GB2155873A - Liquid storage tanks - Google Patents

Abstract

Mitigation of damage to tanks containing liquid, eg, fuel, as a result of energy transfer from shock waves resulting from a penetrating missile is effected by providing the tank walls internally with a series of gas filled shock absorbing pockets 4. The pockets 4 are formed between impervious layers 2, 3 of polymer coated reinforcing cloth or plastics film. The layers 2, 3 may be self sealing to minimise fuel loss following penetration of the tank. The tank walls 1 can be carbon reinforced plastics. The layers 2, 3 may be replaced by a layer of sealed foam. The fuel tank can be mounted in a vehicle or integrally formed in the vehicle structure. <IMAGE>

Description

SPECIFICATION Liquid storage tanks This invention relates to fuel or other liquid storage tanks. It particularly, but not exclusively, relates to those tanks which are formed of composite material, for example carbon or other fibre reinforced plastics. Where such tanks are carried in a vehicle, they may be fabricated and subsequently mounted within the vehicle structure or, more conveniently, they may be integrally formed within the vehicle structure.

Irrespectively, but particularly in the case of integrally formed composite material tanks, the tanks can be significantly damaged by impact of even relatively small projectiles.

In general, structures formed of composite or other rigid materials have a relatively poor resistance to shock load because of their inherent characteristic of low strain to failure compared with conventional metallic materials. The problem is exacerbated in the case of tanks for liquids, e.g. fuel tanks, where shock waves can occur within the liquid. The shock waves and their effects are found to be particularly severe where the tanks are integrally formed; the walls are rigid and also the shock of any penetrating projectile is not attenuated by initial contact with external structure not directly associated with the tank. The waves are the direct result of energy transfer from a decelerating projectile to the liquid.

The present invention has for an objective the mitigation of damage to tanks containing liquid as a result of such energy transfer from a penetrating projectile.

According to the invention, a tank for liquids is provided internally with deformable shock absorbing regions.

Conveniently, the shock absorbing regions are in the form of discrete pockets adjacent one or more interior walls of the tank in which air is trapped.

The pockets are preferably formed between sealed layers of glass fibre or synthetic fibre cloth coated with a suitable polymer. Alternatively, a tough plastics film material could be used.

Some examples of the invention are described by way of example in the accompanying figures in which: Figure 1 is a plan view of an interior surface of a fuel tank, Figure 2 is a cross-sectional view upon Arrows II11 of Figure 1, and, Figure 3 is a similar view to Figure 2 but of an alternative embodiment.

In the Figures, a fuel tank wall 1 has, on its inwardly facing surface, twin imperivous layers 2 and 3 of polymer coated reinforcing cloth, or plastics film. The sheets 2 and 3 are bonded or cocured together in a manner which entraps air in pockets 4, the pockets lying over a large proportion of the surface of the wall to cushion that wall against hydraulic shock. As illustrated, the pockets 4 may be circular in plan form, and either rectangular (Figure 2) or part-spherical (Figure 3) in cross section, although other shapes are perfectly feasible providing a substantial cushioning effect is produced.

The layers 2 and 3, which are joined to form a unitary layer, are loosely attached to the wall 1.

An alternative or addition to the pockets 4 is a layer of foam sealed to prevent the ingress of fuel.

Moroever, the layers 2 and/or 3 or any foam layer could be of a self sealing nature to reduce or minimise fuel loss from the tank following penetration.

1. A tank for liquids provided internally with deformable shock absorbing regions.

2. A tank according to Claim 1, wherein the shock absorbing regions are in the form of discrete pockets adjacent one or more interior walls of the tank in which gas is trapped.

3. A tank according to Claim 2, wherein the pockets are formed between two layers of impervious flexible material having portions attached one to another and portions spaced one from another housing said gas.

4. A tank substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Liquid storage tanks This invention relates to fuel or other liquid storage tanks. It particularly, but not exclusively, relates to those tanks which are formed of composite material, for example carbon or other fibre reinforced plastics. Where such tanks are carried in a vehicle, they may be fabricated and subsequently mounted within the vehicle structure or, more conveniently, they may be integrally formed within the vehicle structure. Irrespectively, but particularly in the case of integrally formed composite material tanks, the tanks can be significantly damaged by impact of even relatively small projectiles. In general, structures formed of composite or other rigid materials have a relatively poor resistance to shock load because of their inherent characteristic of low strain to failure compared with conventional metallic materials. The problem is exacerbated in the case of tanks for liquids, e.g. fuel tanks, where shock waves can occur within the liquid. The shock waves and their effects are found to be particularly severe where the tanks are integrally formed; the walls are rigid and also the shock of any penetrating projectile is not attenuated by initial contact with external structure not directly associated with the tank. The waves are the direct result of energy transfer from a decelerating projectile to the liquid. The present invention has for an objective the mitigation of damage to tanks containing liquid as a result of such energy transfer from a penetrating projectile. According to the invention, a tank for liquids is provided internally with deformable shock absorbing regions. Conveniently, the shock absorbing regions are in the form of discrete pockets adjacent one or more interior walls of the tank in which air is trapped. The pockets are preferably formed between sealed layers of glass fibre or synthetic fibre cloth coated with a suitable polymer. Alternatively, a tough plastics film material could be used. Some examples of the invention are described by way of example in the accompanying figures in which: Figure 1 is a plan view of an interior surface of a fuel tank, Figure 2 is a cross-sectional view upon Arrows II11 of Figure 1, and, Figure 3 is a similar view to Figure 2 but of an alternative embodiment. In the Figures, a fuel tank wall 1 has, on its inwardly facing surface, twin imperivous layers 2 and 3 of polymer coated reinforcing cloth, or plastics film. The sheets 2 and 3 are bonded or cocured together in a manner which entraps air in pockets 4, the pockets lying over a large proportion of the surface of the wall to cushion that wall against hydraulic shock. As illustrated, the pockets 4 may be circular in plan form, and either rectangular (Figure 2) or part-spherical (Figure 3) in cross section, although other shapes are perfectly feasible providing a substantial cushioning effect is produced. The layers 2 and 3, which are joined to form a unitary layer, are loosely attached to the wall 1. An alternative or addition to the pockets 4 is a layer of foam sealed to prevent the ingress of fuel. Moroever, the layers 2 and/or 3 or any foam layer could be of a self sealing nature to reduce or minimise fuel loss from the tank following penetration. CLAIMS

1. A tank for liquids provided internally with deformable shock absorbing regions.

2. A tank according to Claim 1, wherein the shock absorbing regions are in the form of discrete pockets adjacent one or more interior walls of the tank in which gas is trapped.

3. A tank according to Claim 2, wherein the pockets are formed between two layers of impervious flexible material having portions attached one to another and portions spaced one from another housing said gas.

4. A tank substantially as hereinbefore described with reference to the accompanying drawings.