Investigation On Structure-property Relationship Of Flight Feathers And Bioinspired Structured Materials Design

As aerospace high-end equipment development accelerates,the traditional material design concept is no longer sufficient to meet the urgent demands for material performance upgrades in key equipment components.For example,in the aviation field,the carbon fiber reinforced composite(CFRP)blades of civil aircraft turbofan engines encounter challenges such as interlayer delamination and damage,which seriously affect the engine performance and pose significant safety hazards.In the aerospace field,solar wings,serving as the energy source of space stations,present new challenges for the folding and deformation ability of the skeletal structure.The concept of "learning from nature" has long inspired humans in solving engineering and technical problems.In nature,organisms synthesize a variety of natural structural materials with limited composition and gentle environmental conditions.These materials not only exhibit excellent mechanical properties far exceeding those of engineering materials,but also achieve the most optimal mechanical performance coordination through sophisticated multiscale structure design.Thus,deeply exploring the typical biological structure-property relationships in nature and applying them to the design and manufacturing of high-performance engineering materials are anticipated to offer a unique solution to enduring engineering challenges in the aerospace field,which has important research value and practical significance.The flight feather,as the most important structural feature of birds,plays a crucial role in flight.By combining individual discrete vanes to form a complete wing,birds can achieve largearea changes in wing structure.The interaction between microstructures of feathers prevents excessive separation and facilitates an auxetic effect through the rotation of barbs,maintaining the integrity of feather structure and aerodynamic bearing capacity in the expanded state of the wing.Therefore,the interface mechanical properties of feathers and the auxetic effect based on the rotation of barbs provide a natural template for the design of corresponding structured materials.In accordance with the research idea of"Revelation of biological structure-property relationships–Bioinspired structured material design",this dissertation draws inspiration from flight feathers.It explores both the macro and micro mechanical properties of flight feathers and improves the mechanical properties of two bioinspired structured materials.The main research contents are as follows:(1)The research detailed the structure characteristics of single vane and overlapping pairs in typical flight feathers,discovered that single feather vane has self-repair capability and super durability,as well as excellent robustness between overlapping feather pairs.It is revealed that the effect of the cross-scale hierarchical structure between barbs of single vane and the out-ofplane locking structure between overlapping pairs,which collectively contribute to the remarkable mechanical properties exhibited at the wing feather interface.The research also elucidates structure-property relationships between the microstructure and interface of flight feathers,offering valuable design inspiration and theoretical support for addressing interlayer delamination in CFRP.Specifically,inspired by the cross-scale hierarchical structure of single vane,a bioinspired interleaf was prepared by combining electrospinning with hydrothermal growth method,and a bioinspired unidirectional laminate was prepared by hot pressing.The Mode I and Mode II interlaminar fracture toughness of bioinspired CFRP have been increased by 107.0% and 47.40% respectively.Inspired by the interlayer locking structure between overlapping feather pairs,an interleaf with out-of-plane reinforcement was designed and prepared by combining electrospinning with electrostatic flocking method,and a bioinspired woven composite laminate was prepared by vacuum-assisted molding,which increased the Mode I and Mode II interlaminar fracture toughness by 290.00% and 101.83%,respectively.These improvements are attributed to the introduction of nanofiber failure,multi-crack initiation,pinning and locking,etc.,thereby endowing the bioinspired laminate with excellent anti-delamination properties.(2)The research found that flight feathers as a natural metamaterial exhibit a unique auxetic effect at the macro level.A quantitative description method is proposed to calculate the Poisson’s ratio value through engineering strain.The negative Poisson’s ratio value of 8 kinds of flight feathers are calculated.Among them,the minimum Poisson’s ratio value of pigeon flight feather reaches-4.09,which is much lower than other natural metamaterials.A parametric modeling method of the key structure of flight feathers based on SEM images was proposed.Combined with finite element simulation analysis technology,we revealed the mechanism of barbs directional rotation in limited space inducing feather to produce low negative Poisson’s ratio,and clarified the structure-property relationship of the macroscopic auxetic effect of flight feathers,which provides design inspiration for the development of new bioinspired structured metamaterials.Inspired by this,three structural features related to auxetic effect of overlapping feather pairs were extracted,including feather interface microstructure,barb branch angle variability,and redundant structure.Two bioinspired metamaterials based on re-entrant and chiral structures were designed and prepared respectively.Mechanical performance testing and motion analysis were conducted,and the results showed that they exhibit negative Poisson’s ratio and large deformation capabilities during tension and compression.The aspect ratio increased by 26.28% and 85.26% compared with the traditional re-entrant and chiral structure with the same geometric parameters.In summary,this dissertation takes bird flight feathers as bionic model.The structureproperty relationships of wing feathers at macro and micro levels were clarified.A bionic design and preparation plan for the interface structure of CFRP and metamaterial cell structure is proposed,which solves the needs of the above two structured materials for anti-delamination performance and large folding ratio.It is expected to provide theoretical reference and technical support for the design and manufacturing of new bionic structured materials in the aerospace field and has broad application prospects.