Mechanical fatigue of PLA in additive manufacturing

The manufacturing industry increasingly demands mechanical components, which must undergo different loads. Each industry has its own requirements and regulations, where the common demand is that the loads are repetitive according with the components functions. It is then well known that it is necessary to employ the fatigue assessment to evaluate if the component would not fail over its expected working life. In recent years, there has been an increasing interest in additive manufacturing due to it can be an alternative to manufacture designs more organics and enhanced shapes. However, the main weakness with this option is that the obtained components can fail under operational condition with repeated loads. Therefore, these components would not be used as a final product, so up to now this manufacturing process is not suitable for a large-scale production. It is also important to mention that any manufacturing process needs the fatigue prediction to estimate durability considering different sources of dispersion of properties such as the material and manufacturing process. The purpose of this investigation is to proposes an S-N life curve for PLA considering different printers and filament colours to include the scatter in the estimation. This S-N line curve can be used to understand the mechanism of fatigue failure, the structure of the failure was analysed. This curve is based on 5 regions of amplitude depending on the load levels. However, it was not possible to perform it as a percentage of ultimate resistance since it is presented a dispersion in quasi-static loads.