1.1 Definition of Material

Material is a broad term for the (chemical) substance, or a mixture of substances that constitute a thing. Based on their properties they can be used in structures, machines, devices, commercial products, and systems. There is a myriad of materials around us—they can be found in anything from buildings to spacecraft. In short, materials are the useful matter of the universe, the usefulness of materials is governed by the property of material itself.

The term property describes the behavior of materials when subjected to some external impacts such as force, heating, cooling and electric field etc. For examples, the tensile strength of a metal is a measure of the material's resistance to a pulling force and the electrical conductivity of a material refers to the ability of conducting charge under an electric field.

A property may be a constant or may be a function of one or more independent variables, such as temperature, electronic filed etc. Materials properties often vary to some degree according to the direction in the material in which they are measured, a condition referred to as anisotropy. The behavior of material properties that relate to different physical phenomena often can be modeled by the differential constitutive equations. In most case, these behaviors can model as linear in a given operating range and significantly simplify the differential constitutive equations that the property describes.

Some materials properties are used in relevant equations to predict the attributes of a system a priori. For example, if a material of a known specific heat gains or loses a known amount of heat, the temperature change of that material can be determined. Materials properties are most reliably measured by standardized test methods. Many such test methods have been documented by their respective user communities and published through ASTM International.

In general, material properties include but not limit to acoustical properties, atomic properties, chemical properties, electrical properties, environmental properties, magnetic properties, manufacturing properties, mechanical properties, optical properties, radiological properties, thermal properties etc. Our course will deal with the properties related to the physical phenomena such as mechanical and electrical behavior of materials.