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 (_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 111.24. Also, the critical flaw size (c) of the CA fibre was estimated to be 2.35 m. 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.