基于三维显微镜成像的墨西哥红酸枝内部纤维分布及结构形态表征

Characterization of internal fiber distribution and structural morphology of Mexican red acid branch based on three-dimensional microscope imaging

为研究设计出轻质、高强的纤维增强仿木复合材料,借助X射线三维显微镜分析墨西哥红酸枝(MRAB)孔隙结构的形态与分布,测量了孔隙结构的尺寸和面积,并根据孔隙面积计算孔隙率;借助扫描电子显微镜观察木纤维的结构形态,并利用X射线粉末衍射仪测量出微纤丝角来表征木纤维的取向度。研究结果表明:MRAB内部孔隙主要分布在导管、木射线、轴向薄壁组织和微孔等结构中,在横切面上孔隙主要呈线状和类圆形,在径切面上主要呈线状和纺锤状,在弦切面上主要呈类圆形和纺锤状;MRAB内部的孔隙率为31.27%,孔隙率由髓心到树皮逐渐变大,木纤维沿轴向紧密平行排列,微纤丝角为3.27°;可将MRAB微观结构作为仿生依据,通过控制织物种类、树脂、产生孔隙的方法和铺层方向等因素来实现全新高性能仿木纤维增强复合材料的结构设计。

Objective Under the evolution of billions of years,all things in nature have gradually formed the structure that is most suitable for the environment and has excellent performance.Therefore,studying the microstructure of such biomaterials and applying them to the bionic design of composite structures is one of the effective ways to develop high-performance composite materials.Wood is one of the materials with good mechanical properties in nature,and its density is small.At present,most of the imitation wood materials on the market are bionic from the function and appearance.Among them,the most is wood-plastic composite material,which is used for producing products with similar appearance and good mechanical properties at a lower cost,but it can not replace wood in terms of lightweight and elastic modulus.The superior performance of wood is closely related to the composition and distribution of its internal structure.Starting from the internal structure of wood,structural imitation wood is expected to have the advantages of mechanical properties,lightweight and elastic modulus of wood.Method In order to study the structural characteristics and distribution of Mexican red acid branch(MRAB),the structures of pores in MRAB were studied by X-ray three-dimensional microscope.The size and area of pores were measured,and the morphology and distribution of pores in each component structure were analyzed.The porosity is calculated according to the pore area of each structure,and the pore distribution was analyzed.At the same time,the structure of wood fiber was observed by scanning electron microscope,and the microfibril angle was measured by X-ray powder diffractometer to characterize the orientation degree of wood fiber.Results The results showed that:1)the pores of MRAB are mainly distributed in vessels,wood rays,axial parenchyma and micropores,and the pores are mainly linear and round-like on the transverse section.On the radial section,it is mainly linear and spindle-shaped;on the string section,it is mainly round and spindle-shaped.The diameter of the catheter hole was 109.53μm,and the density was 2.83/mm^(2);the average pore diameter of wood ray was 13.01μm and the pores of the axial parenchyma are usually composed of two spindle-shaped cell cavities with an average pore diameter of 20.19μm;2)the porosity of MRAB is 31.27%,and the pore distribution increases slowly from inside to outside;and 3)wood fibers are closely arranged in parallel along the axial direction,and the microfibril angle is 3.27°,which is smaller than the microfibril angle of most wood,giving wood superior mechanical properties.The transverse mechanical properties are mainly provided by wood rays,and lignin acts as a stress buffer between wood fibers.Conclusion Since the Mexican red sour branch is a natural cellulose composite material with excellent performance,it can be used as an object for the design of composite imitation wood.Through the analysis of its internal structure,it can be cut from three aspects:pore,wood fiber,wood ray(fiber reinforcement)and lignin(resin matrix)related to fiber reinforced composites.The structural design of high-performance wood-like fiber reinforced composites was realized by unidirectional fabric,resin,pore generation method and ply direction,and then prepare lightweight and high-strength fiber-reinforced composites.