Kevlar | Properties, Price & Application

About Kevlar

Kevlar has many applications, ranging from bicycle tires and racing sails to bulletproof vests, because of its high tensile strength-to-weight ratio; by this measure it is five times stronger than steel. The high tenacity and thermally stable fibers are used for lightweight bulletproof body armor, and also due to weight-saving it can also replace heavier materials in airplanes, for fuel saving.

kevlar properties density strength price

Summary

Name	Kevlar
Phase at STP	solid
Density	1440 kg/m3
Ultimate Tensile Strength	3600 MPa
Yield Strength	N/A
Young’s Modulus of Elasticity	130 GPa
Brinell Hardness	N/A
Melting Point	477 °C
Thermal Conductivity	0.04 W/mK
Heat Capacity	1420 J/g K
Price	50 $/kg

Composition of Kevlar

Typically it is spun into ropes or fabric sheets that can be used as such or as an ingredient in composite material components. When Kevlar is spun, the resulting fiber has a tensile strength of about 3,620 MPa, and a relative density of 1.44. The polymer owes its high strength to the many inter-chain bonds. These inter-molecular hydrogen bonds form between the carbonyl groups and NH centers.

75%

10%

15%

Applications of Kevlar

Kevlar - Material Table - Applications - Price — Source: wikipedia.org License: CC-BY SA 3.0

Mechanical Properties of Kevlar

Strength of Kevlar

In mechanics of materials, the strength of a material is its ability to withstand an applied load without failure or plastic deformation. Strength of materials basically considers the relationship between the external loads applied to a material and the resulting deformation or change in material dimensions. In designing structures and machines, it is important to consider these factors, in order that the material selected will have adequate strength to resist applied loads or forces and retain its original shape.

Strength of a material is its ability to withstand this applied load without failure or plastic deformation. For tensile stress, the capacity of a material or structure to withstand loads tending to elongate is known as ultimate tensile strength (UTS). Yield strength or yield stress is the material property defined as the stress at which a material begins to deform plastically whereas yield point is the point where nonlinear (elastic + plastic) deformation begins. In case of tensional stress of a uniform bar (stress-strain curve), the Hooke’s law describes behaviour of a bar in the elastic region. The Young’s modulus of elasticity is the elastic modulus for tensile and compressive stress in the linear elasticity regime of a uniaxial deformation and is usually assessed by tensile tests.

Ultimate Tensile Strength of Kevlar

Ultimate tensile strength of Kevlar is 3600 MPa.

Yield Strength of Kevlar

Yield strength of Kevlar is N/A.

Modulus of Elasticity of Kevlar

The Young’s modulus of elasticity of Kevlar is 130 GPa.

Hardness of Kevlar

In materials science, hardness is the ability to withstand surface indentation (localized plastic deformation) and scratching. Brinell hardness test is one of indentation hardness tests, that has been developed for hardness testing. In Brinell tests, a hard, spherical indenter is forced under a specific load into the surface of the metal to be tested.

The Brinell hardness number (HB) is the load divided by the surface area of the indentation. The diameter of the impression is measured with a microscope with a superimposed scale. The Brinell hardness number is computed from the equation:

Brinell hardness of Kevlar is approximately N/A.

Strength of Materials

Elasticity of Materials

Hardness of Materials

Thermal Properties of Kevlar

Kevlar – Melting Point

Melting point of Kevlar is 477 °C.

Note that, these points are associated with the standard atmospheric pressure. In general, melting is a phase change of a substance from the solid to the liquid phase. The melting point of a substance is the temperature at which this phase change occurs. The melting point also defines a condition in which the solid and liquid can exist in equilibrium. For various chemical compounds and alloys, it is difficult to define the melting point, since they are usually a mixture of various chemical elements.

Kevlar – Thermal Conductivity

Thermal conductivity of Kevlar is 0.04 W/(m·K).

The heat transfer characteristics of a solid material are measured by a property called the thermal conductivity, k (or λ), measured in W/m.K. It is a measure of a substance’s ability to transfer heat through a material by conduction. Note that Fourier’s law applies for all matter, regardless of its state (solid, liquid, or gas), therefore, it is also defined for liquids and gases.

The thermal conductivity of most liquids and solids varies with temperature. For vapors, it also depends upon pressure. In general:

Most materials are very nearly homogeneous, therefore we can usually write k = k (T). Similar definitions are associated with thermal conductivities in the y- and z-directions (ky, kz), but for an isotropic material the thermal conductivity is independent of the direction of transfer, kx = ky = kz = k.

Kevlar – Specific Heat

Specific heat of Kevlar is 1420 J/g K.

Specific heat, or specific heat capacity, is a property related to internal energy that is very important in thermodynamics. The intensive properties c_v and c_p are defined for pure, simple compressible substances as partial derivatives of the internal energy u(T, v) and enthalpy h(T, p), respectively:

where the subscripts v and p denote the variables held fixed during differentiation. The properties c_v and c_p are referred to as specific heats (or heat capacities) because under certain special conditions they relate the temperature change of a system to the amount of energy added by heat transfer. Their SI units are J/kg K or J/mol K.

Kevlar – Material Table – Applications – Price