An experimental characterisation of spatial variability in GFRP composite panels

Probabilistic tools are being used to understand the inherent uncertainty of FRP composites. Over the years different approaches have developed, focusing on behaviour and associated uncertainties at a micro-/meso-/macro-scale, each with specific advantages/limitations depending on the type, and scope, of the analysis being undertaken. Consideration of spatial variability, and associated random field modelling, of geometric and material/mechanical properties is believed to be an important factor in seeking to improve strength and reliability estimates but lack of experimental data has hindered the applicability and usefulness of results hitherto obtained. In this paper, modelling strategies for characterising and specifying the spatial variability in terms of random fields are presented for two distinctly different types of GFRP composite panels. Autocorrelations for, and cross-correlations among, strength and stiffness properties are evaluated in terms of coupon spatial distances for various forms of correlation functions. These properties are found to be well represented by an exponential autocorrelation function, and specific values for correlation lengths are evaluated, providing an insight into the influence of material and manufacturing factors on the properties of GFRP composite material systems.