The Effects of In-Service Induced Reduction of Bonding Quality on the Mode I, II, and I-II Fracture Toughness of CNT Nanocomposites

2016 ◽  
Author(s):  
Masoud Yekani Fard ◽  
Brian Raji ◽  
John M. Woodward ◽  
Aditi Chattopadhyay
Keyword(s):  
Fracture Toughness ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Accelerated Aging ◽  
Beam Theory ◽  
Mode I ◽  
Mode Ii ◽  
Initiation And Propagation ◽  
Calibration Methods

Tests were carried out to determine the interlaminar fracture toughness of stitch-bonded biaxial polymer matrix carbon nanotube nanocomposites for mode I, II, and I-II including durability effects. Analysis of the test specimens in terms of mode I energy release rates showed good agreement among Modified Beam Theory, Compliance Calibration, and Modified Compliance Calibration methods. End-Notched Flexure (ENF) and four point End-Notched Flexure (4ENF) tests gave very consistent crack initiation and propagation results for mode II fracture. The results show that the critical mode I energy release rate for delamination decreases monotonically with increasing mode II loading. The effects of accelerated aging (60°C and 90% Rh) on fracture properties were studied. Early accelerated aging (0–12 months) has the dominant diminishing effect on energy release rate initiation and propagation in composites and nanocomposites.

scholarly journals Characterization of cohesive model and bridging laws in mode I and II fracture in nano composite laminates

2018 ◽  
Vol 12 (4) ◽  
pp. 4329-4355 ◽  
Author(s):  
P. Ghabezi ◽  
M. Farahani
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Composite Laminates ◽  
Beam Theory ◽  
Critical Parameters ◽  
Mode I ◽  
Mode Ii ◽  
Reliable Determination ◽  
Cohesive Model

The cohesive model and traction-separation curves have brought a considerable possibility for researchers and fracture engineers to assess and simulate failure in composite laminates. Reliable determination of the traction–separation laws is very pivotal to the success of this approach in finite element methods. The objective of this paper is assessment of nanoparticles effect on bridging laws, cohesive mechanism and traction-separation parameters of nanocomposites mode I and II fracture. To do this analyzing of the experimental data from double cantilever beam, and end notched flexure tests including construction of the R-curves (energy release rate versus crack length), reconstruction of these curves in terms of the pre-crack tip opening and sliding displacement, and calculation of the corresponding bridging and traction-separation laws through the J-integral approach were carried out. For the calculation of the energy release rate in Mode I, three corresponding data reduction schemes namely Corrected Beam Theory, Experimental Compliance Method and Modified Compliance Calibration are utilized, while Compliance Calibration Method, Corrected Beam Theory and Compliance-Based Beam and II fracture are applied for that of mode II. The main concern of this research is introduction of critical parameters of two modified models to simulate mode I and II fracture. Adding 0.43 wt% nanoparticles to composite DCB samples leads to increase of 116%, 68% and 70% in GI,0 calculated by CBT, ECM and MCC respectively, and a 72% increase in GI,ss is measured by CBT, while this value for ECM and MCC is 110% and 48%. Adding 0.2 wt% nanoparticles to the composite samples results in 86% (50 MPa) increase in critical stress in mode II fracture calculated by method CBBM. This method presented the lowest value for critical displacement, fluctuated between 0.08-.11 mm in mode II.

Numerical Examination of Mixed Mode Crack in SSY: A Review

2013 ◽  
Vol 275-277 ◽  
pp. 198-202
Author(s):  
Prasad S. Godse ◽  
Sangram A. Gawande ◽  
Sunil Bhat
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Mixed Mode ◽  
Small Scale ◽  
Mode I ◽  
Mode Ii ◽  
Fracture Parameter ◽  
Conservation Of Energy ◽  
Mixed Mode Crack

The paper reviews the numerical methodology to investigate fracture parameter namely energy release rate, G, of a mixed mode crack. An inclined, through, centre crack is assumed in a ductile steel plate subjected to bi-axial tension. Applied stress and crack size are suitably selected to simulate small scale yielding (SSY) condition at the crack tips. The cracked plate is modelled by finite element method. Both plane stress and plane strain situations are examined. G value is found from J integral. Equations of transformation are employed to obtain normal and shear stress in the plane of the crack. G is then again determined for Mode I and Mode II cracks by modelling each case separately. The analysis is finally validated by fulfilment of the conservation of energy release rate criterion, G (Mixed mode) = G (Mode I) + G (Mode II).

The Characterization of Mixed-Mode Energy Release Rates in Orthotropic Materials

1996 ◽  
Vol 210 (1) ◽  
pp. 33-42 ◽  
Author(s):  
C A Walker ◽  
Jamasri
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Energy Release ◽  
Crack Growth ◽  
Release Rate ◽  
Mode I ◽  
Mode Ii ◽  
Finite Element Models ◽  
Release Rates ◽  
Energy Release Rates

The aim of this work was to predict, from the material constants, mixed-mode energy release rates in orthotropic materials, in particular the general cases in which the crack is aligned at a random angle to the principal material direction, normal to the plane of orthotropy. Two-dimensional finite element models with various fibre orientations were generated. The finite element models were validated by comparing two sets of contour plots of deformation, one resulting from the finite element analysis and the other from moiré interferograms of the experimental work. On comparison there was shown to be a strict similarity between experimentally determined and computational deformation fields. Variations of the energy release rates were investigated for both rapid and stable crack growth. This was accomplished by generating two-dimensional stable crack growth finite element models. In general, energy release rates were found to be strongly affected by the fibre orientation. An increase of the angle of the crack growth direction caused a decrease of the mode I energy release rate and, by contrast, an increase of the mode II energy release rate, but the mode II energy release rate was always a small fraction of the mode I value. Crack extension caused a gradual increase of the mode I energy release rate both for coplanar and non-coplanar crack growth. However, there was no significant effect found on the mode II energy release rate.

Mode I Fracture Toughness of a Tri-Layered Beam with Interfacial Crack

2012 ◽  
Vol 166-169 ◽  
pp. 245-248
Author(s):  
Shiuh Chuan Her ◽  
Wei Bo Su
Keyword(s):  
Fracture Toughness ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Mode I ◽  
Analytical Prediction ◽  
Layered Beam

A tri-layered cracked beam under opening loading is developed for the interfacial fracture toughness measurement. Determination of the mode I strain energy release rate along the second and third layers of the tri-layered beam is carried out analytically. The analytical prediction of the strain energy release rate is validated with the finite element results. The influences of the layer thickness and Young’s modulus on the strain energy release rate are examined through a parametric study.

scholarly journals Analysis of Interfacial Cracks in a TBC/Superalloy System Under Thermo-Mechanical Loading

1997 ◽  
Author(s):  
S. Q. Nusier ◽  
G. M. Newaz
Keyword(s):  
Residual Stresses ◽  
Energy Release Rate ◽  
Energy Release ◽  
Circular Plate ◽  
Release Rate ◽  
Bond Coat ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Processing Temperature

In thermal barrier coatings (TBC) residual stresses develop during cool down from processing temperature due to the thermal expansion mismatch between the different layers (substrate, bond coat, and TBC). These residual stresses can initiate micro cracks at the bond coat/TBC interface and can lead to debonding at the bond coat/TBC interface. The effect of voids or crack like flaws at the interface can be responsible for initiating debonding and accelerate the oxidation process. Effect of oxide layer growth between bond coat and ceramic layer (TBC) can be modeled as volume increase. In this work we represent this change in volume as an induced pressure across the interface. Mixed-mode fracture analysis of a thin circular delamination in an-axisymmetrically multi layer circular plate is developed. Geometrical nonlinearity is included in the analysis, since we have a large deflection case. The elastic deformation problem of a circular plate subjected to a clamped boundary condition at the edge of the delamination, an out of plane pressure load, and a compressive stress due to thermal mismatch between different layers, was solved numerically using a Rayleigh-Ritz method. The strain energy release rate was evaluated by means of the path-independent M-integral. The numerical results of this problem based on the energy method were verified using finite element method. Both methods correlate well in predicting the energy release rate for Mode I and Mode II, deflection, and postbuckling solutions. The energy release rates G, for both Mode I and Mode II using virtual crack extension method were evaluated. The specimen was cooled down from processing temperature of 1000 °C to 0 °C. The variation of the properties as a function of temperature was used for analysis. It was found that the use of temperature dependent properties in contrast to constant properties provides significantly different values of J-integral and G.

An end notched flexure specimen model for mode-II fracture of high-temperature superconductor tapes with thermal effect

2019 ◽  
Vol 34 (03) ◽  
pp. 2050048
Author(s):  
K. F. Wang ◽  
Z. Li ◽  
J. E. Li ◽  
B. L. Wang
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Energy Release Rate ◽  
Thermal Effect ◽  
Energy Release ◽  
Release Rate ◽  
High Temperature Superconductor ◽  
Mode Ii ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

End notched flexure (ENF) experiment using three-point bending beam specimen is a very convenient test configuration to evaluate the mode-II fracture toughness of composites. High-temperature superconductor (HTS) tapes are multi-layered composite that have been widely used in magnets and cables. HTS tapes are manufactured at room temperature ([Formula: see text][Formula: see text]300 K) but are used in the liquid-nitrogen temperature (77 K) environment. The large temperature change leads to large shear stress which may cause delamination of HTS tapes. In this paper, a closed-form expression of energy release rate (and therefore the stress intensity factor) for mode-II fracture of HTS tapes with thermal effect is developed based on the end notched flexure specimen. Results show that HTS tapes in working condition are prone to delaminating. Increasing the thickness of Hastelloy layer can reduce the energy release rate of mode-II cracking thus increase the interface strength. In the design of HTS tapes, the silver and copper layers are used to enhance the stretch of the HTS tapes. While silver and copper layers will increase the energy release rate for mode-II crack. This fact indicates that thicker silver and copper layers are not always good from the fracture mechanics point of view. The results of thermomechanical model and fracture criterion model of this research are useful for determining mode-II fracture toughness of superconducting composites for high-temperature applications.

Analysis of Interfacial Cracks in a TBC/Superalloy System Under Thermomechanical Loading

1998 ◽  
Vol 120 (4) ◽  
pp. 813-819 ◽  
Author(s):  
S. Q. Nusier ◽  
G. M. Newaz
Keyword(s):  
Residual Stresses ◽  
Energy Release Rate ◽  
Energy Release ◽  
Circular Plate ◽  
Release Rate ◽  
Bond Coat ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Processing Temperature

In thermal barrier coatings (TBC) residual stresses develop during cool down from processing temperature due to the thermal expansion mismatch between the different layers (substrate, bond coat, and TBC). These residual stresses can initiate micro-cracks at the bond coat/TBC interface and can lead to debonding at the bond coat/TBC interface. The effect of voids or crack-like flaws at the interface can be responsible for initiating debonding and accelerating the oxidation process. Effect of oxide layer growth between bond coat and ceramic layer (TBC) can be modeled as volume increase. In this work we represent this change in volume as an induced pressure across the interface. Mixed-mode fracture analysis of a thin circular delamination in an-axisymmetrically multi-layer circular plate is developed. Geometrical nonlin-earity is included in the analysis, since we have a large deflection case. The elastic deformation problem of a circular plate subjected to a clamped boundary condition at the edge of the delamination, an out of plane pressure load, and a compressive stress due to thermal mismatch between different layers, was solved numerically using a Rayleigh–Ritz method. The strain energy release rate was evaluated by means of the path-independent M-integral. The numerical results of this problem based on the energy method were verified using finite element method. Both methods correlate well in predicting the energy release rate for Mode I and Mode II, deflection, and postbuckling solutions. The energy release rates G, for both Mode I and Mode II using virtual crack extension method, were evaluated. The specimen was cooled down from processing temperature of 1000°C to 0°C. The variation of the properties as a function of temperature was used for analysis. It was found that the use of temperature dependent properties in contrast to constant properties provides significantly different values of J-integral and G.

Energy Release Rates for an Interface Crack Embedded in a Laminated Beam Subjected to Three-Point Bending

1997 ◽  
Vol 64 (2) ◽  
pp. 375-382 ◽  
Author(s):  
M. Toya ◽  
M. Aritomi ◽  
A. Chosa
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Interface Crack ◽  
Release Rate ◽  
Mode I ◽  
Mode Ii ◽  
Release Rates ◽  
Three Point Bending ◽  
Axial Forces ◽  
Energy Release Rates

Asymmetric three-point bending of a layered beam with an interface crack is analyzed on the basis of the classical beam theory. Axial forces induced by bending in the parts of the beam above and below the delamination are determined by regarding the cracked part as two lapped beams hinged at both ends. The compliance and the energy release rate are then derived. Numerical analyses based on the finite element method are carried out, which show that delamination growth occurs in mixed mode, i.e., both the normal separation (mode I) and mutual sliding (mode II) of the crack surfaces contribute to the fracturing process. Finally the decomposition of the energy release rate into mode I and mode II components is made by combining the analysis of the energy release rates by Toya (1992) and the two-dimensional linear beam solutions by Suo and Hutchinson (1990).

scholarly journals Fracture of Parallel Strand Bamboo Composite under Mode I Loading: DCB Test Investigation

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Yurong Shen ◽  
Dongsheng Huang ◽  
Ying Hei Chui ◽  
Chunping Dai
Keyword(s):  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Release Rate ◽  
Experimental Studies ◽  
Beam Theory ◽  
Initial Crack ◽  
Mode I ◽  
Initial Crack Length ◽  
Test Investigation

This paper describes the experimental studies on Mode I fracture of parallel strand bamboo (PSB) by the double cantilever beam (DCB) test. R-curves based on the elementary beam theory and specimen compliance are proposed in order to overcome the difficulties to monitor the crack propagation during experiments. The results demonstrate that the energy release rate (ERR) is influenced by the specimen geometry, i.e., the specimen width and initial crack length. The ERR at the plateau level is similar for the range of the analyzed widths (B = 20, 40, and 60 mm), while it decreases with width increasing up to 80 mm and 100 mm. The energy release rate for PSB specimens would verge to a stable value with the width increasing up to a specific value, while the value of the energy release rate will be influenced by the initial crack length. Consequently, the DCB tests also show that the obtained R-curve in this study is not a material property.

Sign in / Sign up

Export Citation Format

Share Document