Interfacial Aspects of Electrodeposited Multi-fiber Reinforced Composites Using Electro-micromechanical Techniques and Acoustic Emission

Using electromechanical technique, various conductive carbon fibers and graphite and steel filaments/epoxy micro-composites were evaluated by measuring electrical resistivity to investigate the interfacial properties including the microfailure modes and interfiber distance effect with a aid of acoustic emission (AE). Micromechanical techniques, such as pull-out and fragmentation tests, and electrodeposition (ED) as a surface treatment method were combined. Testing micro-specimens were kept to be contacted electrically using silver paste with very thin copper wire on the conductive fibers. While tensile loading applied, the change of electrical resistivity was detected by fiber breakage and microfailure in microcomposites. In electro-pullout test, electrical resistivity was correlated to interfacial shear strength (IFSS) in a steel filament/epoxy composite by detecting maximum pull-out load and the increment mode of resistivity. Electro-micromechanical test was sensitive effectively to detect microfailure events and inter-fiber distance effect in graphite and carbon multifibers/epoxy composites. There were the correspondence between a fiber breakage and a sudden increment of electrical resistivity. AE was applied to correlate the microfailure occurrence from fiber break and matrix cracking and while testing for the untreated and ED treated specimens. By extending electro-micromechanical technique to 1-ply unidirectional carbon fiber/epoxy laminar under tensile load, electrical resistivity showed different microfailure trends for two narrow and wide specimens.