Damage Mechanism and Fatigue Behaviour of Uniaxially and Sequentially Loaded Wound Tube Specimens

Abstract

In mechanically loaded composites various damage types occur depending on different external load cases. One aspect of this paper is to show the differences in damage and fatigue behaviour under pure tension/compression and pure shear fatigue loading. For this purpose, fatigue tests with nominally defect-free wound tube specimens and non-destructive tests, i.e. thermography, optical fracture analysis with high-speed camera and discrete damage monitoring are performed. Based on the experimental data a comprehensive analysis of the successive failure mechanisms (matrix cracking, delamination and final failure) is conducted. Thereby, the location of final failure can be found in an early stage of the fatigue life observing high temperature areas (hotspots). In the following, the effects of two different uniaxial load directions under sequence loads, which mean a sequently change from pure shear load to pure tension/compression load after several life cycles, are investigated.