单丝定向铺放机针刺伤对复合材料力学性能的影响

Effect of Needle Puncture on Mechanical Properties of Composites by Tailored Fiber Placement Machine

为研究单丝定向铺放机针刺伤对复合材料板材力学性能的影响,本文以碳纤维和环氧树脂为增强材料和基体树脂,根据实际生产中出现的机针刺伤从低到高逐渐变化,设计制备了五种不同机针刺伤等级的预制体,并利用真空辅助模塑成型工艺(VARI)制备复合材料板材。通过测试材料截面C扫图,以及拉伸和压缩性能,结合断裂截面SEM图,分析机针刺伤对复合材料板材力学性能的影响机理。结果表明:当针距为10 mm单次缝合时,刺伤程度最小,材料拉伸断裂时纤维抽拔较多,材料拉伸强度和压缩强度最低。当针距由10 mm减小至8 mm时,缝合针数增加,刺伤程度增加,拉伸断裂时纤维抽拔减少,拉伸强度提升约30%,拉伸模量提升10%;压缩断裂截面基体破损减少,压缩强度提升了20%,压缩模量提升25%;当针距减小至4 mm时,复合材料的拉伸性能和压缩性能变化很小;当针距不变,缝合次数增加1倍时,复合材料的拉伸强度及拉伸模量变化均低于5%,压缩强度基本不变,压缩模量下降5.7%。在保证材料尺寸稳定及机针刺伤对预制体力学性能的前提下,选择8 mm针距有助于提高生产效率。

In order to study the effect of needle puncture on the mechanical properties of composite sheets,five kinds of carbon fiber preforms with various degrees of needle puncture were prepared by using carbon fiber and epoxy resin as reinforcement and matrix resin,according to the actual needle puncture in the actual production which gradually changes from low to high.And the composite material sheet was prepared by vacuum assisted resin transfer moulding(VARI)..The influence mechanism of needle puncture on the mechanical properties of the composite sheet was analyzed by testing the cross-section C,as well as the tensile and compressive properties,combined with the SEM image of the fractured section.It is concluded that when the stitch length is 10 mm in single stitching,the degree of puncture is the smallest,the fiber is pulled out more when the material is stretched and broken,and the material has the lowest tensile strength and compressive strength.When the stitch length is reduced from 10 mm to 8 mm,the number of stitches and the degree of puncture are increased,the fiber drawing is reduced at the time of tensile fracture,the tensile strength is increased by about 30%and the tensile modulus is increased by about 10%;The compressive strength is increased by 20%and the compression modulus is increased by 25%because the damage of the compression matrix is reduced;When the stitching times are doubled by keeping the stitch length constant,the tensile strength and tensile modulus of the composite are lower than 5%,the compressive strength is basically unchanged,and the compressive modulus is reduced by 5.7%.On the premise of ensuring the stability of material size and the mechanical properties of the preform caused by needle puncture,the selection of 8 mm stitch length is helpful to improve the production efficiency.