This study seeks to investigate how the enhanced properties of the nanoclay E-glass/epoxy composite can withstand the combined effects of ultraviolet radiation, moisture, and rain. The montmorillonite nanoclay's affinity to moisture compounded the moisture absorption ability of the nanoclay E-glass/epoxy composites. The moisture in the polymer structure caused delamination, debonding of the fibers/matrix, microvoids, and fiber pullouts. The high clay content (2 wt %), therefore, recorded the highest rate of degradation of 15% in flexural stress for the first 20 days, compared to about 8 and 6% loss for the unmodified (0 wt %) and 1 wt % composites respectively. However, as the aging progressed beyond 20 days, the rate of degradation of the nanoclay E-glass/epoxy composites laminates was steady at 10 and 18%, respectively, for the 1 and 2 wt %, while that of the unmodified polymer continued to degrade progressively. On the contrary, the viscoelastic properties of the nanoclay E-glass/epoxy composites continued to deteriorate at a faster rate than the unmodified polymer composite. (C) 2014 Wiley Periodicals, Inc.