Composite Material
A composite material is an engineered material made from two or more constituent materials with significantly different physical or chemical properties, which remain distinct at the macroscopic level within the finished structure. The resulting composite typically exhibits superior performance characteristics — such as high strength-to-weight ratio, corrosion resistance, and tailored stiffness — compared to either constituent alone. Common composites include carbon fibre reinforced polymers (CFRP), glass fibre reinforced polymers (GFRP), and metal matrix composites (MMC).
Common Composite Materials and Their Properties
| Composite | Matrix | Reinforcement | Tensile Strength (MPa) | Application |
|---|---|---|---|---|
| CFRP | Epoxy resin | Carbon fibres | 600–1500 | Aerospace, sports equipment |
| GFRP | Polyester resin | Glass fibres | 200–700 | Boat hulls, wind blades |
| Kevlar composite | Epoxy resin | Aramid fibres | 500–1200 | Body armour, helmets |
| MMC (Al-SiC) | Aluminium | Silicon carbide | 400–600 | Engine pistons, brake discs |
| Concrete (reinforced) | Concrete | Steel rebar | 400–600 (rebar) | Civil structures |
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Related Terms
Fatigue Life
Fatigue life is the number of stress cycles that a material or component can endure at a given stress amplitude before fracture or failure occurs due to progressive crack initiation and propagation under cyclic loading. It is a critical design parameter for components subjected to repeated loading such as shafts, aircraft wings, and turbine blades. The S-N (Wöhler) curve relates the stress amplitude (S) to the number of cycles to failure (N) for a given material.
Fracture Toughness
Fracture toughness is a material property that quantifies a material's resistance to crack propagation and catastrophic brittle fracture when subjected to stress. Denoted K_Ic for plane-strain mode I (opening mode) fracture, it has units of MPa·√m and represents the critical stress intensity factor at which a crack begins to propagate unstably. High fracture toughness is essential in safety-critical structural applications such as pressure vessels, aircraft fuselages, and pipelines, where the presence of flaws must not lead to sudden failure.
Mechanical Vibration
Mechanical vibration is the oscillatory motion of a mechanical system about an equilibrium position, arising from elastic restoring forces and inertia. It occurs in structures, machines, and vehicles and can be free (natural), forced, or self-excited in nature. Understanding and controlling vibration is critical to prevent fatigue failure, noise generation, and resonance-induced catastrophic damage in engineering systems.
From Latin "compositus", past participle of "componere" meaning "to put together", from "com-" (together) and "ponere" (to place). The engineering term "composite material" emerged in the mid-20th century as fibre-reinforced plastics were developed for aerospace applications.