THE EFFECT OF BIOFOULING ON GRAPHITE EPOXY COMPOSITES/

This research program seeks to determine if the presence of marine mic roorganisms and the biofouling they produce will accelerate the degrad ation of graphite/epoxy composite materials. Graphite/epoxy samples we re conditioned for 4 months in sterilized seawater(no microorganisms), natural seawater (with microorganisms), and air. In addition, half of the tested samples were also subjected to three-point bending while c onditioning. Moisture absorption data was gathered before and after im mersion and correlated with tensile and acoustic emission data. Result s of tensile tests showed seawater in general had a larger effect on u ltimate tensile strength than microorganism effects. However, sample s tress state while conditioning had negligible effect on mechanical pro perties. These results were most likely due to plasticization of the m atrix and relief of fabrication residual stresses through moisture abs orption and fiber dominated behavior of the specimens. Acoustic emissi on results showed that the trend for high amplitude hits for each expo sure condition was consistent with the tensile test results. However, due to the effects of moisture on three different relaxation mechanism s, the low amplitude hits were not as consistent.