A resin-soluble thermoplastic polymer veil toughening element for a curable composition wherein the polymer element is a non-woven veil in solid phase adapted to undergo at least partial phase transition to fluid phase on contact with a component of the curable resin matrix composition in which it is soluble at a temperature which is less than the temperature for substantial onset of gelling and/or curing of the curable composition and which temperature is less than the polymer elements melt temperature; a method for the preparation thereof, a preform support structure for a curable composition comprising the at least one thermoplastic veil element together with structural reinforcement fibers, methods for preparation thereof, a curable composition comprising the at least one thermoplastic veil element or the support structure and a curable resin matrix composition, a method for preparation and curing thereof, and a cured composite or resin body obtained thereby, and known and novel uses thereof.