A corn. unsatd. polyester resin was modified by addn. of halogen-free, hybrid flammability-reducing modifiers (melamine polyphosphates with nanosized org. modified bentonite or SiO2 nanoparticles or expandable graphite) and used for manufg. glass-reinforced polymer-matrix laminates as a pipeline by CC-GRP method. The addn. of melamine polyphosphate (15% by mass) with expandable graphite (5% by mass) resulted in a decrease (above 45%) of heat release rate and the highest decrease in the combustion heat (by 19%).