**1. Introduction**

Among all kinds of low-dimensional materials [1–8], using carbon-based lowdimensional materials to improve their physical, mechanical, and electrical properties has become a trend [9]. These carbon-based nano/micron additives include carbon fibers (CF), single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs) [10–12], graphene oxide (GO) [13–15], and graphene nanoplates (GNP) [16]. The results show that the composites with high strength ductility, dimensional stability, and economy can be produced. They have an attractive application prospect in the fields of microelectronic devices, aerospace, energy, chemical industry, etc.

Different carbon material units have various structures and mechanical, thermal, and electrical properties. By combining with different material composite methods, carbon composite materials with different structures can be prepared. Through the optimization of material structure, carbon composite materials with high performance can be obtained [17, 18]. This chapter mainly introduces the preparation methods, properties, and application fields of carbon-based nanomaterials, such as CNTs,

CF, and GBFs, which are commonly used to assemble macro carbon composites. The preparation methods of GBFs and their composite fibers, as well as their applications in sensors, energy storage, energy conversion, and other aspects, such as supercapacitors, lithium-ion batteries (LIBs), actuators, and solar cells, are mainly introduced. Finally, the existing problems and future development of carbon-matrix composites are summarized.
