Toughening of boron carbide composites by hierarchical microstructuring

Jingyao Dai, Evan Pineda, Brett Bednarcyk, Jogender Singh, Namiko Yamamoto

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Due to a unique combination of properties including high hardness, low density, chemical and thermal stability, semi-conductivity, and high neutron absorption, boron carbide (B4C) is a potential candidate for various applications involving extreme environment. However, B4C’s current application is limited because of its low fracture toughness. In this study, a hierarchical microstructure design with features including TiB2grains and graphite platelets was used to toughen B4C by simultaneously utilizing multiple toughening mechanisms including crack deflection, bridging, and micro-crack toughening. Using field-assisted sintering technology (FAST), B4C composites with dense and hierarchical microstructure were fabricated. Previously, the fracture toughness of fabricated B4C composites was measured at micro-scale using micro-indentation to have up to 56% improvement. In this work, the B4C composites’ fracture toughness was characterized at macro-scale using four-point bending methods and compared with previous results obtained at micro-scale. Micromechanics modeling of fracture behaviors for B4C-TiB2 composites was also performed to evaluate the contributions from experimentally observed toughening mechanisms. From four-point bending tests, B4C composites reinforced with both TiB2 grains (~15 vol%) and graphite platelets (~8.7 vol%) exhibited the highest fracture toughness enhancement from 2.38 to 3.65 MPa·m1/2. The measured values were lower than those obtained using micro-indentation but maintained the general trends. The discrepancy between the indentation and four-point bending test results originated from the complex deformation behaviors triggered by the high contact load during indentation tests. Through micromechanics modeling, introduced thermal residual stress due to thermal expansion mismatch between B4C and TiB2, and weak interphases at B4C-TiB2 boundaries were identified as the main causes for experimentally observed toughness enhancement. These results proved the effectiveness of hierarchical microstructure designs for B4C toughening and can provide reference for the future design of B4C composites with optimized microstructures for further fracture toughness enhancement.

Original languageEnglish (US)
Title of host publication36th Technical Conference of the American Society for Composites 2021
Subtitle of host publicationComposites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021
EditorsOzden Ochoa
PublisherDEStech Publications
Pages1802-1814
Number of pages13
ISBN (Electronic)9781713837596
StatePublished - 2021
Event36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021 - College Station, Virtual, United States
Duration: Sep 20 2021Sep 22 2021

Publication series

Name36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021
Volume3

Conference

Conference36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021
Country/TerritoryUnited States
CityCollege Station, Virtual
Period9/20/219/22/21

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites

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