The concept of the hottest intelligent material

2022-08-01
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The concept of smart materials

specifically, smart materials need to have the following connotations:

(1) have a sensing function, can detect and identify the external (or internal) stimulus intensity, such as electricity, light, heat, stress, strain, chemistry, nuclear radiation, etc

(2) it has driving function and can respond to external changes

(3) the response can be selected and controlled according to the set mode

(4) the response was sensitive, timely and appropriate

(5) when the external stimulus is eliminated, it can quickly return to the original state

intelligent materials can also be called sensitive materials. There are also several kinds of English translations of intelligent materials, intelligent materials and structures, smart materials, smart materials and structures, adaptive materials and structures, etc

the idea of intelligent materials comes from bionics (bionics is to imitate some unique functions of creatures in nature to make tools used by humans, such as imitating dragonflies to make airplanes, etc.). Its goal is to develop a material to make it a "living" material with various functions similar to biology. Therefore, intelligent materials must have three basic elements: sensing, driving and controlling. However, the existing materials are generally single, which is difficult to meet the requirements of intelligent materials. Therefore, intelligent materials are generally composed of two or more materials to form an intelligent material system. This makes the design, manufacturing, processing and performance structure characteristics of intelligent materials involved in the forefront of materials science, and makes intelligent materials represent the most active aspect and the most advanced development direction of material science

in order to increase perceptual knowledge, here is a simple example of using intelligent materials: some Sunglasses' lenses contain intelligent materials, which can sense the surrounding light and judge the intensity of the light. When the light is strong, it becomes dark, and when the light is weak, it becomes transparent

characteristics of smart materials

because the two guiding ideas for designing smart materials are the multi-functional composite of materials and the bionic design of materials, the smart material system has or partially has the following smart functions and life characteristics:

(1) sensor

it can sense the external or its own environmental conditions, such as load, stress, strain, vibration, heat, light, electricity, magnetism, chemistry Intensity and variation of nuclear radiation, etc

(2) feedback function

can compare the input and output information of the system through the sensing network, and provide the results to the control system

(3) information identification and accumulation function

can identify and accumulate all kinds of information obtained by the sensing network

(4) response function

can make timely and dynamic response and take necessary actions according to the changes of external environment and internal conditions

(5) self diagnosis

can self diagnose and correct problems such as system faults and misjudgment by analyzing and comparing the current and past conditions of the system

(6) self recovery

can repair some local damage or damage through regeneration mechanisms such as self reproduction, self growth and in situ recombination

(7) self adjusting

to the changing external environment and conditions, it can automatically adjust its own structure and function in time, and change its own state and behavior accordingly, so that the material system can always respond appropriately to external changes in an optimized way

composition of intelligent materials

generally speaking, intelligent materials are composed of matrix materials, sensitive materials, driving materials and information processors

(1) base material

the base material plays the role of load-bearing. Generally, light materials should be selected. Generally, polymer materials are preferred as matrix materials because of their light weight, corrosion resistance, and especially the nonlinear characteristics of viscoelasticity. Secondly, metal materials can also be selected, mainly light non-ferrous alloys

(2) sensitive materials

sensitive materials undertake the task of sensing, and their main role is to sense environmental changes (including pressure, stress, temperature, electromagnetic field, pH value, etc.). Sensitive materials for the land reclamation project of changnansha islands and reefs, such as shape memory materials, piezoelectric materials, optical fiber materials, magnetostrictive materials, electrochromic materials, current variants, magnetorheological variants and liquid crystal materials

(3) driving material

because the driving material can produce large strain and stress under certain conditions, it undertakes the task of response and control. Commonly used effective driving materials such as shape memory materials, piezoelectric materials, current variants and magnetostrictive materials. It can be seen that these materials not only solve the slip problem, but also are sensitive materials. Obviously, they play a dual role. This is also an idea that can be used in the design of intelligent materials

(4) other functional materials

include conductive materials, magnetic materials, optical fiber and semiconductor materials

the figure shows the basic composition and working principle of intelligent materials

classification of smart materials

smart materials are the fourth generation of functional materials after natural materials, man-made materials and fine materials

because the types of materials that can be used for intelligent materials are expanding, the classification of intelligent materials can only be superficial, and there are many classification methods. Generally, according to the function, they can be divided into optical fiber, shape memory alloy, piezoelectric, current variant and electrostrictive materials. According to the source, intelligent materials can be divided into metal intelligent materials, inorganic non-metal intelligent materials and polymer intelligent materials. At present, there are two kinds of metal intelligent materials: shape memory alloys and shape memory composites; Inorganic nonmetallic smart materials have developed rapidly in the fields of current variant, piezoelectric ceramics, photochromic and electrochromic materials; The range of polymer based smart materials is very wide. As smart materials, the research and development of stimulus responsive polymer gel is very active, followed by smart polymer membrane materials, smart polymer adhesives, smart drug release systems and smart polymer matrix composites

applications in other fields

the use of intelligent material structures in military is not a new topic. Just as all discoveries of high and new technologies are bound to be applied in military, it is also a field that is constantly developing with the development of intelligent materials. Because intelligent material structures can not only bear loads like general functional materials, but also have functions that other functional materials do not have, that is, they can sense changes in the internal and external environment, and can respond by changing their physical properties or shapes, so as to realize self diagnosis, self adaptation, self repair and other functions. Therefore, intelligent materials have great potential in military applications. Its research, development and utilization will have a significant impact on the development of future weapons and equipment

at present, in various military fields, the application of intelligent materials mainly involves the following aspects:

(1) intelligent skin

for example, optical fiber is used as an intelligent sensing element in the intelligent skin of aircraft wings, or sensing elements, driving elements and micro processing control systems are embedded in the skin of weapon platforms. The intelligent skin made by measuring 1 point in the center of all samples can be used for early warning, stealth and communication

at present, the research on smart skin in the United States includes: the US ballistic missile defense agency has developed smart skin with multiple sensors for missile early warning satellites and space-based defense system platforms; Research on structured antenna (i.e. integration of antenna and skin structure) conducted by Wright Laboratory of the US air force; The U.S. Navy focuses on the research of intelligent skin for warships to improve the stealth performance of warships

(2) structure monitoring and life prediction

intelligent structure can be used to measure the strain, temperature and crack inside the structure in real time, detect fatigue and damage, so as to monitor and predict the life of the structure. For example, the intelligent structure using optical fiber sensor array and polyvinylidene fluoride sensor can carry out real-time life monitoring, damage assessment and life prediction for wings, frames and reusable space vehicles; Large on orbit systems such as the space station adopt optical fiber intelligent structure, which can detect the damage caused by rendezvous and docking collision, meteorite impact or other reasons in real time, evaluate the damage and implement self diagnosis. The self diagnosis intelligent structure technologies under study include: optical fiber sensor self diagnosis technology, the "sound" sensor self diagnosis technology that can measure cracks, and other sensor self diagnosis technologies that can monitor composite spalling

(3) vibration and noise reduction

intelligent structures used in aerospace systems can eliminate harmful vibration of the system, reduce interference to electronic systems, and improve system reliability. For example, the helicopter intelligent structure rotor blade developed by Boeing company supported by the Defense Advanced Research Projects Agency of the United States can improve the aerodynamic performance of the rotor and reduce vibration and noise. The intelligent structure used in naval ships can suppress the noise propagation and improve the acoustic stealth performance of submarines and warships. Intelligent structure used in ground vehicles can improve the performance and ride comfort of military vehicles. The intelligent structures with vibration and noise reduction functions being studied abroad are mainly made of piezoelectric ceramics, shape memory alloys, electrostrictive and other new materials

(4) environment adaptive structure

the adaptive wing made of intelligent structure can sense the changes of the external environment in real time, and drive the wing to bend and twist, so as to change the airfoil and angle of attack, so as to obtain the best aerodynamic characteristics, reduce the drag coefficient of the wing and prolong the fatigue life of the aircraft wing. For example, when the aircraft encounters eddy current or strong headwind during flight, the intelligent materials in the wings can quickly deform and drive the wings to change shape, so as to eliminate the influence of eddy current or headwind, so that the aircraft can still fly in balance

an American study shows that using magnetostrictive actuators in the wing structure can reduce the wing drag by 85%. Boeing and Massachusetts Institute of Technology (MIT) jointly researched the insertion of smart fibers in the blades, and the twist of the blades can reach several degrees when the electrorheological fluid is used. The U.S. Army is developing helicopter rotor active control technology, which will be used for RAH-66 armed helicopter. The US Department of defense and NASA are also studying adaptive structures, including wing bending, bending modeling/control surface modeling, etc

it is believed that in the near future, we will use smart materials 10 The universal tensile testing machine has an aircraft wing made of loose belts and smooth appearance materials. It can move freely like a fish tail, bend and change its shape automatically, so as to improve the lift and resistance and make the aircraft fly higher and faster

intelligent materials and intelligent residence

let's imagine what the future residence will look like: the walls can change colors at will; The chair can change the temperature and shape according to different needs of the human body; All electrical appliances are touch type, and there will never be any danger of electric shock; Visible with sensing function. What a wonderful picture of the future! In the past, it may be regarded as fantasy and science fiction, but with the development of intelligent materials, especially

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