Conventional thermosets, widely used in composites, coatings, electronic packing materials, etc., are typically made of non-sustainable fossil resources and cannot be recycled under mild conditions. Degradable thermosets are promising alternatives, while combining ready degradability and high performance is a challenge. In this paper, for the first time, a spiro diacetal structure was utilized to synthesize readily recyclable thermosetting materials with high performance. A renewable bioresource, lignin derived vanillin, was used to produce a rigid spiro diacetal trigger and further built into three thermosets. Among them, spiro diacetal epoxy resin was systematically investigated and was proved to be readily degradable under mild acidic conditions while maintaining stability under neutral or basic conditions and showing outstanding thermal stability. Meanwhile, its glass transition temperature, tensile strength, modulus, elongation at break are comparable to or even better than those of conventional bisphenol A epoxy resin. Moreover, facilely recyclable carbon fiber reinforced composites and convenient-removal coatings were achieved from this epoxy resin accompanied by excellent performances.

Lightweight fiber-reinforced composite structures have been applied in aerospace for decades. Their mechanical properties are crucial for the safety of aircraft and mainly depend on manufacturing technologies such as autoclave, resin transfer molding and automated layup technology. In recent years, the rapid development of intelligent technology such as big data, deep learning, and machine learning has encouraged the development of manufacturing technologies to become low-cost, automatic, and intelligent. However, the current situation and intellectualization of manufacturing technologies is not well summarized. This paper reviews the advances in manufacturing technologies for fiber-reinforced composite structures, including autoclave, out of autoclave, resin transfer molding technologies, automated layup technology and additive manufacturing technology. Then, these technologies are compared in advantages and disadvantages, and their intellectualization development and challenges are also discussed. Finally, the development trend of intelligent manufacturing technologies and intelligent composite structures are discussed. This work can provide a reference for researchers in the related filed.