(584e) Re-Evaluation of Vickers Indentation Toughness Testing On CNT Incorporated Composite Materials

There is a growing interest to improve the toughness of monolithic alumina by adding carbon nanotube (CNT) reinforcement. The intention is to develop novel composites that take advantage of the extremely high elastic modulus and tensile strength of CNTs. The convenience and low cost of Vickers indentation have been drivers for its use in measuring toughness over the last three decades. However, the large discrepancy in toughness measurements reported by different research group raises questions about its suitability for providing accurate toughness measurements. In this study, we prepared samples with 1 wt% (1.9 vol.%) and 3 wt% (4.9 vol.%) multi-walled carbon nanotube reinforcement for alumina composites. Toughness was then measured by both Vickers Indentation and Chevron Notched four-point bending methods. It was found out that the quality of the surface finish has a significant effect on the cracks generated that are used to calculate the toughness of the sample. A comparison of the results indicates that high density and a high quality surface finish are critical factors for accurate toughness testing using the Vickers Indentation method.