THE EFFECT OF FIBER DIAMETER ON DEBONDING FORCE IN COMPOSITE MATERIALS AND THEIR INFLUENCE ON SOME MECHANICAL PROPERTIES

Abstract

The present work is aiming to study the debonding force between fiber and matrix for different fiber diameters through pull out test technique where the fiber was embedded to a depth of (30)µm into the matrix . Kevlar 29 was selected as reinforcing fiber , and the tested diameters were ( 0.2, 0.4, 0.45, 0.5)mm, while the epoxy was of type Euxit 50 . In the second stage of this research a panel of (4)mm thickness, and of three densities, which were ( 3,4,and 5 ) fibers per centimeter , and the fiber reinforcement layer was located at the first third of the specimen thickness . Flexural, tensile, and fatigue tests were performed. The results showed that, in the pull out test , the base area of the fiber should be less than the side area , which affect the debonding force. Also the results of the flexural and fatigue tests for the unidirectional composite, showed that when the reinforcement layer was in the level of tension, the strength of the specimen increased by no less than 50%, in comparison with other case when the reinforcement was in the compression level , in addition to , the increase of the strength with the fiber density increase. The results of the tests can be implemented to determine the types and position of the reinforcement layers in the composite materials