The opportunities of additive manufacturing (3D printing) in the creation of the new generation of

composite materials

Dr. Andras Bela Olah

Additive manufacturing I.

According to the definition of additive manufacturing in the final shape is not achieved through slivering a raw material slug, but through „gluing”many small pieces of raw material together.

There can be used many kind of raw materials. At the beginning there were used thermoplasts due to their relative low melting point and high chemical stability. The term „3D printing” comes from that a prototype „plotter” was made from an ordinary inkjet printer, but it used melted thermoplast instead of ink.

Additive manufacturing II.

The basic method is building up an object from thin layers. Creating such a single thin layer is very similar to ordinary 2D ink layer printing.

The possible raw materials are mostly thermoplasts, but in present days the usage of metal powder is also possible.

In case of thermoplasts the 3D plotter melts the plastic and the print head puts it to the appropriate place, where it becomes solid and is glued to the layer beneath it.

Additive manufacturing III.

A thermoplast using ordinary 3D plotter with a ready prototype.

Additive manufacturing (metals) I.The additive manufacturing could be used only for modelling,while the raw material was only thermoplast.In present days the usage of metals as raw material is also possible. The essence of the process is that the printed area is electrostatically charged, then the whole printing area is covered by a metal powder layer. After this there is a sudden blowdown and due to it only the electrostatically charged metal powder remains on the surface. The next step is melting together the remained metal powder with a high energy laser.Due to this it is melted together also with the metal layerbeneath it (the previous layer). On this way it is possible tocreate metal objects with this technology.

Additive manufacturing (metals) II.

The first jet engine made by additive manufacturing.

Additive manufacturing (metals) III.

The opportunity of using metals as raw material eventuates the sudden propagation of this technology in the near future.In the first time only precision metal tools will be made by this technology, but later (as it becomes cheaper) almost all kind of metal tools will be made on this way and the traditional forging (CNC) will be out to date.The cost of production is determined basicly by two things: the cost of melting (the melting point of the metal) and the cost of the metal powder itself. Naturally, aluminium and iron/steel will be the two primary raw material.

Composite materials I.

The composite materials are proper complex materials. The great advantage of these stuffs that they unite the positive attributes of the raw materials.These advantageous features are typically different mechanical attributes, or a further goal by creating composite materials used to be the decreasing of weight.Nevertheless weight decreasing and incorrodibility used to be achieved by using alloys or alloying materials, so in the following the increasing quality of mechanical attributes will be emphasized.

Composite materials II.The different mechanical attributes used to be on the one hand is great hardiness and great compressive strength, which used to be paired with brittleness and frangibility (ceramics and glasses). On the other hand there are materials with relatively low hardiness and compressive strength, but having great tensile strength and resiliency (metals).It is worth to mention that there exist so called cermets (ceramic + metal) wich can unite these positive mechanical qualities in their chemical structure. These are usually chemical alloys (titanium-diboride, silica-borides). But they are so expensive and the boron is so rare that they can not be used in mass production.

Composite materials III.

The main difference between alloys and composites that composites are not homogenous microscopically (typical examples are concrete and ferroconcrete) as against alloys especially chemical alloys, which even have chemical formula (i.e. titanium-diboride TiB2).The composites used to have two, or sometimes three components. In case of concrete the aggregate and the matrix is the two materials, in case of ferroconcrete there is a third one, the iron mesh structure.

Composite materials IV.

The most well-known composite material: concrete.

Composite materials V.

Glass fiber strengthened plastic (resin). The goal was unequivocally composing advantageous mechanical attributes.

Composite materials and additive manufacturing I.

In case of composite materials, when there is a matrix and aggregate material(-s) the homogenous distribution of aggregates is very important and there can occur great problems on this point.In case of ordinary concrete the mixing is not a problem because the mixture of cement and water is a liquid with high viscosity and this can be mixed very well with aggregates. In case of thermoplast or resin matrices their melting point is relatively low, or they contain some liquifying materials, which can later evaporate, thus they can be also easily mixed with aggregates.

Composite materials and additive manufacturing II.

The situation is quite different in case of metal matrices. Among the widely used structural metals the aluminium has the lowest melting point (660 °C) which is quite advantageous in case of founding, but composing it withaggregates needs a very expensive technological background (there can not be imagined a mixer car with this material temperature).There must be mentioned that there exist such technology, but it is very expensive and used only to produce the composite (metal matrix and ceramic aggregate) armor of modern tanks.

Composite materials and additive manufacturing III.

Modern british main battle tank with composite armor.

Composite materials and additive manufacturing IV.

The previously mentioned additive manufacturing with metal raw materials can be easily adapted to composites:There will be used also metal powder layers, but there will be also used a ceramic powder (or grain) layer before the metal, which can be kept there also electrostatically, thus the shaping is not a problem. During the melting process only the metal powder melts (it

hasmuch lower melting point), so the metal will glue together the ceramic grains and glue them to the beneath layers. On this way there can be obtained a metal-ceramic composite material with arbitrary shape and perfect grain distribution!!!

Composite materials and additive manufacturing (opportunities) I.

The previously mentioned additive manufacturing method can revolutionarize the product of such materials. It will be the same revolution that happened in construction after the invention of concrete, but in this case this will be wider, because all kind of construction material (which was by this time typically aluminium, steel, even titanium or alloys) is involved.The simpliest example is an ordinary knife. If it is made of steel than its hardiness on the Mohs-scale is 4-4.4. If it is an aluminium matrix - sand grain composite, then the hardiness is that of the sand (6.5 on Mohs scale) and the other attributes is that of the metal (and it is easier than steel).

Composite materials and additive manufacturing (opportunities) II.

An other well-known example is the building structures. In present days the greatest steel consumer is the building industry. Currently, it is possible to build many 100 m tall building structures from steel. At the same time, the greatest disadvantage of steel is that it has relatively low compressive strength. Using additive technology and such composites, with steel or aluminium matrices and sand or corundum aggregates, the advantageous features of metals remained, but thecompressive strength can be increased in an order of magnitude (≈ 10 km tall buildings!!!).

Composite materials and additive manufacturing (opportunities) III.

Finally, military applications, possibilites:With such a technology it is not hard to create a composite, which matrix is titanium (basically, because titanium has a little bit lower melting point than iron, and chemically more stabile, it is a little bit easier, although the cost of the raw material itself is greater).In case the aggregate is silica-carbide, then there can be obtained an almost diamond hard, arbitrarily shaped material with the resiliency and tensile strength of titanium, which can revolutionarize the whole defense industry around the world!!!

Thank you for your attention!

Dr. Andras Bela Olah