SERIES 005: COMPOSITE

What is a composite?

A composite is considered to be any multiphase material that exhibits a significant proportion of the properties of its constituent phases such that a better combination of properties is realized.

In simpler terms- A composite is any material that is made from two or more constituent material with distinct properties. When these constituent materials combine, they produce material with different but superior characteristics.

Since the invention of composite in 1500 BC, it has been one of the best things that have happened to mankind.

There are [3] three phases a composite material is composed of, namely:

? MATRIX PHASE also known as the Continuous phase, provides binding & holding of the reinforcements, and also other functional properties. The matrix can either be a polymer, metal, or ceramic material.

? FILLER / REINFORCEMENT PHASE which is surrounded by matrix materials serves as the strong load-bearing material. Reinforcements exist in form of fibers, flakes, or particles.

? INTERPHASE with different structures and properties from the Matrix and filler/reinforcements phase.

The properties of any particular composite are greatly influenced by the concentration, size, shape, distribution & orientation of the constituent phases.

The properties of any particular composite are greatly influenced by the concentration, size, shape, distribution, and orientation of the constituent phases

Composite materials should have the following characteristics:

-         Microscopically it is nonhomogeneous materials and has a distinct interface,

-         There are big differences in the performance of component materials

-         The formed composite materials should have a great improvement in performance

-         The volume fraction of component materials are greater than 10%

Composites are classified based on the various types of matrix and reinforcements, below is a chart of its classification & related examples.

There are 3 main classification of Composites – Based on Reinforcement

1.      Particle Reinforced Composite

2.      Fiber Reinforced Composite

3.      Structural Composite

Particle Reinforced Composite (PRC) - this type of composite consist of particles dispersed in a matrix. They have no long dimension and are less effective in strengthening than fiber. Particle Reinforced composites are composed of two types;

I.                   Large - Particle Composite (LPC) - contains coarse particles (reinforcements) in very large quantities. One example that quickly comes to mind is Concrete. Concrete is composed of cement (the matrix), and sand and gravel (the reinforcement)

II.                 Dispersion Strengthened Composite (DSC) - In this type of composite, the particles are comparatively smaller than LPC. This type of reinforcement is mostly used in metal and metal alloys. It is similar to precipitation hardening; the difference is that the particles are chosen to be unreactive for DSC, and therefore, strength is retained at a higher temperature. An example is Sintered Aluminium Powder (SAP), where aluminum is the matrix, and alumina flakes are the reinforcement.

Fiber Reinforcement Composite (FRC) - The most important composites are those in which the reinforcement phase is fiber. They are strong and stiff. Design goals for FRC often include high strength and stiffness on a weight basis. The mechanical properties of an FRC depend not only on the fiber but also on the degree to which an applied load is transmitted to the matrix phase's fibers.

In an FRC, the fibers carry most of the load. The matrix protects individual fibers from surface damage such as abrasion or chemical reactions with the environment. The matrix is also responsible for binding the fibers together & acts as the medium by which an externally applied stress is transmitted and distributed to the fibers. 

Structural Composite (SC) - This type of composite is mainly composed of homogeneous and composite materials. Structural composites are engineered products made from plastic, wood, glass, or carbon fiber materials. The two most common types of the structural composite are Laminar composite and Sandwich panels.

Types of composite - Based on matrix

Polymer Matrix Composite (PMC) - is defined as materials comprising a polymer as the matrix with fibers as the reinforcement medium. PMCs are the most widely used composite type of composite. Both Thermoset polymers (epoxies, etc.) and thermoplastic polymers (nylon, acrylics, etc.) can be used as matrix polymers.

PMCs can be classified into three types; according to reinforcement

1. Glass Fiber-Reinforced Polymer Composites (GFRP) – This is simply a composite consisting of glass fibers contained a polymer.

Fiber diameter – ranges between 3 and 20 micrometers. Glass fiber is popular among reinforcement because of the following advantages;

a.      They are easily drawn into high-strength fibers from the molten state

1. They are readily available
2. As a fiber, it is relatively strong, and when embedded in a plastic matrix, it produces a composite having a very high specific strength
3. Possesses a chemical inertness that renders the composite useful in a variety of corrosive environments

APPLICATIONS- Transportation vehicles, Medical devices, Sporting goods, Footwear, Personal Protective Equipment (PPE), Plastic pipes, Impellers, Energy Storage devices, etc.

2.      Carbon Fiber-Reinforced Polymer Composite (CFRP) – Carbon is a high-performance fiber material. As a result, carbon fiber has the highest specific modulus and specific strength of all reinforcing fiber materials.

Carbon fibers can retain their high tensile modulus and high strength at elevated temperatures. At room temperature, carbon fibers are not affected by moisture or a wide variety of solvents, acids, and bases. Carbon fibers also exhibit a diversity of physical and mechanical properties, allowing them to have specific engineered properties.

The manufacturing process for CFRP has been developed that is relatively inexpensive and cost-effective. They have a fiber diameter that ranges between 4 and 10 micrometers.

STRUCTURAL PARTS OF AN AIRPLANE MADE WITH COMPOSITES

APPLICATIONS- Pressure vessels, aircraft structural components, sports, and recreational equipment, etc.

3.      Aramid Fiber-Reinforced Polymer Composite (ARFP) – These types of fibers are especially desirable for their outstanding strength-to-weight ratios, which are superior to metals. Aramid fibers are high-strength and high-modulus materials.

Aramids are known for their toughness, impact resistance, and resistance to creep and fatigue failure. They are resistant to combustion and stable within high temperatures. They can retain their mechanical properties between -200°C and 200°C. Aramids are also chemically inert in solvents and chemicals.

The two most common aramid materials are Kevlar? and Nomex?

KEVLAR

APPLICATION- Bulletproof vest and armor, gaskets, sporting goods, missile cases, etc.

TABLE 1 - DIFFERENCES BETWEEN THE CLASSIFICATION OF PMC

Metal Matrix Composite (MMC) – For MMCs, the matrix is a metal. The reinforcement can be another metal, a ceramic, or an organic compound. MMC may be utilized at higher service temperatures than their base metal counterparts.

The reinforcement improves specific stiffness, specific strength, abrasion resistance, creep resistance, etc. MMCs are more expensive than PMCs, and this has restricted their use. As a result, they are found where improved properties and performance can justify the added cost.

The key factors that affect the design of MMCs include;

1. Choice of matrix material
2. Type, size, and amount of reinforcement
3. Type of processing
4. Heat Treatment procedure

The end application influences the choice of matrix material and reinforcement. Titanium-based materials are considered for light-weight applications, while nickel-based are considered for high-temperature applications. The main advantages of MMCs over PMCs are:

1. Higher temperature capabilities
2. Less moisture absorption
3. Better radiation resistance
4. Higher fire resistance
5. Higher thermal and electrical conductivity

MMCs have found their way to Automobile application; some engine components have been introduced consisting of an aluminum-alloy matrix. Some other applications include- Tank armors, high-performance tungsten carbide tools, automotive disk brakes, space systems, high-end sports equipment, aircraft components, etc.

Ceramic Matrix Composite (CMC) – CMCs are being developed to take advantage of ceramics' high-temperature properties while overcoming the low fracture toughness. Ceramic materials are popular for their resilience to oxidation and deterioration at high temperatures; were they not for their disposition to brittle fracture, the ceramics would be ideal for high-temperature and high-stress applications, ergo CMC.

CMCs are a special type of composite material in which both the reinforcement and the matrix are ceramics. In some cases, the same kind of ceramics is used for the composite, while in other cases, different ceramics are used.

CMCs behave differently than their ceramics counterparts. Like ceramics, they are hard and stable even at high temperatures, but they are also light-weight (compared to the materials they are replacing). They can retain a relatively high mechanical strength at elevated temperatures. CMCs offer very good mechanical, chemical, dimensional, and chemical stability. CMCs are not susceptible to fracture like traditional ceramics- their resistance to crack propagation is related to the reinforcing fibers.

CMCs have high corrosion resistance and can handle dynamic loadings very well. They are anisotropic; this means that they have properties strongest along the length of the fibers. This allows them to be tailored to a specific need.

CMC may be produced using hot pressing, hot isostatic pressing, and liquid phase sintering techniques. Some of its applications include – Heat exchangers, turbine blades, bulletproof armor, heating element, etc. 

TABLE 2 - DIFFERENCES BETWEEN THE CLASSIFICATION OF COMPOSITES BASED ON MATRIX

CASE STUDY

Concrete

Concrete is one of the oldest construction materials globally; this is mainly due to its low cost, availability, durability, and ability to withstand extreme weather environments.

Concrete is Large – Particle Composite; it is a heterogeneous mixture that consists of the following component:

a.                  Cement

b.                 Aggregate (sand, gravel, etc.)

c.                  Water

d.                 Additives, and in some cases

e. Reinforcement – Steel, etc.

Concrete is a brittle material with high compressive strength, but its ability to withstand tensile stress is small. Thus reinforcement of concrete is required to allow it to handle tensile stresses. Steel bars or steel wires are used to reinforce concrete to increase its ability to handle tensile stresses.

 One of the important ways to evaluate concrete is by measuring its compressive strength.

To fully appreciate the importance of composite as a technology, we would be comparing the properties of steel-reinforced concrete with that ordinary concrete.

TABLE 3 - DIFFERENCES BETWEEN PLAIN AND CONCRETE

*= Values are calculated

Generally, concrete carries the compressive loads, and the reinforcing steel carries the tensile load

ADVANTAGES OF COMPOSITES

The advantages of a Composite Material over the individual constituent material is that it includes:

?Flexibility in design because it can be molded into complex shapes.

?Improved mechanical properties and low mass i.e. Strength to weight ratio are high.

?High durability.

?High corrosion resistance.

?Relatively low density.

APPLICATIONS OF COMPOSITE:

These materials are widely used in various applications such as:

|Agriculture | Aerospace and Aircraft | Business and Appliance Equipment | Building and Construction | Consumer Product Components | Corrosion-Resistant Equipment | Defense | Electrical and Electronic | Engineering and Industrial | Marine Applications | Transportation | Water Control Engineering and Sewage|

REFERENCES:

·        https://buildipedia.com/knowledgebase/division-06-wood-plastics-and-composites/06-70-00-structural-composites/06-70-00-structural-composites#:~:text=Structural%20composites%20are%20engineered%20products,glass%2C%20or%20carbon%20fiber%20materials.&text=These%20low%20maintenance%20products%20are,have%20a%20simulated%20wood%20grain.

·        https://www.polymerexpert.biz/industries/173-composites

·        https://www.researchgate.net/figure/The-AIRBUS-A380-aircraft-composite-applications-wwwairbuscom_fig1_303144941

• ANIMASHAUN BUKOLA - PROPOSED PROJECT TOPIC.docx
• https://www.azom.com/properties.aspx?ArticleID=764
• https://www.slideshare.net/zubayerskp/introduction-to-steel-fiber-reinforced-concrete-sfrc

·        https://llfurnace.com/blog/what-are-ceramic-matrix-composites/

·        https://www.azom.com/properties.aspx?ArticleID=764

·        https://www.bbshalmstad.se/en/infocenter/hardness-conversion-table

·        https://www.nufins.com/media/2622/nucem-concrete.pdf

·        Callister, William D., 1940-Material Science, and engineering: an introduction / William D. Callister, Jr. – 7th ed.

AUTHORS BIOGRAPHY

Christian E. Emeodi holds a national diploma degree in Mechanical Engineering and currently a final year student at the Department of Metallurgical and Materials Engineering, University of Lagos, Akoka. He was an engineering intern at the AJAOKUTA STEEL COMPANY LIMITED where he gained practical knowledge on the production of Steel. Christian led a team of students that discovered a way to recycle plastic waste into paver bricks. He is currently a member of the Institute of Engineering and Technology, Unilag chapter. He is also a student member of ASTM and NSBE.                          

 Email: [email protected]

Bukola F. Animashaun interned at the AJAOKUTA STEEL COMPANY LIMITED where she learned the technical know-how of commercial production of steel, with exposures at the Sintering and Raw Materials Handling Plant, Coke Oven and By-product Plant, Blast Furnace Plant, and Pig Casting Shop. Bukola was awarded the best student in Physical Metallurgy and the overall best student in 400 level at the Department of Metallurgical and Materials Engineering, University of Lagos, Akoka. She is currently the Regional Vice President of ASHRAE, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (Unilag Nigeria Chapter).                          

 Email: [email protected]