Influence of Arctic seawater exposure on the flexural behavior of woven carbon/vinyl ester composites

Abstract

In this paper, the adverse effects of sea water environment and arctic temperatures on woven carbon fiber/vinyl ester composites are explored in the form of moisture uptake, impact on flexural modulus, strength, and structural damage. The research presented here attempts to relate failure modes to the flexural behavior of these composites exposed to three key environmental conditions: sea water, arctic temperature and combined sea water/arctic condition. Sea water saturation in general degrades the flexural strength up to ≈19.45%. Microstructures of dry and saturated samples are compared using scanning electron microscopy, where a saturated surface with distinctive hue for wet samples is observed as compared to a rough (parched) surface in the dry samples, implying large concentrations of sea water in a thin layer at the specimen boundaries. Arctic exposure and combined condition on these laminates increase the flexural strength by about 23.1% and 36.2%, respectively. However, they tend to shift the post peak behavior from progressive to brittle-type failure as compared to dry samples, which is attributed to matrix and fiber embrittlement in the material system caused by exposure to low temperature. Further, relatively large variations are observed in the flexural strength values of samples exposed to the combined condition (sea water saturated + arctic), which can be attributed to the freezing of sea water that was entrapped during sea water saturation. Variation in the quantity and location of sea water entrapped can alter the flexural strength significantly. Due to the aforementioned flexural responses and failure behavior observed in woven carbon/vinyl ester composites exposed to sea water arctic environment, special consideration is required while designing critical load bearing components in naval applications to avoid possible catastrophic structural failure.