Water absorption characteristics of aluminised E-glass fibre reinforced unsaturated polyester composites O.A.Z. Errajhi * , J.R.F. Osborne, M.O.W. Richardson, H.N. Dhakal Advanced Composite Research Group, Department of Mechanical and Design Engineering, University of Portsmouth, Anglesea Road, Portsmouth, Hampshire PO1 3DJ, UK Abstract NovelaluminisedE-glassfibrereinforcedunsaturatedpolyestercomposites,originallyformulatedforenhancedthermalandelectrical shieldingpropertieswereevaluatedintermsoftheirwaterabsorption.Oneofthemajorobstaclesdelayingtheacceptanceofnovelcom- positesinengineeringapplicationsisthedegradationofthepolymermatrixmaterialbymoisture,whicheffectsthephysicalandmechan- ical performance over time. The objective of this study was to characterise and quantify the degree of water absorption of novel aluminised E-glass reinforced unsaturated polyester composites. Aluminised E-glass composites were compared alongside their unmet- allisedE-glasscounterparts.Twosetsoftemperaturewereusedforthisstudy.ResultsshowthataluminisedE-glasssignificantlyreduces thesaturationpointcomparedtounmetallisedE-glass.Thedifferencesbetweenaluminisedandunmetallisedarecorrelatedtofibrecoat- ings.AtelevatedtemperaturesthealuminisedE-glasssampleisunstableandexhibitssignificantlyhigherwaterabsorptionindicatingthat a new failure mechanism is occurring. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Aluminised E-glass fibre; Moisture effects; Polymer matrix composites 1. Introduction ForsomeyearsaluminisedE-glassfibrehasbeenusedin countermeasuretechnology.UntilnowaluminisedE-glass fibreshaveonlybeenusedinmilitaryapplications.Aircraft releasealuminisedfibresor‘‘chaff’’inordertoconfuseand divert approaching enemy missiles. The main potential advantages of producing modified composites from the same type of fibre are to modify or improve mechanical and the physical properties. Aluminised glass fibre is expected to significantly modify thermal and electric char- acteristics by virtue of an increase in thermal and electrical conductivity [1].Allpolymersandcompositesabsorbmois- ture in humid atmosphere and when immersed in water. Internally glass fibres absorb zero moisture compared to natural fibres. The effect of absorption of moisture is gradual degradation of the materialsÕ interphase, resulting inareductionofmaterialpropertiessuchastensilestrength [2]. Based on experiments on moisture uptake and assum- ing one-dimensional diffusion based on FickÕs law, several researchers have talked about characteristics of moisture absorption. Moisture diffusion in polymeric composites has been shown to be Fickian and non-Fickian [3–7] in character. The viscoelastic nature of the polymers and resultantcracksaresomeofthefactorsleadingtonon-Fic- kiandiffusion.Whenimmersedinwater,therecanbeaddi- tional leaching of matter from the composite. In general moisture diffusion in composite depends on factors such asvolumefractionoffibre,voidvolume,additives,humid- ity and temperature. Water absorption and diffusion char- acteristics are intimately linked to materialsÕ physical properties. Significant progress has been made in under- standing the phenomena of water absorption in synthetic fibre composites and results exist for short-term water absorptionofglassfibreandtheircomposites.Inthiswork, water absorption in an aluminised E-glass fibre reinforced 0263-8223/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.compstruct.2005.09.008 * Corresponding author. Tel.: +44 2392842396; fax: +44 2392842351. E-mail address: osama.errajhi@port.ac.uk (O.A.Z. Errajhi). www.elsevier.com/locate/compstruct Composite Structures 71 (2005) 333–336