Fibrous reinforcement of materials has been employed over many centuries to increase performance. Many early plastics materials of the late nineteenth and early twentieth centuries relied on ‘fibrous’ inclusions, while the development of glass fibres for polymer reinforcement in the 1930s introduced the material known as fibreglass. Eventually, with the development of boron fibres for metal reinforcement and the discovery of high-strength carbon fibres in 1964, the term composites came into general use. More recently, carbon nanotubes and related materials and graphene have led to the development of nano-composites. The Composites Age has arrived.

This chapter describes the synthesis of the principal fibres and provides the range of acicular reinforcing particles, nanofibres, nanotubes, and nanosheets. The properties of the most common fibres – carbon, glass, ceramics, and natural and advanced polymers – are considered. The differing grades and their structural property relationships are also discussed. Surface treatments for adhesion and compatibility are described.

Polymeric matrices absorb moisture, so here we examine how this affects the performance of a composite material. For an aerospace artefact, absorption and desorption is an important issue. For example, on the tarmac the relative humidity (RH) is high, whereas in flight the RH is low. Also, the ambient temperature can vary significantly, whereas the skin of a military aircraft may reach temperatures of 120 °C in flight. Therefore, we consider the effects of RH, temperature, and thermal excursions on moisture absorption and how they influence the micromechanics. Initially we can assume that the fibres are insensitive to water, which is realistic for most common reinforcements apart from aramid fibres.

Protocols for repair and recycling of composites are described. Future developments that embrace self-healing systems are also considered. End-of-life options such as fibre and matrix recovery are also discussed. The economics of differing approaches are briefly considered using a whole-life cost model.

In this chapter the micromechanics of unidirectional fibre composites (see Section 5.1) are extended to laminates, where strain transfer occurs at a matrix crack other than at a fibre-break. The stress distribution under load is also discussed to describe the accumulation of damage under differing loading conditions.

Since the discovery of carbon fibres in the 1960s, the applications have grown. Because of the high specific strength and stiffness, aerospace applications have dominated, especially initially in military aircraft. The intent here is to demonstrate how the choice of material has been identified. Most critical demonstrators have come from the field of aerospace because of the benefits of carbon fibres and the development of confidence in their use in safety-critical designs. The latter has involved much testing and durability studies. Middleton has provided several case histories detailing the development of composite applications in aircraft structures [1]. The use of composite components has increased with improved confidence in the durability and reliability of these materials and structures. The Airbus A380 was introduced in 2006 using a carbon-fibre-reinforced polymer (CFRP) centre wing box, while the fuselage employed an aluminium–glass fibre composite laminate (GLARE). The centre wing box is a critical carbon-fibre composite structure that joins the wings to the fuselage. Together with several other composite components, such as the horizontal and vertical stabilizers, keel beam, and pressure bulkhead, the total composite usage is 22% w/w. In 2011 the Boeing 787 Dreamliner employed carbon-fibre materials for the fuselage and wings. In total, the latter used 80–90% by volume or 50% by weight of composite materials. The Airbus A350, introduced in 2015, also uses CFRP for the fuselage and wings, and in total composite usage is 53% w/w.

This chapter describes the mechanical performance of a fibre composite. A number of variables that control deformation and fracture are discussed: continuous or discontinuous fibres; fibre angle; fibre length; the transfer of stress between matrix and fibre at a short fibre and/or a fibre-break; and the role of the matrix. Individual components can fracture independently and control the micromechanics; the redistribution of stress after these events is discussed.

Using our strict definition of Atomic Scale Analytical Tomography (ASAT), we explore the current landscape of materials characterization tools and discuss how electron microscopy, field ion microscopy, and atom probe tomography are each approaching ASAT. State-of-the-art electron microscopy can achieve sub-angstrom spatial resolution imaging in 2-D and small volumes in 3-D but lacks single-atom chemical sensitivity, especially in 3-D. Field Ion Microscopy can achieve 3-D imaging on small volumes but not for all materials. Atom probe tomography can achieve single-atom elemental quantification in 3-D but lacks the spatial resolution necessary for ASAT. The chapter concludes with a comparison of the different techniques and discusses how different techniques may be complementary.

The historical backdrop for the role of microscopy in the development of human knowledge is reviewed. Atomic-scale investigations are a logical step in a natural progression of increasingly more powerful microscopies. A brief outline of the concept of atomic-scale analytical tomography (ASAT) is given, and its implications for science and technology are anticipated. The intersection of ASAT with advanced computational materials engineering is explored. The chapter concludes with a look toward a future where ASAT will become common.