变厚度三维机织复合材料的抗冲击性能

Impact properties of three-dimensional woven composites with variable thickness

为解决变厚度层合复合材料受到载荷时易分层导致其力学性能变差的问题,使用800 tex玄武岩纱线作为经纬纱,采用分层角联锁结构设计并织造了整体性优异的连续变厚度三维机织物,并采用树脂传递模塑工艺制备了树脂基变厚度三维机织复合材料,同时织造了同纬铺层和同经铺层2种不同结构的层合复合材料进行对比测试。然后对变厚度层合复合材料分别进行25、50、75、100 J的不同冲击能低速冲击实验,并通过单独分析冲击能为100 J时3种复合材料的损伤面积探究其损伤机制。结果表明:在冲击能为25、50、75 J时,变厚度三维机织复合材料与同纬铺层结构复合材料的刚度退化呈现高度一致性,二者抗冲击能力均优于同经铺层结构复合材料,变厚度三维机织复合材料损伤载荷大于2种铺层复合材料;层合材料受到冲击损伤时,因其层间无纱线连接,能量在材料层间传播时消耗,从而产生较大范围的分层损伤;而变厚度三维机织复合材料具有层间连接的经纱,受到冲击时应力在材料经纱连接作用下内部不断传播导致材料整体受载,因此具有更高的损伤容限。

Objective The production costs of most metal variable thickness plates are high and some composite plates with variable thickness are generally based on laminated composites,which are prone to interfacial delamination and property degradation.This study was designed to solve the problem of delamination of laminated composites,aiming to improve the overall performance against impact.Method Basalt yarn is a green and environmentally friendly materials.And,it has high strength and excellent durability.Three-dimensional(3-D)variable-thickness fabrics with 3-layered angle interlocking structure change from 9 to 3 layers were designed and woven on a conventional loom using basalt yarns as warp and weft yarns.Resin-impregnated variable-thickness 3-D woven composites were prepared using a vacuum-assisted resin transfer molding(VARTM)process.The variable thickness laminated composites were subjected to low velocity impact tests at 25,50,75 and 100 J according to American Society of Testing Materials(ASTM)standards.The damage mechanism of the material was analysed by the damage area at 100 J impact.Results The 3-D woven variable thickness composites exhibited high consistency in stiffness and stiffness degradation under impact energy of 25,50 and 75 J compared to the same weft lay-up structure.This was based on the fact that the layers of yarn are interconnected in the 3-D woven variable thickness composites,whereas there was little adhesive action between the the same weft lay-up structure.At the same time,the damage load of the composite with the 3-D woven variable thickness structure was greater than that of the two lay-up composites.This indicated that the composite with the 3-D woven variable thickness structure had a higher damage tolerance and carries more load before damage occurs.At an impact energy of 100 J compared to 25-75 J,the damage load was reduced in a 3-D woven variable thickness structure with co-layered layers.This was due to the large amount of kinetic energy that was instantaneously released by the impact head when a high energy impact occurs.These kinetic energies caused the surface bearing yarns in the material to quickly break and lost their load-bearing capacity.The damage load on the material was reduced because the yarn on the bottom layer of the material had not yet reached a responsive state.When the material was impacted in the forward direction,the damage showed a cross-shaped or rectangular distribution with a greater extension along the weft direction than the material along the warp direction.As the thickness variation of the composite was determined by the number of yarn layers,the energy consumed decreased with the thickness,so that the stress could propagate through the material for a longer period of time.Along the warp direction of the material,the number of layers of material within the same thickness layer remained the same as the thickness,and the stress waves were consumed rapidly,creating a short damage extension range.Damage to the material in the dorsal direction also showed a cross-shaped or rectangular distribution with greater extension along the weft direction than the material along the warp direction.But the damage of the composite material with the same warp-layered structure had slightly less damage along the weft direction than the warp direction.This was because the material encountered a strong impact under the action of 100 J impact energy,the energy of the impact was enough to quickly break through the fabric of all layers of the same layered structure.It completely destroyed the integrity of the material and made the damage to the material more concentrated.Conclusion Compared with laminar composites,3-D woven composites of variable thickness have higher damage tolerance and better impact resistance because of the internal warp connection.Compared with the metal variable thickness plate,the variable thickness 3-D woven composite material has the characteristics of low production costs,low manufacturing and maintenance cost of production equipment and low energy consumption.It has reference significance for future application research of variable thickness plate.