| Abstract: | Acoustic Emission Investigations on Failure Mechanisms in Carbon Fibre Reinforced Plastics For a reliable application of modern high-strength materials such as carbon fibre reinforced plastics the knowledges of failure mechanisms as well as detailed informations about the influence of defects occuring during the manufacturing process are necessary. To study the damage progression in fibrous composites a non destructive manner, a very sensitive test failure processes in the laminate have only microscopic dimensions. In our investigations the damage progression was studied by means of acoustic emission analysis (AEA) for different types of ply orientated containing several artifical defects, as cut-through fibres, disbonded fibres and porous matrix. In a further step internally pressurized tubes were tested to investigate the applicability of AE-results to real components. Additionally, fractographic investigations improve the interpretation of the acoustic emission data. It is shown, that AEA succeeds in monitoring damages already at a very early state of damage. At increasing loads the different types of defect emit characteristic AE, which is correlated with a void-type dependent damage progression in the laminate. These knowledges of the failure mechanisms and their typical acoustic emission allow a classification of the different types of manufacturing defects concerning their influence. So, especially the porous matrix could be shown to be the most significant failure type as it causes the largest decrease of strength. The onset of AE at porous materials, however, was found at very low load levels, so that this type of defect can be detected properly. |
