Thermoplastic aerostructure with localized ply isolation and method for forming aerostructure

A method for forming a composite wingbox, comprising the steps of:

• providing a plurality of spars;
• connecting a plurality of ribs with the plurality of spars;
• forming a composite skin, comprising:
• a plurality of structural layers, each formed of carbon fiber reinforced thermoplastic laminae;
• a plurality of insulating layers each formed of a plurality of spaced apart electrically insulating elements, wherein each insulating element has a length and a width and the length is substantially longer than the width, wherein the insulating layers are aligned with one another and are disposed between the structural layers, wherein the insulating layers are configured so that the insulating elements overlie the spars and ribs when the composite skin overlies the spars and ribs;
• a weld layer formed of carbon fiber reinforced thermoplastic lamina;
• positioning the composite skin over the ribs and spars so that the layers of the composite skin overlie the ribs and spars;
• welding the composite skin to the ribs and spars, wherein the step of welding comprises the step of conveying an induction welding head over the composite laminate adjacent the ribs and spars so the induction welding head imposes an electromagnetic field through the composite laminate so that weld layer is heated above the melting temperature of the thermoplastic in the weld layer while the insulating layers impede heating of the structural layers above the melting temperature of the thermoplastic.