A novel self-healing composite made of thermally reversible polymer and shape memory alloy reinforcement

2019 ◽  
Vol 30 (10) ◽  
pp. 1585-1593 ◽  
Author(s):  
Ali Saeedi ◽  
Mahmood M Shokrieh
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Composite Structures ◽  
Fracture Behavior ◽  
Micromechanical Model ◽  
Self Healing ◽  
Compression Tests ◽  
Healing Efficiency ◽  
Shape Memory Effects ◽  
Good Agreement

A novel self-healing polymer composite made of the thermally reversible polymer matrix and shape memory alloy reinforcement is introduced. The healing system is designed in such a way that by heating the structure, activation of shape recovery in shape memory alloy and chemical reversible reactions in polymer occur simultaneously. In the present healing method, the required crack closure force is provided by activating the embedded shape memory alloy wires in the polymer. Both superelastic and shape memory effects of shape memory alloy are considered on the fracture behavior of composites by investigating the passive and active reinforcement methods, respectively. Double cleavage drilled compression tests are utilized in order to study the fracture behavior and healing efficiency of composites. In the case of passive reinforcement, embedding 2% prestrained shape memory alloy wires caused 15% enhancement in the fracture toughness of composites. In this prestrain level, results of the micromechanical model are in good agreement with experiments. Promising results are also obtained for healing efficiency of composites in the case of active reinforcement. The average healing efficiency of 92% is achieved for shape memory alloy-reinforced thermally reversible epoxy composites. The excellent healing performance, without the necessity of external force and pressure, makes the present healing method as an ideal candidate for utilizing self-healing composite structures.

Self-healing poly(siloxane-urethane) elastomers with remoldability, shape memory and biocompatibility

2016 ◽  
Vol 7 (47) ◽  
pp. 7278-7286 ◽  
Author(s):  
Jian Zhao ◽  
Rui Xu ◽  
Gaoxing Luo ◽  
Jun Wu ◽  
Hesheng Xia
Keyword(s):  
Mechanical Property ◽  
Shape Memory ◽  
Microphase Separation ◽  
Diels Alder ◽  
Good Mechanical Property ◽  
Self Healing ◽  
Healing Efficiency ◽  
Good Biocompatibility

The poly(siloxane-urethane) elastomers with microphase separation structure and Diels–Alder bonds show high healing efficiency, good mechanical property and good biocompatibility.

Mechanical responses of microencapsulated self-healing cementitious composites under compressive loading based on a micromechanical damage-healing model

2021 ◽  
pp. 105678952110112
Author(s):  
Kaihang Han ◽  
Jiann-Wen Woody Ju ◽  
Yinghui Zhu ◽  
Hao Zhang ◽  
Tien-Shu Chang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Micromechanical Model ◽  
Cementitious Composites ◽  
Self Healing ◽  
Damage Degree ◽  
Healing Efficiency ◽  
The Matrix ◽  
Healing Agent ◽  
Damage Healing

The cementitious composites with microencapsulated healing agents have become a class of hotspots in the field of construction materials, and they have very broad application prospects and research values. The in-depth study on multi-scale mechanical behaviors of microencapsulated self-healing cementitious composites is critical to quantitatively account for the mechanical response during the damage-healing process. This paper proposes a three-dimensional evolutionary micromechanical model to quantitatively explain the self-healing effects of microencapsulated healing agents on the damage induced by microcracks. By virtue of the proposed 3 D micromechanical model, the evolutionary domains of microcrack growth (DMG) and corresponding compliances of the initial, extended and repaired phases are obtained. Moreover, the elaborate studies are conducted to inspect the effects of various system parameters involving the healing efficiency, fracture toughness and preloading-induced damage degrees on the compliances and stress-strain relations. The results indicate that relatively significant healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will lead to a higher compressive strength and stiffness. However, the specimen will break owing to the nucleated microcracks rather than the repaired kinked microcracks. Further, excessive higher values of healing efficiency, preloading-induced damage degree and the fracture toughness of polymerized healing agent with the matrix will not affect the compressive strength of the cementitious composites. Therefore, a stronger matrix is required. To achieve the desired healing effects, the specific parameters of both the matrix and microcapsules should be selected prudently.

Nickel–titanium shape memory alloy mechanical components produced by investment casting

2018 ◽  
Vol 29 (19) ◽  
pp. 3748-3757 ◽  
Author(s):  
Jackson de Brito Simões ◽  
Carlos José de Araújo
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Investment Casting ◽  
Mechanical Characterization ◽  
Nickel Titanium ◽  
Compression Tests ◽  
Thermoelastic Martensitic Transformation ◽  
Scanning Calorimetry ◽  
Helical Springs ◽  
Mechanical Components

This work aimed to produce mechanical components of nickel–titanium shape memory alloys using investment casting processes. Then, in order to validate processing, different designs of nickel–titanium shape memory alloy components as staple implants, Belleville springs, meshes, helical springs, screws and hexagonal honeycombs were produced and submitted to thermal and mechanical characterization. Thermoelastic martensitic transformation of the nickel–titanium shape memory alloy parts was determined by differential scanning calorimetry and electrical resistance with temperature, while the superelastic behaviour was verified by cyclic tensile and compression tests. It has been demonstrated that the employed investment casting processes are suitable to manufacture nickel–titanium shape memory alloy mechanical components with simple and complicated designs as well as functional properties related to phase transformation and superelasticity.

Analytical solution for twinning deformation effect of pre-strained shape memory effect beam-columns

2019 ◽  
Vol 30 (14) ◽  
pp. 2147-2165 ◽  
Author(s):  
Alireza Ostadrahimi ◽  
Fathollah Taheri-Behrooz
Keyword(s):  
Shape Memory Alloy ◽  
Analytical Solution ◽  
Shape Memory ◽  
Cross Sections ◽  
Bending Stress ◽  
Deformation Effect ◽  
One Dimensional ◽  
Beam Columns ◽  
Analytical Expressions ◽  
Good Agreement

In this article, an analytical solution is presented for twinning deformation effect of a prismatic shape memory alloy beam-column. To this end, a reduced one-dimensional Souza model is employed to study the bending stress of a pre-strained shape memory alloy beam-column at low temperatures. Analytical expressions for bending stress as well as polynomial approximations for deflection are obtained. Derived equations for bending problem are employed to analyze twinning deformation effect of shape memory alloy beam-columns with rectangular and circular cross sections. Furthermore, the distance of zero-stress fiber from the center line during loading is studied. The results of this work show good agreement when compared with experimental data and finite element results.

Viscoelastic behavior of epoxy resin reinforced with shape-memory-alloy wires

2020 ◽  
pp. 1045389X2097549
Author(s):  
Niloufar Bagheri ◽  
Mahmood M Shokrieh ◽  
Ali Saeedi
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Epoxy Resin ◽  
Volume Fraction ◽  
Niti Alloy ◽  
Micromechanical Model ◽  
Viscoelastic Behavior ◽  
Mechanical Analysis ◽  
Reinforced Polymer ◽  
Small Volume Fraction

The effect of NiTi alloy long wires on the viscoelastic behavior of epoxy resin was investigated by utilizing the dynamic mechanical analysis (DMA) and a novel micromechanical model. The present model is capable of predicting the viscoelastic properties of the shape-memory-alloy (SMA) reinforced polymer as a function of the SMA volume fraction, initial martensite volume fraction, pre-strain level in wires, and the temperature variations. The model was verified by conducting experiments. Good agreement between the theoretical and experimental results was achieved. A parametric study was also performed to investigate the effect of SMA parameters. According to the results, by the addition of a small volume fraction of SMA, the storage modulus of the composite increases significantly, especially at higher temperatures. Moreover, applying a 4% pre-strain caused a 10% increase in the maximum value of the loss factor of the SMA reinforced epoxy in comparison with the 0% pre-strained SMA reinforced epoxy.

Shape memory polymer composite structures with two-way shape memory effects

2012 ◽  
Vol 89 ◽  
pp. 216-218 ◽  
Author(s):  
Zhengdao Wang ◽  
Weibin Song ◽  
Liaoliang Ke ◽  
Yuesheng Wang
Keyword(s):  
Shape Memory ◽  
Polymer Composite ◽  
Composite Structures ◽  
Shape Memory Polymer ◽  
Memory Effects ◽  
Shape Memory Effects

scholarly journals Effects of a Short Heat Treatment Period on the Pullout Resistance of Shape Memory Alloy Fibers in Mortar

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2278 ◽  
Author(s):  
Min Kyoung Kim ◽  
Dong Joo Kim ◽  
Young-Soo Chung ◽  
Eunsoo Choi
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Memory Effects ◽  
Stress Recovery ◽  
Pullout Resistance ◽  
Pullout Tests ◽  
Dog Bone ◽  
Shape Memory Effects ◽  
Short Time

The feasibility of the crack closure of cementitious composites reinforced with shape memory alloy (SMA) fibers was investigated by performing single-fiber pullout tests. To demonstrate the fast crack closing ability, in this study, a heat treatment (300 °C) was applied for a short time (10 min). A short heat treatment was applied for 10 min, after the slip reached 0.5 mm, to activate the shape memory effects of cold-drawn SMA fibers. Two types of alloys were investigated, NiTi and NiTiNb, with two geometries, either smooth or dog-bone-shaped. During the heat treatment, the pullout stress of the SMA fibers initially decreased due to thermal extension, and then increased after heating for 1–3 min, resulting from the shape memory effects. However, their pullout stress recovery during and after the heat treatment was different for the different alloys and fiber geometries. The NiTi fibers generally produced a higher and faster recovery in terms of their pullout stress than the NiTiNb fibers, while the dog-bone-shaped fibers showed a faster pullout stress recovery than the smooth fibers.

An experimental approach to the thermomechanical characterization of a NiTiCu shape memory alloy using strain gauges

2016 ◽  
Vol 231 (1-2) ◽  
pp. 113-121
Author(s):  
Albert Fabregat-Sanjuan ◽  
Francesc Ferrando Piera ◽  
Silvia De la Flor López
Keyword(s):  
Shape Memory Alloy ◽  
Shear Modulus ◽  
Shape Memory ◽  
Twist Angle ◽  
Strain Tensor ◽  
Strain Ratio ◽  
Strain Gauges ◽  
Compression Tests ◽  
Thermal Chamber

In this work, a characterization of a NiTiCu (Ti44.6Ni5Cu (at.%)) shape memory alloy (tube specimens) has been done via tension, compression and torsion tests conditions. Torsion tests were done in a special homemade equipment, which is based on an instrumented dividing head with a specifically designed thermal chamber. This configuration is able to measure torque and twist angle with isothermal tests at different temperatures as well as to apply thermal cycles with a fixed twist angle. Moreover, tube specimens were instrumented with stacked strain gauges rosettes in order to obtain the strain tensor. Strain gauges were also used to calibrate the equipment and to identify the real stress state in torsion tests. The results have shown differences between the shear modulus measured on torsion tests and the shear modulus calculated from the measurements at tension and compression tests due to the tension/compression asymmetry and a non-constant strain ratio value. Thermal cycling tests at different values of fixed twist angles not only have led to characterize the evolution of torque as a function of the temperature but also to understand the different interacting mechanisms in torsion tests.

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