Syntactic foams are
composite materialComposite materials are engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure.- History :The most primitive composite materials were straw...
s synthesized by filling a
metalA metal is a chemical element that is a good conductor of both electricity and heat, forms cations and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions...
,
polymerA polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties.Due to the extraordinary...
or
ceramicA ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
matrix with hollow particles called microballoons. The presence of hollow particles results in lower density, higher strength, a lower
coefficient of thermal expansionWhen the temperature of a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds...
, and, in some cases,
radarRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
or
sonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are two kinds of sonar: active and passive. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water...
transparencyStealth technology also known as LO technology is a sub-discipline of military tactics and passive electronic countermeasures , which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, in order to make them less visible to radar, infrared , sonar and other...
.
Tailorability is one of the biggest advantages of these materials. The matrix material can be selected from almost any metal, polymer or ceramic.
Syntactic foams are
composite materialComposite materials are engineered materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct on a macroscopic level within the finished structure.- History :The most primitive composite materials were straw...
s synthesized by filling a
metalA metal is a chemical element that is a good conductor of both electricity and heat, forms cations and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions...
,
polymerA polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties.Due to the extraordinary...
or
ceramicA ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
matrix with hollow particles called microballoons. The presence of hollow particles results in lower density, higher strength, a lower
coefficient of thermal expansionWhen the temperature of a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds...
, and, in some cases,
radarRadar is an object detection system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was coined in 1941 as an acronym for RAdio Detection And...
or
sonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels. There are two kinds of sonar: active and passive. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water...
transparencyStealth technology also known as LO technology is a sub-discipline of military tactics and passive electronic countermeasures , which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, in order to make them less visible to radar, infrared , sonar and other...
.
Tailorability is one of the biggest advantages of these materials. The matrix material can be selected from almost any metal, polymer or ceramic. A wide variety of microballoons are available, including
cenosphereA cenosphere is a lightweight, inert, hollow sphere filled with inert air or gas, typically produced as a byproduct of coal combustion at thermal power plants. The color of cenospheres varies from gray to almost white and their density is about 0.4–0.8 g/cm³, which gives them a great buoyancy...
s,
glass microsphereGlass microspheres are microscopic spheres of glass manufactured for wide a variety of uses in research, medicine, consumer goods and various industries. Glass microspheres are usually between 1 to 1000 micrometers in diameter. The term is also used for glass spheres between 100 nanometers to 5...
s, and
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
and polymer microballoons. The most widely used and studied foams are glass microballoon-
epoxyEpoxy or polyepoxide is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives.- Chemistry :...
, glass microballoon-
aluminiumAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
and cenosphere-aluminium.
The
compressivePhysical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is rarefraction tension.- Explanation :...
properties of syntactic foams primarily depend on the properties of microballoons, whereas the tensile properties depend on the matrix material that holds the microballoons together. There are two main ways of adjusting the properties of these materials. The first method is to change the volume fraction of microballoon in the syntactic foam structure. The second method is to use microballoons of different wall thickness. In general, the compressive strength of the material is proportional to its density.
These materials were developed in early 1960s as
buoyancyIn physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least seem lighter....
aid materials for marine applications; the other characteristics led these materials to
aerospaceAerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...
and ground transportation vehicle applications. Current applications for syntactic foam include buoyancy modules for marine riser tensioners,
boat hullsA hull is the watertight body of a ship or boat. Above the hull comes the superstructure and deckhouse. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...
, deep-sea exploration,
autonomous underwater vehicleAn autonomous underwater vehicle is a robot which travels underwater. In military applications, AUVs are also known as unmanned undersea vehicles ...
s (AUV), parts of helicopters and airplanes, and sporting goods such as
soccer ballsA football is a ball used to play one of the various sports known as football.In the distant past, crude balls such as inflated pigs' bladders were used, but balls are now designed by teams of engineers to exacting specifications...
.
See also
- Glass microsphere
Glass microspheres are microscopic spheres of glass manufactured for wide a variety of uses in research, medicine, consumer goods and various industries. Glass microspheres are usually between 1 to 1000 micrometers in diameter. The term is also used for glass spheres between 100 nanometers to 5...
- Foam
The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam. Often the term is used in reference to polyurethane foam , XPS foam, Polystyrene, or many...
A mojotr application of Syntactic Foam is for the core of arhery bow limbs