Improvement and practical application of single fiber fragmentation test

Abstract

The single fiber fragmentation test (SFFT) has been used to investigate the interphase in fiber-reinforced composites. However SFFT is still far from a routine test for industrial applications. The aim of this work is to turn SFFT into a practical, quick test. A new approach was developed for SFFT based on the usage of the maximum number of fragments on the fiber to compare different fiber-matrix interphase qualities. This approach does not involve length measurements and shortens the experiment time to few minutes. Test samples were prepared by using E-glass fibers with different commercial sizings and unsaturated polyester resin. SFFT results were in good agreement with the macromechanical test results. The crack modes and debonding phenomena were examined from the microscopic images. Atomic force microscope (AFM) images were examined to get a better knowledge about different fiber surfaces. New improvements were developed to get better interphase adhesive strength. The first improvement was done by adding methacryl silane as coupling agent to the matrix resin directly in different percentages. Higher percentages resulted with higher quality on the adhesive strength but decreased the mechanical properties of the matrix. The second improvement was done by addition of 3- aminopropyltriethoxysilane to unsaturated polyester via Michael addition reaction. Characterization of the product was done by 1H NMR spectroscopy. The results of SFFT showed that the maximum numbers of fragments for the samples prepared from 3- aminopropyltriethoxysilylated polyester are quite high. That means better interphase quality was achieved by aminosilylated polyester matrix.