Tham khảo tài liệu 'composites manufacturing - materials, product, and process engineering part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | For this reason the adhesive supplier seldom reports the tensile strength of the adhesive. The data reported by adhesive suppliers is usually the shear strength obtained from a single lap joint test. An exception to this is that the tensile tests are conducted by sandwich panel manufacturers to calculate the bond strength between skin and honeycomb core materials. This test is performed for quality control purposes or for selecting the correct adhesive for a sandwich structure. In honeycomb-cored sandwich structures the bonded surface area between the core and skin material is much less than the surface area of the skin and therefore failure usually takes place at the interface. The most common test method for shear testing is the single lap joint test ASTM D 1002 . The lap shear test measures the strength of an adhesive in most extent in shear. In this test the specimen is prepared as shown in Figure . Substrate materials are cut into 1 X 4-in. test coupons from a large flat rectangular sheet. The substrate materials are then joined in a . overlap area with the desired adhesive. Once the adhesive is cured the two ends of the substrate materials are pulled under tension as shown in Figure . Because shear at the bonded surface during the lap-shear test is created by applying tensile load on the substrate material this test is also called the tensile-shear test. This test method is used extensively because of its simplicity and low cost for evaluation purposes. However due to nonuniform stress at the joint the strength values obtained by this test method are of little use for engineering design purposes. However this test method can be used to see the effects of lap length adhesive thickness adhesive material etc. on bonded joints. When the bond strength test is performed for two dissimilar materials . glass epoxy and aluminum the thickness of the substrates is maintained such that the stiffness values of the adherend materials are the same . E1t1 .
