GB2224000A

GB2224000A - Fuselage or pressure vessel structure

Info

Publication number: GB2224000A
Application number: GB8824723A
Authority: GB
Inventors: Genrikh Vasilievich Novozhilov; Igor Yakovlevich Katyrev; Vladimir Semenovich Kalenik; Vladimir Konstantinov Rakhilin; Valery Ivanovich Abramov
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-11-10
Filing date: 1988-10-21
Publication date: 1990-04-25
Anticipated expiration: 2008-10-21
Also published as: GB2224000B; GB8824723D0; FR2638708A1; FR2638708B1; DE3900167A1

Description

1 M&C FOLIO: 230P57504 2 ',2 22 4 0 0 0 FUSELAGE WANGDOC: 1352P This

invention relates primarily to an aircraft fuselage. The invention can find application in the construction of a pressure-sealed aircraft fuselage. The invention can also be applied to heavy duty boilers and other hermetic vessels capable of withstanding pressurisation.

There is known an aircraft fuselage comprising an outside skin or shell reinforced by longitudinal and transverse structural members (stringers and bulkheads). The transverse structural members are intended to arrest the development of a longitudinal crack in the shell and are backed-up by additional bands of titanium provided between the shell and bulkhead along the perimeter.

However, the construction of fuselage having no back-up arrangement is susceptible to lateral cracks. Such a crack can grow to an excessive size and result in a failure of the fuselage in flight.

Therefore. this fuselage construction ensures one side back-up of the shell only along the transverse structural members.

2 An aircraft fuselage is known comprising a shell strengthened by intersecting longitudinal and transverse structural members, and having joints in the longitudinal direction.

In order to make the shell more fail-safe. additional reinforcement straps are provided on the transverse structural members at either side of the joint connected by eyed rods or high strength bolts.

In case of a partial failure of the fuselage shell at the longitudinal joint the eyed rods or high strength bolts serve as a back-up strength line for transmitting loads acting in the failure zone. The load carrying capacity (strength) of the structure is therefore maintained when a crack develops in flight.

However. the absence of shell back-up in the longitudinal direction can cause a lateral crack to develop to an excessive size.

What is desired is an aircraft fuselage, in which a crack developing in the longitudinal or lateral direction could be effectively arrested.

The present invention provides an aircraft fuselage (or other vessel) comprising a shell strengthened by longitudinal and transverse structural members. in which the shell has the form of interconnected continuous outer portion and inner grid-shaped portion conforming to the shape of the outer portion and having grid ribs extending along the structural members.

K 11 3 Preferably, the thickness of each grid rib of the inner portion of the shell ranges from 0.2 to 1.0 times the thickness of the outer portion of the shell, whereas the cross-sectional area of the ribs ranges from 0.1 to 1.0 times and from 0.1 to 0.7 times the cross-sectional area of the longitudinal and transverse members, respectively.

Making the shell from interconnected outer and inner portions enables the development of a crack to be effectively arrested within allowable limits during failure of the outer portion of the shell inside the grid, as the crack runs to the border of double thickness of the outer and inner portions of the shell. The crack is thereby arrested as the thickness of the outer portion of the shell comes in'--o play ensuring reduced stresses at the mouth of the expanding crack. The proposed range of the cross-sections and thicknesses of the ribs of the inner portion of the shell is determined by the efficiency of crack arresting. If the crosssectional area of the ribs of the inner portion of the shell is less than 0.1 times the area of the longitudinal or transverse structural members, and the rib thickness of the inner portion of the shell is less than 0.2 times the thickness of the outer portion of the shell, the crack can be arrested as efficiently as in a smooth one-piece shell without the inner grid portion.

An increase in the cross-sectional area of the ribs of 4 the inner portion of the shell to over 0.1 and 0.7 times the area of the longitudinal and transverse structural members respectively. as well as an increase in the rib thickness in the inner portion of the shell to greater than the thickness of the outer portion of the shell in inadvisable because it entails a greater weight of the structure.

The invention will now be described in greater detail, by way of example, with reference to a specific embodiment thereof taken in conjunction with the accompanying drawings, in which:

Figure 1 is a lateral section of an aircraft fuselage; Figure 2 shows the outer portion of the shell of the fuselage; Figure 3 shows the inner portion of the shell of the fuselage; Figure 4 is a section taken along the line W-W in Figure 1; Figure 5 is a section taken along the line V-V in Figure 1.

An aircraft fuselage comprises a shell 1 (Figure 1) strengthened by longitudinal structural members 2 and transverse structural members 3. The shell 1 has the form of a continuous outer portion 4 (Figure 2) and an inner portion 5 (Figure 3) having the shape of the outer portion 4 (Figure 2) and fashioned as a network or grid the ribs of which are arranged along the structural members 2,3 (Figure 1). The outer portion 4 (Figure 2) and inner portion 5 (Figure 3) can be made of the same material or of different materials (metal, non-metal, or a combination thereof). Intersecting ribs 6 (Figures 4,5) of the inner portion 5 (Figure 3) of the shell 1 are positioned along longitudinal and lateral axes 7,8 (Figures 4.5) of the structural members 2,3 (Figure 1). The thickness of each rib 6 (Figures 4,5) of the inner portion 5 (Figure 3) of the shell 1 (Figure 1) ranges from 0.2 to 1.0 times the thickness of the outer portion 4 (Figure 2) of the shell 1 (Figure 1). The cross- sectional area of the ribs 6 (Figures 4,5) ranges from 0.1 to 1.0 times and from 0.1 to 0.7 times the cross-sectional area of the longitudinal and transverse structural members 2 and 3, respectively.

The shell 1 (Figure 1) of the aircraft fuselage in the zone of a pressurized cabin (not shown) has an interior pressurisation acting cyclically with a period of one cycle per flight. During the service life of the aircraft the shell 1 is subject to 20 - 30 thousand load cycles. Routine operation of the aircraft causes fatigue or accidental damage to the shell 1 resulting from cyclic loads or mechanical damage both longitudinally or transversely of the shell 1. In order to prevent catastrophic failures, the proposed fuselage construction has an inner portion 5 (Figure 3) service i 6 as a crack arrester. In the case of formation of a crack in the outer portion 4 (Figure 2) of the shell 1 in one grid cell, accompanied by progressive growth of such a crack, ends of the crack run to the edge of the rib 6 (Figures 4,5) and tend to stop. This phenomenon is associated with the stress level in the shell 1 (Figure 1) which determines the rate of crack growth both in the grid cell and at a portion of the rib 6 (Figures 4,5) where greater localised thickness acts to reduce the stress in the shell 1 (Figure 1) thereby ensuring effective reduction in the crack growth rate. Therewith, the preferred geometry of the ribs ensures a margin of strength at the crack length within one cell even if the crack develops during flight. After-flight inspection is supposed to detect such a crack.

The above-described structure enables an increase in the life of an aircraft fuselage and the more efficient arrest of crack development. Depending on the material of the grid the efficiency of crack arresting is increased by a factor of 5 to 27.

J1 t 7

Claims

Claims:-

1. An aircraft fuselage or other vessel comprising a shell in the form of a continuous outer portion and a grid-shaped inner portion. conforming to the shape of the outer portion, connected therewith. and having grid ribs extending along longitudinal and transverse structural members strengthening the shell.

2. A fuselage or vessel as claimed in claim 1, in which the thickness of each rib of the inner portion of the shell ranges from 0.2 to 1.0 times the thickness of the outer portion of the shell, whereas the crosssectional area of the ribs ranges from 0.1 to 1.0 times and from 0.1 to 0. 7 times the cross-sectional area of the longitudinal and transverse structural members, respectively.

3. A fuselage substantially as described with reference to, and as shown in. the accompanying drawings.

4. An aircraft having a fuselage according to any preceding claim.

Published 1990 atThe Patent Office, State House, 6671 High Holborn. LondonWCIR4TP. Further copies maybe obtainedfrom. The Patent Office Sales Branch. St Mary Cray. Orpington. Kent BR5 3RD- Printed by Multiplex techniques ltd, St Mary Cray. Kent. Con. 1187

4. An aircraft having a fuselage according to any preceding claim.

Amendments to the claims have been filed as follows 1. An aircraft fuselage or other vessel comprising a shell in the form of a continuous outer portion and a grid-shaped inner portion, conforming to the shape of the outer portion. connected therewith, and having longitudinal and circumferential crosspieces extending along longitudinal and circumferential structural members strengthening the shell.

2. A fuselage or vessel as claimed in claim 1, in which the thickness of each crosspiece of the inner portion of the shell ranges from 0.2 to 1.0 times the thickness of the outer portion of the shell. whereas the crosssectional area of the longitudinal crosspieces ranges from 0.1 to 1.0 times the cross-sectional area of the longitudinal and structural member and the cross-sectional area of the circumferential crosspieces ranges from 0.1 to 0.7 times.the cross-sectional area of the circumferential structural members.