Assessing creep behavior of para-aramid fibers during their economic lifetime

For many fiber applications, fiber creep and creep rate are important properties. It is often desirable to be able to estimate creep in case of long term loading. The total creep during the economic lifetime of a para-aramid fiber is almost fully determined by what happens during the first hours or days. Additional creep accumulation in a later stage is small and often negligible. Relatively short creep experiments therefore reveal the vast majority of accumulated creep. During the primary creep regime, the creep rate keeps on declining until an almost constant plateau creep rate is reached. This plateau creep rate itself, defining the secondary creep regime, is not relevant for most applications. It is very low and most fiber creep already accumulated before the second creep regime sets in. In this paper we present our experimental and modelling efforts to classify the para-aramid creep rate and to provide creep predictions with confidence. Both the creep and creep rate performance of para-aramids are superior to UHMWPE fibers. In particular, the clear upswing of the creep rate seen in UHMWPE at elevated temperature, is practically non- existent in case of paraaramids. That is, in the typical load range, relevant for real-life applications.

Author(s): H.Knoester, B.Cornelissen