Effect of environmental humidity on the creep behavior of flax fiber-reinforced polymer composites

Flax fiber-reinforced polymer (FFRP) composites are emerging popular environmental-friendly construction materials. However, their significant creep properties have been a major concern for using FFRP in load-bearing structures. This article presents an investigation of the effect of environmental humidity on the creep behavior of the FFRP. Samples with flax fiber in 0 degrees, 90 degrees, and +/- 45 degrees were manufactured, respectively, by the vacuum infusion method. Accelerated creep tests were conducted on samples in different relative humidities (RH), and the results were analyzed by the time-temperature superposition principle (TTSP). It is found the creep development of samples with 0 degrees and 90 degrees fiber increases with the RH, and their 30-year total strain in 97% RH is about 10 times higher than that in 11% RH. The samples with +/- 45 degrees fiber are found not obviously sensitive to the humidity change. The scanning electron microscope (SEM) check indicates the change in the fiber-matrix interface and cracks between microfibrils in a fiber bundle is the main reason for the change of creep behavior in high humidity. This study may benefit the design of structures made of natural fiber-reinforced polymer composites, especially for load-bearing structures working in high-humidity environments.

Automated summary

This article investigates the effect of environmental humidity on the creep behavior of flax fiber-reinforced polymer (FFRP) composites. The creep of samples with 0 degrees and 90 degrees fiber increases with increasing relative humidity, while the samples with +/- 45 degrees fiber are not significantly affected by humidity. The change in the fiber-matrix interface and cracks between microfibrils in a fiber bundle are the main reasons for the change in creep behavior in high humidity.