REPRESENTATIVE VOLUMES OF COMPOSITE-MATERIALS

Representative volume (RV) of a composite material is important not on ly for experimental determination of materials properties, but also fo r theoretical analysis of various properties of the materials. RV is a random variable; this is especially true for the composites with hete rogeneous microstructures. In the present study, RV is redefined as a relationship among three parameters: the volume under consideration, t he measured or predicted value of a property corresponding to the volu me, and the scattering of the property from the real effective propert y. There are two steps involved to determine RV. The first is to deter mine the relationship among the effective property, the properties of each constituents, and volume fractions, which is the topic in composi te mechanics. The second is determination of the local variation of th e heterogeneity of the composite because, with increasing size of the local volume, the statistics from the local volume asymptotically appr oaches the value from the global average. The main purpose of this stu dy is to develop a theoretical model to determine local variation of h eterogeneity, which is obviously related to the morphological features of the composites. The model accounts for coarseness of grain sizes, volume fractions, spatial arrangement of the constituents, and propert ies of each constituents. By combining the model with available compos ite models for effective properties of composites, RV for various mate rials properties can be developed. As an example, RV for elastic modul i of cementitious materials is demonstrated.