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Introduction to Composite Design 

Materials and their application are the fundamental constituents of any engineering design. Regardless of whether or not the calculations for stress and strain are accurate, the fabrication must be performed according to proper quality-assured procedures. Installation and commissioning must be completed as specified. Incorrect selection of materials will ultimately lead to the component or structure not achieving its potential in terms of performance or lifetime. As a consequence, the concept of tailoring materials at a fundamental level to meet specific design requirements has intrigued engineers for many years. Whilst the principle is by no means new, it is only comparatively recently that the use of 'materials design' has been fully incorporated in the overall product development process. Examples range from the macroscopic level, e.g. steel reinforcing bars in concrete for tensile strength, through the microscopic and molecular levels, e.g. whisker reinforcement of ceramics for enhanced toughness and the co-polymerisation of polypropylene and polyethylene for improved mechanical behaviour below ambient temperatures, to the atomic level, such as ion implantation of surfaces to increase wear properties.

• Introduction

• Historical Perspective

• Advantages and Disadvantages of Composites

• Stages in Design

• Design Approaches

• Nomenclature

Introduction

Considerations in composite design (NDT, non-destructive testing)

This information concerns a family of designer materials - fibre reinforced composites. They represent excellent examples of the principles of material design where the performance of the whole is greater than the sum of its parts. Fibres, lightweight, immensely strong and stiff (in some cases near the theoretical maximum), but easily damaged and in a form of limited engineering application, and the matrix, comparatively weak and often brittle and not usually attractive for structural load-bearing applications. Together, however, they offer a vast array of materials and tremendous scope for optimisation. This is not limited to mechanical characteristics but also extends to thermal properties, acoustic and electromagnetic response, creep and fatigue, ballistic performance and chemical resistance. For the great majority of parameters in which an engineer may be interested, fibre reinforced composites provide alternatives often only limited by the imaginations of the designers themselves. Of course, it would be misleading to suggest that these systems supply answers to all problems: where there are advantages, there are also disadvantages. It is for this reason that this class of materials needs a complement of engineers, not only familiar with the principles of mechanics and design, but also conversant with fabrication science, chemistry, materials physics, and new test and inspection procedures. Only with an appreciation of all these facets will the required levels of structural efficiency and reliability be achieved. It is the purpose of this part of the site to introduce some issues in a design-orientated context and, while claiming not to be exhaustive, to cover the main points of the engineering process from conceiving the materials to completing the component.