Towards a geometry independent traction-separation and angle relation due to large scale bridging in DCB configuration

2020 ◽  
Vol 197 ◽  
pp. 108172 ◽  
Author(s):  
Georgios A. Pappas ◽  
John Botsis
Keyword(s):  
Large Scale ◽  
Scale Bridging

An Investigation of the Effects of Layer Thickness on the Fracture Behavior of Layered NiAl/V Composites

1999 ◽  
Vol 121 (4) ◽  
pp. 453-459 ◽  
Author(s):  
M. Li ◽  
R. Wang ◽  
N. Katsube ◽  
W. O. Soboyejo
Keyword(s):  
Finite Element ◽  
Layer Thickness ◽  
Large Scale ◽  
Small Scale ◽  
Pure Mode ◽  
Crack Bridging ◽  
Maximum Shear Strain ◽  
Element Analysis ◽  
Scale Bridging ◽  
Vanadium Layer

The effects of vanadium layer thickness (100, 200 and 400 μm) on the resistance-curve behavior of NiAl/V, microlaminates are examined in this paper. The fracture resistance of the NiAl microlaminates reinforced with 20 vol.% of vanadium layers is shown to increase with increasing vanadium layer thickness. The improved fracture toughness (from an NiAl matrix toughness of 6˜.6MPam to a steady-state toughness of 1˜5MPam obtained from finite element analysis) is associated with crack bridging and the interactions of cracks with vanadium layers. The reinitiation of cracks in adjacent NiAl layers is modeled using finite element methods and the reinitiation is shown to occur as a result of strain concentrations at the interface between the adjacent NiAl layers and vanadium layers. The deviation of the reinitiated cracks from the pure mode I direction is shown to occur in the direction of maximum shear strain. Toughening due to crack bridging is also modeled using large-scale bridging models. The intrinsic toughness levels of the microlaminates are also inferred by extrapolating the large scale bridging models to arbitrarily large specimen widths. The extrapolations also show that the small-scale bridging intrinsic toughness increases with increasing vanadium layer thickness.

Remarks on Crack-Bridging Concepts

1992 ◽  
Vol 45 (8) ◽  
pp. 355-366 ◽  
Author(s):  
G. Bao ◽  
Z. Suo
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Ceramic Matrix Composites ◽  
Notch Sensitivity ◽  
Small Scale ◽  
Matrix Composites ◽  
Crack Bridging ◽  
Scale Bridging ◽  
Hole Radius ◽  
The Difference

The article draws upon recent work by us and our colleagues on metal and ceramic matrix composites for high temperature engines. The central theme here is to deduce mechanical properties, such as toughness, strength and notch-ductility, from bridging laws that characterize inelastic processes associated with fracture. A particular set of normalization is introduced to present the design charts, segregating the roles played by the shape, and the scale, of a bridging law. A single material length, δ0E/σ0, emerges, where δ0 is the limiting-separation, σ0 the bridging-strength, and E the Young’s modulus of the solid. It is the huge variation of this length—from a few nanometers for atomic bond, to a meter for cross-over fibers—that underlies the richness in material behaviors. Under small-scale bridging conditions, δ0E/σ0 is the only basic length scale in the mechanics problem and represents, with a pre-factor about 0.4, the bridging zone size. A catalog of small-scale bridging solutions is compiled for idealized bridging laws. Large-scale bridging introduces a dimensionless group, a/(δ0E/σ0), where a is a length characterizing the component (e.g., hole radius). The group plays a major role in all phenomena associated with bridging, and provides a focus of discussion in this article. For example, it quantifies the bridging scale when a is the unbridged crack length, and notch-sensitivity when a is hole radius. The difference and the connection between Irwin’s fracture mechanics and crack bridging concepts are discussed. It is demonstrated that fracture toughness and resistance curve are meaningful only when small-scale bridging conditions prevail, and therefore of limited use in design with composites. Many other mechanical properties of composites, such as strength and notch-sensitivity, can be simulated by invoking large-scale bridging concepts.

scholarly journals A mixed mode cohesive model for FRP laminates incorporating large scale bridging behaviour

2020 ◽  
Vol 239 ◽  
pp. 107274
Author(s):  
R.K. Joki ◽  
F. Grytten ◽  
B. Hayman ◽  
B.F. Sørensen
Keyword(s):  
Mixed Mode ◽  
Large Scale ◽  
Cohesive Model ◽  
Scale Bridging

Fatigue Properties of Aerospace Z-Pinned Composites

2016 ◽  
Vol 828 ◽  
pp. 67-75
Author(s):  
Adrian P. Mouritz ◽  
Fabio Pegorin ◽  
Mohd Dali Isa ◽  
Khomkrit Pingkarawat
Keyword(s):  
Volume Content ◽  
Composite Structures ◽  
Large Scale ◽  
Fatigue Properties ◽  
Mode I ◽  
Scale Bridging ◽  
Microstructural Damage ◽  
Out Of Plane ◽  
Cycles To Failure ◽  
Properties Of Composites

This paper presents an experimental study into the effect of through-thickness z-pin reinforcement on the in-plane and out-of-plane (delamination) fatigue properties of carbon-epoxy composites used in aerospace structures. The in-plane fatigue strength and fatigue life (load cycles-to-failure) of aerospace composite materials are reduced by z-pins. The in-plane compressive fatigue properties decrease when the volume content of z-pins is increased. Reductions to the in-plane fatigue properties are due to microstructural damage caused by the z-pins. However, the out-of-plane (delamination) fatigue properties of composites are increased greatly by z-pins. The mode I, mode II and mixed mode I/II delamination fatigue properties increase rapidly with increasing volume content of z-pins. The improvement is due to the z-pins forming a large-scale bridging zone along the delamination which resists fatigue crack growth. The work clearly reveals that a trade-off exists between the in-plane and out-of-plane fatigue properties of z-pinned composites. Improvements to the delamination fatigue properties come at the expense of lower in-plane fatigue performance, and this is a key consideration for the design of z-pinned aerospace composite structures.

Large-scale bridging in composites: R-curves and bridging laws

1998 ◽  
Vol 29 (11) ◽  
pp. 1443-1451 ◽  
Author(s):  
Bent F Sørensen ◽  
Torben K Jacobsen
Keyword(s):  
Large Scale ◽  
Scale Bridging
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