Abstract: Processes for fabricating a honeycomb core composite laminate structure are provided. The processes include subjecting a honeycomb core preform having a honeycomb core and a stabilizing layer of at least one ply of a resin-impregnated fiber reinforced matrix material (“prepreg material”) surrounding the honeycomb core to high temperature curing under an ambient atmospheric pressure condition. A final laminate layer formed of at least one ply of prepreg material may thereafter be laid up onto the stabilized preform to thereby provide a final product preform which is then subjected to high temperature and high pressure autoclave curing conditions sufficient to cure the final laminate layer and provide a final cured honeycomb core composite laminate structure.