Composite materials are those constructed from two or more constituent materials, generating novel or enhanced properties such as mechanical and thermal resistance, vibration damping, corrosion resistance, and so on. These materials are increasingly exploited in construction projects on every scale, allowing more ambitious, durable, and technologically advanced installations to be realized. This article will discuss emerging composite materials and their applications in construction.
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What are Composite Materials?
As discussed, composite materials are those constructed from two or more materials that have been incorporated in some way at the macro-scale, perhaps one of the most prominent examples being the reinforcement of concrete with steel bars. Pure concrete exhibits relatively poor tensile strength, and thus, the steel bars significantly enhance the tensile strength of the composite material, providing superior mechanical properties suitable for larger building projects.
Concrete may be reinforced by steel bars in a variety of configurations, utilizing thicker or thinner bars of varying or identical length and arranged in parallel, lattice, or randomly oriented. Other composite materials of differing construction may also adopt one of these variations, depending on their specific function.
Typically, the harder or more fibrous material incorporated into the composite material in a particular arrangement is termed the reinforcement material, while the surrounding medium is known as the matrix. Besides concrete, the matrix may be constructed from various hardening plastics or soft materials, such as thermosetting polyesters or silicone, while the reinforcement could be constructed from a harder plastic, glass, carbon fibers, or more flexible but tough materials such as flax or hemp fiber.
Why are Composite Materials Needed in Construction?
The pressing call for composite materials is growing stronger in the face of growing environmental concerns; materials will need to be more durable in a range of weather conditions in order to face global climate change, and the environmental impact of constant infrastructure renewal is costly.
Indeed, concrete has been referred to as the “most destructive material on earth”, contributing a significant percentage of the global CO2 output when considering all stages of the production process and also contributing to the urban heat island effect; thus, environmentally friendly alternatives would be preferred.
Further, the recent realization that the corrosion-resistant properties of many steel-reinforced concrete structures may not be as sufficient as expected, highlighted by the Surfside condominium collapse in 2021, in which a 12-story building collapsed due to corrosion of reinforcing steel, killing 98 people, has urged the search for alternatives.
What are the Applications of Composite Materials?
The key properties of composite materials for construction include Young’s modulus (tensile or compressive stiffness), fire resistance, fatigue life, vibration and harmonic load resistance, joinability, and, depending on the application, also chemical resistance. Corrosion-resistant materials such as glass-fiber reinforced polymers (GFRP) have been used as alternatives to steel as concrete reinforcement, prominently within a 23 km concrete flood channel in Saudi Arabia. GFRP and carbon fiber reinforced polymer (CFRP) offer high-temperature resistance and strength for a relatively low cost; CFRP is somewhat stronger and more temperature resistant but with a greater cost.
The strength of the ceramic matrix can be improved by a variety of methods: inclusion of nanoparticles or new elements, microstructure regulation, powder metallurgy, and others. For example, the sintering temperature of the material influences phase formation and material microstructure, therefore affecting ultimate properties such as compressive strength. In combination, a stronger ceramic matrix reinforced with non-corrosive materials may be capable of addressing the limitations of steel-reinforced concrete while also reducing the enormous environmental cost of traditional concrete.
The extremely light weight of fiber-reinforced polymers (FRP) allows constructions to be installed more quickly and easily and may benefit long-term durability. For example, by more than halving the weight of bridges or tall structures the overall strength requirements are lessened, and in one example in Warwickshire, UK, a steel footbridge was replaced in a matter of days by pre-built fiber-reinforced polymer materials. FRPs are typically constructed from materials such as carbon, glass, asbestos, beryllium, molybdenum, or aromatic polyamides, with matrixes of epoxy resin, polyester, or vinyl ester.
Viscoelastic materials are those with viscous and elastic characteristics when undergoing deformation, as does concrete, many plastics, metals at high temperatures, and many other construction materials. Many construction and engineering projects require such materials for the purposes of energy dissipation, acting as dampers that compensate for expected movement in the structure.
Composite materials constructed from alternating viscoelastic and solid reinforcement materials are broadly utilized, and are specifically designed to optimally absorb vibrations of the expected frequency for their given application. Large buildings and bridges must regularly accommodate significant sway within their structure owing to wind and other vibrations, such as those caused by vehicles, and thus advanced, durable composite materials would lessen the occurrence of structural failure and maintenance requirements.
Composite materials possess distinct advantages over monomaterials in enhancing structural integrity, resilience, and reinforcement, and depending on the specific constituent materials and construction method may be of much lighter weight, providing extensive applications in engineering, aerospace, automotive, and construction industries. In particular, the inclusion of nanoparticles and fiber reinforcement into the matrix demonstrates a significant structural reinforcement effect, enhancing the structural properties of traditional materials such as concrete.
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References and Further Reading
Soori, M. (2023) Advanced Composite Materials and Structures. Journal of Materials and Enginnering Studies, 10(2).
Huang, X., Su, S., Xu, Z., Miao, Q., Li, W., & Wang, L.. (2023). Advanced Composite Materials for Structure Strengthening and Resilience Improvement. Buildings, 13(10), 2406.
Javidan, M. M., & Kim, J.. (2020). Experimental and Numerical Sensitivity Assessment of Viscoelasticity for Polymer Composite Materials. Scientific Reports, 10(1).