Carbon–carbon composites (CCCs) are a unique form of carbon fiber-reinforced materials that exhibit excellent thermomechanical properties under extreme environmental conditions. Due to the need for the retention of mechanical properties at temperatures exceeding 2000 °C, CCCs have been utilized in heat shields, rocket nozzles, aircraft brakes, and leading edge material in hypersonic vehicles. In order to expand the applicability of CCCs, the fabrication process must be modified such that there is a reduction in cost or processing time. It is hypothesized that maximizing the permeability of the composite, during processing, will grant the largest reduction in the fabrication time as it leads to a larger volume of pores filled during re-densification. This review attempts to capture the various parameters that have led to increased permeability, as well as outlining process modifications that have demonstrated influence over the carbonized microstructure. In addition, this review seeks to differentiate itself by systematically outlining research advances that have been made in each step of the fabrication process. In doing so, scientific gaps that exist can be expounded upon while simultaneously summarizing what is necessary to advance the field. Graphical abstract

The effect of tensile loading on the mechanical and electrical behaviour of carbon nanotube fibres spun continuously from an aerogel is discussed. While these fibres exhibit moderate strength (0.19 GPa) and elastic moduli (9.16 GPa), their piezoresistive behaviour, evaluated through active resistance measurements during tensile loading, demonstrates their potential for sensing applications in advanced composite materials. Insight into the failure behaviour of the aerogel-spun fibres is gained through microscopic examination of the failed fibres, as well as analysis of their electrical response. A new phenomenon for carbon nanotube fibres is reported—the aerogel-spun fibres are observed to undergo mild to severe kinking due to tensile failure. This kinking is attributed to compressive failure due to recoil from the fibre free ends. A simple analysis of experimental results yields a fibre compressive strength range of 172–177 MPa.

Ballistic impact induces multiaxial loading on Kevlar^® and polyethylene fibers used in protective armor systems. The influence of multiaxial loading on fiber failure is not well understood. Experiments show reduction in the tensile strength of these fibers after axial and transverse compression. In this paper, we use molecular dynamics (MD) simulations to explain and develop a fundamental understanding of this experimental observation since the property reduction mechanism evolves from the atomistic level. An all-atom MD method is used where bonded and non-bonded atomic interactions are described through a state-of-the-art reactive force field. Monotonic tension simulations in three principal directions of the models are conducted to determine the anisotropic elastic and strength properties. Then the models are subjected to multi-axial loads—axial compression, followed by axial tension and transverse compression, followed by axial tension. MD simulation results indicate that pre-compression distorts the crystal structure, inducing preloading of the covalent bonds and resulting in lower tensile properties.