1. Introduction to Composite Materials.pdf

INTRODUCTION TO COMPOSITE MATERIALS 1.1 Historic and Introductory Comments In the most general of terms, a composite is a material that consists of two or more constituent materials or phases. Traditional engineering materials (steel, aluminum, etc.) contain impurities that can represent different phases of the same material and fit the broad definition of a composite, but are not considered composites because the elastic modulus or strength of the impurity phase is nearly identical to that of the pure material. The definition of a composite material is flexible and can be augmented to fit specific requirements. In this text a composite material is consid- ered to be one that contains two or more distinct constituents with significantly different macroscopic behavior and a distinct interface between each constituent (on the microscopic level). This includes the continuous fiber laminated compos- ites of primary concern herein, as well as a variety of composites not specifically addressed. Composite materials have been in existence for many centuries. No record exists as to when people first started using composites. Some of the earliest records of their use date back to the Egyptians, who are credited with the introduction of plywood, papier-miichc-5, and the use of straw in mud for strengthening bricks. Similarly, the ancient Inca and Mayan civilizations used plant fibers to strengthen bricks and pottery. Swords and armor were plated to add strength in medieval times. An example is the Samurai sword, which was produced by repeated folding and reshaping to form a multilayered composite (it is estimated that several million layers could have been used). Eskimos use moss to strengthen ice in forming igloos. Similarly, it is not uncommon to find horse hair in plaster for enhanced strength. The automotive industry introduced large-scale use of composites with the Chevrolet Corvette. All of these are examples of man-made composite materials. Ba