The use of the friction stir welding (FSW) process as a relatively new solid-state welding technology in the aerospace industry has pushed forward several developments in different related aspects of this strategic industry. In terms of the FSW process itself, due to the geometric limitations involved in the conventional FSW process, many variants have been required over time to suit the different types of geometries and structures, which has resulted in the development of numerous variants such as refill friction stir spot welding (RFSSW), stationary shoulder friction stir welding (SSFSW), and bobbin tool friction stir welding (BTFSW). In terms of FSW machines, significant development has occurred in the new design and adaptation of the existing machining equipment through the use of their structures or the new and specially designed FSW heads. In terms of the most used materials in the aerospace industry, there has been development of new high strength-to-weight ratios such as the 3rd generation aluminum–lithium alloys that have become successfully weldable by FSW with fewer welding defects and a significant improvement in the weld quality and geometric accuracy. The purpose of this article is to summarize the state of knowledge regarding the application of the FSW process to join materials used in the aerospace industry and to identify gaps in the state of the art. This work describes the fundamental techniques and tools necessary to make soundly welded joints. Typical applications of FSW processes are surveyed, including friction stir spot welding, RFSSW, SSFSW, BTFSW, and underwater FSW. Conclusions and suggestions for future development are proposed.

Date palm, the most important tree in Saudi Arabia and the Middle East, produces a huge amount of waste yearly in the form of fibrous materials, dried fruits, and seeds. Such waste is a great source of excellent degradable biomass that can be used in numerous applications as natural fiber composites, active carbon precursors, and even nano-featured sheets. That rich resource is yearly burned on date palm farms due to the lack of effective processing strategies. This review offers a scientific evaluation for date palm waste in terms of specifications and applications, and it proposes pre-treatment processes to produce fibrous and powder raw materials to be used in some engineering and industrial applications. Additionally, some possible advanced industrial applications, such as active carbon and natural fiber composites, will be discussed and reviewed.