Principal Types of Matrix

Besides the rectangular matrix discussed above, the following principal types of matrices occur in matrix algebra. 

Square Matrix If the number of columns is equal to the number of rows, that is, p = m, the matrix [A] is said to be a square matrix of order m. 

If necessary, the order of a square matrix will be denoted by a single subscript for example. 

The diagonal of the square matrix that contains the elements (i.e., A, A22, , is called the principal diagonal. 

Column Matrix If the matrix has only one column (m = 1), the m elements are arranged in a single column such a matrix is a column matrix (sometimes called a column vector) and is of order p X 1. A column matrix is denoted by parentheses 

---

Those basic matrix selection factors are used as bases for comparing the four principal types of matrix materials, namely polymers, metals, carbons, and ceramics, listed in Table 7-1. Obviously, no single matrix material is best for all selection factors. However, if high temperatures and other extreme environmental conditions are not an issue, polymer-matrix materials are the most suitable constituents, and that is why so many current applications involve polymer matrices. In fact, those applications are the easiest and most straightforward for composite materials. Ceramic-matrix or carbon-matrix materials must be used in high-temperature applications or under severe environmental conditions. Metal-matrix materials are generally more suitable than polymers for moderately high-temperature applications or for modest environmental conditions other than elevated temperature. 

---