Biomimetic Construction Of New Wood-based Structural Materials And Its Synergistic Study

Following an extensive evolutionary process,natural structural materials have achieved exceptional mechanical properties by assembling brittle components into hierarchical structures,spanning from the nanoscale to the macroscopic level.These materials have gradually become a source of inspiration for the manufacture of next-generation advanced structural materials.The characteristics of natural wood include the uneven distribution of components such as cellulose,hemicellulose,and lignin.The disparity in the distribution of these components results in variations in the physical and mechanical properties of wood in different parts.Processing procedures,such as cutting,drying,and gluing,introduce stress and defects,further influencing the performance of the wood.Moreover,for composite wood,the type,proportion,and arrangement of its constituent materials also affect its overall performance.These factors may act individually or in combination,leading to variations in the toughness of wooden structural materials in different parts.Therefore,this study,based on wood-based materials,investigates and develops new wood-based structural materials through biomimetic design.It comprehensively analyzes the impact of different assembly strategies and interface effects on the mechanical properties of wood-based materials with different structures.By finely tuning the composition and microstructure of the wood,as well as optimizing the structural design,a synergistic enhancement of materials and structures can be achieved.Furthermore,by drawing inspiration from biological structures in nature,the performance and durability of wooden structural materials can be further enhanced.This interdisciplinary research approach not only contributes to the advancement of the science of wooden structural materials but also provides new insights for achieving sustainable structural materials.The research content and conclusions of this study are as follows:1.Inspired by the layered structure of densified wood,this study combines wood fibers,which have been partially stripped of lignin and hemicellulose,with calcium hydrogen phosphate through mechanical thermal grinding.Under the conditions of vacuum water flow directional assembly and hot pressing,a layered structure of densified nanowood fiber/calcium hydrogen phosphate composite material is prepared.This material utilizes the abundant carboxyl and hydroxyl groups on the surface of the wood fiber to form ionic bonds and hydrogen bonds（Velcro effect）with the calcium ions and tetrahedral PO₄on the calcium hydrogen phosphate,thereby generating a strong interaction force.Through the analysis of its fracture mechanism and theoretical simulation model,it is found that during the fracture process,the layered structure undergoes crack deflection,crack branching,and crack bridging,avoiding stress concentration and achieving a flexural strength of 109.9±2.9 MPa.At the same time,the frictional force required for the relative sliding of the layered densified fibers further hinders its fracture.This study achieves effective stress transfer from wood fibers to calcium hydrogen phosphate and analyzes the mechanical interaction mechanism between natural organic molecules and inorganic materials.These results provide a new research strategy for the preparation of wood fiber-based lightweight high-strength structural materials with higher mechanical strength.2.Inspired by the"brick and mortar"structure formed by the alternating arrangement of multi-layer organic matter and inorganic calcium compounds in shells,this study uses mineralized nanowood fibers as reinforcing components and assembles them into a porous layered matrix through freeze casting technology.After hot pressing,the wood fiber"brick layer"is transformed into a resin-like dense layer-pressed artificial wood shell.The prepared artificial wood shell of a few millimeters thick mimics the hierarchical structure of natural shells,forming a large-size composite material.The strength of this material is 68.9±4.6 MPa,almost the same as that of natural shells,while its total inorganic content is only 1/6 of that of natural shells.Compared with engineering alloy materials（such as copper and iron）,the specific strength and toughness of artificial wood shells are superior."Under the influence of impact and vibration loads,the wood shell can absorb a large amount of energy and produce a certain deformation without destruction,which is very necessary for the traditional wood structure field.3.Inspired by the scale-like structure and micrometer-level fiber combination of the Bouligand structure of the giant bone tongue fish,this study has developed a high-damage-tolerance"wood anti-impact material".Using coating-induced assembly and spiral lamination technology,the hard layered wood fiber and soft shear-thickening fluid are precisely assembled into a Bouligand-like structure.Compared with the wood fiber block（119.1 N）,this artificial"wood anti-impact material"（1570.7 N）achieves a 13-fold increase in anti-puncture force,and its anti-impact performance can be comparable to traditional structural materials（such as ceramics,glass,and alloys）.It is worth mentioning that the density of the prepared material is only half of the traditional structural materials,but it can block the impact of a bullet at 214 m/s.The high durability and damage resistance of this"wood anti-impact material"enable it to maintain integrity under impact.This strategy provides a promising method for designing a special safety application of lightweight,high-performance,and sustainable biomaterials.4.Inspired by the use of boric acid cross-linking to strengthen intercellular structures in higher plants,this study has developed a high mechanical strength layered composite material based on boric acid cross-linked nanowood fiber/graphene oxide flake crystal.This composite material uses a mechanical chemistry method to treat the surface of nanowood fibers with borate and deposit graphene oxide.Although the content of borate is very low,the directional assembly of a single nanowood fiber/graphene oxide flake crystal can produce an orderly layered structure,thereby making the material exhibit a synergistic toughening effect.The flexural strength of this composite material is 26.3±0.6 MPa,which is 1.5 times that of pure nanowood fiber,and its performance is also superior to other wood-based materials and can be comparable to medium-density fiberboard（MDF）resin.This high-strength layered composite material has the potential to become a load-bearing material.