Investigation of failure mechanisms in hybrid fiber-reinforced plastics by means of in-situ-CT

The failure mechanisms of fiber-reinforced plastics can be studied in detail with a novel In-situ-CT 4-point bending test, based on the testing standard ISO 14125. The 4-point bending test creates a complex load condition under simultaneous influence of tensile and compressive forces. By non-destructive CT measurement at different load levels the origin and development of defects can be traced. Initial tests performed on a natural and a hybrid fiber reinforced plastic reveal significant differences in defect initiation and development. Ruptures of the yarn on the tensile-loaded side characterize the failure process of the natural fiber-reinforced plastic. In the hybrid fiber-reinforced plastic carbon fibers initially show damage on the compression-loaded side followed by fiber breaks on the tensile-loaded side. Matrix failure as well as pores as potentially weak points apparently have no influence in this example. Relevant relaxation effects could be excluded on the investigated macroscopic scale.