树脂基复合材料钻削缺陷产生机理与控制策略研究

发布时间：2019-01-07 19:12

【摘要】：碳纤维增强树脂基复合材料(CFRP)因其良好的综合性能在航空航天领域得到了广泛的应用。CFRP构件与其他航空结构件装配时,大都需要钻削、铣削等后续机械加工方式,以满足装配的精度要求,其中钻削占后续机械加工总量的50%以上。然而,CFRP具有硬度高、层间结合强度低和各向异性等特点,使其成为典型的难加工材料。在CFRP钻削加工中,以分层、撕裂、毛刺等为代表的加工缺陷,严重制约了CFRP构件的整体性能和服役寿命。在当前的研究中,尚缺乏针对CFRP加工缺陷形成及抑制的有效理论支撑与系统方法。因此,研究CFRP钻削加工缺陷形成机理,构建加工缺陷控制理论支撑体系,建立加工缺陷控制策略,已成为CFRP加工研究领域值得关注的课题。本文以CFRP为研究对象,研究加工缺陷在切削力与切削热作用下的扩展机制与控制策略。首先针对以分层为代表的CFRP加工缺陷,创新地应用“研磨观察法”对分层的三维形貌进行了观察,结合不同钻削深度试验得到了钻削过程中分层的变化趋势,并发现了“隐性分层区”的存在。进而利用cohesive单元进行复合材料切削微观尺度有限元建模,分析不同铺层角度的纤维断裂形式。最终从理论角度对复合材料加工缺陷进行分析,得出力与温度对缺陷产生与扩展的重要影响,为后续的切削力与切削温度分析奠定基础。切削温度对CFRP的性能具有直接的影响。针对切削温度对CFRP加工缺陷的影响,对切削加工过程中的温度分布特性及对表面质量的影响进行分析。借助传热学对高速运动线热源温度场进行研究,分析不同铺层角度CFRP的散热性能。利用半人工热电偶测温方法进行切削温度验证试验,并利用SEM分析0。、90。铺层的复合材料在玻璃化转变温度前后加工质量的变化。最后分析不同切削温度条件下切削力对CFRP加工质量的影响,指出了玻璃化转变温度在CFRP切削加工中的重要影响。对CFRP的切削力进行精确的理论预测,是对加工缺陷进行控制的前提。基于CFRP的力学性质,利用试验观察分析不同铺层角度条件下的CFRP断裂特征,并将其断裂过程分为弯曲切断及弯曲折断两种形式。借助接触力学、复合材料力学、断裂力学等相关理论,根据CFRP在切削过程中纤维变形区、前刀面滑移区与后刀面回弹区的受力情况,建立描述各区域的切削分力数学模型,实现CFRP切削力的有效预测,并进行了切削力模型的试验验证。通过切削力理论预测模型的构建,为CFRP加工缺陷控制策略提供理论支撑。基于CFRP的切削温度与切削力分析,进行CFRP加工缺陷控制策略研究,首先根据切削力理论预测模型完成CFRP钻削刀具前角、后角对切削力的影响分析,通过增强刀具的锋利性,实现了对毛刺及撕裂缺陷的有效控制,并进行了相应的验证试验；进而根据钻头三维结构,完成钻头顶角对单位长度切削刃轴向力影响分析,通过优化顶角实现了刀具寿命的有效提高。针对改进结构的钻头,结合切削力与切削温度的影响,利用响应曲面法完成了以钻削轴向力与钻削温度为优化目标的加工参数优化分析,利用最优参数进行刀具寿命对比试验,验证了优化刀具寿命提高的可靠性。
[Abstract]:The carbon fiber reinforced resin-based composite (CFRP) has been widely used in the field of aerospace because of its good comprehensive properties. When the CFRP member is assembled with other aviation structural members, the following mechanical processing methods such as drilling, cutting and the like are required to meet the accuracy requirement of assembly, wherein the drilling amount is more than 50% of the total amount of the subsequent machining. However, the CFRP has the characteristics of high hardness, low bonding strength between layers and anisotropy, and makes it a typical hard-working material. The whole performance and service life of the CFRP component are seriously restricted by the processing defects such as delamination, tearing, burr and the like in the processing of the CFRP drilling. In the present study, there is a lack of effective theoretical support and system methods for the formation and suppression of the defects of CFRP processing. Therefore, to study the formation mechanism of the processing defect of CFRP drilling, to build the support system of machining defect control, and to set up the control strategy of machining defect, it has become a subject of attention in the research field of CFRP processing. In this paper, the extension mechanism and control strategy of the machining defects under the action of cutting force and cutting heat are studied by using CFRP as the research object. Firstly, aiming at the defects of CFRP processing represented by the layering, the three-dimensional morphology of the layered three-dimensional morphology was observed by using the 鈥済rinding and observation method鈥，

本文编号：2404034