Newly designed GFRP Threaded SFT-Connector and Traditional GFRP Flat SFT-Connector are components in the construction of insulated concrete sandwich panels. The connectors fasten two concrete layers through an insulation layer. Applications include horizontally cast or vertically cast panels. Horizontally cast applications include plant-cast precast panels and site-cast tilt-up panels. Vertically cast applications include plant-cast modular precast units and formed-in-place structures.