Low-defect fabrication of composite materials

A method of forming a composite article, comprising:

• arranging, within an environment, a forest comprising elongated nanostructures between a surface of a first substrate comprising a polymer and a surface of a second substrate comprising a polymer, wherein the elongated nanostructures within the forest have long axes that are substantially aligned with each other and that are substantially perpendicular to the surface of the first substrate and substantially perpendicular to the surface of the second substrate;
• and
• heating the first substrate and/or the second substrate such that polymer within the first substrate and/or polymer within the second substrate softens and/or melts and nanostructures within the forest become at least partially embedded in the first substrate and/or the second substrate to form the composite article;
• wherein:
• the forest of elongated nanostructures has a height;
• the forest of elongated nanostructures has a first dimension that is substantially perpendicular to the height of the forest, the first dimension being at least 5 times greater than the height of the forest;
• the forest of elongated nanostructures has a second dimension that is substantially perpendicular to the height of the forest, the second dimension being at least 5 times greater than the height of the forest;
• during at least a portion of the arranging step, the forest of nanostructures is separate from the first substrate and the second substrate;
• a pressure of the environment does not exceed, during any part of the heating step, 3 bar absolute;
• and
• after the heating, the percentage of an interlaminar region of the composite occupied by voids is less than or equal to 10%.