Fiber-matrix interface characterization in CF/PEEK composites by analysis of single fiber fragmentation

The influence of carbon fiber's surface roughness and chemistry on interfacial properties in a carbon fiber reinforced polyetheretherketone model composite was studied using single fiber fragmentation test. In this study, Weibull parameters determined from acoustic emission data resulting from single fiber fragmentation itself were compared to Weibull parameters determined by carbon fiber dry tow tension. It was shown that interfacial shear strength (IFSS) is deeply influenced by Weibull parameters method used for fiber local strength, σ f ( l c ) , estimation. Further insight on fragmentation mechanism was obtained from synchrotron X-ray microtomography. Microtomography observations showed a fiber fragment's length shrinkage, even after fragmentation saturation. An innovative micromechanical analysis to estimate IFSS from this shrinkage has been proposed. This approach allows to follow the IFSS evolution during the fiber fragmentation. Resulting IFSS evaluations were consistent with IFSS obtained by σ f ( l c ) estimation, and presented an interfacial quality dependent decrease during the fragmentation. These results demonstrate that carbon fiber's surface chemistry has a major influence on IFSS value, comparing to surface roughness. However, surface roughness significantly impacts the interfacial properties evolution after fiber fragmentation.