GB2480609A

GB2480609A - Vehicle seat including natural fibre reinforced resin or aluminium honeycomb layer

Info

Publication number: GB2480609A
Application number: GB1008610A
Authority: GB
Inventors: Trevor Jenkins
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-05-24
Filing date: 2010-05-24
Publication date: 2011-11-30
Also published as: GB201008610D0

Abstract

The seat comprises a core 2 attached to two outer fibre reinforced thermoset resin or aluminium honeycomb layers 1, 3. The reinforcing fibres are derived from biomass (wood fibre, hemp, flax, sisal and jute disclosed). Preferably each fibre reinforced polymer layer 1, 3 includes at least two woven or nonwoven cloths or unidirectionally laid fibres, and thermoplastic material. Preferably the core 2 comprises paper, aluminium or aramid. Preferably the thermoset resin is a phenolic resin treated with an intumescent additive. The preferred seat comprises panels which are adhesively bonded together and to non-metallic legs. The core 2 may comprise a honeycomb or foam. The seat may be used in mass transit systems, such as aircraft, rail, marine and automotive industries.

Description

seat structure and means of attachment thereof.

Background and Description:

The present invention describes a new and innovative design of passenger and/or crew seat for, but not limited to, use in civil and military transport aircraft, automotive vehicles including but not limited to buses and coaches, marine vessels, trains and other forms of mass transport systems. The structure of the seat utilises, by majority, organic or inorganic fibre reinforced thermoplastic polymer or fibre reinforced thermoset resin materials or aluminium sandwich panels to substantially reduce structural mass, the structure may include both non metallic and metallic structural elements to form a so called hybrid structure.

One known problem in developing a predominantly non metallic seat structure is the demand generated by the typical interface loads and certification requirements for airframe, and other vehicle structure types, into which such seats are typically installed. This issue has fundamentally inhibited the evolution of new non metallic seat concepts for commercial and military aircraft use. While organic & inorganic fibre reinforced, thermoplastic or thermoset resin materials are generally characterised as being high in strength in the direction of the reinforcing fibre, the capability of the materials in any engineering application are typically limited by their sensitivity to strain and modes of failure tend to be dominated by their limited strain to failure capacity. Hence, any successful design concept must minimise strain within the material.

Another problem that is known to exist, in particular for aircraft applications, is the early failure of structure during dynamic certification/qualification testing as a consequence of the high level of mechanical strain that results from pre test distortion of the structure to which the seat is attached which is further compounded by the dynamic through-test distortion.

When the mechanical strain that results for this distortion is added to the mechanical strain that results from the test load conditions in a static, quasi-static or dynamic environment, the strain capacity of the material may be significantly exceeded, resulting in structural failure.

With consideration to the above points, it is clear that if predominantly organic or inorganic fibre reinforced thermoplastic polymer or fibre reinforced thermoset resin materials are to be used in the structure of such a product it is necessary to use a design solution that meets the stringent performance criteria with respect to interface to existing systems and structures, and compliance with installation certification requirements particularly for, but not limited to, aircraft use.

The present invention details a design solution which is low in mass and suitable for use in aircraft and other vehicles such as helicopters and hovercraft, passenger ferries, coaches, buses, trains and other systems used for mass transport purposes.

The present invention provides a low mass and simple design solution for seats. An example of the combination of materials used in the manufacture of the seat is a typical skin/core/skin construction.

It is known that companies have tried to manufacture passenger seating for aircraft using honeycomb panels and that one major problem with such design concepts is the attachment of the seat structure to the aircraft in a way that meets all certification requirements of TSO/ETSO 127a, the attachment methods described within the present invention provide a solution to the problem of managing the strain that is induced in the seat structure when the representative aircraft floor or attachments are distorted in accordance with these certification requirements prior to dynamic certification and qualification testing, thereby reducing total strain imparted to the structure during certification testing.

The term organic fibre reinforced, thermoplastic or thermoset resin' refers to bio mass derived fibre or resins which may be thermosetting or thermoplastic in nature and this refers to an emerging family of materials where both fibre and/or polymer/resin are derived from natural sources, in the case of resins and polymers, petrochemical resin or chemically processed polymers are replaced by a vegetable or animal resin in the case of fibre such as, but not limited to, carbon, glass and aramid, these are typically replaced by natural fibre such as, but not limited to, wood fibers, hemp, flax, sisal, jute...) . In the case of this invention, at least one of the constituent materials will be derived from such sources.

Description:

The present invention comprises of a fibre reinforced thermoplastic polymer or fibre reinforced thermoset resin structure that is so design that it carries passenger and other operating loads through the seat into seat attachment fixings and thence into the vehicle/airframe/vessel/cabin floor or other surrounding structure.

The design concept exploits the benefit of such materials and in one embodiment the design concept exploits the inherent strength and stiffness of fibre reinforced thermoplastic polymer or fibre reinforced thermoset resin stiffened core panels. Figure 1 shows a typical stiffened core panel construction.

Components of the structure being joined to make a structural assembly, for example seat legs to seat base, the respective component parts (4), would typically, but not exclusively, be joined together using an adhesively bonded joint (5) of a form that increases the strength of the joint and reduces the number of jigs and fixtures needed during manufacture and assembly. It is typical for structural and load carrying parts to be rigidly bonded, however in the present invention the adhesive used in the joints will possess flexibility in the set or cured state, it is essential that the adhesive layer is more flexible than the structural elements/parts that are being joined. Typically, but not exclusively, the adhesive will be IRS 2125 Flexible Epoxy Adhesive or Scotch-Weld DPi 05 Flexible Epoxy Adhesive, Or such adhesive as described in United States Patent 6740412. The joint is designed such that unlike traditional Dado, Mortise and Tenon, Finger, Lap, Rabbet and other traditional joints that require close fitting parts, there is a minimum of 0.65mm and maximum of 10mm gap between the parts to be joined. During manufacture, the gap is completely filled with adhesive such that once the adhesive is set, or cured, there remains flexibility between the joined parts. This degree of flexibility within the structure is a key contributor to the success of any static or dynamic certification testing for the seat structure. Figures 2 and 2a show a typical joint configuration used in this method of construction.

Furthermore, in the event that the loads passing through the joint exceed the load, stress or strain limitations of the adhesive, the geometry of the interlocking joints is such that as the adhesive begins to fail the components joined mechanically lock to each other as a consequence of the geometry of the joint. Figure 2b shows a typical example of this feature of the joint design.

The joints may further be reinforced through the use of industry standard methods of joint reinforcement such as preformed and adhesively bonded, or otherwise fixed, cleating or with the use of pre-preg cleating that requires vacuum consolidation during cure or through the use of wet layup cleats (6). When such cleats are utilised between the front panel and the leg panels, the cleats are typically designed to take additional tensile and/or compressive loads from the seat bottom panel to the fixing points between the seat and the structure to which it is fixed. The cleated joints also require the same gap 0.65mm to 10mm conditions to be designed into the joint to ensure sufficient strain reduction.

Elements of the seat structure, such as the seat back or seat pan structures may be manufactured utilising tooling that provides form and shape such that they are not planar in form.

At points in the structure where there are concentrated, or point, load inputs for example seat belt attachments (7), arm rest attachments and meal tray attachments, metallic or non-metallic load diffusers (8) are typically used to reduce the load concentration effects such diffusers' will be either mechanically attached or bonder or chemically welded or a combination of joining methods. Figure 3 shows a typical example of such a diffuser.

To reduce load passing through the structure of the seat itself, seat belt attachments/shackle point on the seat may be connected directly to the rear seat to floor fixing point through the use of suitably designed and sized cable or wire that, under load from the passenger through the seat belt, acts to transfer the load through tension if the cable or wire. The cable or wire may be laminated into the material used for the seat construction such that it is not immediately visible. Alternatively the cable or wire may be routed through features in the structure designed for the function. The cable or wire may be made of metallic material such as but not limited to high strength steel or non metallic material such as but not limited to Kevlar or dyneema.

The certification of seats for use in aircraft cabins requires that the seats comply with certification regulations, which include 16g forward and 14 g vertical dynamic testing. Prior to such testing the representative floor mountings, to which the seat structure is attached, are physically distorted to represent distortion in the aircraft floor structure. This requirement typically imparts excessive mechanical strain into the seat structure and provision must be made to absorb, reduce or otherwise attenuate the mechanical strain, both prior to the dynamic test and during the dynamic test. In the present invention, this is achieved by use of compliant bushes within the design of the seat attachment to the floor/structure and within the design of the fixing of this attachment to the seat structure itself. The compliant bushes, typically but not exclusively made from elastomeric materials, have a different stiffness in at least two mutually perpendicular directions, for example radial and axial stiffness of the compliant bush will be different and they are typically designed within the rear fixings. Figure 4 shows a typical mounting arrangement with integration of strain absorbing compliant bushes.

An advantage to the use of elastomeric materials in the joints and the bushes is that a natural damping of the structure is provided in the event of sustained engine imbalance, so called windmilling'. This structural damping can be tuned to optimise performance in both the normal use condition, structural certification testing condition and windmilling certification condition.