Co-authors​ :

 Julia PETRO (AUSTRIA), Eric HELFER , Gernot ORESKI , Margit LANG (AUSTRIA), Thomas ANTRETTER  

Consideration of material degradation is important when designing structural polymeric components exposed to outdoor environmental conditions. This is necessary to be able to guarantee safe and reliable performance of these components over their intended lifespan. Thus, a systematic approach is required to generate relevant mechanical property degradation data and model it in a way that can be implemented in design analysis simulations [1,2]. In this study, aging effects have been assessed using nanoindentation measurements throughout the cross-section of a PC/PBT (polycarbonate-polybutylene terephthalate) material plate. Accelerated artificial weathering with State-of-the-Art Xenon arc lamps have been used to age the material under study according to ISO 4892-2 standard. The variation of the elastic modulus through-the-thickness of the plate has been evaluated showing a significant increase at the exposed side of the plate compared to the unexposed one. A modeling framework is presented to capture the degradation of mechanical properties through-the-thickness of the plate. A gradient is defined to represent the degradation of the modulus through the material thickness using a user subroutine (USDFLD) in Abaqus, where the definition of the material properties is dependent on a field variable via a predefined function. The results show that the model prediction is dependent on element size and therefore, a sensitivity analysis was carried out. A defined load case, i.e. cooling from room temperature (RT) to -40°C is analyzed using a virgin homogenized material definition for the plate versus a functionally graded material model. Non-symmetric deformations can be observed in case of the functionally graded material plate (see Figure 1), compared to symmetric deformation in the case of a plate with homogeneous (virgin, non-degraded) material properties, indicating the necessity of considering material degradation for lifetime assessment of the designed part.