Mixed-Mode Failure of Graphite/Epoxy Composites

2001 ◽  
Vol 123 (3) ◽  
pp. 371-376 ◽  
Author(s):  
M. A. Seif ◽  
M. Shahjahan
Keyword(s):  
Mixed Mode ◽  
Failure Modes ◽  
Crack Opening ◽  
Damage Zone ◽  
Theoretical Data ◽  
Opening Displacement ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Loading Axis ◽  
Mode Failure

An experimental study of the crack displacement and failure modes of graphite epoxyplates, having central cracks at different angles with the loading axis, was conducted. Due to this type of loading arrangement, the material was under mixed-mode loading condition (mode I and mode II). In this investigation, Moire´ Interferometry technique was employed to measure Crack Opening Displacement (COD) and Crack Shearing Displacement (CSD). Detailed studies were performed to investigate the effect of the crack angle on the strength reduction ratio, the damage zone, and the critical stress intensity factors. The comparison between the Linear Elastic Fracture Mechanics (LEFM) solution and the results obtained from this investigation showed a fair agreement between the theoretical data and the experimental ones. This confirms the validity of implementing the LEFM model for this type of materials.

The crack opening displacement approach to fracture mechanics in yielding materials

1966 ◽  
Vol 1 (2) ◽  
pp. 145-153 ◽  
Author(s):  
F. M. Burdekin ◽  
D. E. W. Stone
Keyword(s):  
Fracture Mechanics ◽  
Crack Opening Displacement ◽  
Crack Opening ◽  
Opening Displacement ◽  
Critical Crack ◽  
Absolute Size ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
Critical Crack Opening ◽  
Displacement Approach

An introduction is given to the fracture mechanics approach employing the concept of crack opening displacement for application to situations in which linear elastic fracture mechanics is invalidated by yielding. The hypothesis of a critical crack opening displacement to fracture has been examined experimentally using mild steel specimens of vastly differing dimensions. Subsidiary experiments have been carried out to define the factors responsible for the apparent effect of absolute size on the results. A theoretical analysis simulates elastic-plastic conditions to give a relationship between applied stresses and strains, crack length, and crack opening displacement.

Fully Plastic Solutions and Large Scale Yielding Estimates for Plane Stress Crack Problems

1976 ◽  
Vol 98 (4) ◽  
pp. 289-295 ◽  
Author(s):  
C. F. Shih ◽  
J. W. Hutchinson
Keyword(s):  
Plane Stress ◽  
Large Scale ◽  
Crack Opening ◽  
Opening Displacement ◽  
Stress Strain ◽  
Linear Elastic ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Crack Problems ◽  
Scale Yielding

Fully plastic plane stress solutions are given for a center-cracked strip in tension and an edge-cracked strip in pure bending. In the fully plastic formulation the material is characterized by a pure power hardening stress-strain relation which reduces at one limit to linear elasticity and at the other to rigid/perfect plasticity. Simple formulas are given for estimating the J-integral, the load-point displacement and the crack opening displacement in terms of the applied load for strain hardening materials characterized by the Ramberg-Osgood stress-strain relation in tension. The formulas make use of the linear elastic solution and the fully plastic solution to interpolate over the entire range of small and large scale yielding. The accuracy of the formulas is assessed using finite element calculations for some specific configurations.

Application of Multi-Parameter Fracture Mechanics to Study of Crack Propagation Angle in Selected Mixed-Mode Geometry

2013 ◽  
Vol 592-593 ◽  
pp. 209-212 ◽  
Author(s):  
Lucie Šestáková Malíková ◽  
Václav Veselý
Keyword(s):  
Fracture Mechanics ◽  
Crack Propagation ◽  
Mixed Mode ◽  
Initial Crack ◽  
Propagation Angle ◽  
Linear Elastic ◽  
Higher Order Terms ◽  
Elastic Fracture ◽  
Cracked Specimens ◽  
Crack Propagation Angle

The multi-parameter fracture mechanics becomes more and more significant, because it is shown that it can help to describe fracture processes occurring in cracked specimens more precisely than conventional linear elastic fracture mechanics. In this paper, the concept based on the Williams expansion derived for approximation of stress/displacement crack-tip fields is presented and applied on a mixed-mode configuration. Two fracture criteria for estimation of the initial crack propagation angle are introduced. A parametric study is performed in order to investigate the dependence of the crack propagation angle on the stress intensity factors ratio. Influence and importance of taking into account the so-called higher-order terms of the Williams expansion are discussed and some recommendations are stated.

Fracture mechanics in design and service: ‘living with defects’ - Assessment of defects: the c.o.d. approach

1981 ◽  
Vol 299 (1446) ◽  
pp. 155-167 ◽  
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Opening ◽  
Local Stress ◽  
Concentration Effects ◽  
Opening Displacement ◽  
Widespread Application ◽  
Linear Elastic ◽  
Applied Loading ◽  
Displacement Approach

In welded construction particular problems arise with the application of fracture mechanics for the assessment of the effect of defects on structural performance. In many practical cases the use of plane strain linear elastic fracture mechanics methods is invalidated by the actual material thicknesses of interest, by residual stresses or by local stress concentration effects, and by local yielding. The crack opening displacement approach was originally devised as a means of extending linear elastic methods to more widespread application to welded structures. This required the development of a means of assessing fracture toughness, and a means of relating this fracture toughness to the applied loading conditions, and to sizes and types of defects which might be present. The success of this method of assessing defects over a period of some 10-12 years will be illustrated, together with a discussion of the inherent limitations of the approach and possible improvements resulting from recent research into slow tearing and design curve relationships.

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