Method of manufacturing spars, longerons and fuselage beams having a variable h cross-section

A method of manufacturing a beam of composite material having a variable H cross section along its length, the beam including a lower flange, a web and an upper flange, at least one of the flanges having a non-rectilinear profile when viewed in a longitudinal vertical plane, the method including the steps of:

• preliminarily assembling a beam of fibre-reinforced curable thermosetting composite material in an uncured condition;
• providing a lower forming tool having a lower forming surface shaped to give the lower flange a predetermined shape;
• providing an upper forming tool having an upper forming surface shaped to give the upper flange a predetermined shape, wherein at least one of said forming surfaces has a non-rectilinear profile when viewed in a longitudinal vertical plane;
• providing releasable supporting means for supporting the upper tool above the lower tool with the upper and lower forming surfaces substantially aligned one above the other;
• providing a pair of longitudinally elongate rigid inserts which are axially symmetrical about a vertical longitudinal plane, wherein each of the two inserts has a lower face with a profile congruent with or corresponding to the profile of the lower forming surface, an upper face with a profile congruent with or corresponding to the profile of the upper forming surface, and a side face joining the upper and lower faces;
• enclosing each rigid insert in a respective airtight tubular bag;
• laying the uncured beam on the lower forming tool, provisionally resting the lower flange on the lower forming surface;
• fitting the two inserts into respective side spaces on the two opposite sides of the web, between the upper and lower flanges, with the side faces of the inserts facing the web of the beam to be cured, and supporting the inserts with support means fixed with respect to the lower tool;
• positioning the upper forming tool above the upper flange of the beam, and supporting the upper forming tool with said releasable supporting means;
• sealing laterally the spaces between the upper tool and the lower tool on the two opposite longitudinal sides of the beam;
• sealing the open opposite ends of both of the tubular bags in such a manner that the pressure applied in an autoclave, in a subsequent curing step, will cause the tubular bags to swell, pressing the tubular bags against the two opposite faces of the web and against the pairs of mutually facing surfaces of the upper and lower flanges;
• curing the beam in an autoclave by applying a programmed cycle of temperature and pressure;
• upon completion of the curing, releasing the releasable support means of the upper forming tool, removing the upper forming tool, and extracting the inserts sideways from the beam.