制孔分层损伤对CF/PEEK复合材料拉伸性能和表面应变分布的影响

目的 研究钻削制孔表面分层损伤与拉伸载荷下开孔碳纤维增强聚醚醚酮（CF/PEEK）复合材料表面应变分布的相关性。方法 通过对CF/PEEK复合材料层合板进行钻削制孔实验，分析不同进给速度对钻削温度、钻削轴向力、制孔出口表面分层和孔壁表面损伤的影响。采用数字图像相关技术（DIC）和力学实验相结合的方法，研究分层损伤程度对开孔CF/PEEK复合材料层合板拉伸性能和表面应变分布的影响。使用扫描电镜观测开孔试件的断裂形貌，分析开孔试件受拉伸载荷时的破坏模式。结果 随着进给速度的增加，钻削温度降低，钻削轴向力提高，出口表面分层和孔壁损伤程度加剧。随着分层损伤程度的增加，层合板的拉伸强度呈现出降低的趋势，试件的拉伸强度从558.4 MPa降低到525.63 MPa，降低了5.87%。在中应力和高应力状态下，试件x方向的最大负应变随着分层损伤程度的增加而增加。在高应力状态下，试件y方向的最大正应变随着分层损伤程度的增加而增加。试件的断裂方式主要是基体开裂、分层和纤维撕裂，断口有纤维脱落和纤维拔出，垂直于载荷方向的纤维破坏模式为剥离破坏，与载荷方向一致的纤维破坏模式为拉伸破坏。结论 钻削制孔表面分层损...

Effect of Delamination Damage on Tensile Properties and Surface Strain of Open-hole CF/PEEK Composites

The work aims to investigate the correlation between delamination damage on drilled hole surface and surface strain distribution of open-hole CF/PEEK composites under tensile load. Drilling experiments were carried out on CF/PEEK composite laminates with twist drill. The effects of different feed speed on the drilling temperature, drilling thrust force, surface delamination of the drilled hole outlet and the surface damage of the hole wall were analyzed. The effects of delamination damage on the tensile properties and surface strain distribution of open-hole CF/PEEK composite laminates were investigated through the combination of digital image correlation (DIC) and tensile experiments. The fracture morphology of the specimens was observed by scanning electron microscope, and the failure mode of the open-hole specimens under tensile load was analyzed. With the increase of feed speed, the time used to drill the workpiece was shorter, the accumulation of cutting heat was reduced, and the drilling temperature was reduced. Lower feed speed led to higher drilling temperature and softer matrix, and lower feed speed could produce relatively lower drilling thrust force. The increase of the feed speed led to the increase of the drilling thrust force, which aggravated the delamination damage of the outlet surface. The cutting surface of each specimen was coated with resin and the hole wall showed delamination, crack, fiber pull out and fiber debonding. As the degree of delamination damage increased, the tensile strength of the laminates tended to decrease and the tensile strength of the specimen was reduced from 558.4 MPa to 525.63 MPa, with a reduction of 5.87%. The maximum negative strain in the x-direction of the specimen increased with the degree of delamination damage under middle and high stress states. It could be seen that the maximum negative strain exhibited sensitivity to the degree of delamination damage under middle and high stress states. The maximum positive strain in the y-direction of the specimen increased with the degree of delamination damage under high stress state. It could be seen that the maximum positive strain exhibited sensitivity to the degree of delamination damage under high stress states. At the macroscopic scale, the fracture mode of matrix cracking, fiber splitting and delamination were mainly observed which was mainly due to fiber breakage after drilling process and the strength of the fiber-matrix interface was poor. With the increasing tensile load, the crack/damage areas began to extend along the fiber direction. The specimen exhibited brittle failure on a macroscopic scale. At the microscopic scale, the transverse fiber was perpendicular to the load direction, and the failure mode of the fiber was shear slip. Fiber debonding and shedding were observed. The longitudinal fiber was consistent with the direction of the load and the failure mode of the fiber was tensile failure. The fracture was characterized by fiber pull-out and unbroken fiber. Delamination damage on the drilled hole surface reduces the tensile strength of CF/PEEK composites. The surface strain distribution of open-hole CF/PEEK composite laminates with different delamination damage degrees shows obvious differences. The research results can provide a reference for the optimization of CF/PEEK composite laminates drilling process.