SEMINAL DEVELOPMENTS IN THE DURABILITY AND DAMAGE TOLERANCE ASSESSMENT OF BONDED JOINTS

2021 ◽  
Author(s):  
RHYS JONES ◽  
ANTHONY KINLOCH ◽  
J. MICHOPOULOS ◽  
A. P. ILIOPOULOS
Keyword(s):  
Crack Growth ◽  
Fatigue Cracks ◽  
Growth Curves ◽  
Adhesive Layer ◽  
Cohesive Crack ◽  
Mode I ◽  
Bonded Joints ◽  
Crack Driving Force ◽  
Structural Adhesives ◽  
Epoxy Adhesives

Structural adhesives are widely used for joining composite components in many industries and crack growth in such materials is far more likely to occur when they are subjected to repeated cyclic loading than to monotonic loading. Whilst the Hartman- Schijve equation for fatigue crack growth (FCG) has been shown to hold for cohesive crack growth in adhesives under Mode I, Mode II and Mixed-Mode I/II loading, little attention has been paid to its ability to capture the effects of the thickness of the adhesive layer. The present paper examines the growth of fatigue cracks, that occurs cohesively through the adhesive layer, in two toughened epoxy adhesives typical of those used in the automotive and the aerospace industries. Firstly, it is established that when the crack growth rate, da/dN, curves are expressed as a function of Δ√G, or ΔG, where G is the energy release-rate, then the crack growth curves are a function of the thickness of the adhesive layer. It is then shown that this dependency vanishes when da/dN is expressed as a function of the crack-driving force, Δκ, as defined by the Hartman-Schijve equation. Therefore, it is suggested that the parameter Δκ appears to be a valid similitude parameter.

scholarly journals The effect of modified tannic acid (TA) eco-epoxy adhesives on mode I fracture toughness of bonded joints

2021 ◽  
Vol 96 ◽  
pp. 107122
Author(s):  
Mohamed Nasr Saleh ◽  
Nataša Z. Tomić ◽  
Aleksandar Marinković ◽  
Sofia Teixeira de Freitas
Keyword(s):  
Fracture Toughness ◽  
Tannic Acid ◽  
Mode I ◽  
Bonded Joints ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness ◽  
Epoxy Adhesives

Using an embedded Buckypaper to monitor mode I crack growth in bonded joints

2020 ◽  
pp. 1-19
Author(s):  
Idoia Gaztelumendi ◽  
H. Villaverde ◽  
B. Pérez ◽  
M. Chapartegui ◽  
S. Flórez ◽  
...  
Keyword(s):  
Crack Growth ◽  
Mode I ◽  
Mode I Crack ◽  
Bonded Joints

scholarly journals Requirements and Variability Affecting the Durability of Bonded Joints

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1468 ◽  
Author(s):  
Rhys Jones ◽  
Daren Peng ◽  
John G. Michopoulos ◽  
Anthony J. Kinloch
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Upper Bound ◽  
The United States ◽  
Fatigue Threshold ◽  
Growth Equation ◽  
Bonded Joints ◽  
Cohesive Failure ◽  
Structural Adhesives

This paper firstly reveals that when assessing if a bonded joint meets the certification requirements inherent in MIL-STD-1530D and the US Joint Services Standard JSSG2006 it is necessary to ensure that: (a) There is no yielding at all in the adhesive layer at 115% of design limit load (DLL), and (b) that the joint must be able to withstand design ultimate load (DUL). Secondly, it is revealed that fatigue crack growth in both nano-reinforced epoxies, and structural adhesives can be captured using the Hartman–Schijve crack growth equation, and that the scatter in crack growth in adhesives can be modelled by allowing for variability in the fatigue threshold. Thirdly, a methodology was established for estimating a valid upper-bound curve, for cohesive failure in the adhesive, which encompasses all the experimental data and provides a conservative fatigue crack growth curve. Finally, it is shown that this upper-bound curve can be used to (a) compare and characterise structural adhesives, (b) determine/assess a “no growth” design (if required), (c) assess if a disbond in an in-service aircraft will grow and (d) to design and life in-service adhesively-bonded joints in accordance with the slow-growth approach contained in the United States Air Force (USAF) certification standard MIL-STD-1530D.

Fatigue Crack Growth Thresholds of Deflected Mixed-Mode Cracks in PWA1484

2005 ◽  
Vol 127 (1) ◽  
pp. 2-7 ◽  
Author(s):  
K. S. Chan ◽  
J. Feiger ◽  
Y.-D. Lee ◽  
R. John ◽  
S. J. Hudak,
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Mixed Mode ◽  
Fatigue Cracks ◽  
Symmetry Plane ◽  
Crystallographic Analysis ◽  
Mode I ◽  
Test Technique ◽  
Crack Paths

The fatigue crack growth (FCG) behavior of PWA1484 single crystals was characterized in air under mixed-mode loading at 593°C as a function of crystallographic orientation using an asymmetric four-point bend test technique. Most mixed-mode fatigue cracks deflected from the symmetry plane and propagated as transprecipitate, noncrystallographic cracks, while self-similar fatigue crack growth occurred on the (111) planes in (111)/[011] and 111/[112]¯ oriented crystals. The local stress intensity factors and the crack paths of the deflected mixed-mode cracks were analyzed using the finite-element fracture mechanics code, FRANC2D/L. The results indicated that the deflected crack path was close to being normal to the maximum tensile stress direction where the Mode II component diminishes. Crystallographic analysis of the deflected crack paths revealed that the Mode I and the deflected mixed-mode cracks were usually of different crystallographic orientations and could exhibit different Mode I FCG thresholds when the crystallography of the crack paths differed substantially. These results were used to identify the driving force and conditions for cracking mode transition.

scholarly journals Fatigue Crack Growth under Non-Proportional Mixed Mode Loading in Rail and Wheel Steel Part 2: Sequential Mode I and Mode III Loading

2019 ◽  
Vol 9 (14) ◽  
pp. 2866 ◽  
Author(s):  
Makoto Akama ◽  
Akira Kiuchi
Keyword(s):  
Crack Growth ◽  
Mixed Mode ◽  
Fatigue Cracks ◽  
Rolling Contact ◽  
Material Strength ◽  
Shear Mode ◽  
Mode I ◽  
Mode Iii ◽  
Plane Shear ◽  
Branch Crack

Rolling contact fatigue cracks in rail and wheel undergo non-proportional mixed mode I/II/III loading. Fatigue tests were performed to determine the coplanar and branch crack growth rates on these materials. Sequential and overlapping mode I and III loading cycles were applied to single cracks in round bar specimens. Experiments in which this is done have been rarely performed. The fracture surface observations and the finite element analysis results suggested that the growth of long (does not branch but grown stably and straight) coplanar cracks was driven mainly by mode III loading. The cracks tended to branch when increasing the material strength and/or the degree of overlap between the mode I and III loading cycles. The equivalent stress intensity factor range that can consider the crack face contact and successfully regressed the crack growth rate data is proposed for the branch crack. Based on the results obtained in this study, the mechanism of long coplanar shear-mode crack growth turned out to be the same regardless of whether the main driving force is in-plane shear or out-of-plane shear.

Using acoustic emissions (AE) to monitor mode I crack growth in bonded joints

2020 ◽  
Vol 224 ◽  
pp. 106778 ◽  
Author(s):  
J. Manterola ◽  
M. Aguirre ◽  
J. Zurbitu ◽  
J. Renart ◽  
A. Turon ◽  
...  
Keyword(s):  
Crack Growth ◽  
Acoustic Emissions ◽  
Mode I ◽  
Mode I Crack ◽  
Bonded Joints

Crack growth analysis at adhesive–adherent interface in bonded joints under mixed mode I/II

2008 ◽  
Vol 75 (18) ◽  
pp. 5122-5133 ◽  
Author(s):  
G.V. Marannano ◽  
L. Mistretta ◽  
A. Cirello ◽  
S. Pasta
Keyword(s):  
Crack Growth ◽  
Mixed Mode ◽  
Growth Analysis ◽  
Mode I ◽  
Bonded Joints

Deviant Crack Path Behaviour of Aluminium-Lithium Alloy AA8090 Plate

1996 ◽  
Vol 210 (2) ◽  
pp. 117-121
Author(s):  
P J Gregson ◽  
I Sinclair
Keyword(s):  
Crack Growth ◽  
Mixed Mode ◽  
Fatigue Testing ◽  
Fatigue Cracks ◽  
Elastic Strain Energy ◽  
Strain Energy Release ◽  
Mode I ◽  
Mixed Mode Crack ◽  
Energy Release Rates ◽  
Strain Energy Release Rates

The unusual susceptibility of the Al-Li alloy AA8090 to sustained macroscopic deviation of fatigue cracks from a nominal mode I path during conventional fatigue testing is discussed. It is demonstrated that the mixed mode crack growth associated with macroscopic deviation may be characterized in terms of elastic strain energy release rates for a range of mixed mode loading conditions. It is specifically shown that this form of mixed mode crack growth may lead to non-conservative crack growth predictions when these materials are subjected to conventional, mode I based structure lifing techniques.

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