Interfacial and microfailure evaluation of modified single fiber-brittle cement matrix composites using an electro-micromechanical technique and acoustic emission

Interfacial and microfailure properties of the modified steel, carbon, and glass fiber-cement composites were investigated using the electro-pullout test under tensile and compressive tests with acoustic emission (AE). The hand-sanded steel composite exhibited higher interfacial shear strength than the untreated and even neoalkoxy zirconate (Zr) treated steel fiber composites. This might be due to the enhanced mechanical interlocking, compared to possible hydrogen or covalent bonds. During the curing process, the contact resistivity decreased rapidly at the initial stage and then leveled off. Compared to the untreated case, the contact resistivity of either Zr-treated or hand-sanded steel fiber composites increased to infinity at the latter stage. The number of AE signals of hand-sanded steel fiber composite was much greater than those of the untreated and Zr-treated cases because of many interlayer failure signals. AE waveforms for pullout and frictional signals of the hand-sanded composite are larger than those of the untreated case. Under compressive loading for dual matrix composite, AE energy was much higher and the waveform was larger than those under tensile loading, because of their brittle but well-enduring ceramic nature against compressive stress. Vertical multicrack exhibits for the glass-fiber composite under tensile test, whereas buckling failure appeared under compressive loading. The electro-micromechanical technique with AE can be used as an efficient nondestructive method to evaluate the interfacial and microfailure mechanisms for conductive fiber-cement composites of the brittle and nontransparent type. (C) 2001 Elsevier Science.