Abstract: In order to make a structure of a composite material including elongated hollow shapes, such as hollow shapes associated with stiffeners of a stiffened panel, the invention comprises making cores including a bladder made of an elastomer material. The invention relates to a method for making such extractable cores in order to obtain cores having a very important length, and allowing the use of said cores for the industrial production of composite parts. The bladder is a cylindrical bladder that is conformed in a core mould, wherein the core itself does not have to be cylindrical, before being filled with a granular material and submitted to a negative pressure in order to impart a stable shape to the core by compaction of the granular material.

Abstract: A connecting rod is composed of two or more assembled shells made of a composite, open over the entire length of the connecting rod. The shells incorporate clevis joints for introducing stress at each of their ends. The shells are produced separately then assembled together to form a sealed section. Each shell is made from a material preimpregnated with long fibres. The production of each shell is simplified due to the overall shape of the shell as a simple curve, thus a shell may be produced industrially, for example, by thermoforming a flat composite preform. The two shells are assembled by simultaneous polymerization of the shells, by bonding, by welding, by riveting or any other assembly process or combination of assembly processes that are compatible with one another. The structural composite connecting rod obtained has very good mechanical properties, especially in compression, with a simple and economic production process.

Abstract: A stiffened panel made of a composite includes a skin and at least one stiffener having a more or less closed volume. In order for the fibres of the composite to be held in place during fibre deposition and during pressure application while the resin of the composite is being cured, a moulding core is placed between the fibres at the position of the more or less closed volume of the stiffener. The moulding core includes a flexible bladder filled with a granular solid material, the thermal expansion coefficient of which is close to that of the composite used to produce the stiffened panel. The pressure in the bladder is increased before the composite is cured, so as to compensate for the forces applied for compressing these fibres during production of the panel.

Abstract: A method for producing a composite material part having a so-called non-strippable shape includes producing mold components, or cores, which are to be extracted from the part after the composite material has been cured. In a first step a core is produced from an elastomeric bladder the granular solid material and the bladder is depressurized. In a second step, after setting the core and the composite material the volume of the core is modified in a controlled manner for example by selecting the solid granular material based on its thermal expansion properties or by acting on the pressure in the bladder.

Abstract: The invention mainly concerns a method for making a composite RTM part (23) which consists in producing a dry fibrous preform (8) by inserting in said dry preform (8) composite parts (10, 11) made of prepregs. Said parts, pre-impregnated with a first resin, are partly polymerized. The assembly is placed in a mold (16). A second resin is injected into the mold and impregnates the dry fibers (7). The two resins are polymerized simultaneously. The partial polymerization of the pre-impregnated parts (10, 11) results in a good chemical bonding between the two resins. The pre-impregnated parts (10, 11) have better mechanical properties, in particular in compression, than RTM parts. This is particularly due to a better alignment of the fibers (12) in the direction of stresses, and to a higher fiber volume ratio. The final component (23), reinforced with pre-impregnated parts, has better mechanical properties than the same RTM component without pre-impregnated reinforcements, in particular in compression.