A glazing assembly for a vehicle, notably an aircraft, and associated vehicle

Abstract

A glazing assembly for a vehicle, notably an aircraft, and associated vehicle The invention concerns a glazing assembly (12) for a vehicle (10), notably an aircraft, comprising a laminated glazing (24) and a peripheral attachment device (26) comprising superimposed first, second, third and fourth straps (S1, S2, S3, S4), the first strap being the closest to an attachment portion of the vehicle. In one transverse plane crossing the straps, passing through one point P of the contour (C1) of a midplane surface (M1) of one structural ply of the glazing and being normal to the tangent of said contour at point P: a local stiffness of the first strap is strictly greater than a local stiffness of the second strap, the local stiffness of the first strap is less than or equal to a local stiffness of the third strap, and the local stiffness of the third strap is strictly greater than a local stiffness of the fourth strap.

Description

DESORPTIONTITLE : A glazing assembly for a vehicle, notably an aircraft, and associated vehicle

[0001] The invention concerns a glazing assembly for a vehicle, notably an aircraft, of the type comprising two structural plies and a peripheral attachment device configured to attach the laminated glazing to a structural attachment part of the vehicle, the peripheral attachment device comprising a set of superimposed straps arranged along the periphery of the laminated glazing, the set of superimposed straps comprising a first strap, a second strap, a third strap and a fourth strap superimposed on each other in this order along a superposition direction, the first strap being the strap of the set of superimposed straps configured to be the closest to an attachment portion of the vehicle mechanically attached to the structural attachment part or forming part of the structural attachment part of the vehicle, the first and the second straps forming a first pair of straps and the third and fourth straps forming a second pair of straps, each pair of straps delimiting between the straps of this pair of straps a housing, for each pair of straps, the housing delimited by this pair of straps having a first peripheral extremity portion delimiting a connecting portion accommodating a respective ply portion of a structural ply among the two structural plies, a second peripheral extremity portion accommodating a spacer and a peripheral intermediate portion extending between the first peripheral extremity portion and the second peripheral extremity portion, the portion of each strap of this pair of straps delimiting the intermediate portion having a length, said “free length”.

[0002] The invention also concerns a vehicle comprising such glazing assembly.

[0003] The invention advantageously belongs to the field of aeronautical glazing and applies, advantageously, for aircrafts, such as airliners, helicopters, air drones, air taxis, business jets, both for civil and military applications.

[0004] The glazing assembly according to the invention is, for example, intended to form a windshield or at least a part of the windshield of a cockpit of an aircraft. Generally, a windshield of an aircraft comprises a plurality of glazing assemblies.

[0005] The glazing assembly according to the invention belongs to the field of hoop loaded glazing also known as “load bearing glazing” and, in particular, to the field of hoop loaded windshields.

[0006] Pressurization of an aircraft causes the airframe of the aircraft to carry circumferential and longitudinal forces, also referred as “membrane forces”, due to the fuselage expansion.

[0007] T raditionally, an aeronautical glazing, in particular being part of a windshield was not designed to be a structural member. Consequently, the airframe around the windshield was reinforced so that the membrane forces were diverted around the windshield rather than transferred through it. This reinforcement, however, leads to an increase of weight of the aircraft.

[0008] One way to reduce the overall weight of the aircraft is to allow the windshield to participate in carrying the membrane forces thereby allowing the airframe reinforcement to be reduced. Glazing assemblies’ designs using this approach are, as mentioned above, referred to “hoop loaded glazing assembly” and also sometimes to “load bearing glazing assemblies”.

[0009] The hoop loaded glazing assemblies, notably forming part of hoop loaded windshields, are thus subjected to the membrane forces when the fuselage of the aircraft is pressurized. We call this the nominal membrane forces. In particular, due to the membrane forces, the glazing assembly is “stretched” on all its sides. In other words, the membrane forces are applied to the edges of the glazing assembly. An ultimate loading condition is defined as being the application of A times the nominal membrane forces to the glazing assembly with all structural plies of the laminated glazing intact, where A is a predefined safety factor. A failsafe loading condition is defined as being the application of B times the nominal membrane forces to the glazing assembly with any one of the structural plies of the laminated glazing having failed and no longer participating in carrying forces, where B is a predefined safety factor. Typically, A is different from B.

[0010] Known glazing assemblies forming hoop loaded windshields are not entirely satisfactory since it has been observed that, in both ultimate loading condition and in failsafe loading condition, the straps of those known glazing assemblies non uniformly carry the membranes forces. This is notably because the straps of the set of straps have a same stiffness and because the set of superimposed straps is mechanically fixed to the attachment portion of the vehicle only by one of its two sides among the internal side and the external side. Such a non-uniform strap force distribution may increase the likelihood of failure in the straps carrying the highest forces within the peripheral attachment device. Such a non-uniformity in the force distribution in the set of superimposed straps thus affects the strength of the peripheral attachment system.

[0011] In particular, in such known glazing assemblies, in the ultimate loading condition, the strap that is the closest to the attachment portion of the vehicle carries the highest force and is more predisposed to breakage.

[0012] One aim of the invention is thus to obtain a glazing assembly having an improved strength, in particular under both ultimate and failsafe loading conditions.

[0013] For this purpose, the invention relates to a glazing assembly wherein in at least one transverse plane crossing the set of superimposed straps, passing through one point P of the contour of a midplane surface of one of the two structural plies and being normal to the tangent of said contour at point P:- a local stiffness of the first strap is strictly greater than a local stiffness of the second strap,- the local stiffness of the first strap is less than or equal to a local stiffness of the third strap, and- the local stiffness of the third strap is strictly greater than a local stiffness of the fourth strap, and in said transverse plane, the local stiffness kj of each i-th strap of the set of superimposed straps is defined by the following formula:wherein:- i identifies the i-th strap of the set of superimposed straps with i = {1; 2; 3; 4},- Ej is the in-plane tensile modulus of elasticity of the i-th strap along a direction of load,- the direction of load in the transverse plane is parallel to the tangent at point P of the curve defined by the intersection of said transverse plane and said midplane surface, the direction of load being oriented opposite to the laminated glazing,- tj is the thickness of the i-th strap along the superposition direction, and- Li is the free length of the i-th strap.

[0014] The distribution of the membrane forces depends notably on the stiffnesses of the four straps.

[0015] Thanks to the invention, by adapting the local stiffnesses of the different straps, the tensile stress induced by the membrane forces carried by the set of superimposed straps is better distributed among the straps.

[0016] Moreover, thanks to the invention, the strength of the peripheral attachment device in ultimate and failsafe loading conditions is improved regardless of the choice of glass and interlayer.

[0017] In particular, thanks to the invention, the local stiffness of the different straps is tuned to increase the strength of the peripheral attachment device and thus the strength of the glazing assembly.

[0018] According to some embodiments, in the transverse plane, the peripheral attachment device is such that:- a first ratio of the local stiffness of the first strap to the local stiffness of the second strap is greater or equal to 1.5 and less than or equal to 2,- a second ratio of the local stiffness of the first strap to the local stiffness of the third strap is less than or equal to 1 , and- a third ratio of the local stiffness of the third strap to the local stiffness of the fourth strap is greater than or equal to 2.

[0019] By tuning the local stiffnesses of the straps so that the three ratios of strap stiffnesses verify the above-mentioned specific ranges according to the invention, the strength of the peripheral attachment device and thus the strength of the glazing assembly are increased, notably both in ultimate loading conditions and in failsafe loading conditions.

[0020] In particular, in the transverse plane, each strap carries a nominal tensile stress depending on the strap’s thickness in the free length, the force per length unit and the bending moment.

[0021] In the ultimate loading condition, the maximum tensile stress is defined as being the maximum of the nominal tensile stresses over the four straps that are both intact. In the failsafe loading condition, the maximum tensile stress is the maximum of the nominal stresses over the two straps that are not attached to the broken structural ply (i.e. attached to the intact structural ply).

[0022] By tuning the local stiffnesses of the straps so that the first, second and third ratios verify the above-mentioned specific ranges, the maximum tensile stress both in ultimate loading conditions and in failsafe loading conditions is reduced.

[0023] More precisely, by tuning the local stiffnesses of the straps so that the three ratios verify the specific ranges, the membrane forces are more evenly distributed across the four straps. In particular, tailoring the three ratios of strap stiffnesses according to the above-mentioned specific ranges leads to a redistribution of the applied membrane forces on the four straps which corresponds to a reduction of the maximum tensile stress.

[0024] Hence, the tuning of the local stiffnesses of the straps so that the three ratios verify the above-mentioned specific ranges enables to reduce the peak stress in the glazing assembly for a given applied membrane force.

[0025] The tuning of the local stiffnesses of the straps of the peripheral attachment device so that the three ratios verify the above-mentioned specific ranges thus leads to an increasing of the strength of the peripheral attachment device and thus of the glazingassembly, as compared to glazing assemblies that do not verify the specific ranges of the three ratios.

[0026] The glazing assembly according to the invention may comprise one or more of the following features, taken into consideration in isolation or according to any technically feasible combinations:- in said transverse plane, the in-plane tensile modulus of the first strap, the in-plane tensile modulus of the second strap, the in-plane tensile modulus of the third strap and the in-plane tensile modulus of the fourth strap are constant, and the free length of the first strap, the free length of the second strap, the free length of the third strap and the free length of the fourth strap are constant.- in said transverse plane, said first ratio corresponds to the thickness of the first strap to the thickness of the second strap, said second ratio corresponds to the thickness of the first strap to the thickness of the third strap, and said third ratio corresponding to the thickness of the third strap to the thickness of the fourth strap.- the peripheral attachment device has an attachment zone to said attachment portion of the vehicle, the attachment zone of the peripheral attachment device being configured to be mechanically attached to the attachment portion of the vehicle, the first strap being the strap of the set of superimposed straps the closest to the attachment zone.- the peripheral attachment device comprises a plurality of coupling members configured to pass through the first, second, third and fourth straps, the plurality of coupling members being designed to be attached to the attachment portion of the vehicle.- each coupling member comprises a first extremity and an opposed second extremity, the first extremities or the second extremities configured to cross the attachment portion of the vehicle forming at least in part the attachment zone.- each strap of the set of the superimposed straps is formed from at least one corresponding strip having at least in part the shape of the strap, the or each strip comprising two extremity portions and each strap including at least one junction zone, for each strap, the junction zone comprising the two extremity portions of one corresponding strip in adhesive contact with each other or the junction zone comprising one extremity portion of a first strip and one extremity portion of a second strip in adhesive contact with each other, the at least one transverse plane crosses the set of superimposed straps outside each junction zone.- the first, second, third and fourth straps are continuous along the periphery of the laminated glazing.- each of the first, second, third and fourth straps is made of at least one composite material, the composite material being, preferentially, a fiber reinforced polymermaterial.- at least one of the first, second, third and fourth straps is made in a quasi-isotropic composite material.- at least one of the first, second, third and fourth straps is made in an anisotropic composite material having fibers extending along a predefined alignment direction.- each in-plane tensile modulus of elasticity is determined using a uniaxial tension test, such as the standard test method defined in the American Standards of Technical Material (ASTM) D3039 / D3039M.- the free lengths of the first, second, third and fourth straps are constant.- for each pair of straps, the spacer located in the housing delimited by this pair of straps is configured to maintain a predefined spacing between the straps of this pair of straps along the superposition direction.- the peripheral attachment device comprises two flexible layers made of a flexible material, for each pair of straps, a respective flexible layer of the two flexible layers being arranged in the peripheral intermediate portion of the housing delimited by this pair of straps, the flexible material being preferably less stiff than the material of the spacer and the flexible material being preferably less stiff than the material of the straps.- the glazing assembly is configured to form at least a portion of a windshield of the vehicle.- the midplane surface of a ply of the two plies is the set of points in the ply that are equidistant from the first and second principal surfaces of this ply.- the contour of the midplane surface is the contour of the midplane surface of the ply whose ply portion is housed in the housing delimited by the first strap and the second strap.- in each transverse plane, the local stiffness of the first strap is strictly greater than the local stiffness of the second strap, the local stiffness of the first strap is less than or equal to the local stiffness of the third strap, and the stiffness of the third strap is strictly greater than the stiffness of the fourth strap.- in each transverse plane, the first ratio of the local stiffness of the first strap to the local stiffness of the second strap is greater or equal to 1.5 and less than or equal to 2, the second ratio of the local stiffness of the first strap to the local stiffness of the third strap is less than or equal to 1 , and the third ratio of the local stiffness of the third strap to the local stiffness of the fourth strap is greater than or equal to 2.- in each transverse plane, the in-plane tensile modulus of the first strap, the in-plane tensile modulus of the second strap, the in-plane tensile modulus of the third strap and the in-plane tensile modulus of the fourth strap are constant, and the free length of thefirst strap, the free length of the second strap, the free length of the third strap and the free length of the fourth strap are constant.- in each transverse plane outside each junction zone, the local stiffness of the first strap is strictly greater than the local stiffness of the second strap, the local stiffness of the first strap is less than or equal to the local stiffness of the third strap, and the local stiffness of the third strap is strictly greater than the local stiffness of the fourth strap.- in each transverse plane outside each junction zone, the first ratio of the local stiffness of the first strap to the local stiffness of the second strap is greater or equal to 1.5 and less than or equal to 2, the second ratio of the local stiffness of the first strap to the local stiffness of the third strap is less than or equal to 1 , and the third ratio of the local stiffness of the third strap to the local stiffness of the fourth strap is greater than or equal to 2.- in each transverse plane outside each junction zone, the in-plane tensile modulus of the first strap, the in-plane tensile modulus of the second strap, the in-plane tensile modulus of the third strap and the in-plane tensile modulus of the fourth strap are constant, and the free length of the first strap, the free length of the second strap, the free length of the third strap and the free length of the fourth strap are constant.- at least one strap is made of an anisotropic composite material, said in-plane tensile modulus of elasticity of this strap depending on the in-plane tensile modulus of elasticity of this anisotropic material in a predefined alignment direction of the fibers and the relative angle between said direction of load and the predefined alignment direction of the fibers.- the first structural ply is in mineral glass or in a transparent ceramic and the second structural ply is in mineral glass or in a transparent ceramic.- the first and the second structural plies are bonded to one another by an interlayer, the second and third straps being bonded to each other by said interlayer.

[0027] The invention also concerns a vehicle, notably an aircraft, comprising the glazing assembly as defined above.

[0028] According to some embodiments, the vehicle comprises a first mounting element and a second mounting element arranged on both parts of a portion of the set of superimposed straps, one of the two mounting elements defining the attachment portion of the vehicle attached to the structural attachment part of the vehicle or forming part of the structural attachment part of the vehicle, the peripheral attachment device comprising a plurality of coupling members configured to pass through the first, second, third and fourth straps and the first and second mounting elements, the plurality of coupling members being attached to the attachment portion of the vehicle.

[0029] The invention and its advantages will be better understood upon reading the following description, which is given solely by way of non-limiting example and which is made in reference to the appended drawings in which:- figure 1 is a schematic front view of a part of an aircraft comprising the glazing assembly according to the invention; and- figure 2 is a schematic cross section view of the part of the aircraft of figure 1 according to the cross sectional plane ll-ll.

[0030] In the following of the description, the expression according to each an “element is comprised between a first value V1 and a second value V2” means that the element is greater than or equal to V1 and less than or equal to V2.

[0031] In reference to figures 1 and 2, a vehicle 10 comprising a glazing assembly 12 according to the invention is described.

[0032] Figures 1 and 2 show the glazing assembly 12 mounted in the vehicle 10. Such configuration of the glazing assembly 12 is referred to the “mounting configuration” of the glazing assembly 12 in the following.

[0033] In the present example, the vehicle 10 is an aircraft.

[0034] For example, the aircraft is an airliner.

[0035] Alternatively, the aircraft is a helicopter, an air drone, an air taxi, a business jet.

[0036] The vehicle 10 may be a civil vehicle or a military vehicle.

[0037] In the present invention, the glazing assembly 12 is part of a windshield of the aircraft. The windshield of the aircraft delimits at least in part the cockpit of the aircraft. Typically, the aircraft comprises several glazing assemblies 12 forming the windshield.

[0038] Although the glazing assembly 12 is here described as forming a part of a windshield, this aspect is not limitative and the glazing assembly 12 can be part of any window of the aircraft such as a porthole delimiting at least in part the passenger cabin.

[0039] As shown in figures 1 and 2, the vehicle 10 comprises a structural attachment part 14 of a glazing assembly 12, a first mounting element 16, a second mounting element 18, at least one glazing assembly 12, optionally a first sealing layer 21 , optionally a second sealing layer and optionally a peripheral seal 23. The vehicle 10 comprises an attachment portion that is part of the structural attachment part 14 or mechanically attached to the structural attachment part 14.

[0040] In the present example, as shown in figure 2, the structural attachment part 14 and the first mounting element 16 are made from a single piece.

[0041] According to a variant, the structural attachment part 14 and the first mounting element 16 are different elements. In a such case, the structural attachment part 14 and the first mounting element 16 are attached to each other.

[0042] In the specific example of figures 1 and 2, the first mounting element 16 extends on the internal side of the glazing assembly 12 and forms an internal mounting element.

[0043] In the present example, the first mounting element 16 defines said attachment portion of the vehicle 10.

[0044] In the present example, the structural attachment part 14 and the attachment portion form a single piece.

[0045] As a variant, the structural attachment part 14 and the attachment portion are distinct pieces for example mechanically attached to each other by a fixing device, for example bolts.

[0046] In the specific example of figures 1 and 2, the second mounting element 18 extends on the external side of the glazing assembly 12 and forms an external mounting element.

[0047] The first mounting element 16 and the second mounting element 18 extends on both side of a portion of the glazing assembly 12.

[0048] The glazing assembly 12 comprises a laminated glazing 24, hereinafter referred as “glazing 24” and a peripheral attachment device 26 configured to attach the glazing 24 to the structural attachment part 14 of the vehicle 10.

[0049] In the present example, the glazing assembly 12 is an aeronautical glazing assembly.

[0050] The glazing assembly 12 according to the invention is a hoop loaded glazing subjected to membrane forces when the fuselage of the aircraft is pressurized.

[0051] As used herein, a “structural ply” is a rigid sheet constitutive of the laminated glazing 24, capable to ensure the mechanical resistance of the glazing 24 and to transmit the membrane forces. The structural ply has, for example, an elastic modulus at least equal to 70 gigapascal (GPa).

[0052] As used here, the terms “internal”, “inner” and “external”, “outer” are relative terms. “Internal”, “inner” refer to elements configured to be directed towards the interior of the vehicle 10 on which the glazing assembly 12 is mounted and “external”, “outer” refer to elements configured to be directed towards the exterior of the vehicle 10 on which the glazing assembly 12 in mounted.

[0053] The glazing 24 comprises two structural plies 31 , 32, hereinafter referred to “first structural ply 31” and “second structural ply”, an additional ply 34, a first interlayer 41 and a second interlayer 42.

[0054] The glazing 24 is in this example an aeronautical glazing.

[0055] The glazing 24 exactly comprises two structural plies 31 , 32.

[0056] The first and second structural plies 31 , 32 are transparent.

[0057] The glazing 24 comprises a first principal face 24A and a second principal face 24B, opposed to the first principal face 24A.

[0058] The first principal face 24A forms an internal face of the glazing 24.

[0059] The second principal face 24B forms an external face of the glazing 24.

[0060] The first and second structural plies 31 , 32 are superimposed on each other along a first superposition direction. The first superposition direction is defined by the distance separating the principal surfaces of the first and second structural plies 31 , 32 of the glazing 24.

[0061] The first structural ply 31 forms, in this example, the innermost structural ply among the two structural plies 31 , 32.

[0062] In the example represented in figures 1 and 2, the first structural ply 31 is flat. As a variant, the first structural ply 31 is curved.

[0063] The first structural ply 31 is delimited by a first principal surface 31A, an opposed second principal surface 31 B and an edge 31 C connecting the first principal surface 31 A and the second principal surface 31 B to each other.

[0064] The first principal surface 31 A of the first structural ply 31 forms, in this example, the internal surface of the first structural ply 31 .

[0065] The first principal surface 31 A of the first structural ply 31 forms, in this example, the internal face 24A of the glazing 24.

[0066] The second principal surface 31 B of the first structural ply 31 forms, in this example, the external surface of the first structural ply 31.

[0067] The second principal surface 31 B of the first structural ply 31 extends in front of the first principal surface 32A of the second structural ply 32. Otherwise said, the second principal surface 31 B faces the first principal surface 32A.

[0068] For example, the first structural ply 31 is in glass.

[0069] For example, the Young’s modulus of the glass is 70 GPa.

[0070] For example, the first structural ply 31 is made of mineral glass.

[0071] The mineral glass may be soda-lime silica, aluminosilicate, borosilicate or the like.

[0072] For example, the first structural ply 31 is thermally tempered or chemically reinforced.

[0073] Alternatively, the first structural ply 31 is in a transparent ceramic.

[0074] The transparent ceramic may be sapphire (AI2O3), spinel (MgAhCU) or aluminum oxynitride ((AIN)x (AhO3)i-x with 0.30 < x < 0.37).

[0075] For example, the Young’s modulus of the sapphire is 350 GPa.

[0076] For example, the Young’s modulus of the spinel is 270 GPa.

[0077] The first structural ply 31 has, for example, a thickness comprised between 2 millimeters (mm) and 12 mm, in particular comprised between 2 mm and 10 mm and advantageously comprised between 3 mm and 9 mm.

[0078] It is defined for the first ply 31 a midplane surface that is the set of points that are equidistant between the first principal surface 31 A and the second principal surface 31 B of the first structural ply 31. This midplane surface of the first ply 31 is called in the following “first midplane surface M1”.

[0079] A portion of the first midplane surface M1 is schematically represented in figure 2 in dotted line.

[0080] The contour C1 of the first midplane M1 surface is called, in the following, “first contour C1”. In other words, the contour C1 is the external contour or boundary contour of the first midplane surface M1 .

[0081] The first contour C1 is schematically represented in figure 1.

[0082] The second structural ply 32 is, in this example, the outermost structural ply among the two structural plies 31 , 32.

[0083] In the example represented in figures 1 and 2, the second structural ply 32 is flat. As a variant, the second structural ply 32 is curved.

[0084] The second structural ply 32 comprises a first surface 32A, an opposed second surface 32B and an edge 32C connecting the first surface 32A and the second surface 31 B to each other.

[0085] The second structural ply 32 extends between the additional ply 34 and the first structural ply 31.

[0086] The first principal surface 32A of the second structural ply 32 forms an internal surface of the second structural ply 32.

[0087] The first principal surface 32A of the second structural ply 32 extends in front of the first structural ply 31 and, in particular, in front of the second principal surface 31 B of the first structural ply 31. Otherwise said, the first principal surface 32A of the second structural ply 32 faces the second principal surface 31 B of the first structural ply 31.

[0088] The second principal surface 32B of the second structural ply 32 forms an external surface of the second structural ply 32.

[0089] The second principal surface 32B of the second structural ply 32 extends in front the additional ply 34.

[0090] For example, the second structural ply 32 is in glass.

[0091] For example, the Young’s modulus of the glass is 70 GPa.

[0092] For example, the second structural ply 32 is made of mineral glass such as sodalime silica, aluminosilicate, borosilicate or the like.

[0093] For example, the second ply 32 is thermally tempered or chemically reinforced.

[0094] Alternatively, the second structural ply 32 is in a transparent ceramic.

[0095] The transparent ceramic may be sapphire, spinel or Aluminum Oxynitride.

[0096] The second structural ply 32 has for example a thickness comprised between 2 mm and 12 mm, for example comprised between 2 mm and 10 mm and advantageously comprised between 3 mm and 9 mm.

[0097] It is defined for the second ply 32 a midplane surface that is the set of points that are equidistant between the first principal surface 32A and the second principal surface 32B of the second structural ply 32. This midplane surface of the second ply 32 is called in the following “second midplane surface”.

[0098] The contour of the second midplane surface is called, in the following, “second contour” (not shown in the figures).

[0099] The additional ply 34 forms an external ply of the glazing 24.

[0100] The additional ply 34 comprises a first surface 34A, a second surface 34B, and an edge 34C connecting the first surface 34A and the second surface 34B to each other.

[0101] The first surface 34A of the additional ply 34 forms an internal surface of the additional ply 34.

[0102] The first surface 34A of the additional ply 34 extends in front of the second surface 32B of the second structural ply 32.

[0103] The second surface 34B of the additional ply 34 forms an external surface of the additional ply 34.

[0104] The second surface 34B of the additional ply 34 delimits the external face 24B of the glazing 24.

[0105] It should be noted that the additional ply 34 is a thin protective sheet that is not structural. In other words, the additional ply 34 does not transmit the membrane forces.

[0106] The additional ply 34 is for example made of mineral or organic glass.

[0107] For example, the additional ply 34 has a thickness comprised between 0.5 mm and 5 mm, preferably between 2 mm and 4 mm.

[0108] The first surface 34A of the additional ply 34 is, for example, carrying a network of electroconductive wires or a thin electroconductive layer such a layer in indium oxide doped with tin (ITO for “Indium Tin Oxide”), silver, gold or equivalent, suitable for defrosting the laminated glazing 24.

[0109] The interlayers 41 , 42 do not form structural plies.

[0110] As shown in figure 2, the first interlayer 41 extends in sandwich between the first structural ply 31 and the second structural ply 32.

[0111] The first interlayer 41 adhesively bonds the first and second structural plies 31 , 32 to each other.

[0112] As shown in figure 2, the first interlayer 41 comprises a first portion 411 and a second portion 412.

[0113] The first portion 411 of the first interlayer 41 extends in sandwich between the first and second structural plies 31 , 32.

[0114] The thickness of the first portion 411 of the first interlayer 41 is greater than or equal to 1 mm and less than or equal to 20 mm, for example comprised between 2 mm and 4.5 mm.

[0115] The second portion 412of the first interlayer 41 extends in sandwich between the second and third straps S2, S3 of the peripheral attachment device 26 and adhesively bonds the second and third straps S2, S3 to each other.

[0116] The first interlayer 41 is an adhesive layer, for example, in polyurethane thermoplastic, polyvinyl butyral (“PVB” in the relevant literature), in ethylene-vinyl acetate copolymer (“EVA” in the relevant technical literature), in an ionomer resin or in a casting resin.

[0117] As also shown in figure 2, the second interlayer 42 extends in sandwich between the second structural ply 32 and the additional ply 34.

[0118] The second interlayer 42 adhesively bonds the second structural ply 32 and the additional ply 34 to each other.

[0119] As shown in figure 2, the second interlayer 42 comprises a first portion 42i and a second portion 422.

[0120] The first portion 42i of the second interlayer 42 extends in sandwich between the second structural ply 32 and the additional ply 34.

[0121] For example, the thickness of the first portion 42i of the second interlayer 42 is greater than or equal to 2 mm and less than or equal to 8 mm, in particular less than or equal to 4 mm.

[0122] The second portion 422of the second interlayer 42 extends in sandwich between the additional ply 34 and a fourth strap S4 of the peripheral attachment device 26 and adhesively bonds the additional ply 34 and said fourth strap S4.

[0123] The second interlayer 42 is an adhesive layer, for example, in polyurethane thermoplastic, in PVB, in EVA, in an ionomer resin or in a casting resin.

[0124] The peripheral attachment device 26 comprises a set of superimposed straps, a first spacer 51 , a second spacer 52, optionally a third spacer 53, flexible layers, namely a first flexible layer 61 , a second flexible layer 62. According to a particular example, the peripheral attachment device 26 comprises a plurality of coupling members 64.

[0125] The peripheral attachment device 26 ensures the connection between the laminated glazing 24 and structure of the vehicle 10.

[0126] As shown on figure 2, the peripheral attachment device 26 has an attachment zone 28 to the attachment portion of the vehicle 10.

[0127] The attachment zone 28 is localized on one side of the peripheral attachment device 26, its internal side in the present example.

[0128] The attachment zone 28 of the peripheral attachment device 26 is configured to be mechanically attached to the attachment portion of the vehicle 10.

[0129] As shown on figure 2, in the mounting configuration, the attachment zone 28 of the peripheral attachment device 26 crosses the attachment portion of the vehicle 10 and is mechanically fixed to the attachment portion of the vehicle, for example by bolting.

[0130] The peripheral attachment device 26 is bonded to the laminated glazing 24.

[0131] The set of superimposed straps is arranged along the periphery of the glazing 24. Otherwise said, the set of superimposed straps runs along the periphery of the glazing 24.

[0132] In particular, the set of superimposed straps is arranged along the whole periphery of the glazing 24.

[0133] The set of superimposed straps comprises four straps, namely a first strap Si, a second strap S2, a third strap S3 and a fourth strap S4.

[0134] Each strap Si , S2, S3, S4 is identified by an index number i with i={1 , 2, 3, 4}.

[0135] The first strap Si (strap with index number 1), the second strap S2 (strap with index number 2), the third strap S3 (strap with index number 3) and the fourth strap S4 (strap with index number 4) are superimposed on each other along a second superposition direction.

[0136] Otherwise said, the first strap Si, the second strap S2, the third strap S3 and the fourth strap S4 are stacked on each other along the second superposition direction Z.

[0137] The second superposition direction is, in the specific example of figures 1 and 2, parallel to the first superposition direction.

[0138] In the particular example shown in figures 1 and 2, the first and second superpositions direction being both parallel to an axis Z are called “superposition direction Z”.

[0139] As shown in figure 2, the straps Si , S2, S3, S4 are separated from each other along the superposition direction Z. Otherwise said, the straps Si , S2, S3, S4 are not in contact with each other. The straps Si , S2, S3, S4 are separated two by two by a gap.

[0140] The first strap Si is the strap of the set of superimposed straps that is configured to be the closest to the attachment portion of the vehicle 10 along the superposition direction Z.

[0141] As shown in figure 2, in the mounting configuration, the first strap Si is the strap the closest to the first mounting element 16 forming the attachment portion forming part of the structural attachment part 14 of the vehicle 10.

[0142] The first strap Si is the strap of the set of superimposed straps that is the closest to the attachment zone 28 of the peripheral attachment device 26 along the superposition direction Z.

[0143] As shown in figure 2, the first strap Si is the innermost strap.

[0144] As shown in figure 2, the fourth strap S4 is the outermost strap.

[0145] The straps Si , S2, S3, S4 frame the laminated glazing 24.

[0146] The straps S1 , S2, S3, S4 are continuous along the whole periphery of the laminated glazing 24. “Continuous” means that each strap S1 , S2, S3, S4 runs along the whole periphery of the glazing 24. Hence, each strap S1 , S2, S3, S4 is uninterrupted along the periphery of the laminated glazing 24.

[0147] The straps Si, S2, S3, S4 are substantially flat.

[0148] The straps Si, S2, S3, S4 generally extend in a plane that is perpendicular to the superposition direction Z.

[0149] As shown in figure 2, each strap Si, S2, S3, S4 comprises a first surface S1A, S2A, S3A, S4A and a second surface S1B, S2B, S3B, S4B opposed to the first surface S1A, S2A, S3A, S4A.

[0150] The surfaces S1A, S1B, S2A, S2B, S3A, S3B, S4A, S4B of the straps Si, S2, S3, S4 are perpendicular to the superposition direction Z.

[0151] For example, the first surfaces S1A, S2A, S3A, S4A of the straps Si , S2, S3, S4 form the internal surfaces of the straps Si, S2, S3, S4.

[0152] For example, the second surfaces S1B, S2B, S3B, S4B of the straps Si, S2, S3, S4 form the external surfaces of the straps Si, S2, S3, S4.

[0153] Each strap Si , S2, S3, S4 is made in at least one composite material.

[0154] For example, the composite material is a fiber reinforced polymer material.

[0155] The fibers of the fiber reinforced polymer material are inorganic fibers, organic fibers and / or natural fibers.

[0156] The inorganic fibers may be, for example, carbon fibers and / or glass fibers.

[0157] The organic fibers may be, for example, aramid fibers.

[0158] The natural fibers may be, for example, fibers made of flax or hemp.

[0159] The polymer material is, for example, made of a thermoset polymer material and / or a thermoplastic polymer material.

[0160] For example, the composite material is a quasi-isotropic composite material or an anisotropic composite material.

[0161] A quasi-isotropic material has isotropic properties in one plane. This plane, in the present description, corresponds to the plane in which the straps extend, namely the plane perpendicular to the superposition direction Z.

[0162] An anisotropic composite material has properties varying when measured in different directions.

[0163] In the present example, the first, second, third and fourth straps Si, S2, S3, S4 are in a glass fiber composite material.

[0164] Moreover, in the present example described in relation to figures 1 and 2, the glass fiber reinforced polymer material is a quasi-isotropic material.

[0165] According to a particular example, each strap Si , S2, S3, S4 comprises one layer of said composite material.

[0166] For example, each strap Si , S2, S3, S4 is made from at least one corresponding strip comprising having at least in part the shape of the strap Si , S2, S3, S4, the or each strip comprising two extremity portions and each strap Si , S2, S3, S4, S5, Se including at least one junction zone.

[0167] For each strap Si , S2, S3, S4, in the present example, the junction zone comprises the two extremity portions of a single corresponding strip in adhesive contact with each other.

[0168] For example, in the junction zone (not shown in the figures), the extremity portions of the strip are joined on top to each other by an adhesive.

[0169] According to a variant, in the junction zone, the extremities of the strip are joined edge to edge to each other.

[0170] According to a variant, each strap Si, S2, S3, S4 is made from at least two strips, namely a first strip and a second strip. Each of the first and second strips has two extremity portions. The junction zone comprises one extremity portion of the first strip and one extremity portion of the second strip in adhesive contact with each other. For example, the extremity portions in adhesive contact with each other are arranged on top of the other or are joined edge to edge to each other.

[0171] As shown in figure 2, the first strap Si and the second strap S2 form a first pair of straps, and the third strap S3 and the fourth strap S4 form a second pair of straps.

[0172] Each pair of straps delimits a housing between the two straps S1-S2, S3-S4 of this pair of straps Si , S2, S3, S4.

[0173] More precisely, the first pair of straps Si, S2 delimits a first housing 71 and the second pair of straps S3, S4 delimits a second housing 72.

[0174] Each housing 71 , 72 extends along the periphery of the glazing 24.

[0175] The first housing 71 and the second housing 72 correspond to the gap between the first and second straps Si, S2, respectively to the gap between the third and fourth straps S3, S4.

[0176] For each pair of straps, the housing 71 , 72 of this pair of straps Si, S2, S3, S4 has a first peripheral extremity portion delimiting a connecting portion accommodating a respective structural ply portion of a structural ply among the two structural plies 31 , 32, a second peripheral extremity portion accommodating a spacer among the two spacers 51 , 52 and a peripheral intermediate portion extending between the first peripheral extremity portion and the second peripheral extremity portion, the portion of each strap Si , S2, S3, S4 of this pair of straps delimiting the intermediate portion having a length said “free length”.

[0177] As shown in figure 2, the first housing 71 is delimited between the second surface S1B of the first strap Si and the first surface S2A of the second strap S2.

[0178] In particular, the first housing 71 has a first extremity delimiting a connecting portion accommodating a ply portion of the first structural ply 31 .

[0179] The first housing 71 extends in the extension of the first structural ply 31.

[0180] The ply portion of the first structural ply 31 is a peripheral portion of the first structural ply 31 comprising the edges 31 C of the first structural ply 31 .

[0181] The first and second straps Si , S2 and the first structural ply 31 and are, for example, adhesively bonded to each other by an adhesive layer (not shown in the figures), for example a layer of glue.

[0182] In particular, the first and second straps Si, S2 are adhesively bonded to said peripheral portion of the first structural ply 31.

[0183] In particular, the first strap Si and the second strap S2 are bonded to the first surface 31 A, respectively the second surface 31 B of the first structural ply 31 .

[0184] The second peripheral extremity portion of the first housing 71 accommodates the first spacer 51.

[0185] The first and second straps Si , S2 are, for example, in adhesive contact with the first spacer 51 and are, for example, glued to the first spacer 51.

[0186] The first structural ply 31 is attached to the first spacer 51 by the first and second straps Si , S2.

[0187] The peripheral intermediate portion of the first housing 71 extends between the first extremity and the second extremity of the first housing 71.

[0188] In particular, the peripheral intermediate portion extends between the first spacer 51 and the portion of the first structural ply 31 .

[0189] The peripheral intermediate portion of the first housing 71 accommodates the first flexible layer 61 .

[0190] As shown in figure 2, the second surface S3B of the third strap S3 and the first surface S4A of the fourth strap S4 delimits the second housing 72.

[0191] The second housing 72 has a first extremity delimiting a connecting portion accommodating a ply portion of the second structural ply 32.

[0192] The second housing 72 extends in the extension of the second structural ply 32.

[0193] The ply portion of the second structural ply 32 is a peripheral portion of the second structural ply 32 comprising the edge 32C of the second structural ply 32.

[0194] The third and fourth straps S3, S4 and the second structural ply 32 are adhesively bonded to each other, for example, by layer of adhesive (not shown in the figures) such a layer of glue.

[0195] In particular, the third and fourth straps S3, S4 are adhesively bonded to said peripheral portion of the second structural ply 32.

[0196] In particular, the third strap S3 and the fourth strap S4 are bonded to the first principal surface 32A, respectively the second principal surface 32B of the second structural ply 32.

[0197] The second peripheral extremity portion of the second housing 72 accommodates the second spacer 52.

[0198] The third and fourth straps S3, S4 are for example in adhesive contact with the second spacer 52 and are, for example, glued to the second spacer 52.

[0199] The second structural ply 32 is attached to the second spacer 52 by the third and fourth straps S3, S4.

[0200] The peripheral intermediate portion of the second housing 72 extends between the first extremity and the second extremity of the second housing 72.

[0201] In particular, the peripheral intermediate portion extends between the portion of the second structural ply 32 and the second spacer 52.

[0202] The intermediate portion of the second housing 72 accommodates the second flexible layer 62.

[0203] As shown in figure 2, in the present example, the first surface S1A of the first strap Si is bonded to the third spacer 53. In the specific example shown in figure 2, the first surface S1A of the first strap Si is in adhesive contact with the third spacer 53.

[0204] Advantageously, the third spacer 53 enables to accommodate the existing first and second mounting elements 16, 18 in retrofit designs.

[0205] The second surface S2B of the second strap S2 is in contact with the first interlayer 41 and in this example with the second portion 412 of the first interlayer 41.

[0206] The first surface S3A of the third strap S3 is in adhesive contact with the first interlayer 41 and, in particular, with the second portion 412 of the first interlayer 41.

[0207] As shown in figure 2, in the mounting configuration, the second surface S4B of the fourth strap S4 is in contact with the first sealing layer 21 and the second sealing layer 22.

[0208] According to the invention, in at least one transverse plane crossing the set of superimposed straps Si, S2, S3, S4 and passing through one point P of the contour of a midplane surface of one of the two structural plies 31 , 32 and normal to the tangent of said contour at point P:- a local stiffness ki of the first strap Si is strictly greater than a local stiffness k2 of the second strap S2,- the local stiffness ki of the first strap Si is less than or equal to a local stiffness k3of the third strap S3, and- the local stiffness k3of the third strap S3 is strictly greater than a local stiffness k4 of the fourth strap S4.

[0209] Thanks to the tuning of the local stiffness ki of the first strap Si , the tuning of the local stiffness k2 of the second strap S2, the tuning of the local stiffness k3of the third strap S3 and the local stiffness k4 of the fourth strap S4, the glazing assembly 12 according to the invention has an improved strength, in particular under both ultimate and failsafe loading conditions. By adapting the local stiffnesses ki , k2, k3, k4 of the four straps Si , S2, S3, S4, the tensile stress induced by the membrane forces carried by the set of superimposed straps is better distributed among the straps.

[0210] More precisely, according to the invention, in said transverse plane, the peripheral attachment device 26 is such that:- a first ratio R1 of the local stiffness ki of the first strap Si to the local stiffness k2of the second strap S2 is greater than or equal to 1 .5 and less than or equal to 2,- a second ratio R2 of the local stiffness ki of the first strap Si to the local stiffness k3is less than or equal to 1 , and- a third ratio R3 of the local stiffness k3of the third strap S3 to the local stiffness k4 of the fourth strap S4 is greater than or equal to 2.

[0211] In the transverse plane, the above ratios R1 , R2, R3 are expressed as:

[0212] In other words, in said transverse plane, the peripheral attachment device 26 is such that:1.5 < R1< 2 (1)R2 < 1 (2)R3 > 2 (3)

[0213] By tuning the local stiffnesses ki , k2, k3, k4of the straps Si , S2, S3, S4so that they verify the inequalities (1), (2) and (3), the strength of the peripheral attachment device 26 and thus the strength of the glazing assembly 12 is increased, notably both in ultimate loading conditions and in failsafe loading conditions.

[0214] In particular, by tuning the local stiffnesses ki, k2, k3, k4of the straps Si, S2, S3, S4so that the ratios R1 , R2, R3 verify the inequalities (1), (2) and (3), the membrane forces are more evenly distributed across the straps Si, S2, S3, S4. In particular, the highest load on a single strap Si , S2, S3, S4would decrease, thereby increasing the strength of the glazing assembly 12, notably under both ultimate and failsafe loading conditions.

[0215] Advantageously, the transverse plane crosses the set of superimposed straps S1 ,52, S3, S4 and passes through point P that is on the first contour C1 of the first midplane surface M1 of the first structural ply 31.

[0216] One point P of the first contour C1 and its tangent TG1 at point P are shown in figure 1.

[0217] The tangent TG1 of the first contour C1 at point P is a straight line that “touches” the contour C1 as closely as possible in the vicinity of point P. The contour C1 and its tangent TG1 form a zero angle at point P. More precisely, the tangent TG1 of the first contour C1 at point P has for direction a vector of unit length extending from point P in a parallel direction to the derivative of C1 at P.

[0218] Said transverse plane is located outside each junction zone of the straps Si, S2,53, S4. Otherwise said, the transverse plane does not cross any junction zone.

[0219] Figure 2 is a view of a portion of the glazing assembly 12 in said transverse plane at point P.

[0220] In said transverse plane, the local stiffness kj of each i-th strap Si of the set of superimposed straps is defined by the following formula (F):

[0221] Where:- the index number i identifies the i-th strap Si with i={1 ; 2; 3; 4}.- Ei is the in-plane tensile modulus of elasticity of the i-th strap Si along a direction ofload DL. The direction of load DL in the transverse plane is parallel to the tangent TG2 at point P of the curve dQ defined by the intersection of said transverse plane and the midplane surface M1. The direction of load DL is oriented opposite to the laminated glazing 24 in the transverse plane.- tj is the thickness of the i-th strap Si along the superposition direction Z,- Li is the free length of the i-th strap Si.

[0222] In said transverse plane, the local stiffnesses ki , k2, k3, k4are the local stiffnesses of the straps Si , S2, S3, S4along the direction of load DL.

[0223] Each local stiffness ki, k2, k3, k4is distinct from zero.

[0224] In particular, in the above formula (F), the local stiffness ki of the strap Si is identified by the same index number i as the corresponding strap Si. Hence, ki is the local stiffness of the first strap Si , k2is the local stiffness of the second strap S2, k3is the local stiffness of the third strap S3and k4is the local stiffness of the fourth strap S4.

[0225] In said transverse plane, the in-plane tensile modulus Ej is identified by the same index number i as the corresponding strap Si. Hence, Ei is the in-plane tensile modulus of elasticity of the of the first strap Si along the direction of load DL, E2is the in-plane tensile modulus of elasticity of the second strap S2in the direction of load DL, E3is the in-plane tensile modulus of elasticity of the third strap S3in the direction of load DL and E4is the in-plane tensile modulus of elasticity of the fourth strap S4along the direction of load DL.

[0226] The direction of load DL in the transverse plane corresponds to the general direction of the membrane forces applied to the glazing assembly 12.

[0227] The tangent TG2 of the curve dQ at point P is a straight line that “touches” the contour curve dQ as closely as possible in the vicinity of point P. The curve dQ and its tangent TG2 form a zero angle at point P. More precisely, the tangent TG2 of the curve dQ at point P has for direction a vector of unit length extending from point P in a parallel direction to the derivative of the curve dQ at P.

[0228] For example, each in-plane tensile modulus Ei, E2, E3, E4of the straps Si , S2, S3, S4along the direction of load DL is determined using a uniaxial tension test such as the standard test method defined in the American Standards of Technical Material (ASTM) D3039 / D3039M.

[0229] For example, each in-plane tensile modulus Ei, E2, E3, E4is determined using the standard test method defined in the ASTM D3039 / D3039M - 17.

[0230] As a variant, each in-plane tensile moduli Ei , E2, E3, E4may be determined from the nature of the materials forming the corresponding strap Si , S2, S3, S4and the orientation of the fibers in the strap Si , S2, S3, S4. The nature of the materials forming the strap Si ,S2, S3, S4 and the orientation of the fibers in the strap Si, S2, S3, S4 may be determined by elemental analysis and / or microstructure analysis known per se. The in-plane tensile moduli E1, E2, E3, E4 may be computed from the determined nature of the materials and the determined orientation of the fibers in the straps Si , S2, S3, S4.

[0231] In the specific example described in view of figures 1 and 2, the in-plane tensile moduli of elasticity E1 , E2, E3, E4 are equal to each other in the transverse plane.

[0232] The thickness tj is identified by the same index number i as the corresponding strap Si. Hence, h is the thickness of the strap Si along the superposition direction Z, t2the thickness of the strap S2 along the superposition direction Z, t3the thickness of the strap S3 along the superposition direction Z and k4the thickness of the strap S4 along the superposition direction Z.

[0233] The thickness ti, t2, ts, t4 of each strap Si, S2, S3, S4 corresponds to the distance between its first and second surfaces S1A and S1B, S2A and S2B, S3A and S3B, S4A and S4B along the superposition direction Z.

[0234] The thicknesses ti, t2, ts and t4 are shown in figure 2.

[0235] In particular, each thickness tj is the thickness of the portion of the strap Si delimiting the peripheral intermediate portion.

[0236] Each thickness tj is constant in the transverse plane.

[0237] The free lengths Lj are identified by the same index number i as the corresponding strap Si. As mentioned above, Li is the free length of the first strap Si , L2 is the free length of the second strap S2, L3 is the free length of the third strap S3 and L4 is the free length of the fourth strap S4.

[0238] The free lengths Li, L2, L3 and L4 in the transverse plane are shown in figure 2.

[0239] The first free length Li in the transverse plane corresponds to the portion of the first strap Si delimiting the peripheral intermediate portion of the first housing 71. This portion of the first strap Si is in contact with the first flexible layer 61.

[0240] The second free length L2in the transverse plane corresponds to the portion of the second strap S2 delimiting the peripheral intermediate portion of the first housing 71. This portion of the second strap S2 is in contact with the first flexible layer 61 .

[0241] The third free length L3 in the transverse plane corresponds to the portion of the third strap S3 delimiting the intermediate portion of the second housing 72. This portion of the third strap S3 is in contact with the second flexible layer 62.

[0242] The fourth free length L4 in the transverse plane corresponds to the portion of the fourth strap S4 delimiting the intermediate portion of the second housing 72. This portion of the fourth strap S4 is in contact with the second flexible layer 62.

[0243] Each free length Li , L2, L3, L4 is measured in the transverse plane along the direction of load DL.

[0244] The thicknesses ti, t2, ts, t4 and the free lengths Li, L2, L3, L4 of the straps Si, S2, S3, S4 may be measured though analysis of optical micrographs.

[0245] In the transverse plane, the local stiffnesses ki, k2, k3, k4 of the four straps Si , S2, S3, S4, so that the local stiffness ki of the first strap Si is strictly greater than the local stiffness k2of the second strap S2, the local stiffness ki of the first strap Si is less than or equal to the local stiffness k3of the third strap S3, and the local stiffness k3of the third strap S3 is strictly greater than the local stiffness k4of the fourth strap S4 may be adapted by selecting the in-plane tensile moduli E1 , E2, E3, E4for example by adapting the nature of the materials forming the straps Si , S2, S3, S4, and / or the orientation of the fibers in the straps Si , S2, S3, S4 and / or by selecting the free lengths Li , L2, L3, U, L5, Le of the straps Si , S2, S3, S4 and / or by selecting the thicknesses ti , t2, ts, t4 of the straps Si , S2, S3, S4.

[0246] The ratios R1 , R2, R3 of strap stiffnesses so that they verify the inequalities (1), (2) and (3) may be obtained by selecting the in-plane tensile moduli E1, E2, E3, E4 for example by adapting the nature of the materials forming the straps Si , S2, S3, S4 and / or the orientation of the fibers in the straps Si , S2, S3, S4 and / or by selecting the free lengths Li, L2, L3, L4, L5, Le of the straps Si, S2, S3, S4 and / or by selecting the thicknesses ti, t2, t3, t4 of the straps Si, S2, S3, S4.

[0247] In the present example shown in figure 2, the free lengths Li, L2, L3, L4 are equal to each other.

[0248] In particular, in the present example, in each transverse plane outside each junction zone, the peripheral attachment device 26 is such that :- the local stiffness ki of the first strap Si is strictly greater than a local stiffness k2of the second strap S2,- the local stiffness ki of the first strap Si is less than or equal to a local stiffness k3of the third strap S3, and- the local stiffness k3of the third strap S3 is strictly greater than the local stiffness k4of the fourth strap S4.

[0249] In particular, in the present example, each transverse plane outside each junction zone, the peripheral attachment device 26 is such that :- the first ratio R1 of ki to k2 is greater than or equal to 1.5 and less than or equal to 2,- the second ratio R2 of ki to k3is less than or equal to 1 , and- the third ratio R3 of k3to k4 is greater than or equal to 2.

[0250] In the particular example described in relation to figures 1 and 2, the three ratios R1 , R2, R3 are independent from the in-plane tensile moduli of elasticity E1, E2, E3, E4since the in-plane tensile moduli of elasticity E1 , E2, E3, E4are constant. In other words, the in-plane tensile moduli of elasticity E1, E2, E3, E4have the same value. Otherwise said E-i = E2= E3= E4.

[0251] In the present example describes in relation to figures 1 and 2, the three ratios R1 , R2, R3 are also independent from the free lengths Li, L2, L3, L4since the free lengths Li, l_2, L3, L4are constant. In other words, the free lengths Li, L2, L3, L4have the same value. Otherwise said, Li = L2= L3= L4.

[0252] Thus, in the present example, the first, second and third ratios R1 , R2, R3 only depend on the thicknesses ti , t2, t3, t4of the straps Si, S2, S3, S4.

[0253] In particular, in the transverse plane, the first ratio R1 can be expressed as:

[0254] In the transverse plane, the second ratio R2 is expressed as:

[0255] In the transverse plane, the third ratio R3 can be expressed as: / r3^3S3 = -i = - rC4t4

[0256] In the present example, in each transverse plane outside the junction zone, the first, second and third ratios R1 , R2, R3 only depend on the thicknesses ti, t2, ts, t4of the straps Si, S2, S3, S4.

[0257] In particular, as schematically represented in figure 2, the thickness ti of the first strap Si is strictly greater than the thickness t2of the second strap S2, the thickness ti of the first strap Si is strictly less than the thickness t3of the third strap S3and the thickness t3of the third strap S3is strictly greater than the thickness t4of the fourth strap S4.

[0258] Moreover, in the transverse plane, as shown in figure 2, the thicknesses ti, t2, t3, t4of the straps Si, S2, S3, S4of the peripheral attachment device 26 are such that:- the first ratio R1 of h to t2is greater than or equal to 1.5 and less than or equal to 2,- the second ratio R2 of h to t3is less than or equal to 1 , and- the third ratio R3 of t3to is greater than or equal to 2.

[0259] The first spacer 51 extends in the second peripheral extremity portion of the first housing 71.

[0260] The first spacer 51 enables to maintain the spacing between the first and second straps Si , S2.

[0261] The first spacer 51 is, for example, in a composite material.

[0262] For example, the composite material of the first spacer 51 is a fiber reinforced polymer material.

[0263] The fibers of the fiber reinforced polymer material are inorganic fibers, organic fibers or natural fibers.

[0264] The inorganic fibers may be, for example, carbon fibers and / or glass fibers.

[0265] The organic fibers may be, for example, aramid fibers.

[0266] The natural fibers may be, for example, fibers made of flax or hemp.

[0267] The polymer material is, for example, made of a thermoset polymer material and / or a thermoplastic polymer material. The second spacer 52 extends in the second peripheral extremity portion of the second housing 72.

[0268] The second spacer 52 enables to maintain the spacing between the third and fourth straps S3, S4.

[0269] The second spacer 52 is, for example, in a composite material.

[0270] For example, the composite material of the second spacer 52 is a fiber reinforced polymer material.

[0271] The fibers of the fiber reinforced polymer material are inorganic fibers, organic fibers or natural fibers.

[0272] The inorganic fibers may be, for example, carbon fibers and / or glass fibers.

[0273] The organic fibers may be, for example, aramid fibers.

[0274] The natural fibers may be, for example, fibers made of flax or hemp.

[0275] The polymer material is, for example, made of a thermoset polymer material and / or a thermoplastic polymer material. The straps Si, S2, S3, S4 notably enable to transfer the membrane forces between the corresponding spacers 51 , 52 housed in the housings 71 , 72 and the structural plies 31 , 32.

[0276] In particular, in the mounting configuration, the membrane forces are transferred from the straps Si, S2 to the first spacer 51 and the first spacer 51 transmit the membrane forces to the first structural ply 31.

[0277] In the mounting configuration, the membrane forces are transferred to the third and fourth straps S3, S4 to the second spacer 52 and the second spacer 52 transfers the forces to the second structural ply 32.

[0278] In the mounting configuration, the third spacer 53 extends between the first strap Si and the first mounting element 16.

[0279] The third spacer 53 is, for example, in a composite material.

[0280] For example, the third spacer 53 is in glass fiber reinforced polymer. As a variant, the third spacer 53 is in carbon fiber reinforced polymer.

[0281] The third spacer 53 located outside the housings 71 , 72 enables to adjust the position of the laminated glazing 24 in relation to the first and second mounting elements 16, 18.

[0282] The first flexible layer 61 extends in the first housing 71 between the first spacer 51 and the edge 31 C of the first structural ply 31.

[0283] The first flexible layer 61 is in a flexible material.

[0284] The flexible material is a soft filler material.

[0285] The flexible material of the first flexible layer 61 is less stiff than the material of the spacer 51 housed in the first housing 71.

[0286] The stiffness may be measured by a tensile test known commonly known by the person skilled in the art.

[0287] For example, the first flexible layer 61 is in polyurethane, in thermoplastic elastomer, in silicone or in PVB.

[0288] The second flexible layer 62 extends in the second housing 72 between the second spacer 52 and the edge 32C of the second structural ply 32.

[0289] The second flexible layer 62 is in a flexible material.

[0290] The flexible material is a soft filler material.

[0291] The flexible material of the second flexible layer 62 is less stiff than the material of the spacer 52 housed in the second housing 72.

[0292] For example, the second flexible layer 62 is in polyurethane, in thermoplastic elastomer, in silicone or in PVB.

[0293] For each housing 71 , 72, the spacer 51 , 52 being stiffer than the flexible layer 61 , 62 enables to create a portion of the peripheral attachment device 26 in which the straps of the pair of straps S1-S2, S3-S4 defining this housing 71 , 72 is carrying most of the forces.

[0294] For example, each flexible layer 61 , 62 is less stiff than the corresponding straps so that the strap Si, S2, S3, S4 is transmitting the force across the intermediate portion between the spacer 51 , 52 and the edge 31 C, 32C of the structural ply 31 , 32.

[0295] As shown in figure 1 , the plurality of coupling members 64 are, for example, regularly distributed along the peripheral attachment device 26.

[0296] The plurality of coupling members 64 pass through the four straps Si , S2, S3, S4.

[0297] The plurality of coupling members 64 pass through the first and second spacers 51 , 52 arranged respectively in the first and second housing 71 , 72.

[0298] The coupling members 64 extend perpendicularly to the straps Si , S2, S3, S4 and in particular to the planes in which the straps Si , S2, S3, S4 extend.

[0299] The coupling members 64 provides mechanical cohesion between the straps Si , S2, S3, S4 to the structural attachment part 14 of the vehicle 10.

[0300] As shown in figure 2 in the mounting configuration, the plurality of coupling members 64 are attached to the attachment portion of the vehicle 10.

[0301] Each coupling member 64 comprises an elongated main body 74 having a first extremity 76 and a second extremity 78 opposed to the first extremity 74.

[0302] The first extremities 76 of the coupling members 64 are part of the attachment zone 28 of the peripheral attachment device 26.

[0303] The first extremities 76 are attached to the attachment portion of the vehicle 10 in the mounting configuration.

[0304] In the mounting configuration, the first extremities 76 cross the attachment portion of the vehicle 10.

[0305] In the example of figure 2, the first extremities 76 are bolted to the attachment portion of the vehicle 10.

[0306] The first extremities 76 of the coupling members 64 form at least in part of the attachment zone 28 of the peripheral attachment device 26.

[0307] The second extremities 78 of the coupling members 64 define an abutment surface configured to cooperate with a complementary abutment surface arranged in the second mounting element 18 in the mounting configuration.

[0308] It should be understood that this arrangement is not limitative and that the second extremities 78 of the coupling members 64 may form at least in part the attachment zone 28 of the attachment device 26 instead of the first extremities 76 in case the second extremities 78 are mechanically attached to the attachment portion of the vehicle 10.

[0309] In the mounting configuration of the glazing assembly 12, as shown in figure 2, the coupling members 64 pass through the four straps Si , S2, S3, S4 and the first and second spacers 51 , 52 arranged in the extension of the two structural plies 31 , 32 and are mechanically linked to the first and second mounting elements 16, 18 so that the laminated glazing 24 is attached to the vehicle 10.

[0310] A portion of the superimposed set of straps and the first and second spacers 51 , 52 extend in sandwich between the attachment portion of the vehicle 10 and the second mounting element 18.

[0311] In particular, in the mounting configuration of the glazing assembly 12, the first extremities 76 of the coupling members 64 cross the first mounting element 16 and are attached by bolting to the attachment portion of the vehicle 10 forming part, in this example, of the structural attachment part 14.

[0312] As shown in figure 2, in the mounting configuration of the glazing assembly 12, the second extremities 78 of the coupling members 64 cross the second mounting element 18 and the abutment surface of the second extremities cooperate with the complementary abutment surface arranged in the second mounting element 18 so that the movement of the coupling members 64 along the superposition direction is prevented.

[0313] In the specific example represented in figure 2, each coupling element 64 comprises a rod and a nut.

[0314] The rod comprises an elongated body and the enlarged extremity part.

[0315] As shown in figure 2, the rods extend across the first, second, third and fourth straps Si, S2, S3, S4. Moreover, the rods cross the first and second spacers 51 , 52 and second portions 412, 422 of the first and second interlayers 41 , 42.

[0316] As shown in figure 2, the rods of the coupling members 64 crosses the third spacer 53.

[0317] In the mounting configuration, the coupling members 64 cross the first and second mounting elements 16, 18 and the second sealing layer 22.

[0318] The first extremity of each coupling member 64 comprises a first extremity of the elongated body of the rod and the nut.

[0319] The first extremity of the elongated body of the rod passes through the first mounting element.

[0320] The nut is bolted to the first extremity of the elongated body of the rod to the first mounting element 16 forming the attachment portion of the vehicle 10.

[0321] The second extremity of each coupling member 64 comprises the enlarged extremity part.

[0322] As shown in figure 2, in the mounting configuration of the glazing assembly 12 to the vehicle 10, the rods cross the first mounting element 16 and are bolted with the nut on the first mounting element 16 forming, in the present example, the attachment portion of the vehicle 10.

[0323] The first sealing layer 21 forms a seal extending between and the fourth strap S4 and the second face 24B of the glazing 24.

[0324] The first sealing layer 21 is arranged at the exterior of the space defined between the second mounting element 18 and the fourth strap S4.

[0325] The first sealing layer 21 is, for example, in a sealing material such polysulfide.

[0326] The second sealing layer 22 extends between the second mounting element 18 and a portion of the fourth strap S4.

[0327] The second sealing layer 22 is, for example, in a sealing material such polysulfide.

[0328] For example, the peripheral seal 23 extends between the second mounting element 18 and the structural attachment part 14 of the vehicle 10.

[0329] Alternatively, the peripheral seal 23 extends between the second mounting element 18 and a portion of a skin of the vehicle 10.

[0330] According to a particular embodiment, at least one strap among the first, second, third and fourth straps Si , S2, S3, S4 is made in an anisotropic composite material.

[0331] The fibers of the anisotropic material extend along at least one principal alignment direction.

[0332] Knowing the elastic modulus of the anisotropic composite material in the principal alignment direction and the relative angle between the principal alignment direction and the direction of load DL, each in-plane tensile modulus of elasticity E1 , E2, E3, E4of the straps Si , S2, S3, S4along the direction of load DL can be calculated.

[0333] This calculation is well known from the person skilled in the art and is thus not detailed here.

[0334] These in-plane elastic moduli along the principal alignment direction may be for example determined using a uniaxial tension test, such as the standard test method described in ASTM D3039 / D3039M, in particular ASTM D3039 / D3039M - 17.

[0335] As a variant, each in-plane tensile moduli along the predefined alignment direction may be determined from the nature of the materials forming each strap Si , S2, S3, S4and the orientation of the fibers in the strap Si, S2, S3, S4. The nature of the materials of the strap Si , S2, S3, S4and the orientation of the fibers in the strap Si , S2, S3, S4may be determined by elemental analysis and / or microstructure analysis known per se. The in-plane tensile moduli E1, E2, E3, E4in the predefined alignment direction may be computed from the determined nature of the materials and the determined orientation of the fibers in the material.

[0336] According to a particular embodiment, each strap Si , S2, S3, S4comprises at least two layers made of a composite material.

[0337] The layers are stacked on each other along the superposition direction Z.

[0338] For example, for each strap Si , S2, S3, S4, each layer of this strap Si , S2, S3, S4is made in a fiber reinforced polymer material.

[0339] According to another embodiment, the straps Si, S2, S3, S4are devoid of junction zone.

[0340] In such case, in each transverse plane, the peripheral attachment device 26 is such that:- the local stiffness ki of the first strap Si is strictly greater than the local stiffness k2of the second strap S2,- the local stiffness ki of the first strap Si is less than or equal to the local stiffness k3of the third strap S3, and- the local stiffness of the third strap k3is strictly greater than the local stiffness k4 of the fourth strap S4.

[0341] In particular, in this case, in each transverse plane, the peripheral attachment device 26 is such that:- the first ratio R1 of ki to k2is greater than or equal to 1.5 and less than or equal to 2,- the second ratio R2 of ki to k3is less than or equal to 1 , and- the third ratio R3 of k3to k4is greater than or equal to 2.

[0342] Advantageously, in each transverse plane, the first, second and third ratios R1 , R2,R3 only depend on the thicknesses ti, t2, t3, t4 of the straps Si, S2, S3, S4.

[0343] It is to be understood that this arrangement is not limitative and that the invention may apply to a glazing assembly mounted from the inside of the vehicle. In such a case, the glazing assembly 24 would not comprise the fourth spacer 54. Additionally, in such a case, the second mounting element 18 would form the internal mounting element and the first mounting element 16 connected to the structural attachment part 14 defining the attachment portion of the vehicle would form the external mounting element. Moreover, in such a case, the numbering of the straps will be reversed as compared to figure 2. In particular, the first strap would be the outermost strap and the fourth strap would be the innermost strap. Additionally, the first and second sealing layers 21 , 22 may be arranged between the first mounting element 16 and the first strap. Also, in such a case, the third interlayer would bond the first structural ply 31 to the additional ply 34.

[0344] In use, when the glazing assembly 12 is in the mounting configuration as shown in figures 1 and 2, the glazing assembly 12 carries the membrane forces generated by the pressurization of the interior of the vehicle 10.

[0345] Thanks to the invention, the maximum tensile stress carried by the straps Si , S2, S3, S4 is reduced in both ultimate and failsafe loading conditions.

[0346] The glazing assembly 12 according to the invention has an improved strength, in particular under both ultimate and failsafe loading conditions.

[0347] Moreover, the glazing assembly 12 according to the invention is resistant to pressure.

[0348] Hence, the glazing assembly 12 according to the invention has improved strength, in particular, in both ultimate and failsafe loading conditions.

Claims

CLAIMS1. A glazing assembly (12) for a vehicle (10), notably an aircraft, comprising a laminated glazing (24) comprising two structural plies (31 , 32) and a peripheral attachment device (26) configured to attach the laminated glazing (24) to a structural attachment part (14) of the vehicle (10), the peripheral attachment device (26) comprising:- a set of superimposed straps arranged along the periphery of the laminated glazing (24), the set of superimposed straps comprising a first strap (Si), a second strap (S2), a third strap (S3) and a fourth strap (S4) superimposed on each other in this order along a superposition direction (Z), the first strap (Si) being the strap of the set of superimposed straps configured to be the closest to an attachment portion of the vehicle (10) mechanically attached to the structural attachment part (14) or forming part of the structural attachment part (14) of the vehicle, the first and the second straps (Si , S2) forming a first pair of straps and the third and fourth straps (S3, S4) forming a second pair of straps, each pair of straps (S1-S2, S3-S4) delimiting between the straps of this pair of straps a housing (71 , 72), for each pair of straps (S1-S2, S3-S4), the housing (71 , 72) delimited by this pair of straps (S1-S2, S3-S4) having a first peripheral extremity portion delimiting a connecting portion accommodating a respective ply portion of a structural ply (31 , 32) among the two structural plies, a second peripheral extremity portion accommodating a spacer (51 , 52) and a peripheral intermediate portion extending between the first peripheral extremity portion and the second peripheral extremity portion, the portion of each strap (Si, S2, S3, S4) of this pair of straps (S1-S2, S3-S4) delimiting the intermediate portion having a length, said “free length”, characterized in that, in at least one transverse plane crossing the set of superimposed straps (Si, S2, S3, S4), passing through one point P of the contour (C1) of a midplane surface (M1) of one of the two structural plies (31 , 32) and being normal to the tangent (TG1) of said contour (C1) at point P:- a local stiffness (ki) of the first strap (Si) is strictly greater than a local stiffness (k2) of the second strap (S2),- the local stiffness (ki) of the first strap (Si) is less than or equal to a local stiffness (k3) of the third strap (S3), and- the local stiffness (k3) of the third strap (S3) is strictly greater than a local stiffness (k4) of the fourth strap (S4), andin that, in said transverse plane, the local stiffness kj of each i-th strap (Si) of the set of superimposed straps is defined by the following formula:wherein:- i identifies the i-th strap (Si) with i = {1; 2; 3; 4},- Ei is the in-plane tensile modulus of elasticity of the i-th strap (Si) along a direction of load (DL),- the direction of load (DL) in the transverse plane is parallel to the tangent (TG2) at point P of the curve (dQ) defined by the intersection of said transverse plane and said midplane surface (M1), the direction of load (DL) being oriented opposite to the laminated glazing (24),- ti is the thickness of the i-th strap (Si) along the superposition direction (Z), and- Li is the free length of the i-th strap (Si).

2. The glazing assembly according to claim 1 , wherein in said transverse plane:- the in-plane tensile modulus (Ei) of the first strap (Si), the in-plane tensile modulus (E2) of the second strap (S2), the in-plane tensile modulus (E3) of the third strap (S3) and the in-plane tensile modulus (E4) of the fourth strap (S4) are constant, and- the free length (Li) of the first strap (Si), the free length (L2) of the second strap (S2), the free length (L3) of the third strap (S3) and the free length (L4) of the fourth strap (S4) are constant.

3. The glazing assembly according to claim 1 or 2, wherein, in the transverse plane, the peripheral attachment device (26) is such that:- a first ratio (R1) of the local stiffness (ki) of the first strap (Si) to the local stiffness (k2) of the second strap (S2) is greater than or equal to 1.5 and less than or equal to 2,- a second ratio (R2) of the local stiffness (ki) of the first strap (Si) to the local stiffness (k3) of the third strap (S3) is less than or equal to 1 , and- a third ratio (R3) of the local stiffness (k3) of the third strap (S3) to the local stiffness (k4) of the fourth strap (S4) is greater than or equal to 2.

4. The glazing assembly according to claims 2 and 3, wherein, in said transverse plane, said first ratio (R1) corresponds to the thickness (ti) of the first strap (Si) to the thickness (t2) of the second strap (S2), said second ratio (R2) corresponds to thethickness (ti) of the first strap (Si) to the thickness (t3) of the third strap (S3), and said third ratio (R3) corresponding to the thickness (t3) of the third strap (S3) to the thickness (k4) of the fourth strap (S4).

5. The glazing assembly according to claim any one of the preceding claims, wherein the peripheral attachment device (26) has an attachment zone (28) to said attachment portion of the vehicle (10), the attachment zone (28) of the peripheral attachment device (26) being configured to be mechanically attached to the attachment portion of the vehicle (10), the first strap (Si) being the strap of the set of superimposed straps (Si , S2, S3, S4) the closest to the attachment zone (28).

6. The glazing assembly according to any one of the preceding claims, wherein the peripheral attachment device (26) comprises a plurality of coupling members (64) configured to pass through the first, second, third and fourth straps (Si, S2, S3, S4), the plurality of coupling members (64) being designed to be attached to the attachment portion of the vehicle (10).

7. The glazing assembly according to claims 5 and 6, wherein each coupling member (64) comprises a first extremity (76) and an opposed second extremity (78), the first extremities (76) or the second extremities (78) configured to cross the attachment portion of the vehicle (10) forming at least in part the attachment zone (28).

8. The glazing assembly according to any one of the preceding claims, wherein each strap (Si , S2, S3, S4) of the set of the superimposed straps is formed from at least one corresponding strip having at least in part the shape of the strap (Si , S2, S3, S4), the or each strip comprising two extremity portions and each strap (Si , S2, S3, S4) including at least one junction zone, for each strap (Si , S2, S3, S4), the junction zone comprising the two extremity portions of one corresponding strip in adhesive contact with each other or the junction zone comprising one extremity portion of a first strip and one extremity portion of a second strip in adhesive contact with each other (Si , S2, S3, S4), the at least one transverse plane crosses the set of superimposed straps (Si, S2, S3, S4) outside each junction zone.

9. The glazing assembly according to any one of the preceding claims, wherein the first, second, third and fourth straps (Si, S2, S3, S4) are continuous along the periphery of the laminated glazing (24).

10. The glazing assembly according to any one of the preceding claims, wherein each of the first, second, third and fourth straps (Si, S2, S3, S4) is made of at least one composite material, the composite material being, preferentially, a fiber reinforced polymer material.

11. The glazing assembly according to any one of the preceding claims, wherein at least one of the first, second, third and fourth straps (Si, S2, S3, S4) is made in a quasi- isotropic composite material.

12. The glazing assembly according to any one of the preceding claims, wherein at least one of the first, second, third and fourth straps (Si , S2, S3, S4) is made in an anisotropic composite material having fibers extending along a predefined alignment direction.

13. The glazing assembly according to any one of the preceding claims, wherein each in-plane tensile modulus of elasticity (E1, E2, E3, E4) is determined using a uniaxial tension test, such as the standard test method defined in the American Standards of Technical Material (ASTM) D3039 / D3039M.

14. The glazing assembly according to any one of the preceding claims, wherein, for each pair of straps (S1-S2, S3-S4), the spacer (51 , 52) located in the housing (71 , 72) delimited by this pair of straps (S1-S2, S3-S4) is configured to maintain a predefined spacing between the straps (Si , S2, S3, S4) of this pair of straps (S1-S2, S3-S4) along the superposition direction (Z).

15. The glazing assembly according to any one of the preceding claims, wherein the peripheral attachment device (26) comprises two flexible layers (61 , 62) made of a flexible material, for each pair of straps, a respective flexible layer of the two flexible layers (61 , 62) being arranged in the peripheral intermediate portion of the housing (71 , 72) delimited by this pair of straps (S1-S2, S3-S4), the flexible material being preferably less stiff than the material of the spacer (51 , 52) and the flexible material being preferably less stiff than the material of the straps (Si, S2, S3, S4).

16. The glazing assembly according to any one of the preceding claims, wherein the glazing assembly (12) is configured to form at least a portion of a windshield of the vehicle (10).

17. A vehicle (10), notably an aircraft, comprising the glazing assembly (12) according to any one of the preceding claims.

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