Crack onset assessment near the sharp material inclusion tip by means of modified maximum tangential stress criterion

2017 ◽  
Author(s):  
Ondej Krepl ◽  
Jan Klusák
Keyword(s):  
Stress Concentration ◽  
Crack Initiation ◽  
Tangential Stress ◽  
Maximum Tangential Stress ◽  
Reinforced Composites ◽  
Singular Stress ◽  
Stress Criterion ◽  
Maximum Tangential Stress Criterion ◽  
Particle Reinforced Composites ◽  
Material Discontinuities

In the case of particle reinforced composites, where the particles are in a form of sharp material inclusions, singular stress concentration exists on each tip of each inclusion. This is due to the geometric and material discontinuities between matrix and particle. These points of stress concentration are susceptible of crack initiation and thus often responsible for failure of the whole structure. The modified maximum tangential stress criterion is employed in order to predict crack onset conditions.

Evaluation of size effect on mixed-mode fracture behavior of epoxy/silica nanocomposites

2017 ◽  
Vol 52 (4) ◽  
pp. 239-248 ◽  
Author(s):  
Ahmad Ghasemi-Ghalebahman ◽  
Javad Akbardoost ◽  
Yaser Ghaffari
Keyword(s):  
Fracture Toughness ◽  
Tangential Stress ◽  
Mixed Mode ◽  
Fracture Behavior ◽  
Process Zone ◽  
Maximum Tangential Stress ◽  
Mixed Mode Fracture ◽  
Mode Fracture ◽  
Stress Criterion ◽  
Maximum Tangential Stress Criterion

The aim of this study was to examine the effect of size on the mixed-mode fracture toughness of quasi-brittle nanocomposites with the help of modified maximum tangential stress criterion. The literature reveals that the effect of size on mixed-mode fracture behavior of brittle nanocomposites has not been well investigated previously using modified maximum tangential stress criterion. The studied nanocomposites were made of epoxy resin reinforced with 7 wt%, 20–30 nm nanosilica. The accuracy of the method was assessed by taking into account the high-order terms of Williams series expansion along with finite element over-deterministic method. To investigate the effect of size on fracture toughness, a number of three-point semi-circular bending tests with different radii and four angles of edge–crack orientation were conducted and subjected to mixed-mode loading. The size of fracture process zone and apparent fracture toughness ( Kc) were also evaluated as a function of sample size. Experimental results showed that the proposed approach can accurately predict the fracture behavior of studied nanocomposites.

Prediction of the path of unstable extension of internal and edge cracks

1980 ◽  
Vol 15 (4) ◽  
pp. 183-194 ◽  
Author(s):  
S K Maiti
Keyword(s):  
Energy Density ◽  
Tangential Stress ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Experimental Studies ◽  
Stress Singularity ◽  
Maximum Tangential Stress ◽  
Stress Criterion ◽  
Maximum Tangential Stress Criterion ◽  
Edge Cracks

The criteria of strain energy density and maximum tangential stress have been applied to the entire stress field existing just before the onset of instability to predict the path of extension of both internal and edge cracks. The stress analysis has been carried out by a finite-element scheme employing the quarter point square-root stress singularity elements. In the case of internal cracks, the unstable paths based on both the criteria are in good agreement with the results available in the literature. Theoretical and experimental studies on edge crack extensions during bar shearing of brittle materials have facilitated a comparison, and it appears that, although the maximum tangential stress criterion may be applicable, the strain energy density criterion is unsuitable for this case.

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