A Fracture Mechanical Based Lifetime Assessment Approach for Polyamide Used for Integrated Storage Collectors
Abstract
A novel test method simulating the superimposed mechanical, thermal and environmental service loads representative for single-loop integrated storage collectors (ICS) was developed. Engineering polyamide (PA) grades with glass fiber reinforcement, which are of high relevance for endcaps of steel-pipe ICS absorbers and all-polymeric absorbers and storage-tanks, were characterized on laboratory specimen level. An in-situ testing facility for fracture mechanics specimen was used on an electrodynamic testing machine. By in-situ characterization in hot water, a significant decrease in crack growth resistance compared to air (same temperature) was detected. For these specific loading conditions, an extrapolation to static loading was performed to better resemble the loading situation in the ICS and to calculate critical stress levels for cylindrical pipes.
Keywords
Integrated storage collector, polyamide, superimposed loading, lifetime assessment approach, fatigue crack growth kinetics