The structure of the composite is very simple – it consists of three-dimensional preforms that form the skeleton of the designed part. The reinforcement can be in form of fiber mat, individual fibers, yarn, weave structure, woven fabric, knitted fabric, braided fabric, nonwoven fabric, and triaxial fabric. Also, it may be 2-D or 3-D fabrics. The matrix binds the fibers, holding them in the pre-determined form, to protect the reinforcement from the environment effect, as well as to transfer the applied loads in all the directions to all the fibers in the preform as the reinforcement is the main bearing load element. The interface between the matrix and the fiber plays the important 158role in the transfer the loads from the matrix to the fibers. Hybrid composites, which may be formed from several reinforcements of different material or filler [1, 2], are presented in single matrix, as shown in Figure 5.1. The variety of the components for a composite are usually used to reach the properties which can’t be obtained with single reinforcement or single matrix. Various composite structure combinations. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9781315207513/29b5c7c7-c676-476e-9185-e5b61d41882d/content/fig5_1.tif"/>