Siriruk, A.; Woracek, R.; Puplampu, S.B.; Penumadu, D.; Withers, P.; Lowe, T.; Kardjilov, N.; Manke, I.: Size Effects in Testing of Carbon Fiber Vinyl Ester Laminate For Marine Application and Damage Evolution. In: Hyonny Kim ... [Ed.] : Proceedings of the American Society for Composites-Twenty-Ninth Technical Conference. DEStech Publications, 2014 (CD-ROM). - ISBN 978-1-60595-124-9, p. SESSION XXV: MARINE COMPOSITES/1-14

Abstract:
This study reports a series of mechanical tests on carbon fiber reinforced vinyl ester composites (CF/VE), consisting of fiber dominated samples of [0/90]2S and matrix dominated samples of [±45]2S orientation, while employing variable specimen sizes. In order to extend the observations from coupon based mechanical tests of fiber reinforced polymer composites, towards the design and application of large ship structures, it is important to consider the effect of the physical specimen size. Previous studies indicate that the strength of fiber reinforced composites which are subjected to tensile loading, decreases as the specimen size increases, strongly depending on manufacturing parameters. Three sizes of CF/VE composite specimens were made (12.5 mm wide by 100 mm long, 25 mm by 200 mm, and 25 mm by 300 mm), all with an average uniform thickness of 2.8 mm. The composite laminates were prepared using Vacuum Assisted Resin Transfer Molding (VARTM) process. The mechanical strengths of the samples were experimentally evaluated and are compared, The present study also reports different CF/VE failure mechanisms of matrix crack interactions, such as matrix dominated transverse tension, tension along fibers, and fiber delamination. Digital Image Correlation (DIC) technique was implemented to track the evolution of surface damage showing the existence of localized damage for both fiber and matrix dominated CF/VE composites. Additionally, high resolution x-ray and neutron tomography under in-situ mechanical loading was used for the investigation of damage evolution at different stress levels. Specimen of 12.5 mm by 100 mm were incrementally loaded under tension and torsion, while in-situ tomography using x-ray and neutron radiation was performed, which also enables a comparison between interior specimen damage and surface damage (readily observable using DIC).