正交三向纤维增强纳米孔树脂基复合材料的力学特性及失效预测

Mechanical properties and failure prediction of three-dimensional orthogonal fiber reinforced nanoporous resin composites

针对飞行器的极端防隔热承载需求,以正交三向石英纤维预制体为增强体、高强度纳米孔酚醛树脂为基体,制备出正交三向纤维增强纳米孔树脂基复合材料(3DIPC)。所制备的3DIPC具有中等密度(~1.46 g·cm^(-3))、较低的室温热导率(<0.30 W·(m·K)^(-1))和线烧蚀率(~0.15 mm·s^(-1))及优异的力学性能(拉伸强度>400 MPa,压缩强度>390 MPa,弯曲强度>300 MPa,层间剪切强度>30 MPa)。通过调整不同方向纱线的细度,系统地研究了纤维预制体细观结构改变对3DIPC力学性能的影响。结果表明:增大Z纱的细度可以提高3DIPC的压缩模量和层间剪切强度,但会导致其拉伸性能与压缩强度的降低;增大经纱的细度可以提高材料经向的拉伸与弯曲性能,但纬向的拉伸与弯曲性能呈降低趋势。最后,基于3DIPC的实际形貌建立了包含表面与内部结构的细观有限元模型,并结合复合材料的渐进损伤模型,采用ABAQUS有限元软件模拟了3DIPC的拉伸失效行为。结果表明:3DIPC的损伤始于纱线中的基体处,并随应变的增加扩展至纯基体与纤维。3DIPC的经纬向拉伸失效分别是由经向和纬向纤维断裂主导的,且表面Z纱和表面纬纱的纤维断裂是造成3DIPC在纬向拉伸前期损伤的主要原因。

To meet the extreme thermal protection and load-bearing requirement of aerospace vehicle,threedimensional orthogonal fiber reinforced nanoporous resin composites(3DIPC)have been prepared using threedimensional quartz fiber preform as reinforcement and high-strength nanoporous phenolic resin as matrix.The as-prepared 3DIPC exhibit a mid-density of~1.46 g·cm^(-3),low room-temperature thermal conductivity(<0.30 W·(m·K)^(-1)),low linear ablation rate(~0.15 mm·s^(-1))and excellent mechanical properties with tensile strength>400 MPa,compressive strength>390 MPa,bending strength>300 MPa and interlaminar shear strength>30 MPa.By adjusting the yarn fineness in different directions,the effects of meso-structure variations in fiber preforms on the mechanical properties of 3DIPC were systematically studied.The results show increasing the fineness of the Z yarn can enhance the compressive modulus and interlaminar shear strength of composite materials,but it leads to a deterioration of tensile properties and compressive strength.Increasing the fineness of the warp yarn can improve the tensile and bending properties in the warp direction,but the tensile and flexural properties in the weft direction will be reduced.Finally,a mesoscale finite element model incorporating both surface and internal structures was established based on the actual morphology of 3DIPC.Combining with the progressive damage model of the composite material,the tensile failure behavior of the 3DIPC was simulated using the finite element software ABAQUS.The results show that the damage in 3DIPC initiates at the matrix of yarns and propagates to pure matrix and the fibers of yarns as the strain increases.The failure of 3DIPC under tensile loading in the warp and weft direction is dominated by the fracture of fibers of warp and weft yarns,respectively.Furthermore,the fracture of fibers of surface-Z yarns and surface-weft yarns is the primary cause of early-stage damage in 3DIPC under tensile loading in the weft direction.