Multifunctional properties of shape memory materials
Talking about advanced materials, structures and techniques is one of the topics that has received special interest among researchers during the last two decades, since numerous techniques have even been developed for these materials.
Furthermore, "intelligent structural systems have recently become a fundamental research topic in the construction industry. Developing numerous intelligent technologies to improve the structural performance and the useful life of the infrastructure. These smart systems are designed by incorporating smart materials into structural systems. So far, different types of smart materials have been explored and developed" 1.
Shape Memory Materials (SMM) are an important group of intelligent multifunctional materials used in civil engineering applications, having great popularity for their unique ability to memorize their original shape, that is, after deformation, they can return to their original shape. initial form under stimuli, e.g. heat. Within these we find four main categories:
- Shape memory alloys (SMA): are a class of alloys which can memorize their original shape; when the alloy is deformed, it can return to its original shape under the effect of temperature as a stimulus. They can have two solid crystalline microstructures: martensite and austenite. At low temperature, the material has a relatively lose packed crystalline microstructure, which is a body centered lattice. This phase is called thermoelastic martensite. At high temperature, the material has a well packed crystalline structure, which is a hexagonal lattice, known as austenite.
- Magnetic shape memory alloys (MSMA): are a group of SMAs which possess ferromagnetic properties in addition to SE and SME. Thus, they are sometimes called ferromagnetic shape memory alloys (FSMAs), too. They also have better fatigue resilience than SMAs. In civil applications, MSMAs can serve as both actuators and sensors. Due to their remarkable potential to produce large strains (of up to 10%) under magnetic field in a short response time, i.e. less than 0.2 ms (about 100 time faster than SME), MSMAs are used in actuators systems in many fields.
- Shape memory polymers (SMP): are materials capable of transforming from a temporary shape to their permanent (original) shape through stimuli not only temperature [61] but also light, electric or magnetic field, microwave, water or another solution, etc. However, most SMPs are thermally responsive.
As a group of SMMs, SMPs exhibit either one-way or two-way SME. The two-way SMPs used in the past were only capable of memorizing two shapes, i.e. temporary and the original shape. But recently, production of SMPs able to memorize three or more shapes has been made possible through combining two or more SMPs with different shape transition characteristics.
- Shape memory ceramics (SMC): Superelastic shape memory ceramics (SMCs) exhibit a combination of high strength, large recoverable strain, large energy damping, and are light weight. These features are useful as an energy-damping layer for armor systems or as an energy absorber for automobiles, sports equipment, and aerospace applications.
Let us note that in different situations, these multifunctional materials can be used in actuator systems, structural health monitoring systems, self-repair applications, etc.
(1). THIS SECTION "Multifunctional properties of shape memory materials" IS BASED ON INFORMATION FROM: Abavisani, I., Rezaifar, O. & Kheyroddin, A. (2021, diciembre). «Multifunctional properties of shape memory materials in civil engineering applications: A state-of-the-art review». Science Direct, Bidi UNAM. Recuperado 28 de septiembre de 2022, de: https://www-sciencedirect-com.pbidi.unam.mx:2443/science/article/pii/S2352710221005155?via%3Dihub
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