Patent ID: 8647548

Claim:
A method to reduce porosity in a composite structure, the method comprising: adding an additive to a resin material to form an additive-resin mixture, the additive comprising a phase transition material having an additive phase transition temperature greater than a resin cure temperature of the resin material; combining the additive-resin mixture with a plurality of reinforcement fibers to form a composite prepreg material; forming the composite prepreg material into a composite structure; heat curing the composite structure in a heating apparatus under a vacuum device at an effective vacuum pressure for an effective time period at the resin cure temperature sufficient to decrease a viscosity of the resin material; heating the composite structure to an increased temperature above the additive phase transition temperature and above the resin cure temperature and maintaining the increased temperature for a time period sufficient for the additive to undergo a phase transition and to form an additive gas that substantially displaces one or more gases out of the composite structure; reducing the increased temperature back down to the resin cure temperature to allow the additive gas to undergo a phase transition to a condensed phase, resulting in a substantially reduced vacuum pressure in the composite structure, and resulting in a reduction in porosity of the composite structure; and, cooling the composite structure.