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Engineered Interfaces in Fiber Reinforced Composites Part 3

Tham khảo tài liệu 'engineered interfaces in fiber reinforced composites part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 44 Engineered interfaces in fiber reinforced composites 3.2. The mechanical properties of fiber-matrix interfaces 3.2.1. Introduction Test methods using microcomposites include the single fiber compression test the fiber fragmentation test the fiber pull-out test the fiber push-out or indentation test and the slice compression test. These tests have a variety of specimen geometries and scales involved. In these tests the bond quality at the fiber-matrix interface is measured in terms of the interface fracture toughness Gic or the interface shear bond strength IFSS Tb for the bonded interface and the interface frictional strength IFS Tfr which is a function of the coefficient of friction p and residual fiber clamping stress qo for the debonded interface. Therefore these tests are considered to provide direct measurements of interface properties relative to the test methods based on bulk composite specimens. Microcomposite tests have been used successfully to compare composites containing fibers with different prior surface treatment and to distinguish the interface-related failure mechanisms. However all of these tests can hardly be regarded as providing absolute values for these interface properties even after more than 30 years of development of these testing techniques. This is in part supported by the incredibly large data scatter that is discussed in Section 3.2.6. 3.2.2. Single fiber compression test The single fiber compression test is one of the earliest test methods developed based on microcomposites to measure the bond strength of glass fibers with transparent polymer matrices Mooney and McGarry 1965 . Two different types of specimen geometry are used depending on the modes of failure that occur at the fiber-matrix interface one has a long hexahedral shape with a uniform cross-section Fig 3.1 a the other has a curved neck in the middle Fig 3.1 b . When the parallel-sided specimen is loaded in longitudinal compression shear stresses are generated near the .