The dispersed phase can be in the form of long bers, short bers, whiskers, akes, sheets, or particulates. Among these forms, ber forms are widely used in the composites because of their superior properties and load transfer characteristics. A ber can be dened as an elongated material, mostly with a circular cross-section having a more or less uniform diameter of less than 250 μm and an aspect ratio (length to diameter ratio) of more than 100 (Chawla and Chawla 2006). Fiber form is stronger than bulk form due to the size effect, that is, the defect size in the ber is restricted to the size ( diameter) of bers. Figure 2.1 shows the strength of different material types in three forms, namely, bulk, ber, and whisker forms. Whiskers are monocrystalline short bers. The diameter of whiskers is 0.1 to a few micrometers and length can be up to a few millimeters. Silicon carbide whiskers are the common whisker materials used in composites. Unless there is a specic need, whiskers are rarely used because of the reasons given in the previous chapter.