They consist of ceramic fibers embedded in a ceramic matrix. The fibers and the matrix both can consist of any ceramic material, whereby carbon and carbon fibers can also be regarded as ceramic material.  Without composite materials, new technology couldn’t exist as it does today. Thanks to the merging of alloys, ceramics, carbon fibers, and other durable materials, humanity can move forward at a rapid pace, developing technology that saves and improves lives every day. Ceramic matrix composites play an important role in these technological strides. Ceramic matrix composites are strong, long-lasting materials used in several tech-filled industries. They have enough flexibility to find their place in many disparate types of machinery. Ceramic matrix composites gain their strength by doubling up on inorganic ceramic materials, implanting ceramic fibers into a ceramic matrix. The resulting composite material is stronger than either the ceramic fibers or the ceramic matrices on their own.

Application areas of Ceramic matrix composites

Ceramic matrix composites (CMCs) have been developed to overcome the intrinsic brittleness and lack of reliability of monolithic ceramics, with a view to introducing ceramics in structural parts used in severe environments, such as rocket and jet engines, gas turbines for power plants, heat shields for space vehicles, fusion reactor first wall, aircraft brakes, heat treatment furnaces, etc. Further advantages include weight reductions and higher operating temperatures compared to metals and metal matrix composites.

Ceramic matrix composites may be classified into two categories:

One is a group of toughened ceramics reinforced with particulates and whiskers. These materials exhibit brittle behavior in spite of considerable improvements in fracture toughness and strength. The maximum in fracture toughness is around 10 MPam1/2 or more. The second consists of continuous-fiber composites exhibiting quasi-ductile fracture behavior accompanied by extensive fiber pull-out. The fracture toughness of this class of materials can be higher than 20 MPam1/2 when produced with weak interfaces between the fibers and matrix.

Manufacture

The manufacturing processes usually consist of the following three steps:

1. Lay-up and fixation of the fibers, shaped like the desired component
2. Infiltration of the matrix material
3. Final machining and, if required, further treatments like coating or impregnation of the intrinsic porosity.

The first and the last step are almost the same for all CMCs: In step one, the fibers, often named rovings, are arranged and fixed using techniques used in fiber-reinforced plastic materials, such as lay-up of fabrics, filament winding, braiding, and knotting. The result of this procedure is called fiber-preform or simply perform.

For the second step, five different procedures are used to fill the ceramic matrix in between the fibers of the preform:

1. Deposition out of a gas mixture
2. Pyrolysis of a pre-ceramic polymer
3. Chemical reaction of elements
4. Sintering at a relatively low temperature in the range 1,000–1,200 °C (1,830–2,190 °F)
5. Electrophoretic deposition of a ceramic powder

Procedures one, two, and three find applications with non-oxide CMCs, whereas the fourth one is used for oxide CMCs; combinations of these procedures are also practiced. The fifth procedure is not yet established in industrial processes. All procedures have sub-variations, which differ in technical details. All procedures yield a porous material.

The third and final step of machining – grinding, drilling, tapping or milling – has to be done with diamond tools. CMCs can also be processed with a water jet, laser, or ultrasonic machining.