Experimental study on the effect of hygrothermal environments combined with the sustained mechanical loads on the strength of composite rings

Despite the high strength-to-weight ratio and corrosion resistance, the performance of composite pipes is strongly affected by the hygrothermal conditions. In this study, the E-glass/Epoxy composite pipes are produced by the filament winding method. The specimens are cut according to ASTM D2290 standard and exposed to three different environmental conditions. The first group of samples is kept intact, the second group is immersed in water, and the third group is subjected to transverse diametrical load and then immersed in water at different temperatures. M the specified time intervals, samples are subjected to the split-disk test method (ASTM D2290) to determine the Hoop Tensile Strength (HTS) of samples. The results show that the moisture uptake behavior at low temperatures followed the Fick's law and at higher temperatures the non-Fickian behavior is seen. The applied preload has no significant effect on the type of moisture absorption behavior. Applying the hygrothermal and strain corrosion conditions to the samples, the HTS of the samples decreases. SEM images shows that the moisture absorption decreases the bonding between the fibers and matrix and also reduction of bonded epoxy on the outer surface of the fiber in saturated specimens is clearly seen.

Automated summary

The study shows that the performance of composite pipes is significantly affected by hygrothermal conditions, with different moisture uptake behaviors observed at low and high temperatures. The type of moisture absorption behavior was not significantly influenced by the applied preload. Applying hygrothermal and strain corrosion conditions resulted in a decrease in Hoop Tensile Strength of the samples, as seen in SEM images showing decreased bonding between fibers and matrix.