复合材料层板断裂韧性的实验研究

 本文应用各向异性线弹性断裂力学的理论和方法对复合材料层板的断裂特性进行了实验研究。文中采用三种不同的方法,即K标定法、J积分法以及能量法测定了3240玻璃钢和碳/环氧层板两种复合材料的断裂韧性。三种方法均给出了较为满意的结果。

EXPERIMENTAL INVESTIGATIONS ON FRACTURE TOUGHNESS OF LAMINATED COMPOSITES

The objective of this paper is mainly to study the fracture toughness of 3240 Glass-Weave/Epoxy andO2/±45/±45/O2]s Graphite/Epoxy laminated composites by using theory and techniques of anisotropic linear elastic fracture mechanics. In order to determine the fracture toughness of the two laminates three different techniques including K-Calibration, J-Integral and Energy methods are utilized. Anisotropic factors in K-Calibration formula and J-Integral equation are calculated by the use of authors' SI-FJTAP finite element program capable of handling eight-node isoparametric elements and their collapse modes. The equation J = 2U （ 1+1/2（W -a）/（W + a））/（B（W-a））is applied in Energy method. Experiments for compact tension specimens over a range of ratios of crack length to specimen width, a/W, and different pre-notched directions （a） to one of the laminate's principal axes are conducted on INSTRON 1251 material testing machine. The critical load is determined based on the load versus notch opening displacement （P- ） curves.Experimental results show that the anisotropic theory of linear elastic fracture mechanics can be used to study the fracture behavior of laminated composites prior to initiation. The fracture toughness of the two kinds of laminates are found to be constant for varying ratio a/w but strongly dependent on the principal moduli of the laminates and on the angle a. Both parameters, KQ and JQ, characterizing fracture resistance of composite laminates are equivalent and good agreement exists among the three distinct approaches.