The paper will detail the validation work carried out on various Rapid Prototyping (RP) materials to determine their suitability for the application of Thermoelastic Stress Analysis. The overall objective is to drastically reduce the product design cycle, by providing "real experimental data" for correlation with Finite Element Analysis (FEA), prior to any expensive manufacturing process. In order to achieve this the homogeneity of the Rapid Prototyping material has to be established to ensure a valid transfer of results from model to actual part.