Fracture Resistance of Brittle Materials Under Local Loading by Scratching to Edge Chipping. Part. 1. Methodical Grounds of Research

The process of edge flaking of brittle materials is a significant limitation in design, handling and use of components. Simple quasistatic tests to identify resistance to edge flaking can be based on near-edge indentation and scratching towards an edge, and these produce rankings of materials that broadly correlate with GIc or KIc. However, most edge damage occurs in practice by impact. Using a drop-weight impact tester, edge chipping tests have been performed dynamically on a range of brittle materials, using repeated impact with step-wise height increments until fracture. It has been found that when impact energy rather indentation force is used as the correlative parameter against distance of the impact site from the edge of the test-piece, a similar relationship to that of quasistatic indentation is found. The shapes of edge flakes produced may also similar. This suggests that even when a relatively blunt impactor is used, compared with conventional indenters, the mechanics of the failure are similar. However, the occurrence of ring cracks can lead to unusual flake shapes. It follows that simpler-to-perform quasistatic tests can model the less well-defined dynamic impact situation in terms of testing for the effects of geometry or for comparing performance of different material types.

Download Full-text

A Fracture Resistance Measurement Procedure for Brittle Materials

Transactions of the Japan Institute of Metals ◽

10.2320/matertrans1960.29.573 ◽

1988 ◽

Vol 29 (7) ◽

pp. 573-579 ◽

Cited By ~ 3

Author(s):

M. Jenkins ◽

J. Mikami ◽

T. Chang ◽

A. Okura

Keyword(s):

Fracture Resistance ◽

Brittle Materials ◽

Measurement Procedure ◽

Resistance Measurement

Download Full-text

Quantifying the role of mineral bridges on the fracture resistance of nacre-like composites

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1805094115 ◽

2018 ◽

Vol 115 (50) ◽

pp. 12698-12703 ◽

Cited By ~ 14

Author(s):

Madeleine Grossman ◽

Florian Bouville ◽

Kunal Masania ◽

André R. Studart

Keyword(s):

Flexural Strength ◽

Fracture Resistance ◽

Brittle Materials ◽

Nacreous Layer ◽

Structure Property ◽

Design Concepts ◽

Experimental Systems ◽

Brick And Mortar ◽

Balance Of Forces

The nacreous layer of mollusk shells holds design concepts that can effectively enhance the fracture resistance of lightweight brittle materials. Mineral bridges are known to increase the fracture resistance of nacre-inspired materials, but their role is difficult to quantify due to the lack of experimental systems where only this parameter is controllably varied. In this study, we fabricate tunable nacre-like composites that are used as a model to experimentally quantify the influence of the density of mineral bridges alone on the fracture properties of nacre-like architectures. The composites exhibit a brick-and-mortar architecture comprising highly aligned alumina platelets that are interconnected by titania mineral bridges and infiltrated by an epoxy organic phase. By combining experimental mechanical data with image analysis of such composite microstructures, an analytical model is put forward based on a simple balance of forces acting on an individual bridged platelet. Based on this model, we predict the flexural strength of the nacre-like composite to scale linearly with the density of mineral bridges, as long as the mineral interconnectivity is low enough to keep fracture in a platelet pullout mode. Increasing the mineral interconnectivity beyond this limit leads to platelet fracture and catastrophic failure of the composite. This structure-property correlation provides powerful quantitative guidelines for the design of lightweight brittle materials with enhanced fracture resistance. We illustrate this potential by fabricating nacre-like bulk composites with unparalleled flexural strength combined with noncatastrophic failure.

Download Full-text

Chipping Brittle Materials: A Finite Element Analysis

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.443.433 ◽

2010 ◽

Vol 443 ◽

pp. 433-438 ◽

Cited By ~ 2

Author(s):

Seyed Saleh Mostafavi ◽

Liang Chi Zhang ◽

Jason Lunn

Keyword(s):

Finite Element ◽

Brittle Materials ◽

Front Surface ◽

Free Edge ◽

Element Analysis ◽

External Work ◽

Edge Chipping ◽

Compressive Stresses ◽

Initiation And Propagation ◽

Crack Tips

Edge chipping by an indenter has been used to investigate the fragmentation of brittle materials. This paper proposed a constitutive model for studying both the initiation and propagation of cracks during the chipping of concrete. The analysis was carried out by the finite element method using a commercially available code, LS-DYNA. The results showed that a zone with very high compressive stresses appears beneath the indenter and causes the material to break or crush. Most of the external work, about 78%, was dissipated in the crushing zone while only a small percentage (less than 17%) contributed to form chips/fragments. As the indentation proceeded, radian-median cracks initiated and propagated downward and parallel to the front surface of the material to form a half penny crack. The crack tips from both sides of the indenter on the surface would then deviate toward the free edge, leading to a chipping scallop at a critical load.

Download Full-text