Sun Chengcheng, Min Junying, Lin Jianping, Wan Hailang
School of Mechanical Engineering, Tongji University, Shanghai 201804, China.
Key Lab of Vehicle Aerodynamics and Vehicle Thermal Management Systems of Shanghai, Tongji University, Shanghai 201804, China.
Polymers (Basel). 2019 Jan 15;11(1):139. doi: 10.3390/polym11010139.
To improve the strength of the adhesive-bonded carbon fiber reinforced polymer (CFRP) joints, atmospheric pressure plasma treatment (APPT) was used to treat a CFRP substrate surface. This study investigated the effects of nozzle distance (i.e., the distance between plasma nozzle and CFRP substrate) and nozzle speed (i.e., the moving speed of plasma nozzle relative to CFRP substrate) of APPT on the lap-shear strength of adhesive-bonded CFRP joints. Results show that the lap-shear strength of plasma-treated CFRP joints increased to a peak value and then decreased as the nozzle distance increased, and the nozzle distance associated with the peaked joint strength depends on the applied nozzle speed. The lap-shear strength of plasma-treated adhesive-bonded CFRP joints reaches up to 31.6 MPa, compared to 8.6 MPa of the as-received adhesive-bonded CFRP joints. The surface morphology of plasma-treated CFRP substrates was investigated by scanning electron microscope observation, and the mechanism associated with the improved joint strength after applying APPT was revealed through surface chemistry analysis. It is found that APPT not only effectively removed the content of Si element and ⁻CH₃ (i.e., the main compositions of release agent) from the as-received CFRP substrate surface, but also generated many polar groups (i.e., ⁻NH₂, ⁻OH, ⁻COOH, etc.), which has a positive effect on increasing the wettability and interfacial bonding strength of CFRP substrates and consequently results in a significant improvement of lap-shear strength of plasma-treated CFRP joints. In addition, the result of differential scanning calorimetry (DSC) test shows that the surface temperature of CFRP substrate should not exceed 175.3 °C during APPT. In this study, an empirical model governing temperature, nozzle distance and nozzle speed was established to guide the selection of atmospheric pressure plasma treatment process parameters in industrial manufacture.
为提高粘结碳纤维增强聚合物（CFRP）接头的强度，采用常压等离子体处理（APPT）对CFRP基材表面进行处理。本研究考察了APPT的喷嘴距离（即等离子体喷嘴与CFRP基材之间的距离）和喷嘴速度（即等离子体喷嘴相对于CFRP基材的移动速度）对粘结CFRP接头搭接剪切强度的影响。结果表明，经等离子体处理的CFRP接头的搭接剪切强度随着喷嘴距离的增加先升高至峰值然后降低，且与峰值接头强度相关的喷嘴距离取决于所施加的喷嘴速度。经等离子体处理的粘结CFRP接头的搭接剪切强度高达31.6MPa，而未处理的粘结CFRP接头的搭接剪切强度为8.6MPa。通过扫描电子显微镜观察研究了经等离子体处理的CFRP基材的表面形貌，并通过表面化学分析揭示了施加APPT后接头强度提高的相关机理。研究发现，APPT不仅有效地去除了未处理的CFRP基材表面的Si元素和⁻CH₃（即脱模剂的主要成分）含量，还产生了许多极性基团（即⁻NH₂、⁻OH、⁻COOH等），这对提高CFRP基材的润湿性和界面粘结强度具有积极作用，从而显著提高了经等离子体处理的CFRP接头的搭接剪切强度。此外，差示扫描量热法（DSC）测试结果表明，在APPT过程中CFRP基材的表面温度不应超过175.3℃。在本研究中，建立了一个关于温度、喷嘴距离和喷嘴速度的经验模型，以指导工业制造中常压等离子体处理工艺参数的选择。
