Estimation of the fracture toughness of tungsten fibre-reinforced tungsten composites. (1st June 2020)

• Record Type: Journal Article
• Authors: Gietl, H.; Olbrich, S.; Riesch, J.; Holzner, G.; Höschen, T.; Coenen, J.W.; Neu, R.
• Is Part Of: Engineering fracture mechanics. Volume 232(2020)
• Publication Date: 2020-06-01
• Subjects: Tungsten -- Tungsten fibre -- Fibre-reinforced composite -- Metal matrix composite -- Fracture toughness; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2020.107011
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: Stable crack propagation of tungsten reinforced with tungsten fibers. Fracture surface observations. Using fiber reinforcement improves the fracture toughness of tungsten. The fracture toughness of tungsten fibre-reinforced tungsten composites was investigated with different methods. Discussion of the applicability of the used methods for tungsten fibre-reinforced tungsten composites. Abstract: Tungsten fibre-reinforced tungsten composites (Wf /W) have been developed to overcome the inherent brittleness of tungsten, which is a promising candidate for the plasma-facing material in a future fusion power plant. As the development of Wf /W evolves, the fracture toughness of the composite is in the focus of interest for further component design. In this contribution fracture mechanical tests on two different types of chemical vapour deposited (CVD) Wf /W are presented. Three-point bending tests according to ASTM E399 as a standard method for brittle materials were used to get a first estimation of the toughness. A provisional fracture toughness value of up to 241 MPa m 1 / 2 was calculated for the as-fabricated and of up to 20.5 MPa m 1 / 2 for a heat-treated and thus embrittled state. As the material does not show a brittle fracture in the as-fabricated state, the J-Integral approach based on the ASTM E1820 was additionally applied for this state. A maximum value of the J-integral of 7.5 kJ/ m 2 (57.6 MPa m 1 / 2 ) was determined. A detailed post mortem investigations was used to obtain the active mechanisms.