Use of UV-Curing Adhesive Systems on Non-transparent Joining Parts by Using Sidelight Activated Polymer Optical Fibres

The long curing times of the adhesives are an essential deficit of the bonding technology. UV-curing adhesives enable complete curing within seconds, but require at least one light-transparent joining partner. In order to make use of the advantages of UV-curing adhesives also on non-transparent joining parts, the approach of light transfer into the adhesive joint is pursued. A polymer optical fibre (POF) is embedded in the adhesive as a waveguide. With a lateral activation of the fibre surface, a radial curing is realized. In this paper, the effects of side light activation by thread cuts and gradual micro cuts on a PMMA POF with a diameter of 1.0 mm are characterized and validated in corresponding adhesive tests. An experimental setup is established to characterize the activated fibre with regard to sidelight intensity and homogeneity. The wavelengths of the UV light used are 365 and 400 nm. While lateral homogeneous adhesive layer depths of up to 2.5 mm are achieved at 400 nm, the use of UV light at 365 nm proves to be unsuitable for the selected tests.