Design And Fabrication Of Bioinspired Fiber Reinforced Composites Based On Bubo Bubo Feather With Lightweight And High-strength Properties

Design and Fabrication of Bioinspired Fiber Reinforced Composites Based onBubo bubo Feather with Lightweight and High-Strength PropertiesWith the continuous development of science and technology,the demand for lightweight and high-strength materials in the fields of aerospace and rail transportation is increasing.However,traditional materials can no longer adequately meet their performance requirements.Fiber reinforced composites have good specific strength,specific stiffness and specific modulus.They can significantly reduce weight while ensure sufficient strength and safety,which have been widely used in many fields,especially carbon fiber reinforced composites.However,the traditional carbon fiber reinforced composites(CFRCs)still have some problems that need to be solved,such as carbon fiber as a brittle material will be easy to break if the force is too large;carbon fiber and fiber matrix interface bonding strength is pretty low,etc.Therefore,there is an urgent need to seek new theoretical guidance for the rational design of new lightweight and high-strength CFRCs.In nature,organisms have evolved many superior functional characteristics far beyond those of mankind in order to adapt to the harsh environment in which they live.The feathers of large raptors are an important part of their flight movements and are characterized by their lightweight,high-stiffness and high-strength properties,which are precisely what many high-performance structural materials are designed for.In particular,the study of the structure-function relationships of typical raptor feathers not only provides a unique scientific perspective for an in-depth understanding of the functional properties of biological excellence,but also provides a reliable reference and theoretical basis for the design of lightweight and high-strength materials.In this study,a large owl Bubo bubo was selected as a bionic prototype to reveal the mechanism of the lightweight and high-strength properties of the Bubo bubo feather shaft.The high-strength mechanism was mainly based on the orientation of the cortical layer of the feather shaft and the interlayer connection by fiber struts.Meanwhile,the lightweight mechanism mainly based on the multi-level pore structure of the medullary layer of the feather shaft.Thus,bionic sandwich composites inspired by the feather shaft lightweight and high-strength mechanism were designed and manufactured through simulation analysis and experimental verification.Moreover,their mechanical properties and failure modes were analyzed to reveal the intrinsic mechanism of the lightweight and high-strength characteristics of the bionic sandwich composites.The main contents of this study are as follows:Firstly,Bubo bubo was selected as the research object.The feather shafts and feather vane were morphologically characterized.Moreover,multi-scale observations and parametric measurements of the feather shafts were made in two different directions:Axial and radial directions.It was found that the feather shaft has a cross-sectional gradient along the axial direction.In detail,a gradual transition from nearly circular at the root to nearly square at the tip of the feather was experimentally confirmed.In contrast,feather shaft has a typical sandwich structure along the radial direction,which can be divided into a dense cortical layer and a porous medullary layer.Both of them have complex fibrous structures and the cortical and medullary layers can be tightly bound due to the presence of fiber struts.It was showed that the interlaminar density gradient properties of the feather shaft contributed to the overall lightweight and highstrength properties of the feathers.On this basis,the mechanical properties of the feather shaft were tested and analyzed.The key mechanical parameters of the feather shaft structure were extracted for the construction and optimization of the 3D physical model.With the finite element method(FEM),the functional mechanism of the feather shaft's lightweight and high-strength properties was revealed by mechanics simulation and theoretical analysis.Then,based on the feather shaft sandwich structure and interlayer fiber struts,bionic sandwich composites with micro-/nanoscale fiber struts were designed and fabricated.The bionic sandwich composites consist of skinning,core and relevant interface.Particularly,the skinning was a kind of carbon fiber reinforced resin matrix composites and the core was a polymethacrylimide(PMI)-based closed cell foam panel.In order to improve the overall mechanical properties of the composites,inspired by fiber struts of feather shaft,short carbon fibers(SCFs)were incorporated into the interfacial area between fibers as well as skinning-core.Multi-walled carboxylated carbon nanotubes(MWCNTs)were attached to the SCFs' surface to form a micro-/nano network,which can increase time and energy requirement for fiber pullout or fiber fracture and further improve the overall strength of the bionic sandwich composites.Finally,the mechanical performances of the bionic sandwich composites were tested,mainly including bending performance test and impact performance test.In addition,failure sections were also characterized in details to analyze the failure modes of the bionic sandwich composites.Further,the inner mechanism of the lightweight and high-strength performance of the bionic sandwich composites were revealed by mechanical tests and systemic analysis.This study could provide theoretical reference and technical support for the design and manufacture of new fiber reinforced composites.