Experimental Investigation of Plane Shear Fracture Characteristics of Sandstone after Cyclic Freeze–Thaw Treatments

2021 ◽  
pp. 103214
Author(s):  
Ri-hong Cao ◽  
Tao Hu ◽  
Changsong Wang ◽  
Rubing Yao ◽  
Tianbing Li ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Shear Fracture ◽  
Plane Shear ◽  
Fracture Characteristics ◽  
Freeze Thaw

A mechanism of apparent inter-sonic propagation of shear fractures

2021 ◽  
Author(s):  
Elena Pasternak ◽  
Arcady Dyskin
Keyword(s):  
Shear Zone ◽  
Wave Velocity ◽  
Shear Fracture ◽  
Fracture Propagation ◽  
P Wave ◽  
Spherical Particles ◽  
Fracture Mechanisms ◽  
Longitudinal Deformation ◽  
Plane Shear ◽  
Limiting Case

<p>Inter-sonic (faster than the shear wave velocity) propagation of zones of shear over faults are observed both in the Earth’s crust and in specially designed laboratory experiments. This is usually interpreted as propagation of shear fractures caused by postulated special fracture mechanisms. This interpretation is however at variance with experimental facts that shear fractures in solids do not propagate in their own planes, kinking instead. Extensive (and fast) in-plane shear fracture propagation seems to only be possible over pre-existing planes considerably weaker than the surrounding material. A limiting case of fracture propagation over such a weak plane is the propagation of a sliding zone resisted by friction only. Another limiting case is shearing over a narrow elastic layer (shear Winkler layer) without rupture. The shear Winkler layer models both traditional elastic connections (positive stiffness) and rotation of non-spherical particles of the fault gouge (negative stiffness), e.g. [1, 2].</p><p>In both cases propagation of sliding/shear zone also involve longitudinal deformation in the surrounding material. Using a configuration different from [3, 4] we demonstrate that the presence of the longitudinal deformation makes the sliding/shear zone propagate with p-wave velocity. Propagation of such zones create seismic signals with power spectra resembling those observed in earthquakes.</p><p><strong>Acknowledgement</strong>.   AVD and EP acknowledge support from the Australian Research Council through project DP190103260.</p>

In-plane shear of nanoprepreg/nanostitched three-dimensional carbon/epoxy multiwalled carbon nanotubes composites

2019 ◽  
Vol 53 (24) ◽  
pp. 3413-3431 ◽  
Author(s):  
Kadir Bilisik ◽  
Nesrin Karaduman ◽  
Gulhan Erdogan ◽  
Erdal Sapanci ◽  
Sila Gungor
Keyword(s):  
Carbon Nanotubes ◽  
Multiwalled Carbon Nanotubes ◽  
Shear Fracture ◽  
Three Dimensional ◽  
Carbon Fabric ◽  
Multiwalled Carbon ◽  
Plane Shear ◽  
The Matrix ◽  
Delamination Area ◽  
Base Structure

The in-plane shear properties of nanostitched three-dimensional (3D) carbon/epoxy composites were investigated. Adding the stitching fiber or multiwalled carbon nanotubes or nanostitched fiber into carbon fabric preform slightly improved the shear strength and modulus of stitched and stitched nanocomposites. The in-plane shear fracture of the base and nanostructures was extensive delamination and tensile fiber failures in the sheared region. But, the stitched and stitched nanocomposites had angular deformation of the stitching yarns in the fiber scissoring areas, shear hackles in the matrix and successive fiber breakages in the interlayers. Probably, this mechanism prohibited extensive interlayer opening in the nanostitched composites. The results exhibited that introducing the stitching fiber (1.44%) and multiwalled carbon nanotubes (0.03125%) in the base structure enhanced its transverse fracture properties as a form of confined delamination area. Therefore, the damaged tolerance properties of the stitched nanocomposites were enhanced.

scholarly journals Graphene fatigue through van der Waals interactions

2020 ◽  
Vol 6 (42) ◽  
pp. eabb1335
Author(s):  
Teng Cui ◽  
Kevin Yip ◽  
Aly Hassan ◽  
Guorui Wang ◽  
Xingjian Liu ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Flexible Electronics ◽  
Shear Fracture ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Pristine Graphene ◽  
Plane Shear ◽  
Dynamic Reliability ◽  
Polymer Interface ◽  
Out Of Plane

Graphene is often in contact with other materials through weak van der Waals (vdW) interactions. Of particular interest is the graphene-polymer interface, which is constantly subjected to dynamic loading in applications, including flexible electronics and multifunctional coatings. Through in situ cyclic loading, we directly observed interfacial fatigue propagation at the graphene-polymer interface, which was revealed to satisfy a modified Paris’ law. Furthermore, cyclic loading through vdW contact was able to cause fatigue fracture of even pristine graphene through a combined in-plane shear and out-of-plane tear mechanism. Shear fracture was found to mainly initiate at the fold junctions induced by cyclic loading and propagate parallel to the loading direction. Fracture mechanics analysis was conducted to explain the kinetics of an exotic self-tearing behavior of graphene during cyclic loading. This work offers mechanistic insights into the dynamic reliability of graphene and graphene-polymer interface, which could facilitate the durable design of graphene-based structures.

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