Fractographic analysis of vitreous calcia-alumina eutectic fibres produced by inviscid melt spinning (IMS)

The mechanical properties of inviscid melt spun (IMS) CaO-Al₂O₃ (46.5 wt % CaO-53.5 wt % Al₂O₃) eutectic fibres were examined by fractographic analysis as well as four-point bending and micro-indentation. The averaged fracture strength and elastic modulus values of the IMS Calcia-Alumina (CA) fibre were determined to be 460 MPa and 99.8 GPa, respectively by using four-point bending tests. The inner mirror constant (M) was determined to be 2.39 MPa · m^1/2 by using the plot of the fracture strength (σ_f) obtained from the bending tests as a function of r^-1/2, where r is the inner mirror radius measured from scanning electron microscopy (SEM) on the fractured CA fibres. The flaw-to-mirror ratio (c/r) for the CA fibre was calculated to be 1:11.24. Also, the critical flaw size (c) of the CA fibre was estimated to be 2.35 μm. The averaged elastic modulus value from Knoop micro-indentation was determined to be 102.5 GPa which is in good agreement with that from the four-point bending tests.