A normalization method of measured elastic properties of glass NCF composites with respect to fiber volume fraction based on periodic microstructure micromechanics

Abstract

International standards have requested the normalization of fiber-dominated properties in composites with respect to fiber volume fraction. However, the normalization of matrix-dominated properties has not yet been requested because there is no clear model. This partial normalization might deteriorate accuracy in design and analysis. This study developed a systematic approach for normalizing both fiber-dominated and matrix-dominated properties of composites, based on periodic microstructure micromechanics (PMM). To evaluate the accuracy of PMM, this study started from comparing the elastic properties calculated by PMM to those calculated by FEA. Then, the eight measured elastic properties were obtained by testing three different types of glass NCFs/epoxy laminates. Since PMM needs the elastic properties of raw materials, the three unknown properties among them were determined by using the back-calculation procedure developed in this study. After all, the PMM gave us highly accurate properties of the laminates, resulting in a maximum error of less than 1% when comparing the calculated elastic properties with the measured ones. Lastly, the orthotropic elastic properties of the laminates were normalized with respect to fiber volume fraction. This study makes a significant step forward in composite structures by providing a systematic approach for normalizing full elastic properties in composites.