Embodiments of the invention are directed to carriers providing a primary toughening function and incorporating a secondary toughening agent therein. According to embodiments of the invention, the carrier/agent combination may be used in liquid resin infusion applications. The carrier may be any polymer-based material having a solubility characteristic in a thermosetting resin. The secondary toughening agent may be of a material such as a thermoplastic, a thermoset, a cross-linked thermoset, a rubber, a rubbery-like material or a combination thereof and may be in the form of a particle, a micro -fiber (fibril) or a fibrous network. In some embodiments, the earner is soluble in the resin while the secondary toughening agent is insoluble in the resin when subjected to a cure cycle.