A Fundamental Investigation into the Deformation and Failure Behavior of Heterogeneous Materials with the Aim of Developing Design Guidelines

2004 ◽  
Author(s):  
Krishnaswarmy Ravi-Chandar
Author(s):  
Andrew Lees ◽  
Michael Dobie

Polymer geogrid reinforced soil retaining walls have become commonplace, with routine design generally carried out by limiting equilibrium methods. Finite element analysis (FEA) is becoming more widely used to assess the likely deformation behavior of these structures, although in many cases such analyses over-predict deformation compared with monitored structures. Back-analysis of unit tests and instrumented walls improves the techniques and models used in FEA to represent the soil fill, reinforcement and composite behavior caused by the stabilization effect of the geogrid apertures on the soil particles. This composite behavior is most representatively modeled as enhanced soil shear strength. The back-analysis of two test cases provides valuable insight into the benefits of this approach. In the first case, a unit cell was set up such that one side could yield thereby reaching the active earth pressure state. Using FEA a test without geogrid was modeled to help establish appropriate soil parameters. These parameters were then used to back-analyze a test with geogrid present. Simply using the tensile properties of the geogrid over-predicted the yield pressure but using an enhanced soil shear strength gave a satisfactory comparison with the measured result. In the second case a trial retaining wall was back-analyzed to investigate both deformation and failure, the failure induced by cutting the geogrid after construction using heated wires. The closest fit to the actual deformation and failure behavior was provided by using enhanced fill shear strength.


2000 ◽  
Vol 116 (7) ◽  
pp. 565-571 ◽  
Author(s):  
Yasuyuki FUJITA ◽  
Yoshiaki FUJII ◽  
Yoji ISHIJIMA

1984 ◽  
Vol 20 (2) ◽  
pp. 204-211 ◽  
Author(s):  
O. B. Naimark ◽  
M. M. Davydova ◽  
A. M. Postnykh

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2325 ◽  
Author(s):  
Jingxin Hao ◽  
Xinfeng Wu ◽  
Gloria Oporto ◽  
Jingxin Wang ◽  
Gregory Dahle ◽  
...  

A new type of Taiji honeycomb structure bonded outside with wood-based laminates was characterized from a mechanical standpoint. Both theoretical and experimental methods were employed to analyze comprehensively the deformation behavior and failure mechanism under a three-point bending test. The analytical analysis reveals that a Taiji honeycomb has 3.5 times higher strength in compression and 3.44 times higher strength in shear compared with a traditional hexagonal honeycomb. Considering the strength-weight issue, the novel structure also displays an increase in compression strength of 1.75 times and shear strength of 1.72 times. Under a three-point bending test, indentation and core shear failure played the dominant role for the total failure of a wooden sandwich with Taiji honeycomb core. Typical face yield was not observed due to limited thickness-span ratio of specimens. Large spans weaken the loading level due to the contribution of global bending stress in the compressive skin to indentation failure. A set of analytical equations between mechanical properties and key structure parameters were developed to accurately predict the threshold stresses corresponding to the onset of those deformation events, which offer critical new knowledge for the rational structure design of wooden sandwich composites.


MRS Advances ◽  
2020 ◽  
Vol 5 (33-34) ◽  
pp. 1783-1790
Author(s):  
Jacob M. Ludwick ◽  
Michelle L. Oyen

ABSTRACTArticular cartilage plays an important role in synovial joint function, but this function is diminished when cartilage tissue breaks down in osteoarthritis. Tissue engineering is a promising approach for replacing failed cartilage, as cartilage is a relatively simple tissue with no blood supply and very few biological cells. To imitate the structure of natural cartilage extracellular matrix material, three components must be included: the hydrated ground substance, the charges that contribute to compressive stiffness via electrostatic repulsion, and the nanofibrous collagen network that resists tensile deformation and failure. Here, the nanofiber network is considered, with examination of its fracture behavior in an as-electrospun state and following a mild chemical crosslinking process. Mode III fracture testing was used to quantify the tear toughness of the fibrous mats, and failure behavior was qualitatively examined with scanning electron microscopy. In ongoing work, this nanofibrous structure will be combined with a charged polyelectrolyte hydrogel gel to create a biomimetic cartilage-like material. By using biomimicry to replicate what is present in native cartilage tissue, a superior material can be designed and fabricated for use in tissue repair and replacement.


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