of 30–70%. Approximately 300 pulse-echo ultrasonic A-scans were performed on each sample. The laminate samples produced from only CSM tended to contain more voids compared with those produced from a combination of CSM and WR, resulting in the relative density of the former being lower than the design value, particularly for high glass fiber contents of ≥50%. The velocity of the ultrasonic waves through the CSM-only laminates was also lower for higher glass fiber contents, whereas it steadily increased for combined CSM–WR laminates. Burn-off tests of the laminates further revealed that the fabric configuration of the combined CSM–WR laminates was of higher quality, prevented the formation of voids, and improved inter-layer bonding. These findings indicate that combined CSM–WR laminates should be used to achieve more accurate ultrasonic NDE of GFRP composite structures.
Highlights
Glass fiber-reinforced polymer (GFRP) composites have been widely used for decades to build small ships, such as fishing boats, yachts, and patrol boats [1,2], owing to their suitable specific strength, corrosion resistance, and excellent workability [3].Overall, considerable progress has been achieved in the marine application of tailored materials and optimal structural design technology
Pulse-echo ultrasonics can be performed on aircraft for quantitative defect detection and quality characterization, it is more often used for damage repair or maintenance of GFRP ships [10]
The designs mens were produced by varying glass fiber content (Gc) from 30% to 70% and by combining chopped strand mat (CSM) and of the GFRP laminate specimens are illustrated in Figures 3 and 4
Summary
Glass fiber-reinforced polymer (GFRP) composites have been widely used for decades to build small ships, such as fishing boats, yachts, and patrol boats [1,2], owing to their suitable specific strength, corrosion resistance, and excellent workability [3].Overall, considerable progress has been achieved in the marine application of tailored materials and optimal structural design technology. Nondestructive evaluation is one of the most commonly used quality evaluation methods and is widely applied to composites [6,7] While it is widely employed in the aviation industry for quantitative defect detection and quality characterization of fiber-reinforced polymer (FRP) structures, it is not often applied to GFRPs used to produce ships owing to the much larger thickness of the GFRP structures and the limitations of the measurement environment. Pulse-echo ultrasonics can be performed on aircraft for quantitative defect detection and quality characterization, it is more often used for damage repair or maintenance of GFRP ships [10] This is because the GFRPs used in ships are generally produced by the hand lay-up method [11,12], which tends to unevenly, inadequately, or excessively distribute the polymer resins in the GFRP structure, resulting in more defects in the laminates, such as porosity, voids, and delamination. The pulse-echo velocity (C, m/s) is the speed at which the ultrasonic wave travels through the specimen and is determined isby thethe speed at which the ultrasonic wave travels through(E, thekgf/mm specimen and is specimen, determinedas
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