The effects of hygric pressure, salt concentration and temperature on the hygric expansion of composite material

Moisture absorption causes the expansion of composite material. Such expansion is physically reversible and dominated by the characteristic property of the composite material. However, many environmental factors can alter this hygric behavior. This work addresses the effects of external hygric pressure, salt concentration and environmental temperature, upon the hygric expansion of composite material submerged in water. Embedded strain gages were used to monitor hygric expansion. The final hygric strains of glass/epoxy submerged in water under different environmental conditions were measured and the corresponding diffusivities were calculated. The results confirm that hygric pressure, salt concentration, and temperature importantly affect the hygric behavior of composite materials. The process and results of this work are critical to designing composite structures—especially those serving in marine environment.