Water absorption behaviour of vinyl ester laminates reinforced with aramid and glass fibres
Krystyna Imielińska*, Rafał Wojtyra** *Politechnika Gdańska, Wydział Mechaniczny, ul. Narutowicza 11/12, 80-952 Gdańsk **Politechnika Gdańska, Wydział Oceanotechniki i Okrętownictwa, ul. Narutowicza 11/12, 80-952 Gdańsk
Annals 3 No. 7, 2003 pages 192-197
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abstract Two vinyl ester laminates reinforced with aramid and glass fibres have been tested in dry condition and after immersion in water. Materials were tested for their potential use in marine applications. The reinforcement was in the form of woven hybrid aramid-glass fabric (1) or woven aramid fibre layers interleaved with woven glass fibre layers (2). Accellerated water immersion tests (70oC) have been conducted followed by flexure and interlaminar shear strength (ILSS) tests. Water absorption curves have been plotted (Fig. 1) and diffusion coefficients have been calculated. Despite only slightly higher fraction of hygroscopic aramid fibres moisture absorption saturation values as well as diffusion coefficients were found higher for composite (2). Flexural strength and modulus and interlaminar shear strength have also been found superiour for hybrid fabric-reinforced laminates (Figs. 2, 3). This refers both to the dry and wet condition. It has been demonstrated that water causes serious damage in the microstructure of the laminates consisting mainly of fibre/matrix debonding (Figs. 4, 5). These defects have little effect on the flexural strength properties of the laminates. ILSS and flexural strength of the laminates in the dry and wet condition were very similar. However, the reduction in the elastic modulus and dramatic decrease in the deflection of the samples have been observed following water saturation. Key words: polymer composites, hybrid laminates