The consequences of selecting materials with lower tensile strength than required by the application might be severe. Engineers use yield strength during the design process to ensure that the stress never exceeds that limit. For example, if a material has a yield strength of 100 MPa (MPa), an applied load of 50 MPa would not cause it to fail.

If a material's yield strength is lower than this, it will eventually fail under **the applied load**. The location where failure occurs depends on how the load is distributed between the two components of the material: fiber and matrix. If the load is shared equally by both, the material will fail at the same place regardless of **its yield strength**. But if the load is distributed in such a way that most of it goes into the matrix, then the fiber component does not need to bear as much stress as if it had higher yield strength. In this case, the material will survive longer than expected, which could lead to future failures due to permanent deformation or damage.

For example, consider a material composed of long fibers embedded in **a polymer matrix**. If we assume that the fibers have a diameter of 5 microns and the matrix has a density of 1 g/cm3, then the fiber volume fraction is 0.5.

Material toughness An engineering subject concerned with a material's capacity to withstand mechanical forces when in use. The strength of a material in a specific application is determined by a variety of characteristics, including its resistance to deformation and fracture, and it frequently depends on the geometry of the member being constructed. In general, the higher the yield strength and tensile strength of a material, the more capable it will be of withstanding loads over its life.

Strength of materials As used in **civil engineering**, the term "strength of materials" refers to the ability of a material to resist deformation under load. It is usually expressed in pounds per **square inch** (psi) or newtons (N), which are equivalent for most common materials except metals. The strength of a material can be compared using **relative values**: for example, aluminum has less than one-fifth the strength of steel. An absolute value can also be given, such as the strength of concrete, which is about 15 MPa (2,250 psi).

Concrete is by far the most commonly used material in civil engineering projects. It is strong, easily worked, and relatively inexpensive. However, it has some drawbacks. Concrete loses strength over time as it ages due to the loss of cement paste from within the mortar matrix and the reduction of aggregate contact area due to erosion. This loss of strength may require that larger members be used in structures built with concrete, which increases the cost of construction.

The Advantages of **Strength Design** The strengthdesign technique takes into account the non-linear linear form of stress-strain design, resulting in a more accurate calculation of load bearing capability. The strength design technique results in more cost-effective constructions. It also allows for better utilization of material properties. Finally, it provides a way to calculate load capacity that is not possible with simple dimensional analysis.

When a structure is loaded in tension, the maximum load that can be supported by the beam depends on its diameter, while the volume of steel in the beam requires only that it be sufficient to support the maximum load. But when the beam is loaded in compression, the maximum load it can support is proportional to the area of its cross section, whereas the volume of steel in the beam requires that it be strong enough to support this maximum load. The strength design technique combines the ideas of maximum load and volume of steel required for **a given project** to produce an accurate estimate of how much load a beam will be able to carry.

In order to determine how much load a beam can carry, first find the deflection of the beam under load. Deflection is the term used to describe how far away from **its original position** a beam will bend under load. Once the beam has been deflected under load, you can use its current deflection to find its maximum load bearing capacity.