A method of non-destructively determining the physical property of a material surface, the method including irradiating a surface with infrared energy over a spectrum of wavelengths; detecting said infrared energy reflected from said surface over said spectrum of wavelengths; performing multivariate calibration of said reflected infrared energy at a plurality of selected wavelengths including said spectrum of wavelengths; using results of said multivariate calibration to predict one or more physical properties of said model material; and, determining said one or more physical properties of said surface. Details are included for the case where uni-directional fiber CFRP materials are to be calibrated and predicted because special care must be taken for that material to insure the incident light from the spectrometer is at the proper orientation for calibration and for prediction of samples in question.