Fiber reinforced composites have been widely used in aerospace, rail transit, automobiles, civil engineering and other fields due to their characteristics of light weight, high strength, high modulus, and good fatigue resistance. However, most of the reinforcing fibers used in preparing these advanced composite materials are artificial fibers, which require a lot of energy in the manufacturing process and will have a serious impact on the environment after use. As countries around the world pay increasing attention to environmental protection, there is an urgent need to develop new technologies to reduce the impact of fiber reinforced composite materials on the environment. This project uses plant fibers from nature instead of artificial fibers to prepare fiber reinforced composite materials. Compared with artificial fibers, plant fibers are lighter, greener and environmentally friendly. At present, the research and development of resource and environmentally friendly green aviation, green vehicles and green buildings has become a consensus in the international advanced technology field. Plant fibers have a multi-level and multi-scale microstructure that is completely different from traditional synthetic fibers. After being combined with a resin matrix to form a composite material, a unique multi-level and multi-scale interface structure is formed, which has a significant impact on the mechanical damage and failure mechanism of the composite material. Research on mechanical theory has raised new challenges and problems. Solving these challenges and problems is crucial to achieving high-performance and multi-functional mechanical properties of plant fiber reinforced composites and replacing the currently widely used glass fiber reinforced composites. The main findings of this project are as follows: 1. Through the design of the interface structure of plant fiber reinforced composites, a multi-level and multi-scale mechanical damage and failure model is constructed, and the failure model of composite materials is developed from the single and mostly microscopic failure model of traditional synthetic fiber reinforced composites to become a multi-level and multi-scale composite interface fracture model that includes meso-, microscopic and even nano-scale, achieving the improvement of interface and other mechanical properties. 2. The concept of multi-level and multi-scale interface mechanical design for composites is proposed, which provides a new scientific method for high-performance composite materials. 3. Through the proposed new design concept of multi-level and multi-scale plant fiber reinforced composite mechanics/acoustics/flame retardant, the multi-functionality of this composite material has been realized, and its competitiveness with glass fiber reinforced composite materials has been improved. It is expected to replace it. This is of great significance for solving resource and environmental problems such as non-recycling and energy consumption caused by the current large-scale use of these synthetic fibers, and has obvious social and economic benefits. This project has successively received funding from the National Key Basic Research and Development Plan, the National Natural Science Foundation of China, etc., and has published 31 SCI papers as its corresponding author in famous journals in the field of composite materials (as of December 31, 2016), and has obtained 4 authorized patents. The research results have received widespread attention and recognition from domestic and foreign colleagues, including academicians of the Canadian Academy of Engineering. He cited SCI-E 357 times. The proposed new concepts of multi-level and multi-scale composite interface fracture damage design and mechanical/acoustic/flame retardant design have been successfully demonstrated and applied in key model missions such as national aviation and rail transit, including: the cabin interior wall panel developed by Jiaolong 600 Institute produced China General Aircraft Co., Ltd., the train interior structure of Kunming Metro Line 1, and the cockpit interior wall panel and anti-ice plate structure of XX military aircraft. The research results have also been recognized by Boeing Company of the United States, pointing out that their research work demonstrates the potential of this green material for application in the challenging field of aviation.