热轧复合板的界面结合强度的实验与理论研究

Experimental and Theoretical Investigation of Interfacial Bond Strength of Hot Rolled Composite Plates

界面结合强度是影响层合板整体力学性能的主要因素,但是当层合板总厚度小,弹性模量较低,绝对刚度较小时采用常规测试方法难以获得其准确的界面结合强度.针对具有上述特点的薄层状复合材料提出了一种新的测试方法,即采用胶黏剂将测试试样固定于刚度远大于复合板以及胶黏剂的钢棒上形成对接接头,并对其进行单轴拉伸和四点弯曲测试.实验结果表明,对接接头中的胶黏剂固化时,在边缘环状区域内由于气泡的溢出而呈现理想结合状态,因此在该区域内可以承受更高的断裂应力.四点弯曲时高应力出现在该边缘区域内,因而可以测试界面结合强度高于胶黏剂平均拉伸强度的复合板的结合性能.同时由于弯曲时钢棒的弹性模量远高于胶黏剂,界面的应力分布规律和同一均匀材料的分布规律不同,常规的弯曲应力公式不再适用.依据新的变形方式和新的应力分布规律推导了新的弯曲应力公式.并针对两种具有不同界面微结构的Al/Mg/Al热轧复合板为例进行了界面结合强度的理论和实验研究及验证.

The interfacial bond strength is the main factor of influencing the overall mechanical performance of laminated plates.However,the traditional measurements were hard to obtain the accurate interfacial bond strength due to the tiny total thickness,low elastic modulus,and low absolute stiffness.Therefore,a novel test method was present to the mentioned characterized thin laminated plates,that is,the specimen was fixed at the steel bar by adhesive to form butt joint.The elastic modulus of steel bar was far away than that of the adhesive composite plates.Then,the uniaxial tensile test and fourpoint bending were performed to test the interfacial bond strength of the thin laminated composite plates.The experimental results indicate that the bubbles located at annular region of the edge are escaped during the cured procedure.Accordingly,the excellent circular bond zone is formed at the edge of interface.In which zone can bear higher fractured stress.For four-point bending,the high stress zone occurs at the circular bond zone.Therefore,despite the interfacial bond strength of the thin laminated composite plate is higher than the average ultimate strength of adhesive,the interfacial bond strength of the thin laminated composite plate can be obtained.And the traditional bending stress formula can not be used any more due to the fact that the stress distribution at the interface is different from the homogeneous materials because the elastic modulus of steel bar is large more than that of the adhesive at bending.The new bending stress formula is derived according to the new deformed style and the new stress distribution.For examples,the interfacial bond strength of two different interfacial microstructure of hot rolled Al/Mg/Al are investigated,meanwhile,the validity of the new formula is confirmed.