Abstract:
The present invention relates to a system to manufacture composite material parts comprising a supporting mandrel having at least one compacting zone configured to contain at least one composite material element to be compacted by applying a certain degree of vacuum. The system comprises also at least one compacting equipment comprising a frame having a plurality of interconnected arms along a predetermined perimeter, at least one vacuum bag attached to a side of the frame along its perimeter and configured to compact the element, at least one porous material attached to the vacuum bag along the frame&#39;s perimeter and configured to adhere in a removable way to the compacting zone and to impede the air influx during the compacting of element. The invention also relates to a compacting equipment and to a method to manufacture composite material parts.

Description:
TECHNICAL FIELD 
     The present invention relates, in general, to a method to manufacture components made of composite materials, to a system comprising equipment to manufacture composite material components and to the equipment to manufacture those components. In particular, the present invention relates to a method, system and equipment to manufacture cylindrical components, assembled to obtain an aircraft&#39;s fuselage. 
     To simplify the description, unless specified otherwise, from now on it will be referred as a method and system to manufacture cylindrical parts (fuselage parts) to be assembled to obtain an aircraft&#39;s fuselage. 
     RELATED ART 
     It is known, that one way to improve the aircraft&#39;s performance is to use composite materials, for example, materials made of carbon fibers, that have, in general, the characteristic to associate a great rigidity to a low specific weight. 
     The introduction of composite materials to the manufacturing of fuselage components requires methods and systems particularly complex and highly labor-intensive. 
     Referring to a fuselage&#39;s section, this part comprises reinforcing elements (stringers)  21  ( FIG. 1  and  FIG. 2 ) and a protective layer placed on a substantially cylindrical surface, even though other shapes are possible, bonded to the stringers after polymerization. 
     According to the known art, for example, the stringers  21 , made of non-polymerized composite material, are mounted on a mandrel  11  of a substantially cylindrical structure, and compacted over a plurality of compacting zones  12  using vacuum bags  15 , mounted and manually secured on the compacting zones of the mandrel  11 . After the compacting of the stringers, a composite material fabric is placed over the stringers, followed by further compacting using vacuum bags  15  mounted and manually secured, and lastly the polymerization is done by placing, for example, the stringers and the fabric inside an oven. 
     The first typical problem of the known art is that the stringers compacting phase, requiring the manual mounting of the vacuum bags  15  and their securing to the compacting zone  12  using a manually applied sealer, beside having particularly elevated costs, causes also an inconsistent level of quality, which depends on the skill level of the individual operators that effectuate the manual operations of mounting and securing the vacuum bags. 
     A second problem of the known art is that the compacting is followed by the destruction of the vacuum bags  15 . 
     In fact, because the vacuum bags  15  are glued to the first compacting zone, they can only be destroyed when removed. 
     DESCRIPTION OF THE INVENTION 
     The scope of the present invention is a method and a system to manufacture composite material parts that do not require manual labor for the compacting phase of the stringers and/or for the compacting of the layer of fabric covering the fuselage on the stringers. 
     The scope of the present invention is also a system and equipment that do not require the destruction of the vacuum bags after their use. 
     The scope is achieved by the method and system to manufacture composite material parts, particularly reinforced parts for aircraft&#39;s fuselage, as claimed. 
     The claims are an integral part of the technical teaching regarding the invention. 
     According to a preferred embodiment, the system comprises at least one compacting equipment which includes a vacuum bag designed to be applied in a removable manner to the compacting zones on the mandrel to compact the composite material parts not yet polymerized. 
     According to a further feature of the present invention, the compacting equipment comprises a frame having on one side, to be in contact with the mandrel, a porous material having the characteristics of blocking the air flow in the compacting zone. 
     According to another feature of the present invention, the frame of the compacting equipment comprises a connector, eventually equipped with a non-return valve, to which connect the vacuum pump generating the vacuum inside the compacting zone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This and other features of the present invention will be clear from the following description of the preferred embodiment of the invention, documented as an example and not as a limitation, with the support of the attached drawings wherein elements labeled with the same number or similar numeric reference indicate components having the same or similar function, and wherein: 
         FIG. 1  is a schematic representation of a system to manufacture composite material fuselage components, according to the known art; 
         FIG. 2  is a schematic representation of an application phase of the vacuum bags according to the known art; 
         FIG. 3   a  is a schematic representation of a system to manufacture the composite material for fuselage components according to the invention; 
         FIG. 3   b  is a schematic representation of a phase of the vacuum bags application according to the invention; 
         FIG. 4  is a schematic representation of an automated equipment for the vacuum bags application according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to  FIGS. 3   a  and  3   b , a system  10  to manufacture composite material parts, particularly reinforced parts with stringers  21  of composite material, comprises, for example, a mandrel or polymerization tool  11  and a plurality of equipment or compacting tools  30 . 
     The system  10  according to its preferred embodiment, comprises also, a first numeric-controlled machine  16  configured to retrieve the compacting equipments from a storage area and to position them on the mandrel  11 , as it will be described further in more details. 
     The mandrel  11  can rotate around its own axis, continuously or according to predetermined angles, and show in the upper area, at least one compacting zone  12 . 
     The compacting zone  12  comprises one or more slots  14 , eventually in a different number among different areas, configured to hold, for example, the stringers  21 . 
     The shape, dimensions and the number of slots  14  can vary considerably, according to the type of the reinforced parts to produce. 
     In case of an aircraft&#39;s fuselage, the number of slots in a compacting zone can be, for example, ten or twelve. 
     The stringers  21 , made of composite material, such as non-polymerized (not cured) carbon, thanks to the fact they are not yet polymerized, have the characteristic of being deformed to take the slots&#39; shape after being inserted into the slots  14 . Preferably, the stringers  21  are positioned inside the respective slots using a second numeric-controlled machine  26  designed to retrieve the stringers from a stringers storage area and position them in the slots  14  inside the compacting zone that at interval times is presented on the upper area of the mandrel  11 . 
     In other embodiments, the stringers can also be positioned manually inside the slots. 
     The compacting tools  30 , according to the preferred embodiment of the invention, are in a number to “cover” the entire mandrel  11 , but, naturally, in other embodiments, they can also be in a lower number. 
     Every compacting tool  30  ( FIG. 4 ) comprises preferably, a frame  31 , for example a rectangular steel frame, having an upper side  32   a  and a lower side  32   b , two straight arms, respectively  31   a  and  31   b , and two arms, respectively  31   c  and  31   d , curved according to a curving radius slightly bigger than the radius of the mandrel  11  ( FIG. 3   a ,  FIG. 3   b ,  FIG. 4 ). 
     Naturally, according to other embodiments, all arms can be straight, or the frame can be differently shaped, beside being rectangular. 
     Every frame&#39;s arm, from  31   a  to  31   d , has preferably a quadrangular section, comprising a plurality of holes  43   a  on the lower side and it is configured to create an internal channel communicating with the correspondent internal channels of the other arms. 
     Preferably, at least one of the arms, for example the arm  31   a , comprises a connecting element  37  communicating with the arms&#39; conduits to which to connect a pump  53  (a vacuum pump), of known kind, to generate a vacuum condition. The connecting element can comprise also a non-return valve, of known kind, to stop the air influx inside the frame&#39;s conduits, in case the vacuum pump  53  is disconnected. 
     Preferably, the frame comprises hooking elements of mechanical type, for example dowel pins or hooks, to fasten the compacting equipment  30  to the mandrel  11  inside the compacting zone. 
     In the preferred embodiment, the lower side  32   b  of the frame  31  is connected to a layer of porous material  33 , for example a semi-closed strip of foam of E.P.D.M type (Ethylene-Propylene-Diene Monomer) NITTO 686 or a foam with substantially similar characteristics. 
     Between the porous material (foam or strip of foam)  33 , in particular between the first side of the foam  33  and the lower side  32   b  of the frame  31  a vacuum bag is interposed. Said vacuum bag  35  is attached, glued for example, to the first face of the foam  33  and to the lower side  32   b  of the frame, so that the foam  33 , vacuum bag  35  and the frame make one body. 
     The foam  33  and the vacuum bag  35  have respective holes,  43   b  and  43   c , in correspondence to the holes  43   a  of the lower side  32   b . The foam strip  33 , preferably, has the first face connected to the entire perimeter of the lower side  32   b  of the frame  31  and has a second face configured to become in contact with the compacting zone; the foam has a thickness to compensate possible curving differences between the compacting zone  12  and the curved arms,  31   c  and  31   d , and/or possible irregularities in the compacting zone  12 , when the second face of the foam comes in contact with the compacting zone. 
     In the preferred embodiment, in which the frame has a width of about 2.5 m, a depth comprised between 8 and 16 m, and the mandrel has a curving radius of about 3 m, the foam has a thickness between 20 and 30 mm. 
     Naturally, in other embodiments, the foam  33  can have a different thickness but still capable to compensate shape differences between the compacting zone  12  and the frame  31 . Preferably, the foam  33  has the function, when used, to stop the air influx inside the vacuum bag following the mounting of the vacuum pump  53  to the connecting element  37  and to maintain a predetermined vacuum level in a predetermined area, e.g. the area delimited by the foam  33  of the compacting tool  30  when in contact with the compacting zone  12  on the mandrel  11 . 
     The functioning of the system  10 , as previously described, is the following. 
     In a first phase, the compacting zone  12 , positioned in the upper area of the mandrel  11 , is loaded, for example, using the second numeric-controlled machine  26 , with a number of stringers equal to the number of the slots  14  in the compacting zone  12 . 
     In a second phase, the first numeric-controlled machine  16  retrieves from a storage area a compacting equipment  30  and positions it in correspondence, for example, of the compacting zone  12 , to make, thanks to the presence of the foam  33 , a kind of sandwich with the inside being the stringers  21 . 
     In a third phase, the pump ( 53 ) is applied to the compacting equipment to produce a vacuum in the stringers area. The vacuum force pushes the vacuum bag, as illustrated in  FIG. 3   b , against the stringers to shape them by making them to take the slots&#39; shapes; the porous foam material applies pressure on the compacting zone  12  surface preventing the air from entering the stringers area. 
     In a fourth phase, for example, the mandrel  11  is rotated to show the next compacting zone ( 12 ) in the upper area. In such a phase, and in the subsequent phases until the completion of the compacting phase of all required stringers, the vacuum pump  53  remains connected to different connecting elements for a predetermined time, for example, the time necessary to shape conveniently the stringers, for example one hour. 
     After completion of the fourth phase, the compacting procedure restarts from the first phase until the compacting phase completion. 
     After the compacting phase is completed, the compacting equipment  30  are taken by the first numeric-controlled machine  16  and returned to the storage area for the next use. 
     The described process can be repeated, with equivalent steps, even after the positioning of the fabric over the stringers, according to the known process. 
     Thanks to the invention, the vacuum bags are fully reusable. 
     Furthermore, the use of foam guarantees a constant or better quality level with respect to the known process. 
     In fact, the inventor has detected with experimentation that the vacuum level that can be obtained with the system and the equipment according to the invention (0.8 Kg/cm 2 ) is better than the one obtained by the manual process, which is about 0.6 Kg/cm 2 . 
     This description refers to the manufacturing of parts made of composite material for aircrafts, but it is easily understood that that same procedures can be applied to the manufacturing of body parts made of composite material for high speed vehicles such as trains, high performance cars etc. 
     Although a mandrel has been chosen for the manufacturing of composite material parts, it is easily understood that the described method is also applicable whenever a rotating mandrel is not present, but the manufacturing of composite material parts simply requires a vacuum bag&#39;s use. 
     The description refers to a compacting equipment to be used only for the compacting phases. 
     Naturally, in other embodiments, in which, for example, the compacting equipment comprises a vacuum bag and a foam that, although has substantially similar features to the one described, it can be resistant also to high polymerizing temperatures, to allow the equipment to be used during the polymerization phase. 
     Obvious modifications or variations are possible according to the description above, in the dimensions, shapes, materials, components, as well in the construction details as illustrated and in the operating method without deviating from the spirit of the invention, as defined in the following claims.