WO2016059147A1

WO2016059147A1 - Car face wall architecture for a car such as a train car made from sandwich composite material

Info

Publication number: WO2016059147A1
Application number: PCT/EP2015/073863
Authority: WO
Inventors: Sylvain Claudel; Marcel Auberon
Original assignee: Airbus Defence And Space Sas
Priority date: 2014-10-17
Filing date: 2015-10-15
Publication date: 2016-04-21
Also published as: EP3206931A1; US20170240188A1; FR3027273A1; JP2017532255A; FR3027273B1

Abstract

The invention relates to a car (1) belonging to a rolling vehicle, characterised in that it comprises sidewalls (2) in the form of a single piece made from composite material comprising a sandwich structure (10) provided with a first skin (11) on the outside of the car, a second skin (12) on the inside of the car and a closed-cell foam (13a) or honeycomb (13b) core between the skins, said walls being provided with window openings (20) formed by interruptions in the drapes of longitudinal fibres, transverse fibres and intersecting diagonal fibres (100), said openings (20) having a polygonal shape that reduces the surface area of interrupted diagonal fibres (100) in the corners of the openings.

Description

FACE WALL ARCHITECTURE SUCH AS A SANDWICH COMPOSITE TRAIN CAR

Field of the invention

The present invention relates to a car face wall architecture such as a composite sandwich train car equipped with openings.

The invention relates to a design solution of a structural panel made of composite material equipped with openings: windows, portholes, windows intended to reduce the overall weight of the structure and applicable in particular on the walls of a rail transport crate whether it is urban equipment, metro, tramway, regional train or cars for high speed lines.

Technological background

Train structure designers must compromise between various, sometimes contradictory, requirements:

They seek to reduce the mass of structures to increase the payload and / or reduce energy consumption but they must control production costs and therefore find simple solutions while ensuring the comfort and safety of passengers, and in particular without limitation:

- By limiting the structural deformations of train cars which implies a sufficient bending stiffness of these cars, this stiffness is also important to avoid coupling with the modes of suspension trains;

- limiting noise inside cars;

- By providing a guarantee against fire and smoke to passengers;

- By supporting the pressure waves; - Supporting pulls and compression related to traction.

More specifically, a train body structure behaves mechanically like a bending box whose flag (the roof) and the frame (the floor) constitute the soles and the faces constitute the vertical sails.

As shown in FIG. 1, the faces, when they are, are subjected mainly to shear stresses 201.

In addition, the panels are also subjected to bending stresses induced by the pressure waves of the order of 8000Pa experienced during crossings and / or tunneling for a high-speed train, to the effect of vertical loads 201, mass of equipment and passengers on the chassis, local efforts or others.

To date the crates are essentially composed of metal structures, for example steel sheets or mechanically welded aluminum profiles, as described for example in the document EP0392828A1 or JP2000264200A.

In general, it is found that these structures are presented as in JP4427273B2 in the form of sandwich walls, that is to say two metal skins interconnected by elements, or by panels reinforced by stiffeners as described in JP2000264200A or by a combination of two types of solutions

Nevertheless, it is natural for transport to consider lighter solutions, using high-performance composite materials, as has been the case in the past in the pioneering fields of aeronautics and space. This has been proposed for example in the documents EP0544473A1 and EP0544498A1 in the form of honeycomb core sandwich panels with insertion of stiffeners.

The need for longitudinal flexural rigidity of the side panels is due to the fact that a train structure is a beam resting on its axles. This rigidity must be controlled on the one hand to limit the arrows, but also to control the vibrations and resonances - related to the speed of movement of trains.

Beyond the issue of stiffness, note two patents that show the difficulties of controlling this stiffness due to the presence of windows, the document JP2000264200A which proposes stiffeners that are not simply vertical, but whose angle relative to the vertical is optimized. In this patent, it is even proposed a continuous window, simply locally hidden by inclined pillars of ground / ceiling connection.

The document US8656841 B1 proposes oblong and non-rectangular windows as usual and in both cases, the shape of the window is modified to be compatible with a control of the rigidity of the panels.

Structural composite materials that provide the desired mass gain with the required level of performance are based on long, continuous carbon or glass fibers. In this type of material, the fiber represents approximately 50% to 60% of the volume, the remainder consisting of an organic matrix (generally an epoxy type resin but also sometimes polyester, vinylester, etc., and optionally thermoplastic resins such as polyamides, peek, etc.).

For the manufacture of structures, there are two main families of composite materials:

So-called monolithic materials, consisting of a pile of fibers;

Sandwich materials, consisting of two skins of identical nature to monolithic materials separated by a soul.

This soul is often made of a very low density material, honeycomb type, or foam, or other (balsa sometimes). This makes it possible to obtain the desired off-plane bending inertia properties. This type of structure is advantageous in terms of performance and cost.

In a sandwich material, the flexural inertia of the panels, in the direction of their thickness, is provided naturally by the spacing of the skins. This is one of the major advantages of this type of architecture.

Other core materials may be used, for example denser materials for providing sound damping capabilities to the sandwich structure. See for example JP2001278039A.

Composite materials therefore make it possible to implement the same technical solutions as metal materials, namely structures monolithic stiffened or sandwich structures, but with a wide variety of possible solutions, because many combinations are possible between the various fibers (carbon, glass, SiC, vegetable fibers, ...), the resins (epoxy, polyester, vinylester, PEEK, polyamides, ... thermosetting or thermoplastic) and souls (metal honeycombs, foams or other).

Furthermore, since the optimum mechanical properties of the composite materials are provided by the fibers, these materials are by nature anisotropic, and therefore their optimization of the structures requires that the orientations of the fibers in the thickness of the material be defined as a function of the mechanical stresses. that sees the structure.

Thus, for the roof and the chassis, the stiffness requirements lead to preferentially orient the fibers in the direction of the length. On the other hand, with regard to the face panels, the shear stress that applies must be taken up by fibers oriented at + and -45 °. It is in fact under these conditions that the structure is optimized in its mechanical operation, and therefore in mass and cost.

Like all passenger vehicles (cars, coaches, trains, airplanes, even spacecraft), train cars must have windows. These windows being made of different materials from the rest of the vehicle structure, they must be the object of a specific design.

A device for fixing the windows to the remainder of the wall or structure must be put in place, as for example in the patent FR 291 1 1 12A1 relating to aircraft. In addition, a reinforcement of the structure in their vicinity must be provided as described in this US patent 2012 / 0223187A1.

In the case of cars that are composite material structures as seen above, the shear stress that applies to the face must be taken up by fibers oriented at + 45 ° and -45 ° relative to the horizontal.

However, as shown in FIG. 3, at the level of the panels of the faces, the presence of the conventional rectangular berry angles leads to cutting the fibers between the top and the bottom of the front panel, which may require increasing the distance between two windows or the local thickness of materials between two windows which complicates the manufacture of the panel and makes it more expensive Also, it has been proposed to modify the shape of the windows in the case of composite materials structure and the document US 2012 / 0223187A1 proposes in this case "diamond" shaped portholes for an aircraft fuselage, as well as the how to do their sizing. This form of small portholes is obviously unsuitable for a passenger train.

Brief description of the invention

It is therefore known to make train crates made of composite materials, in particular in the form of sandwich panels.

This being the case, the technologies that can be envisaged are numerous, both in terms of materials (fibers, resins, cores) and the method of implementation (draping of prepregs, infiltration and its variants, etc.). It is also known then to adapt the shape of the windows to improve the longitudinal stiffness of the body and, for the planes, a diamond-like shape has been proposed for the portholes so as to adapt them better to the preferential orientations of the fibers which involves optimization in composite materials. The same is true of the modification of the skins of composite sandwich materials to improve their ability to spend more effort locally.

On the other hand, it is not known to optimize the windows of cars made of composite material, it is the same with regard to how to do it.

However, the train windows are distinguished from those of aircraft by their unit area, much larger than that of aircraft, by their geometry, which is characterized by an elongation (ratio of the length squared on the surface) greater than 2 for the the majority of the windows of a box, by the total glazed surface compared to the wall surface of the lateral structure, also much higher than that of the planes. These aspects are justified by the need to ensure maximum comfort for travelers during the journey, visibility and brightness being important aspects of this comfort.

In addition to these distinctions, the dimensioning of the running part of a body section of a train is also different from that of an aircraft fuselage by the following specificities:

a lack of stress induced by the need for static pressurization of the structure, but in contrast pressure constraints in the form of overpressure waves followed by depression impacting the structure and the bays in rapid dynamics during tunnels and / or crossovers. The levels of these pressures (peak values) are of the order of ± 5000 to ± 6000 Pa up to 8000 Pa for the high speed;

the need to control the natural frequency of the structure, to avoid resonance when moving the car typically> 1 1 hz;

the need to withstand the efforts (traction / compression) of traction between cars.

Finally, and even if the costs are to be taken into account in any industrial activity, the requirements in the field of rail in terms of cost reduction are even more severe than in aeronautics (the cost per kg accepted is more than 10 times lower ), which makes it an even more important criterion for choice of solutions.

The invention therefore aims to propose a solution for reducing the mass of structures of a train body by the use of composite materials while maximizing the glass surface available to passengers.

The invention makes it possible to design a face (wall) of a car made of composite material in the form of a monoblock sandwich, locally reinforced only for the interfaces, based on high strength carbon fibers for the most part, sampled to optimize at best the mechanical stresses, but also taking into account the requirements of finishing and integration, having apertures of suitable shape for a better use of this sampling.

The invention more particularly proposes a car of a rolling vehicle which comprises one-piece side walls made of composite material comprising a sandwich structure provided with a first skin on the outside of the car, a second skin on the inside of the car and a closed-cell foam or honeycomb core between said skins, said walls being provided with window openings formed by lay-ups of longitudinal fibers, transverse fibers and crossed diagonal fibers, said openings having a polygonal shape reducing the area of interrupted diagonal fibers in the corners of the openings.

The invention makes it possible to dispense with stiffeners or wire mesh elements to reinforce the structure. For increased rigidity of the body, the openings preferably have a hexagonal or octagonal general shape with two large horizontal sides connected by convex lateral edges with two segments, three segments or an oval shaped segment.

Advantageously, the openings are equipped with a reinforcing edge provided with a tubular frame.

According to a particular embodiment, the reinforcing edge has an internal flange for fixing the edge on the edge of the opening on the inner side of the wall.

The tubular frame is advantageously of rectangular section, the inner wing extending one face of the tubular frame on the inside of the wall.

The inner wing preferably attaches to the inside of the wall by means of screws, rivets or other fastening means which solidarize the wing and the inner skin of the composite panel.

Advantageously, a face of the tubular frame facing the inside of the car is fixed by means of screws, rivets or other fastening means on a rim of the opening made by the second skin protruding from the core of the wall.

According to a particular embodiment, the reinforcing edge has an internal collar accommodating a fixing of a window.

According to a particular embodiment, at least one of the two skins of the sandwich structure is made by means of folds oriented in 4 preferred directions 0 ° (longitudinal axis of the body), 90 °, + 45 ° and -45 °.

According to an advantageous embodiment, the plies are prepreg plies with a basis weight of between 125g / m ² and 500g / m ² .

According to an advantageous embodiment limiting the number of interrupted folds, the corner segments of said openings are inclined between 45 ° and 60 ° with respect to a longitudinal direction of the wall and preferably inclined between 45 ° and 50 ° with respect to a longitudinal direction (L) of the wall.

The 45 ° yarns are advantageously in the form of at least two folds of +/- 45 ° carbon fiber.

According to a preferred embodiment, the core of the sandwich is made of a material chosen from polyethylene terephthalate (PET), polymethacrylimide (PMI), polyetherimide (PEI), an aluminum honeycomb or a poly (m-phenyleneisophthalamide) (MPD-I) honeycomb (structure impregnated with phenolic resin).

Brief description of the drawings

Other characteristics and advantages of the invention will become apparent on reading the following description of a nonlimiting exemplary embodiment of the invention with reference to the drawings which represent:

in FIG. 1: a basic representation of the shear stresses in the longitudinal direction of a train car side panel;

in Figure 2: a detail of a panel of the invention;

in FIG. 3: a representation of a panel of the prior art;

in Figure 4: a perspective view of a panel portion and openings according to the invention;

Figures 5A, 5B: a sectional detail of a reinforcing frame at a window opening in the wall according to two embodiments;

in FIG. 6: a front view of an exemplary embodiment of a panel of the invention for a two-storey car;

in FIG. 7: a schematic representation of the structure of the wall of the invention between window openings;

in Figure 8: a perspective view of a car body with walls according to one aspect of the invention;

in FIG. 9A: a schematic view of inclined fiber passages between openings;

in FIGS. 9B and 9C: representative curves of the stresses and shear at the cutting level of the openings within the scope of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is mainly described in FIGS. 2 and 4 to 8.

Its principle is to make a train car 1, an example of which is given in FIG. 8, which comprises side walls 2 made of a single piece of composite material.

The material chosen has a sandwich structure 10 shown in FIG. 2 and provided with a first skin 1 1 on the outside of the car, a second skin 12 on the inside of the car and a closed cell core 3a or honeycomb 13b between said skins. According to the invention, the walls are provided with window openings 20 formed by lay-ups of longitudinal fibers, transverse fibers and crossed diagonal fibers 100 of the sandwich structure, said openings 20, as shown in FIG. having a hexagonal shape having two large horizontal sides and side walls 29 with a convex V profile or an oval profile which reduce the diagonal fiber surface 100 interrupted in the corners of the openings and in FIG. 7 an octagonal shape for which the lateral sides have three segments.

Compared to a monolithic structure equipped with stiffener, the sandwich structures offer the following advantages in particular:

Reduced manufacturing and mass costs, thermal insulation function performed by the soul.

The monolithic panels have with respect to such a solution of sandwich structure the following disadvantages:

- Cost of manufacturing (assembly of frames and stiffeners on skins) higher, cost of assembly (local assembly in areas of frames) important.

In addition, the frames are thicker than the sandwich which locally reduces the internal volume of the structures built.

The materials, composite and core, of the panel must be chosen to meet many constraints, which leads to eliminate many potential solutions, and ultimately to retain solutions that are compromises once again among the multiple solutions considered.

The main constraints to be taken into account are described below with in the first place the mechanical constraints.

For skins:

- The modules of traction / compression of the elementary folds, an elementary fold being the basic element of the fiber stacks, a monolayer layer of unidirectional (UD) or a fabric, must provide the desired stiffness in the stack. The choice of the fiber intervenes here in the first order. For reasons of cost, the choice fell on fibers "HR" (high strength) of industrial grade, including T700 from Hexcel, TR50S from Mitsubishi, Pannex 35 from Zoltec.

- The mechanical strength of the elementary fold under service loads must be verified. The properties of the resin are just as important as the properties of the fiber.

Given the intended structural application and the severe constraints to which the material must respond (30-year life in wet environment, withstand temperature> 60 ° C, cyclic fatigue up to 10 million cycles, ..), shock resistance (...), an epoxy resin was retained.

The minimum mechanical properties of the unidirectional carbon fiber / resin fold considered at end of life and at maximum operating temperature are as follows:

The minimum mechanical properties of the unidirectional fiberglass / resin fold considered at end of life and at maximum operating temperature are as follows: Data

(max T ° / end of life) composite resistance - traction 0 ° (Mpa)> 472 composite module - traction 0 ° (Gpa)> 35

Composite resistance in compression 0 ° (Mpa)> 331

-compressed composite module at 0 ° (Gpa)> 30

composite modulus at 90 ° (Gpa)> 3.0 plane shear strength - Tau_12 (Mpa)> 29 plane shear modulus - G_12 (Gpa)> 2.0

ILSS (inter-laminar shear stress)

> 21

(Mpa)

For the soul of the panel:

The shear modulus intervenes in the bending stiffness of the panel. The tensile / compressive and shearing strengths of the material must in particular be adapted to ensure sufficient mechanical strength under service loads. The density of the material is an important data in a view of minimizing the mass of the structure.

In addition to the mechanical behavior, the choice of sandwich panel materials involves other considerations, such as compatibility with the intended manufacturing process. The cost constraints associated with the large dimensions of the parts justify the selection of a manufacturing process under vacuum (excluding autoclave). The impact of this choice comes first on the selection of the resin.

Therefore, the core material must be able to withstand the stresses (pressure = 0.1 Mpa + temperature up to 120 ° C) induced during the implementation of the polymerization cycle. These constraints lead to the exclusion of certain products (eg PET foam with a density of less than 100 kg / m3). The material must also comply with rail standards for fire behavior, in particular the EN45545 standard in its 2013 version.

For cellular foams, certain families of materials such as polyethylene terephthalate (PET) in certain densities, polymethacrylimide (PMI), polyetherimide (PEI) meet all these requirements. bee or aluminum honeycomb poly (m-phenyleneisophthalamide) (MPD-I) (structure impregnated with phenolic resin) (known under the trademark NOMEX for example) also satisfy.

Thermal insulation is also a constraint to take into account. The use of a core material made of closed cells inherently having excellent thermal insulation properties offers the advantage of integrating the thermal protection function in the manufacture of the panel, and thus gain cost and cycle on the realization of this function generally performed at the level of the cash structure.

To avoid phenomena of accelerated aging of the materials by water absorption but also the risk of degradation under the action of the gel, the choice of a closed cell core material is therefore also preferred.

Given the points mentioned above and by integrating cost constraints, the preferred solutions are described in the context of an application as follows:

The face of the car is a one-piece sandwich panel pierced to make openings such as window, doors, display devices or others. The openings include reinforcements for fixing the elements on these openings (windows, doors, ...) and to compensate for the loss of stiffness of the face panel related to the presence of the hole. This reinforcement at the level of the window openings is provided by a reinforcing border with a border frame (metal in the case of the example) as shown in FIG. 4 and in section of the hole of the composite panel bordered by the border of reinforcement 21 in FIGS. 5A and 5B.

According to these examples, the reinforcing edge 21 is provided with a tubular frame 30. In the case of FIG. 5A, the border comprises a wing 31 known as an inner wing which makes it possible to fix the border on the edge 2a of the opening on the internal face of the panel, ie the face lying inside of the fund.

The tube of embodiment of the tubular frame 30 is of rectangular section, the inner wing 31 extending a lateral face 21a of the tubular frame of the reinforcing border 21.

The inner wing 31 is fixed on the wall on the inside of the car by means of screws, rivets or other fastening means 32 which, in the case of rivets, will grip the outer wing and the skin forming the inner face of the car. wall of the car. A seal 37a is interposed between the wing 31 and the inner face of the wall.

The lateral face 21b of the tubular frame 30 directed towards the outside of the car is fixed by means of screws, rivets or other fastening means 32 on a rim of the opening made by the skin 2b of the panel forming the outer face of the car. the box and which overflows with respect to the soul of the panel. A seal 37b is interposed between the lateral face 21b and the second skin 2b.

The reinforcing rim 21 further comprises an internal collar 34 for fixing the window.

The lateral face 21b of the tubular frame 30 directed towards the outside of the car is fixed by means of screws, rivets or other fastening means 32 on a rim of the opening made by the skin 2b of the panel forming the outer face of the car. the box and which overflows with respect to the soul of the panel.

In the case of Figure 5B, in addition to the previously seen elements, a frame plate 36 is fixed on the outer side face 21b of the edge and on the panel 2. In this case, the frame plate 36 and the outer skin are beveled in complementary manner and the fastening elements 33b solidarisant the plate and the panel are fixed in the core of the panel. A seal 37c is interposed between the plate on one side and the border and the panel on the other side.

The skins are made with "HR" grade carbon fibers and E-glass depending on the areas and requirements and an epoxy resin having, when impregnated with the above fibers in a monolithic panel with a thickness of between 2 and 8 mm, FST properties> HL1 R1, R7 (according to EN45545 standard).

The thickness of a skin is 2 to 5 mm and the fibers are in the form of unidirectional sheets or pre-impregnated fabrics.

For the soul, a PET foam with a density greater than or equal to 100 kg / m ³ is chosen, a PMI foam with a density greater than or equal to 50 kg / m ³ or a honeycomb with a density greater than or equal to 50 kg / m ³ , depending on the areas and needs. The thickness of the soul is 10mm to 200mm there also depending on the areas and needs.

The process used is a vacuum bag polymerization (except autoclave) with a temperature not exceeding 120 ° C.

The precise thickness of the skins, the soul, and the orientations of the fibers in the skins obviously depend on the stresses on the body.

As indicated above, these specifications concern the natural frequency of the vehicle, which must be greater than about 10 Hz; it is then necessary to dimension the face in stiffness, the compression / traction forces related to the circulation of the car, which are of the order of a hundred tons; bending forces, related to pressure waves of the order of 10 OOOPa.

Overall, for a car of about fifteen meters between bogies, to carry about forty passengers in this area, conventional calculations by finite elements lead to a sandwich material of about forty mm thick.

According to one embodiment of the invention, in particular for a two-stage car with lower window 20a and upper windows 20b, the wall will have different skin thicknesses between the lower part of the face and the upper part. According to the example given in FIG. 6, the lower part of the panel (301) is made with a skin thickness of 2.78 mm and a thickness the upper portion 302 is made with a skin thickness of 3.33 mm and a core thickness of 38 mm.

It will be noted in particular that each skin has a thickness of about 3 mm, which is in the passage much greater than the thicknesses of aircraft fuselages, which do not exceed 2 mm.

In common parts (excluding binding and particular points) at least one and preferably the two skins of the sandwich structure are for example made with plies of high strength carbon prepregs, for example of T700 type Toray company.

To make the skin or skins, it is possible to use as an example as basic elements: a pre-assembly of fiber folds oriented at + 45 °, 0 °, -45 ° respectively dry weight 125g, 250g, 125g, a unidirectional fold oriented at 0 ° dry weight 500g and a fold which is a fabric oriented at 0 ° / 90 ° dry weight 500g, these values being given with a tolerance of ± 10%.

The table below describes the fibrous architecture that can be achieved depending on the areas of application of the composite.

In general, it is found that the optimization of the structure requires the presence of fibers at 0 °, 90 ° and +/- 45 °. The 45 ° fibers are particularly suitable for taking up the shear forces in the context of the panel considered.

In this example, preference is given to a distribution of 50% of unidirectional fibers at 0 °, 17% of fibers at 90 ° and 33% of fibers at ± 45 ° to make a flag, of 33% of unidirectional fibers at 0 °, 33% of fibers at 90 ° and 33% of fibers at ± 45 ° for a superior vertical facade and 40% of unidirectional fibers at 0 °, 20% of fibers at 90 ° and 40% of fibers at ± 45 ° for a facade lower.

Optimally, the shear stress Tau (t) that applies to the front panel must be taken up by fibers 100 oriented at + 45 ° and -45 ° on each of the two skins of the structure, as illustrated. Figure 3.

It is in fact under these conditions that the structure is optimized in its mechanical operation, and therefore in mass and cost.

However, at the level of the panels of the faces, the presence of angles of bays leads to cut the fibers.

In such a configuration, the shear stresses pass through the resin, which results in a need to over-thicken the sandwich panel skins in the inter-bay area (trumeau) in order to lower the shear stress below the level. admissible by the resin. As a reminder, the permissible shear stress permissible by the resin (stack at + 45 ° and -45 ° with all the cut fibers) is of the order of 30 MPa when it is 500 MPa in the direction of the fiber when it is solicited in compression. Cutting the fibers also makes the structure much more sensitive to environmental conditions and fatigue. Under fatigue loads, the permissible plane shear stress of the resin is evaluated to be about 10 MPa when it is possible to assume a strength greater than 200 MPa in the direction of the fiber.

This again results in a need for additional thickness or a risk of weakening the structure over time.

The proposed solution shown schematically in Figure 7 where the large windows have an octagonal profile for which the lateral sides are provided with a convex profile with three segments, an upper 45 ° segment an intermediate vertical segment and a segment less than 45 ° consists in modifying the geometry of the bays so that a certain section of oriented fibers 100 at + 45 ° and -45 ° can be continuous between the upper and lower part of the face and thus transfer the shear stresses. This gives a configuration reminiscent of the portholes described in document US2012 / 0223187A1 but differs in the large area of the windows and the fact that their long side is along the axis of the car. This makes it possible to increase the section of working fibers, without significantly reducing the area of windows.

As the car is under low pressure, the optimum fiber orientation is around ± 45 °, not around 70 ° as for an aircraft fuselage.

One question concerns the optimization of the cutting angle of the bays (for an imposed spacing), in order to maximize the glass surface. Indeed, for a given spacing between bays, this cutting angle directly affects the section of working fibers.

An analytical calculation simulation was conducted to evaluate the yarn stress in the folds at +/- 45 ° and the plane shear stresses in the 0/90 ° folds as a function of the cutting angle of the windows. according to the configuration of Figure 9A where the short sides of the window are convex V profile.

This simulation whose parameters show that the cutting angle at

45 ° is obviously optimal allows to note that this angle could be raised to 50 ° with at least a fold of carbon at + -45 ° and that an angle of 60 ° can also be acceptable with the criteria retained but with 2 folds of carbon at + - 45 °.

The stack of the composite panel (draping at 0 °, +45, -45 ° and 90 °) corresponds to that which has been defined to meet the mechanical need in the current zone of the body. For a bay configuration corresponding to the case studied (L_trumeau = 384mm and H_baie = 620mm), the angle "a" cutting of the bay is varied. As a result, the length "L_fibre_non uncut" decreases, from a maximum value when a = 45 ° to a value of zero for a certain value of a (about 70 ° in the case treated).

The results of the analysis are presented in Figure 9-2 and 9-3. This analysis shows that, when the angle of the bay is greater than 70 °, all fibers at + -45 ° are cut and the shear stress in the plies at 0 ° and 90 ° is greater than the allowable value, point P in Figure 9-2. Consequently, a reinforcement should be implemented in the area of the piers (increase the thickness of + 250% in the studied case), with an impact on the mass and the cost.

This analysis also shows that the cutting angle at 45 ° is obviously optimal, since the shear flow is correctly taken up by the fibers at + 45 ° and -45 ° uncut as shown in Figure 9-2, while the plane shear stress is also less than the allowable value, see Figure 9.3.

The analysis also shows that the angle of the bays could be opened up to about 55 ° without needing reinforcements.

FIG. 8 shows the complete box of the car with the flag 35, the door openings 23 and its frame 25, service openings 22, 26 such as the air-conditioning and their frame 24, 27 as well as the end frames. 28 on which are fixed the walls 2.

The self-rigidized body can be directly assembled with a frame carrying the bogies of the car.

The present invention can be used on all types of rail transport vehicles intended for passenger transport.

Claims

1 - Rolling vehicle car (1) characterized in that it comprises side walls (2) each in one piece formed of a composite sandwich panel in one piece (10) provided with a first skin (1). 1) on the outside of the car, a second skin (12) on the inside of the car and a closed-cell foam core (13a) or honeycomb core (13b) between said skins, said walls being provided with openings of windows (20) formed by lay-ups of longitudinal fibers, transverse fibers and crossed diagonal fibers (100) forming said skins, said openings (20) having a polygonal shape reducing the area of diagonal fibers (100) interrupted in the corners of the openings, said walls realizing the faces of the car.

2 - Car according to claim 1 wherein the openings have a hexagonal or octagonal general shape with two large horizontal sides connected by convex lateral edges.

3 - car according to claim 1 or 2 wherein the openings (20) are equipped with a reinforcing edge (21) provided with a tubular frame (30).

4 - Car according to claim 3 wherein the reinforcing edge (21) has an inner wing (31) for fixing the edge on the edge (2a) of the opening on the inner side of the wall.

5 - Car according to claim 4 for which the tubular frame is of rectangular section, the inner wing (31) extending one side of the tubular frame on the inside of the wall (2).

6 - Car according to claim 5 wherein the inner wing (31) is fixed on the inside of the wall by means of screws, rivets or other fastening means (32).

7 - Car according to any one of claims 3 to 6 for which a face of the tubular frame (30) directed towards the interior of the car is fixed by means of screws, rivets or other fastening means (32) on a rim the opening made by the second skin protruding from the soul of the wall. 8 - Car according to any one of claims 3 to 7 wherein the reinforcing edge (21) has an inner flange (34) accommodating a fixing of a window.

9 - Car according to any one of the preceding claims wherein at least one of the two skins (1 1, 12) of the sandwich structure is made by means of folds oriented in 4 preferred directions 0 ° (longitudinal axis of the body), 90 °, + 45 ° and -45 °.

10 - Car according to claim 9 for which the plies are prepreg folds unit weight of between 125g / m ² and 500g / m ² .

1 1 - car according to any one of the preceding claims wherein the corner segments (40) of said openings are inclined between 45 ° and 60 ° relative to a longitudinal direction (L) of the wall and preferably inclined between 45 ° and 50 ° with respect to a longitudinal direction (L) of the wall.

12 - Car according to claim 9 or 1 1 for which the 45 ° son are in the form of at least two folds of +/- 45 ° carbon fiber.

13 - Train car according to any preceding claim wherein the core of the sandwich (13a, 13b) is made of a material selected from polyethylene terephthalate (PET), polymethacrylimide (PMI), Polyetherimide (PEI), an aluminum honeycomb or a poly (m-phenyleneisophthalamide) (MPD-I) honeycomb (phenolic resin impregnated structure).