Defects and Damage in Composite Materials & Structures

Abstract

The concept of self-assembly derives from observing that, in natural biological processes, molecules self-assemble to create complex structures with nanoscale precision. For example a protein, guided by information content into the DNA, self-assembles in a specific structure with the lowest free energy consume. By similar mechanisms it is possible to create new materials as polymers, block copolymers and nanocomposite materials made by the use of natural or man-made compounds. Thus, nanocomposite is a conventional material reinforced by nanoscale particles or nanostructures which are dispersed through the bulk material (matrix).
The idea is to use building blocks with dimensions in the nanometer range for creating new materials with unprecedented flexibility and improvements in their physical properties, mimicking the hierarchical composition of the human bone. Nanostructured fibrous materials, or nanofibers, are another important class of Nanomaterials now available thanks to recent development in electrospinning and related fabrication technologies. The geometry and degree of order of all these structures depend on the concentration and the volume ratio between the polymers and/or components used to form, for example, sandwich-like membranes. Advanced composite materials refer to those fiber/resin composite systems that have greater strength and stiffness properties over conventional glass fiber material. These new composite materials provide many significant advantages over conventional metal used in structures applications, as well as possess some distinct attributes. The fibers and matrix remain, in fact, individual constituents. Moreover, while the fibers provide the strength and stiffness of the composite, the matrix protects the brittle fibers, providing load transfer between adjacent fibers. In any way, the basic premise of the term composite material is that the combination of different materials to form a new material is done in such a way that each constituent material does not lose its individual form or property. It is, however, to remember that the right freedom design gives composite materials their greatest advantages and uniqueness, providing an increase in the damage tolerance and toughness of the final product.