Last reviewed 16 Sept 2026 · 9 min read
Classification of properties
| Category | Examples |
|---|---|
| Physical | Density, specific gravity, porosity, water absorption, permeability, colour |
| Mechanical | Strength, elasticity, stiffness, ductility, hardness, toughness, fatigue, creep |
| Thermal | Thermal conductivity, expansion, specific heat, melting point, fire resistance |
| Electrical | Conductivity/resistivity, dielectric strength |
| Magnetic | Permeability, coercivity |
| Optical | Transparency, refractive index, reflectivity |
| Chemical | Corrosion resistance, reactivity, chemical stability |
| Durability | Resistance to weathering, abrasion, freeze–thaw, chemical attack |
| Technological (manufacturing) | Machinability, weldability, castability, formability, workability (concrete) |
Physical properties
FormulaPhysical property relations
Density (kg/m³); specific gravity Bulk density — mass per unit volume including pores/voids Porosity Water absorption Permeability — ease of fluid flow through a material (Darcy's law )
- Higher porosity → lower strength, higher water absorption, poorer durability, better thermal insulation.
Mechanical properties
Stress–strain behaviour
- Elastic region — deformation recovers on unloading; Hooke's law .
- Yield point / proof stress — onset of plastic deformation.
- Ultimate tensile strength (UTS) — maximum engineering stress.
- Fracture — final separation.
- Ductile materials (mild steel, aluminium, copper) show large plastic deformation and necking; brittle materials (cast iron, glass, concrete, stone) fracture with little plastic deformation.
Definitions
| Property | Definition | Measure / note |
|---|---|---|
| Strength | Ability to resist applied stress without failure | Tensile, compressive, shear, flexural (modulus of rupture) strengths |
| Stiffness | Resistance to elastic deformation | Modulus of elasticity E; shear modulus G; bulk modulus K |
| Elasticity | Ability to return to original shape after unloading | Elastic limit |
| Plasticity | Ability to undergo permanent deformation without rupture | Important in forming |
| Ductility | Ability to deform plastically under tension (drawn into wires) | Percentage elongation, reduction in area |
| Malleability | Ability to deform under compression (rolled/hammered into sheets) | Gold, lead, aluminium |
| Toughness | Energy absorbed up to fracture | Area under entire stress–strain curve; impact energy (Charpy/Izod); fracture toughness |
| Resilience | Energy absorbed within elastic limit (recoverable) | Modulus of resilience |
| Hardness | Resistance to indentation, scratching, abrasion | Brinell, Rockwell, Vickers, Mohs |
| Brittleness | Fracture with little deformation | Opposite of ductility |
| Fatigue | Failure under cyclic/fluctuating loads below static strength | S–N curve; endurance limit (steels) below which failure does not occur for very large cycles; aluminium has no clear endurance limit |
| Creep | Time-dependent deformation under constant stress (significant at high temperatures for metals; at normal temperatures for concrete, timber, polymers) | Primary, secondary (steady), tertiary stages |
| Stress relaxation | Decrease in stress under constant strain | Prestressing steel losses |
| Impact strength | Resistance to sudden loads | Notched bar tests |
| Ductile–brittle transition | Change from ductile to brittle fracture as temperature decreases (BCC metals such as ferritic steels) | Charpy tests at various temperatures |
| Poisson's ratio | = lateral strain/axial strain | Steel ≈ 0.3; concrete ≈ 0.15–0.2 |
FormulaElastic constant relations
For isotropic materials (ν = 0.5 → incompressible).
Specific strength and specific stiffness
High values are important where weight matters (aircraft, long-span structures, FRP strengthening).