Abstract: Geopolymer matrix composites (GMCs) offer distinct advantages over conventional materials such as lower density compared with titanium and superalloys, higher service temperature compared with polymer matrix composites, and lower cost and simpler processing compared with traditional ceramic matrix composites. Consequently, GMCs effectively fill the temperature performance gap between metal materials and polymer matrix composites and ceramic matrix composites. Furthermore, the fabrication process of thermosetting resin composite structures can be used to manufacture GMCs parts with low bulk density (≤2.5g/cm³). So GMCs are excellent candidate materials for lightweight and low-cost optimization design of intermediate temperature structures like rotorcraft engine exhaust dusts, firewalls and battery pack shells. Despite more than a decade of research and development on GMCs for aircraft intermediate temperature structures application, their engineering applications have been largely limited to e-VTOL battery pack shells. This is primarily attributed to persistent challenges such as the thermal/chemical compatibility of different components in GMCs, the porous toughening mechanism of geopolymer matrix, the unique failure characteristic of GMCs structures, and the difficulties for the connecting integration, inspection and maintenance of GMCs structures and surrounding structures. For rotorcraft intermediate temperature structures, GMCs therefore remain within the category of new materials, new processes and new technologies. To address the engineering application requirements of GMCs for lightweight and low-cost optimization development of intermediate temperature structures in domestic rotorcraft, this paper reviews and examines the key technologies that need to be broken. Based on the analysis, the following recommendations are proposed for the application and development of GMCs in intermediate temperature structures of domestic rotorcraft: developing a series of high-performance fiber (carbon fiber/Al₂O₃ fiber) reinforced GMCs; constructing the manufacturing processes that ensure high stability for performance of intermediate temperature structures of GMCs; establishing the connection induced damages control technologies between the intermediate temperature structures and surrounding structures; building a scientific and reasonable verification test matrix for GMCs application in rotorcraft intermediate temperature structures, and realizing efficient non-destructive evaluation (NDE) and rapidly in-situ repairing of manufacturing defects and service-induced damage in intermediate temperature GMCs structures.

Key words: rotorcraft, intermediate temperature, inorganic polymer matrix composites, lightweight and low-cost, defects and damage control, high stability, review