Evaluation Of Interlaminar Shear Strength Of Laminates

The development and application status of the test method for interlaminar shear strength of laminates was introduced; practical importance of its study was pointed out. The advantages and disadvantages of available interlaminar shear strength test at home and abroad were summarized. The double-notch method was set as the main study object of this article, and the shape and dimension of the specimen were improved and redesigned. Theoretical and experimental methods were used for the analysis of the relationship between the specimen's key dimension and the results, and the favorable shape and dimension of the specimen were established.Double-notch interlaminar shear strength test is an effective testing method used to test the interlaminar shear strength of laminates. The dimensions of its fixtures are small, its structure is simple, and the interlaminar shear break is easy to acquire. Those considerations become more important in cryogenic temperature. But in the test, the stresses on the shear plane are not total shear stress, the existence of the vertical stress takes different effects in tension and in compression test, and the results are different. The testing standard in compression has supporting jig, and the testing standard in tension has grip, which produce friction. This paper aimed at acquiring the real interlaminar shear strength in tension test. A new specimen was designed, two holes were opened at the ends of the specimen along the shear plane .So, the problems caused by specimen holding were solved.To verify the feasibility and reliability of the test method, two kinds of laminates were selected. Both of them used glass fiber plain weaved fabric as reinforced material. The matrix in material No.l was unsaturated polyester, and three kinds of specimens with different notch sizes were made. The matrix in material No.2 was epoxy resin, five kinds of specimen were made. The maximum loads were obtained by electronic universal strength testing machine, and the load-displacement curves were given. The results were processed by Microcal Origin software. Fracture surfaces were examined by scanning electron microscopy to verify the failure mechanisms.Finite element analyses were performed to analysis the stress distribution. Properties of the test materials were derived using RVE method. ANSYS5.4/ED software was used to set up model, mesh elements, load forces and solve the problem. The result was analyzed in interactive mode.The consistency of the experimental and numerical results was analyzed. The effects of notch distance, material properties and loading method to the apparent interlaminar shear strength were studied. The effect of the vertical stress to apparent interlaminar shear strength was investigated. Analysis showed that notch size 4.8mm could produce a more reliable result.