Abstract: Cleaning of thermoset FRP part surfaces to be bonded together is accomplished by the application of low intensity, i.e., 0.05 to 10 watts per cm.sup.2, short wavelength ultraviolet radiation in the range of 170 to 300 nm, for a period of time of usually less than 10 seconds which results in removing an effective amount of material, e.g., from about 1 to about 200 angstroms. The cleaning increases the adhesive potential of FRPs to polyurethane adhesives. Furthermore, FRP polymer surfaces treated by this process retain more adhesive strength after aging at elevated temperature in the presence of moisture than untreated surfaces or surfaces washed with isocyanate in MeCl.sub.2. Epoxy adhesives, also, can be used.