碳纤维复合材料钻孔出口椭圆形分层缺陷的研究

STUDY ON DEFECT OF ELLIPTIC DEL-AMINATION OF HOLE EXIT ZONE IN DRILLING CARBON FIBRE-REINFORCED PLASTICS

碳纤维复合材料钻削孔出口附近孔壁周围材料的分层是整个孔分层缺陷的最严重部位,它主要是由于钻削轴向力引起的Ⅰ型(张开型)裂纹破坏造成的。将钻头前端未切削的工件材料部分定义为叠合层,指出叠合层的刚度分布情况是决定各个层间分层形状的关键因素。通过对叠合层刚度取向及其与分层尺寸间关系理论分析发现,以钻头轴线为中心的分层尺寸与周向角度之间存在着椭圆或近似椭圆函数关系,从而阐明了多向碳纤维复合材料孔出口椭圆形分层产生的基本原因。叠合层上刚度最大的方向也是产生最大分层缺陷的方向,叠合层主刚度方向弯曲刚度与椭圆分层长轴角间的函数关系式可以通过一系列分析和相应的力学公式推导求得,在对该函数关系式微分后即可求得椭圆形分层长轴角的数值。

Delamination of hole exit zone in carbon fibre-reinforced plastics is the most severer section in whole hole zone existing delamination defect caused by drilling. Main reason for causing the delamination of hole exit zone is the opening mode (mode Ⅰ) fracture in interplies which due to thrust force. Uncut layers in front of drill is called remaining layer, and its distribution of stiffness is the key factor to determine the delamination shapes of the interplies. As a result, based on analyzing the distribution of stiffness of the remaining layer, forming mechanism of elliptic delamination of hole exit zone in multi-directional carbon fiber-reinforced plastics caused by drilling is presented theoretically. On the other hand, orien-tation producing maximum delamination defect is as same as direction with maximum stiffness on the remaining layer. So based on determinadon of maximum stiffness orientation of the remaining layer, calculating method of major axis angle of the elliptic delamination is established.