Seawater effects on transverse tensile strength of carbon/vinylester as determined from single-fiber and macroscopic specimens

The main objective of this work is to characterize the effect of seawater immersion on the transverse tensile strength of a carbon/vinylester composite. A recently developed single-fiber test was used to determine the tensile strength of the fiber/matrix interface at dry and seawater saturated conditions. Measured loads at onset of fiber/matrix debonding were combined with finite element stress analysis to determine the tensile strength of the fiber/matrix interface. It was found that seawater exposure had an insignificant influence on the interface strength. The transverse tensile modulus and strength of macroscopic composite test specimens were slightly reduced by exposure to seawater. The modulus only slightly exceeds the lower bound estimate for both the dry and seawater saturated composite. This may be a consequence of insufficient load transfer between fiber and matrix due to interface voids. The fiber/matrix interface strengths measured at dry and seawater saturated conditions were used as input in the Cooper–Kelly micromechanical model to predict the transverse tensile strength of the composite. Predictions of strength at dry and seawater saturated conditions, based on measured fiber/matrix interface strengths, were unconservative, which again may be the results of voids at the fiber/matrix interface.