Anisotropic hierarchical porous hydrogels with unique water loss/absorption and mechanical properties

RSC Advances ◽  
2014 ◽  
Vol 4 (57) ◽  
pp. 30308-30314 ◽  
Author(s):  
Di Zhao ◽  
Jintang Zhu ◽  
Zhongcheng Zhu ◽  
Guoshan Song ◽  
Huiliang Wang

Anisotropic hierarchical porous poly(2-hydroxyethyl methacrylate-co-acrylamide) hydrogels show unidirectional solution diffusion, fast water loss/absorption and linear tensile stress–strain curves.

1975 ◽  
Vol 48 (5) ◽  
pp. 830-844 ◽  
Author(s):  
D. C. Blackley ◽  
M. W. Sheikh

Abstract This paper presents and discusses the mechanical properties of crosslinked poly (ethyl acrylates) containing various amounts of microscopic glass beads. The adhesion between the glass beads and the elastomer matrix was varied by subjecting the beads to different surface treatments. That the adhesion is affected by surface treatment has been demonstrated in two ways: (1) Unfilled elastomer sheets have been cast in contact with glass surfaces which had been treated with the same reagents as the beads. The force required to peel the elastomer from the glass was then measured and found to depend strongly upon the surface treatment. (2) Scanning electron micrographs of the ruptured surfaces of used tensile test pieces cut from filled elastomer sheets confirm that surface treatment has a profound effect upon the adhesion between bead and matrix. Results are presented for the hardness and tensile stress-strain properties of elastomers containing various amounts of beads. In all cases, the stiffening effect of the beads increases as the adhesion between beads and matrix is improved. Beads which had been treated in such a way as to minimize the adhesion to the matrix were found to cause an apparent softening of the material as revealed by the tensile stress-strain curve. It has been shown that this effect can be satisfactorily explained if it is assumed that in this case the beads merely serve to increase the void content of the material.


2007 ◽  
Vol 340-341 ◽  
pp. 247-254 ◽  
Author(s):  
Dong Wei Shu ◽  
Wei Zhou ◽  
Guo Wei Ma

An ultralight magnesium alloy AM50A has been investigated for its potential to be used in aerospace and automotive industry. The dynamic stress strain relation of aluminum 6061 T6 and the magnesium alloy AM50A have been obtained by using the Hopkinson bar apparatus. The strain rates range between 600 s-1 and 1300 s-1. The Al 6061 T6 results tally well with those in literature. The magnesium alloy AM50A displays about 50% higher tensile stress at the strain rate of about 1300 s-1 than at static.


2021 ◽  
Vol 2021 (1) ◽  
pp. 92-100
Author(s):  
I. Derevianko ◽  
◽  
K. Avramov ◽  
B. Uspensky ◽  
A. Salenko ◽  
...  

Additive manufacturing is very promising for aerospace engineering and aircraft construction. Using these technologies, light structures with preset strength properties can be made. For lack of tables of the mechanical properties of materials made by additive technologies, any calculation must be accompanied by the experimental determination of their mechanical properties. This paper presents an experimental approach to the determination of the mechanical characteristics of parts printed by FDM technologies. Parts manufactured from polymers by FDM technologies are shown to be orthotropic. Therefore, their elastic properties are described by nine constants: three Young’s moduli, three shear moduli, and three Poisson ratios. A cube is printed for the experimental determination of these constants. Six specimens are cut out from the cube. Three specimens are cut parallel to the cube edges, and the other three are cut at an angle of 45° to them. Each such specimen is manufactured in five pieces. This makes it possible to average the tensile stress–strain diagrams obtained for all the components of the stress tensor. The mechanical properties of the material are determined from these diagrams. The three Young’s moduli and the three Poisson ratios are determined from the three specimen types parallel to the cube edges. The three shear moduli are determined from the specimens cut at an angle of 45° to the cube edges. To determine these constants, tensile stress–strain diagrams are obtained experimentally. A technology is presented for manufacturing specimens on a Stratasys FORTUS 900 MC 3D printer. The mechanical properties of two polymer materials (ULTEM 9085 and PLA) are determined and compared. PLA has higher Young’s moduli and shear moduli and lower Poisson ratios than ULTEM 9085.


Author(s):  
Kazumune KATAGIRI ◽  
Kazuo WATANABE ◽  
Koshichi NOTO ◽  
Koichi KASABA ◽  
Yoshitaka SHOJI

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 345 ◽  
Author(s):  
Lianzan Yang ◽  
Yongyan Li ◽  
Zhifeng Wang ◽  
Weimin Zhao ◽  
Chunling Qin

High-entropy alloys (HEAs) present excellent mechanical properties. However, the exploitation of chemical properties of HEAs is far less than that of mechanical properties, which is mainly limited by the low specific surface area of HEAs synthesized by traditional methods. Thus, it is vital to develop new routes to fabricate HEAs with novel three-dimensional structures and a high specific surface area. Herein, we develop a facile approach to fabricate nanoporous noble metal quasi-HEA microspheres by melt-spinning and dealloying. The as-obtained nanoporous Cu30Au23Pt22Pd25 quasi-HEA microspheres present a hierarchical porous structure with a high specific surface area of 69.5 m2/g and a multiphase approximatively componential solid solution characteristic with a broad single-group face-centered cubic XRD pattern, which is different from the traditional single-phase or two-phase solid solution HEAs. To differentiate, these are named quasi-HEAs. The synthetic strategy proposed in this paper opens the door for the synthesis of porous quasi-HEAs related materials, and is expected to promote further applications of quasi-HEAs in various chemical fields.


Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1099
Author(s):  
Qingqing Chen ◽  
Yuhang Zhang ◽  
Tingting Zhao ◽  
Zhiyong Wang ◽  
Zhihua Wang

The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states.


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