Drilling of Composite Material Using Vibration

复合材料因其强重比高、易成型等优点，被广泛应用于建筑结构中。大尺寸结构通常采用复合材料拼装连接。因此，在装配和连接复合部件时，往往需要进行钻孔、锯切等二次加工。复合材料加工时，在层合层之间的粘结层发生脱层现象。在工业加工中需要防止分层。从振动的角度来看，在切削过程中使用相对较小的振动载荷来切削硬材料，并提高加工表面的精度是可能的。然而，利用振动载荷切割复合材料的研究尚未发表。提出了利用振动防止钻孔过程中复合材料分层的方法。在这种方法中，只要产生较小的振动载荷，并使用小型激振器或超声波激振器就足够了。更重要的是，所提出的方法有望是实用的。首先，通过实验对所提出的方法进行了验证。复合材料被支撑在支撑装置上，在钻孔过程中使用小型振动筛进行震动。在一定的激励频率、刀具材料、刀具直径和刀具转数条件下，测量了分层的发生情况。通过考虑试件的频响函数确定激励频率。测量了白噪声激励下试样响应的功率谱密度函数。选择功率谱密度函数有峰值的频率作为激励频率。为了比较，一些试件在没有振动载荷的情况下加工。通过加工表面的表面粗糙度来检测分层。钻孔后，用金刚石刀具从孔的中心切开标本。测量了加工表面的中心线平均高度粗糙度。实验发现，在多种条件下，振动加工复合材料的表面粗糙度都小于无振动加工复合材料的表面粗糙度。因此，当复合材料在振动下加工时，分层的发生就会减少。最后，用理论方法对实验结果进行了验证。粘接层被认为是阻尼元件。得到了粘接层的耗散能，导出了发生分层的条件。少

Composite materials are used in many structures since there are high strong-to-weight ratio and easy formational. Composite materials are usually assembled and joined together for large size structure. Therefore, secondary machining process such as drilling, sawing etc. are often required for assembling and joining composite components. When composite materials are machined, delamination occurs at adhesive layer between laminated layers. It is required to prevent delamination during machining in industry. From view point of vibration, it is possible to cut hard materials using relatively small vibrational load during cutting and to improve precision of machined surface. However, study on cutting composite material using vibrational load has not been published.In this study, preventing method of delamination of composite material during drilling using vibration is proposed. In this method, it is enough to generate small vibrational load and to use small shaker or ultrasonic vibrator. He … More nce, the proposed method is expected to be practical.First, the proposed method is examined by some experiments. Composite material is supported onto the supporting device and shaken during drilling using a small shaker. For some conditions of excitation frequencies, tool materials, tool diameters and tool revolutions, occurrence of delamination is measured. Excitation frequencies are determined by considering frequency response function of the specimen. The power spectral density function of response of the specimen subjected to white noise excitation is measured. Frequencies at which power spectral density function has peaks are chosen as excitation frequencies. For comparison, some specimens are machined without vibrational load. Delamination is examined by surface roughness of machined surface. After drilling, the specimens are cut by a diamond cutter through center of holes. Center line average height roughness of machined surface is measured.From the experiments, it is found that surface roughness of composite material machined with vibration is less than that without vibration for many conditions for each condition. Hence, when composite materials are machined with vibration, occurrence of delamination becomes less.Finally, results of experiments are examined by a theoretical method. Adhesive layer is considered to be damping component. Dissipated energy in adhesive layer is obtained and condition where delamination occurs is derived. Less