Abstract
The critical shear stress intensity factor, KIIc, here-in referred to as the shear fracture toughness, KIIc (MPa√m), of two grades of graphite are reported. The range of specimen volumes was selected to elucidate any specimen size effect, but smaller volume specimen tests were largely unsuccessful, shear failure did not occur between the notches as expected. This was probably due to the specimen geometry causing the shear fracture stress to exceed the compressive failure stress. In subsequent testing the specimen geometry was altered to reduce the compressive footprint and the notches (slits) made deeper to reduce the specimen's ligament length. Additionally, we added the collection of Acoustic Emission (AE) during testing to assist with the identification of the shear fracture load. The means of KIIc from large specimens for PCEA and NBG-18 are 2.26 MPa√m with an SD of 0.37 MPa√m and 2.20 MPa√m with an SD of 0.53 MPa√m, respectively. The value of KIIc for both graphite grades was similar, although the scatter was large. In this work we found the ratio of KIIc/KIc ≈ 1.6.
| Original language | English |
|---|---|
| Pages (from-to) | 267-279 |
| Number of pages | 13 |
| Journal | Carbon |
| Volume | 98 |
| DOIs | |
| State | Published - Mar 1 2016 |
Funding
This work is sponsored by the U.S. Department of Energy, Office of Nuclear Energy Science and Technology under contact DE-AC05-00OR22725 with Oak Ridge National Laboratories managed by UT-Battelle, LLC. COPYRIGHT NOTICE: This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).