Polymer Matrix Composites: Properties, Production, and Applications

Polymer matrix composites (PMCs) are present in almost all aspects of modern life - from gadget components to a vast selection of automotive accessories. Derived from its name, meaning many repeating units, polymers are often made up of branches of carbon and hydrogen chemically linked together to make a chain.

Polymers that are often used as composites are either thermoplastic polymers, thermosetting polymers or elastomers. They are a source of a wide variety of low-priced, raw materials which offer many advantages like [1]:

• Low specific weight
• High material stability against corrosion
• Good electrical and thermal insulation
• Ease of shaping and economic mass production
• Attractive optical properties

Yet, they suffer from some deficiencies as in strength and stiffness. To make up for those deficiencies, reinforcements are integrated into polymer materials to enhance their mechanical properties.

What is a polymer matrix composite?

Polymer matrix composites are materials made up of fibres that are embedded in an organic polymer matrix. These fibres are introduced to enhance selected properties of the material [2].

Polymer matrix composites are classified based on their level of strength and stiffness into two distinct types:

• Reinforced plastics - confers additional strength by adding embedded fibrous matter into plastics
• Advanced Composites - consists of fibre and matrix combinations that facilitate strength and superior stiffness. They mostly contain high-performance continuous fibres such as high-stiffness glass (S-glass), graphite, aramid, or other organic fibres [3]

Properties of a PMC

The constituents of a PMC, which affect its overall properties, are [3]:

• Matrix - This is the polymer, which is a continuous phase and is classified as the weak link in a PMC structure.
• Reinforcement - This is a discontinuous phase and is a principal load-bearing component. It can either be glass, quartz, basalt, or carbon fibre.
• Interphase - The interphase between the reinforcement and matrix phases where load transmission takes place.

Aside from the types of matrix and reinforcement used, other factors affecting the properties of a PMC are the constituents’ relative proportions, the reinforcement geometry and the nature of the interphase [3].

The main advantages of polymer matrix composite materials are their strength and stiffness. Other qualities that come with the reinforcement of polymers are as follows [4]:

Improved processing	Density Control	Thermal Conductivity	Thermal Expansion Control
Flame retardancy	Cost reduction	Greater toughness	Impact resistance
Fatigue resistance	Fracture resistance	Abrasion resistance	Corrosion resistance
High specific strength to weight ratio	High specific stiffness to weight ratio	Improved fatigue strength	High creep resistance

Despite these many desirable qualities, polymer matrix composites are limited to service temperatures below 600° F (316° C), above which, polymers start to degrade [3].

Production of polymer matrix composites

Polymers are reinforced with fibres which are 8 to 12 μm in diameter either as continuous single or chopped multi-filaments that are woven into cloth and other types of preformed textiles. These fibres are then impregnated into the matrix polymer in liquid form by injection, extrusion, pressing or stamping and then cured to produce the final composite [5].

During the fabrication and shaping of polymer matrix composites into finished products, often the formation of the material itself is incorporated in the fabrication process. These processes include [4,5]:

• Hand lay-up
• Vacuum moulding
• Spray lay-up
• Pultrusion
• Resin transfer moulding (RTM)
• Filament winding

What is a PMC used for?

PMCs are regarded due to their low cost and straightforward fabrication methods. Applications for PMCs include [4,6]:

Automotive industry - Body panels, leaf springs, driveshaft, bumpers, doors, racing car bodies, and so on.

Aircraft and aerospace industry - Used in the construction of structural parts for military aircraft, space shuttles, and satellite systems. The main purposes of using PMCs are to reduce aircraft weight, which can improve its performance, and to reduce its costs.

Marine - Fibreglass boat bodies, as well as canoes and kayaks.

Sports goods - Used in performance footwear, sports equipment and other sporting goods because of their lightweight and high-strength properties.

Biomedical applications - Medical implants, orthopaedic devices, MRI scanners, X-ray tables, and prosthetics.

Electrical - Panels, housing, switchgear, insulators, and connectors. It also covers electronic devices like capacitors, Li-ion and flexible batteries and covers for digital portable equipment like headphones, etc.

Protective equipment - Since polymer matrix composites can withstand extreme hot or cold and other hazardous conditions, they are often made as raw materials for bulletproof vests and other armour.

Industrial - Chemical storage tanks, pressure vessels, pump housing, and valves. PMCs are also used in impellers, blades, blower and pump housings, and motor covers.

Structural - Polymer matrix composites are used to repair bridges and other construction materials and equipment like booms and cranes.

 

[1] M. Akay, 2015, An introduction to polymer matrix composites,” from: https://www.academia.edu/37778336/An_introduction_to_polymer_matrix_composites

[2] S.G. Advani, K.T. Hsiao, 2012, Manufacturing Techniques for Polymer Matrix Composites (PMCs), UK: Woodhead Publishing ltd.

[3] “Chapter 3 Polymer Matrix Composites,” n.d., from: https://www.princeton.edu/~ota/disk2/1988/8801/880106.PDF

[4] J.P. Jose et al., 2012, “Advances in Polymer Composites: Macro- and Microcomposites – State of the Art, New Challenges, and Opportunities,” In Polymer Composites: Volume 1, First Edition. S. Thomas, K. Joseph, S.K. Malhotra, K. Goda, and M.S. Sreekala (ed.s), Wiley-VCH Verlag GmbH & Co. KGaA.

[5] “Processing of polymer composites,” 2012, from: http://www-materials.eng.cam.ac.uk/3C1archive/handout6.pdf

[6] “Introduction to polymer matrix composites,” In Polymer Matrix Composites and Technology, R.M. Wang, S.R. Zheng, and Y.P. Zheng (ed.s), UK: Woodhead Publishing ltd.