Abstract
Compression testing of continuous fiber reinforced materials is challenging, because a great number of competing failure modes and instabilities on different length scales have to be considered. In comparison to tensile testing, the results are more affected by the chosen test set-up. Effects introduced by the test set-up as well as the type of damage in continuous fiber reinforced materials are mainly investigated for quasi-static loading. This is not the case for cyclic compression loading. Neither standardized methods nor a great deal of literature for reference exists. The aim of this work is to increase the understanding by analyzing the potential effects the set-up in fatigue loading might have on the damage for two common testing strategies by fatigue tests, load increase creep tests and supplementary analytical models. The results show that damage modes can be altered by the testing strategy for the investigated woven glass fiber reinforced polyamide 6. The tools both experimentally and analytically provide the basis to choose the correct set-up in future investigations.
Highlights
The benefits of fiber-reinforced materials are well known and proven for a lot of applications like car bodies, airframes and maritime applications
Fiber kinking was initiated by fiber failure near the specimen’s edge. These findings suggest that the use of an anti-buckling guide might not necessarily affect the initiation of a kink band but it is likely that the propagation is influenced
Localized buckling can be identified as a pre-failure mechanism for compressioncompression loading and is precursor for final failure
Summary
The benefits of fiber-reinforced materials are well known and proven for a lot of applications like car bodies, airframes and maritime applications. The literature on cyclic compression tests is small in comparison [4,5,6,7,8,9,10]. Both factors along with a better material performance lead to the paradigm to use designs where the material is loaded in tension, only. Standardized methods and great efforts to improve those methods make the characterization comparable over many different studies. This is not the case for compressive fatigue testing. A transfer of procedures and methods from quasi-static testing assumes similar damage mechanisms for both loading cases, which is unlikely considering the results in [10,11]
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