Composite Materials

Abstract

Fiber reinforced composite materials have gained popularity in engineering applications during the past decades due to their flexibility in obtaining the desired mechanical and physical properties in combination with lightweight components. For this reason they are now being widely used for aerospace and other applications where high strength and high stiffness-to-weight ratios are required. These materials are usually made of glass, graphite, boron, or other fibers embedded in a matrix. Modeling the mechanical and failure behavior of fiber composites is not a simple task. The materials are heterogeneous and have several types of inherent flaws. Failure of fiber composites is generally preceded by an accumulation of different types of internal damage. Failure mechanisms on the micromechanical scale include fiber breaking, matrix cracking, and interface debonding. They vary with type of loading and are intimately related to the properties of the constituents, i.e., fiber, matrix and interface/interphace. While the above failure mechanisms are common in most composites, their sequence and interaction depend on the type of the loading and the properties of the constituents. The damage is generally well distributed throughout the composite and progresses with an increasingly applied load. It coalesces to form a macroscopic fracture shortly before catastrophic failure. Study of the progressive degradation of the material as a consequence of growth and coalescence of internal damage is of utmost importance for the understanding of failure.