Topic
Fracture toughness
About: Fracture toughness is a research topic. Over the lifetime, 39642 publications have been published within this topic receiving 854338 citations.
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11 Feb 2015-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the influence of graphene reinforcement on the sintering process, microstructure, and mechanical properties (Vickers hardness and fracture toughness) of ZrB2-SiC composite is discussed.
Abstract: In this paper, the hot pressing of monolithic ZrB2 ceramic (Z), ZrB2–25 vol% SiC composite (ZS), as well as 5 wt% graphene reinforced ZrB2–25 vol% SiC composite (ZSG) is investigated. The hot pressing at 1850 1C for 60 min under a uniaxial pressure of 20 MPa resulted in a near fully-dense ZSG composite (499% relative density). In addition, the influence of graphene reinforcement on the sintering process, microstructure, and mechanical properties (Vickers hardness and fracture toughness) of ZrB2–SiC composite is discussed. It was disclosed that the grain growth of the ZrB2 matrix was effectively stopped by SiC particles and graphene nano-platelets. The fracture toughness of ZSG composite (6.4 MPa m 1/2 ) was strongly enhanced by incorporating the mentioned reinforcements into the ZrB2 matrix, which is higher than that of Z ceramic (1.8 MPa m 1/2 ) and ZS composite (4.3 MPa m 1/2 ). After the hot pressing process, the fractographical outcomes revealed that some graphene nano-platelets were kept in the composite microstructure, apart from SiC grains, which lead to the toughening of the composite through graphene nano-platelets wrapping and pull out, crack deflection, and crack bridging. & 2014 Elsevier B.V. All rights reserved.
142 citations
TL;DR: In this paper, the authors investigated the microstructure development and resulting fracture toughness of Si3N4 materials with different mixtures of sintering aids and found that the observed changes were in fact caused by the difference in secondary-phase chemistry.
Abstract: Silicon nitride materials that contained different mixtures of sintering aids were investigated with respect to microstructure development and resulting fracture toughness. Postsintering annealing at 1850°C for various times was adopted in order to coarsen the respective microstructures. Although constant processing conditions were used, a marked variation in fracture toughness of the Si3N4 materials was evaluated. With a larger grain diameter of the Si3N4 grains, an increase in fracture resistance was generally observed. However, a correlation between fracture toughness and apparent aspect ratio could not be established. The observed changes in microstructure were in fact caused by the difference in secondary-phase chemistry. Si3N4 grain growth was dominated by diffusion-controlled Ostwald ripening and was hence affected by the viscosity of the liquid at processing temperature. In addition, crystallization at triple pockets also depends on the sintering additives employed and was found to influence fracture toughness by altering the crack-propagation mode as a consequence of local residual microstresses at grain boundaries. The stress character (compressive vs tensile) is governed by the type of crystalline secondary phase formed. Moreover, a variation in interface chemistry changes the glass network structure on the atomic level, which can promote transgranular fracture, i.e., can result in a low fracture resistance even in the presence of favorable large Si3N4 matrix grains. Therefore, secondary-phase chemistry plays a dominant role with respect to the mechanical behavior of liquid-phase-sintered Si3N4. Fracture toughness is, in particular, influenced by (i) altering the residual glass network structure, (ii) affecting the secondary-phase crystallization at triple pockets, and (iii) changing the Si3N4 grain size/morphology by affecting the diffusion rate in the liquid. The first two effects of secondary-phase chemistry are superimposed on the merely structural parameters such as grain diameter and apparent aspect ratio.
142 citations
TL;DR: Yttria-doped zirconium oxide was prepared by varying the yttria conent as discussed by the authors, and the fracture toughness of the materials were 11.6, 8.7, and 2.5 Mpa · m½, respectively.
Abstract: Yttria-doped zirconium oxide was prepared in the fully tetragonal, mixed tetragonal and cubic, and the fully cubic phases by varying the yttria conent. The fracture toughnesses of the materials were 11.6, 8.7, and 2.5 Mpa · m½, respectively. The wear resistance, measured in air at room temperature in slow sliding (1 mm/s speed and 9.8 N load), increases by a factor of 1200 from the brittle to the toughest material; it is proportional to the fourth power of toughness. Wear occurs predominantly by fracture in the brittle (cubic) material; plastic deformation is observed in the tougher zirconium oxide.
142 citations
TL;DR: In this article, the mechanical behavior of Nylon-6 blends modified by two types of CaCO3 particles of 0.7 and 3.5μm diameter with particle volume fractions ranging from 0.05 to 0.28 was studied between −30 and 60°C in slow tension, and at 20°c in bending impact.
142 citations
TL;DR: In this article, the variations of the amplitude of the stress field, the triaxiality of stress and the crack tip opening displacement against the Triaxial stress constraint T = are analyzed in detail based on the work of Part I and Part II of this study.
142 citations