Flexible armour panel

Abstract

A flexible armour panel, comprising: a fibre pack (310, 330) comprising a first plurality of layers of a fibre reinforced polymer matrix; and a scale pack (300) overlapping the fibre pack (310, 330). The scale pack (300) comprises a plurality of articulating imbricated rigid scales (100). Each scale of the plurality of articulating imbricated scales (100) is coupled directly to at least one adjacent scale of the plurality of articulating imbricated scales (100).

Description

[0001] FLEXIBLE ARMOUR PANEL

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a flexible armour panel and more particularly to a flexible armour panel that is wearable for torso protection.

[0004] BACKGROUND

[0005] Armour is useful in the context of armed conflict and security provision. Personal, wearable, armour must strike a balance between protection and mobility. Heavy and rigid armour is not good for mobility but may be good for protection. Lightweight flexible armour is good for mobility but may not be good for protection.

[0006] Current stab-resistant body armour is typically manufactured from polycarbonate to create a non-flexible breast plate structure. Whilst the protective performance of these articles has progressed since their introduction, users of such armour frequently report of ill-fitting and uncomfortable use. This, combined with their high weight and low breathability, at-best results in impaired performances such as reduced running speeds or operational manoeuvrability, and at worst can lead to physiological effects including nerve damage and severe musculoskeletal injuries.

[0007] In an attempt to enhance the design and development of the next generation of body armour, researchers have studied the mechanical performance of biological scale armour in animals such as armadillos, alligators, and fish. One of the most common predatory attacks these animals must endure is a localised impact from a sharp object such as a tooth, which is similar to the situation in a stab

[0008] Johnson (Johnson, A. A., G. A. Bingham, and Candice E. Majewski. "The design and assessment of bio-inspired additive manufactured stab-resistant armour." Virtual and Physical Prototyping 13.2 (2018): 49-57) proposes that a stab resistant armour might be made of overlapping scales.

[0009] Although considerable progress has been made in the development of wearable armour that strikes the right balance between mobility and protection, an improved flexible armour panel is desirable. SUMMARY

[0010] According to an aspect of the invention, there is provided a flexible armour panel, comprising: a fibre pack comprising a first plurality of layers of a fibre reinforced polymer matrix; and a scale pack overlapping the fibre pack, comprising a plurality of articulating imbricated rigid scales, wherein most scales of the plurality of articulating imbricated scales are coupled directly to at least one adjacent scale of the plurality of articulating imbricated scales.

[0011] Most of the scales will be coupled to two adjacent scales (except the scales around the perimeter of the scale pack). Subsequent reference to “most scales” may be understood as a reference to “more than 50% of the scales in the scale pack”.

[0012] An armour panel comprising both a scale pack and a fibre pack can provide the advantages of both, with good stab and spike resistance and good ballistic resistance.

[0013] The fibre pack may be a front fibre pack. The flexible armour panel may further comprise a back fibre pack comprising a second plurality of layers of a fibre reinforced polymer matrix. The scale pack scale pack may be sandwiched between the front fibre pack and the back fibre pack.

[0014] The number of layers in the first plurality of layers may be within 20% of the number of layers in the second plurality of layers. Preferably, the number of layers on the front side of the scale pack is approximately equal to the number of layers on the back side of the scale pack.

[0015] Each scale (or most scales of the scale pack) may have a length of between 20mm and 45mm and a width of between 12mm and 25mm. The scale length may, for example, be between 30mm and 40mm or between 32.5mm and 37.5mm. The scale width may be approximately half the scale length. The scale width may, for example be between 15mm and 20mm or between 17mm and 19mm. Each scale may have has a central thickness (e.g. along a central longitudinal axis) of between 2mm and 4mm. The average scale thickness may be less than 3mm or less than 2.5mm.

[0016] Each scale may comprise a rectangular body portion comprising a proximal end of the scale, and a triangular end portion comprising a distal end of the scale.

[0017] The triangular end portion may comprise a distal tip chamfer configured to present a surface which is parallel to a plane of the scale pack. The distal tip chamfer may be at the imbrication angle to a plane of the rectangular body portion.

[0018] Each scale may comprise a pair of holes adjacent to a proximal end of the scale. Each of the pair of holes may be configured to receive a peg from an identical adjacent scale.

[0019] The scale may comprise a first peg and a second peg protruding from the scale and adjacent to the pair of holes. Each of the first peg and the second peg may comprise a shaft and a foot.

[0020] The shaft of the peg may comprise a shaft longitudinal axis. The foot may comprise a foot longitudinal axis. The foot longitudinal axis may be at an angle of between 1 and 10 degrees to the shaft longitudinal axis.

[0021] Each scale may comprise a maximum thickness along a central longitudinal axis. The scale thickness may taper down with lateral distance from the central longitudinal axis. For example, the thickness of the scale at the edge may be 1mm less than the central thickness of the scale.

[0022] The scales may be configured to have an imbrication angle of between 15 degrees and 30 degrees.

[0023] The peg diameter may be between 4mm to 4.5mm. More generally, the peg diameter may be between 3.5mm and 5mm.

[0024] A central scale thickness, along a central longitudinal axis of each scale, may be between 2.5mm and 2.75mm. Each layer of the fibre pack may comprise a plurality of plies of unidirectional fibres.

[0025] There may be two plies per layer. The two plies may be arranged in a 0 / 90 degree fibre orientation.

[0026] The scale pack may be formed by an additive manufacturing method (e.g. powder bed fusion) in an assembled condition and the scale pack may be configured to require destruction of a coupling between scales to remove a scale from the scale pack. It is possible to determine, by inspection, that a scale pack must have been manufactured additively in an assembled condition, because this approach enables designs that could not otherwise have been assembled.

[0027] The scale pack may comprises or consists of nylon / polyamide. The scale pack may mostly comprise nylon / polyamide (e.g. at least 60% by weight of the scale pack may be nylon / polyamide). The scale pack may comprise or consist of glass loaded nylon / polyamide. The glass may be replaced by any other suitable fibre reinforcement (e.g. carbon, carbon nanotubes etc).

[0028] The scale pack may comprise or consist of PA11 (e.g. at least 60% by weight of the scale pack may be PA11).

[0029] The scale pack may comprise a variable scale size. A central region of the scale pack may comprises scales with a first size. A peripheral region of the scale pack may comprise scales with a second size, smaller than the first size. At least some of the scales in the peripheral region may not be edge scales.

[0030] According to a second aspect, there is provided a method of producing a flexible armour panel with a defined ballistic protection and a defined stab protection, comprising: determining a scale pack thickness required to provide a defined stab protection, wherein the scale pack comprises a plurality of articulating imbricated rigid scales, wherein each scale of the plurality of articulating imbricated scales is coupled directly to at least one adjacent scale of the plurality of articulating imbricated scales; providing a fibre based pack comprising a plurality of layers of a fibre reinforced polymer matrix, the fibre based pack capable of providing a defined level of ballistic protection; determining a reduced scale pack thickness by reducing the scale pack thickness by at least 20%; producing a flexible armour panel comprising a scale pack with the reduced scale pack thickness, sandwiched between the plurality of layers of the fibre based pack.

[0031] In some embodiments the reduced scale pack thickness may be between 20% and 30% smaller than the scale pack thickness.

[0032] According to a third aspect, there is provided a scale pack for use in a flexible armour panel, comprising a plurality of articulating imbricated rigid scales, wherein each scale of the plurality of articulating imbricated scales is coupled directly to at least one adjacent scale of the plurality of articulating imbricated scales.

[0033] The features of each aspect may be combined with those of any other aspect, including the optional features thereof. Features from each example embodiment may be combined with the aspects described above. For example, the scale pack of the third aspect may include any of the features described with reference to the first embodiment. As a further example, the armour panel produced according to the second aspect may include any of the features described with reference to the first aspect. Features of scale packs or fibre packs from the detailed description may be combined with the first aspect, second aspect or third aspect.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Example embodiments will be described with reference to the accompanying drawings, in which:

[0036] Figure 1 shows a top view, side view, end view and orthographic view of an example scale;

[0037] Figure 2 shows a dimensioned view of an example scale;

[0038] Figure 3 shows a top view, side view and sectional view of imbricated scales; Figure 4 shows an example front panel scale pack;

[0039] Figure 5 shows an example back panel scale pack; and

[0040] Figure 6 shows an example scale pack draped over a curved body;

[0041] Figure 7 shows example armour panels prior to assembly comprising both fibre packs and scale packs;

[0042] Figure 8 shows stab tests performed on scale pack only specimens;

[0043] Figure 9 shows a trend of ballistic performance (back face signature, BFS) vs the mass of two different example fibre packs; and

[0044] Figure 10 shows example flexible armour panels after ballistic testing.

[0045] DETAILED DESCRIPTION

[0046] Figure 1 shows a scale 100, which is formed as part of a scale pack (as will be understood with reference to Figures 3 to 5). The scale 100 comprises: a rectangular body portion 101 comprising a proximal end of the scale 100, and a triangular end portion 102 comprising a distal end of the scale 100.

[0047] The scale 100 comprises a central longitudinal axis 105 along a length of the scale 100. A lateral width of the rectangular body portion 101 of the scale (at right angles to the longitudinal axis 105, between opposite long edge faces 106 of the rectangular body portion 101) is roughly half the length of the scale 100. The thickness of the scale 100 is at a maximum along the central longitudinal axis 105, and the scale tapers away from this maximum thickness with increasing lateral distance, to reach a minimum at the long edge faces 106.

[0048] The top surface of the scale 100 comprises a first flat face 110 and a second flat face 111 , which slope downward from the central longitudinal axis 105 to the long edge faces 106. The bottom surface of the scale 100 comprises corresponding flat faces 120, 121 which each slope upward from the central longitudinal axis to the long edge faces 106, so that the scale 100 tapers towards the long edge face 106 at the front side and the back side in the same way. First top face 110 is opposite first bottom face 120 through the thickness of the scale 100, and second top face 111 is opposite second bottom face 121 through the thickness of the scale 100. The lateral tapering of the scale 100 at the front and back side is symmetric about the plane of the scale 100 and there is 1mm total reduction in thickness from the centre thickness to the edge thickness.

[0049] The scale 100 comprises a distal tip chamfer 103, which is configured to present a surface which is parallel to a plane of the scale pack when the scale is formed into a scale pack (as will be understood more clearly with reference to Figure 3). The scale 100 further comprises edge chamfers 104 along the upper edges of the triangular body portion 102 that are truncated by the distal tip chamfer 103.

[0050] The example scale 100 is symmetric about the central longitudinal axis 105, so on one lateral side of this axis (in the top view) are mirror versions of corresponding features on the opposite lateral side of this axis. A scale plane may be defined as including the central longitudinal axis 105 and including a lateral line joining a centroid of each of the long edges 106.

[0051] Attached to and protruding from a bottom side of the rectangular body portion 101 there is provided a first peg 117 and a second peg 127. A first foot 118 is provided at the end of the first peg 117 and a second foot 128 is provided at the end of the second peg 127. The first peg 117 and second peg 127 are each cylindrical and each protrude in a direction normal to the scale plane. The first foot 118 is attached to a distal end of the first peg 117. The first foot 118 is a disc shaped flange that is parallel to the first top face 110 (so is at an angle to the axis of the first peg). The second foot 128 is attached to a distal end of the second peg 127. The second foot 138 is a disc shaped flange that is parallel to the second top face 120 (so is at an angle to the axis of the second peg). This orientation of the first foot 118 and second foot 128 means that the first and second foot will be parallel to an adjacent bottom surface of the scale that they engage with (e.g. in an imbricated arrangement such as the example of Figure 3).

[0052] A first through hole 112 and a second through hole 122 are provided through the rectangular body 101 of the scale 100, between the pegs 117, 127 and a proximal end of the scale 100. Each of the through holes 112, 122 is configured to receive a peg from an identical further scale (or a similar further scale with a peg corresponding with the hole) and each peg is configured to be received in a hole of a corresponding identical scale. The length of the pegs 117, 127 may therefore vary in proportion to the thickness of the scale 100, so that the distance between the bottom surface 120, 121 and the upper face of the respective foot 118, 128 varies with a thickness of the scale body.

[0053] A clearance distance (or overall tolerance) can be defined as a minimum gap between surfaces of a linked pair of scales (i.e. between the surface of a peg and the receiving hole).

[0054] Figure 2 shows a dimensioned view of an example scale, in which:

[0055] DI is peg diameter (4mm in this example);

[0056] D2 is peg length (1.2 times the scale thickness D3 in this example);

[0057] D3 is central scale thickness (3.5mm in this example);

[0058] D4 is foot diameter (1.5 times the peg diameter in this example);

[0059] D5 is foot thickness (1mm in this example);

[0060] D6 is the fillet radius (0.75 times the space between the peg diameter and top surface of the foot in this example);

[0061] D7 is the scale length (35mm in this example);

[0062] D8 is the nose taper angle (50 degrees in this example);

[0063] D9 is the imbrication angle (~23 degrees in this example).

[0064] A “benchmark DC3” design, as defined herein, has the geometry shown in Figure 2, with a tolerance of 0.30mm between adjoined scale and a central thickness D10 of 3.75mm. A tolerance of 0.3mm provides a good balance between protection and drapability.

[0065] Figure 3 shows a top view of example array of imbricated scales 200 with a side view 220 and sectional view 210 along A-A. Each scale in the array 200 is an accordance with the example described with reference to Figures 1 and 2. Columns of scales 221- 225 are arranged with long edge faces 106 adjacent (e.g. separated by a clearance distance sufficient to allow articulation of the scales). Neighbouring columns of scales are offset by a distance equal to half of the pitch between scales in each column, so that gaps between tiles are blocked by the overlapped tile of the next column. Each scale (that is not at the edge of the array) is coupled to two scales in an overlying column (via the holes 112, 122) and to two scales in an underlying column. For example, scale 231 in column 222 is linked to two scales in the overlying column 221 via the holes of scale 231 and to two scales in the underlying column 223 via the pegs of scale 231.

[0066] The tiles are formed in the assembled state by additive manufacturing (e.g. powder bed fusion or a similar technology). In the examples described herein, the scales were formed from Polyamide (PAI 1), but any other material can be used with similar or better mechanical properties. The PA11 may be virgin PA11 , a mix of recycled and virgin PA11 (e.g. up to 80% recycled PA11) and / or may comprise carbon-filled PA11. Metal materials can also be formed using powder bed fusion, and scales may be formed from metal. Composite materials may also be used, such as glass loaded polymer, or carbon fibre / graphite / carbon nanotube loaded polymer.

[0067] Suitable design parameters for a scale were explored. The range of design parameters explored are set out in Table 1 , below:

[0068] Table 1 : Scale design parameters

[0069] Figure 4 shows a front flexible armour panel 300 comprising imbricated scales similar to those shown in Figures 1 to 3, and Figure 5 shows a rear flexible armour panel 400 comprising imbricated scales similar to those shown in Figures 1 to 3. Notably, it can be seen that, although most of the panel comprises identical scales, not all the scales are the same. The scales around the perimeter are not linked to as many scales as those in the centre (for obvious reasons), and are typically a different shape. Figure 6 shows the flexibility and drapeability that is achieved by an example scale pack 360. The minimum radius of curvature and drapability of the scale pack is anisotropic, because of the way the scales are linked together and their geometry. The minimum curvature diameter of a DC benchmark scale pack was measured approximately 70mm and 95mm in machine and cross directions. The minimum curvature diameter of an optimised scale pack (according to table 2, below) was measured approximately 160mm and 170mm in machine and cross directions.

[0070] A set of stab resistance experiments were performed in order to investigate suitable design parameters for an example scale like that shown in Figures 1 and 2. A rail drop test apparatus was used as defined in the 2017 UK Home Office Body Armour Standard (CAST publication 012 / 17, “the Standard”). Pl / B stand test knives were used. Following each test each knife was replaced (test implements were only used once). Backing materials were in accordance with the Standard.

[0071] Strikes were performed in the middle of each single strike test specimen, with an impact energy of 24 Joules (corresponding with KR1-E1 in the Standard). When panel testing, the location and orientation of each strike was in accordance with the Standard.

[0072] Pre-conditioning was performed for some tests. For wet testing, specimens were immersed in water at 15 to 20 degrees C for a period of 15 minutes (plus or minus 3 minutes). Specimens were hung vertically for 5 minutes before testing and the first strike or shot conducted within 5 minutes of the end of the hanging period. Elevated temperature testing was performed in which the specimens were warmed to 50 degrees C and cooled to -20 degrees C. Once the test samples were removed from heating or cooling, they were hung at ambient temperature for 30 minutes (plus or minus five minutes) before testing. The first shot / strike was conducted within 5 minutes of the end of the ambient hanging period and tests were conducted within 45 minutes of conditioning finishing.

[0073] Stab testing results

[0074] A maximum penetration of 8mm is permitted at KR1-E1 , with a maximum penetration for a single stab in a test series of 9mm. Analysis of designs was carried out over the range specified in Table 1 , based on two criteria: i) minimising penetration depth; ii) minimising the number of failed tests. Examples of stab tests performed on scale pack only specimens 350 are shown in Figure 8, in which shows a) no penetration, b) a failed penetration test, with a penetration distance of more than 8mm, and c) a partial penetration of less than 8mm.

[0075] For the type of example scale shown in Figures 1 to 3, the following combination of design parameters was found to produce good performance.

[0076] Table 2: Optimal scale design parameters

[0077] Good performance in this context is a design that passes a KR1-E1 test, and the values listed in Table 2 provide good performance (i.e. stab resistance) in the context of an armour panel consisting only of a scale pack with a central scale thickness of 3.5mm or more. The most significant parameter listed in table 2 for good performance was found to be the peg diameter with values in a range of 4mm to 4.5 mm found to perform particularly well. The fillet was also found to have a significant impact, with values over 50% found to perform well. For tolerance, values in the range 0.25mm to 0.35mm were found to perform well. The performance is relatively insensitive to peg length ratio, foot thickness and foot diameter ratio. An areal density for a 3.5mm thick scale pack with the design parameters shown in Table 2 is ~8.7 kg.m2and an areal density for a 3.75mm thick scale pack is ~9.3 kg.m2.

[0078] Spike testing

[0079] Spike testing was carried out at SP1-E1 according to the Standard. The results showed that scale packs with good performance against stab testing also had good performance against spike testing.

[0080] Ballistic and stab / spike resistance - hybrid panels While armour consisting only of a scale pack can provide good stab resistance (i.e. passing a KR1-E1 test), improved performance is possible using a hybrid armour panel, comprising both a scale pack (similar to that shown and described with reference to Figures 1 to 5) and a fibre pack comprising a fibre reinforced polymer matrix. Aramid fibres are suitable for use in such fibre packs but any other fibre with suitable mechanical properties can also be used, for example ultra-high molecular weight polyethylene, carbon, para-aramid, and polybenzoxazole. The orientation and weave of the fibres in such a layer may take any suitable configuration, and a wide range of fibre based ballistic impact resistant panels have been made available to the public.

[0081] Examples of hybrid armour panels, comprising a scale packs in combination with at least one fibre pack, are shown in Figure 7. For clarity, the packs are shown prior art assembly, with an offset, so that each pack is visible. At the top of Figure 7 an armour panel is shown comprising a scale pack 300 with a back fibre pack 330 (between the scale pack 300 and the wearer) and no front fibre pack. At the bottom left of Figure 7 an armour panel is shown comprising a front fibre pack 310, scale pack 300 and back fibre pack 330. The scale pack 300 is sandwiched between the front and back fibre packs 310, 330. At the bottom right of Figure 7 an armour panel is shown comprising a front fibre pack 310 and a scale pack 300 (with no back fibre back).

[0082] An example of a suitable fibre pack layer is Honeywell Goldshield 2115. Each layer of Honeywell Goldshield 2115 comprises a pair of plies of unidirectional aramid fibres at a 0 / 90 degree orientation in a polyurethane resin matrix. Multiple layers of this material can be built up to produce a fibre pack, which may be combined with a scale pack to produce a hybrid flexible armour panel. This approach may provide better stab and spike resistance than would be available from only a fibre pack, and lower weight and better ballistic resistance than would be achievable with only a scale pack. Other layers of fibre based ballistic protection can be used in a similar way - the Honeywell product is merely exemplary of a general type of ballistic resistant fibre based layer.

[0083] A fibre pack based flexible armour that meets NIJ level 11+ was obtained from Vestguard UK. Each panel of this armour consists of 27 layers and the panel has an areal density of ~6.6 kg.m2. 35 layers of Goldshield 2115 was identified as being roughly equivalent to this pack, providing a suitable balance for supporting both ballistic performance and stab protective performance, in conjunction with a scale pack. 35 layers of Goldshield 2115 has an areal density of ~3.8 kg.m2.

[0084] Ballistic testing was carried out against a range of different panels comprising both a scale pack and fibre pack. The test round was the NIJ 010801 9mm 124 grn RN FMJ, with a target test velocity of 365 m / s (plus or minus 10 m / s). All ballistic tests were carried out within a temperature range of 21.5 - 22.5 degrees C and an RH of 46-56%. For the backing material, steel trays (420mmx350mmxl00mm), open at the top face were filled with Roma Plastilina No. l clay. No gaps existed within the material and the top surface was smooth. The trays were conditioned overnight at 34 degrees C and calibrated with a drop test sphere (in accordance with the UK Home Office Body Armour Standard CAST 012 / 17).

[0085] Ballistic protection at protection level HOI has a defined permissible back face signature (BFS) of 44mm.

[0086] For the 27 layer Vestguard armour panel (without modification) a BFS of 24.9mm was measured (a pass, as expected). Reducing the number of layers reduces performance. Using 14 layers of the Vestguard panel results in a BFS of 41mm (just within the limit).

[0087] Armour panels comprising only Honeywell Goldshield 2115 layers were similarly tested for ballistic protection. It was found that 35 layers provided similar ballistic resistance in this test to the Vestguard armour panel, and BFS exceeding the limit occurs with fewer than 23 layers. A graph plotting mass vs BFS for Vestguard and Honeywell based specimens is shown in Figure 9. It can be seen that the trend from each layer type is somewhat aligned, which tends to indicate that a suitable hybrid armour pack can be provided using fibre packs from a range of different suppliers. Other embodiments are possible using layers provided by different suppliers with equivalent performance.

[0088] Armour panels comprising a scale pack and a fibre pack were tested for ballistic resistance. It was found that the addition of a scale pack to a fibre pack improves ballistic performance. A DC3 benchmark scale pack (which is stab resistant by itself to KR1-E1) was combined with a 27 layer Vestguard fibre pack resulting in a BFS of 15.5mm (an improvement over the ~25mm measured for the same fibre pack in isolation). Layering configuration was explored with Goldshield 2115 fibre packs having a total of 35 layers, with the scale pack placed: i) on the top; ii) sandwiched between fibre packs; iii) on the bottom. Ballistic testing of these armour configurations showed that the sandwiched configuration works well, as shown below in Table 3.

[0089] Table 3: HOI ballistic testing results

[0090] Figure 10 shows example results from the ballistic testing that is summarised in Table 3, with Figure 10 showing a) scale pack top; b) scale pack middle; and c) and d) scale pack bottom. The sandwich type construction shows excellent performance, and no tearing or pencilling within the ballistic pack. In contrast, the scale back top arrangement shows tearing in the fibre pack, and scale pack bottom shows broken linkages in the scale pack. The results of this testing suggests that the scale pack middle / sandwich arrangement performs surprisingly well.

[0091] Combining a DC3 scale pack (which is stab resistant to KR1 in isolation) with a fibre pack that is HOI ballistic resistant results in a relatively heavy panel.

[0092] It was found that stab resistance to KR1 can be achieved with a hybrid fibre pack having a scale pack that is, by itself, not stab resistant to KR1. A reduced thickness of the scales in the scale pack can be used in a hybrid armour arrangement, compared to what would be required if the scale pack alone were responsible for providing all of the stab resistance. Ballistic testing of armour panels comprising a scale pack with scales according to the optimised design set out in Table 2 and having a central scale thickness of 2.75mm and 2.5mm was carried out. The results showed that (with the exception of wet conditions), good ballistic performance was achieved (for both 2.5mm and 2.75mm central scale thicknesses, with a maximum mean BFS measurement of 21.9mm across all tests (and no failed tests).

[0093] The stab resistance of armour panels comprising the optimised 2.5mm or 2.75mm thick scale pack in a sandwiched configuration with a fibre pack capable of providing ballistic resistance to HOI (e.g. comprising 35 layers of Goldshield 2115) is excellent. Testing with a reduced fibre pack thickness of 29 layers of Goldshield 2115 in a scale pack top configuration gave mean penetration depths at KR1-E1 of ~4.8mm with a standard deviation of 0.85mm, with no tests having a penetration depth greater than ~6mm. This is a pass at KR1 -E1 for that configuration. Configurations with higher numbers of layers perform better and “scale pack middle” configurations also perform better.

[0094] Testing at the higher energy KR1-E2 (with an energy of 36 Joules and a maximum penetration of 20mm) showed that excellent performance was obtained for armour panels comprising: i) a scale pack according to Table 2 with a 2.5mm or 2.75mm scale centre thickness; and ii) in a sandwich configuration with 17 layers Goldshield 2115 - scale pack - 18 layers Goldshield 2115. The panel with scale thickness of 2.75mm had a mean penetration (at KR1-E2) of ~1.6mm and a std dev of 0.36mm, and the panel with scale thickness of 2.5mm had a mean penetration of ~7.8mm and a std dev of 1.4mm. Such panels therefore appear to be excellent solutions for providing both ballistic and stab / spike protection, without compromising mobility.

[0095] In general, excellent ballistic and stab resistance is provided by the combination, of: i) a scale pack capable of providing stab resistance (at full thickness), but with reduced thickness; and ii) a fibre pack configured to provide ballistic protection, with layers distributed approximately 50:50 around the reduced thickness scale pack. In the present example, a reduction in thickness of the scale pack of around 30% was used (from 3.5mm to 2.5mm), with improved stab resistance in the composite. The ballistic performance was also improved over the performance of the fibre pack thickness in isolation.

[0096] In the example embodiments of Figure 4 and Figure 5 the scale size is uniform, except for the edge scales on an edge of the armour panel (those that are not connected to the same number of scales as the central scales). In these examples, each central scale is connected to four other scales, whereas edge scales are linked to fewer scales (e.g. three or two scales).

[0097] In some embodiments, the scale pack may comprise a variable scale size, with a central region of the scale pack comprising scales with a first size, and a peripheral region of the scale pack comprises scales with a second size, smaller than the first size. The peripheral region in such embodiments may comprise scales that are not edge scales.

[0098] Figure 11 shows example embodiments with this variable scale size. Figure I la shows a line drawing of a front armour scale pack and Figure 11b shows a line drawing of a back armour scale pack. Figure 11c shows a photograph of a front armour scale pack and Figure l id shows a photograph of a back armour scale pack. Figure l ie and I lf show the an armour panel comprising the scale pack of Figures 11c after ballistic testing.

[0099] A central region with a substantially elliptical (or stadium shaped) extent is visible comprising scales with a first size (within line 901), and the scale size transforms smoothly (e.g. linearly) to a second size, smaller than the first size over a transition region (between line 901 and line 902. A peripheral region, outside this transition region (i.e. outside line 902), comprises scales with the second size. The peripheral region comprises scales that are not at the edge - for example there may be at least two, three, four or five peripheral scales between the end of the transition region and an edge of the panel in some locations.

[0100] Although specific embodiments have been described, it will be understood that variations are possible, within the scope of the appended claims.

Claims

CLAIMS1. A flexible armour panel, comprising: a fibre pack comprising a first plurality of layers of a fibre reinforced polymer matrix; and a scale pack overlapping the fibre pack, comprising a plurality of articulating imbricated rigid scales, wherein each scale of the plurality of articulating imbricated scales is coupled directly to at least one adjacent scale of the plurality of articulating imbricated scales.

2. The flexible armour panel of claim 1 , wherein the fibre pack is a front fibre pack, and further comprising a back fibre pack comprising a second plurality of layers of a fibre reinforced polymer matrix; wherein the scale pack is sandwiched between the front fibre pack and the back fibre pack.

3. The flexible armour panel of claim 2, wherein the number of layers in the first plurality of layers is within 20% of the number of layers in the second plurality of layers.

4. The flexible armour panel of any preceding claim, wherein each scale has a length of between 20mm and 45mm and a width of between 12mm and 25mm.

5. The flexible armour panel of any preceding claim, wherein each scale has a central thickness of between 2mm and 6mm6. The flexible armour panel of any preceding claim, whereinwat each scale comprises a rectangular body portion comprising a proximal end of the scale, and a triangular end portion comprising a distal end of the scale.

7. The flexible armour panel of claim 6, wherein the triangular end portion comprises a distal tip chamfer configured to present a surface which is parallel to a plane of the scale pack.

8. The flexible armour panel of any preceding claim, wherein each scale may comprises a pair of holes adjacent to a proximal end of the scale, each of the pair of holes configured to receive a peg from an identical adjacent scale.

9. The flexible armour panel of claim 9, wherein the scale comprises a first peg and a second peg protruding from the scale and adjacent to the pair of holes, each of the first peg and the second peg comprising a shaft and a foot.

10. The flexible armour panel of claim 9, wherein the shaft of the peg comprises a shaft longitudinal axis and the foot comprises a foot longitudinal axis, and the foot longitudinal axis is at an angle of between 1 and 6 degrees to the shaft longitudinal axis.11 . The flexible armour panel of any preceding claim, wherein each scale comprises a maximum thickness along a central longitudinal axis, wherein the thickness tapers down with lateral distance from the longitudinal axis.

12. The flexible armour panel of any preceding claim, wherein the scales are configured to have an imbrication angle of between 15 degrees and 30 degrees.

13. The flexible armour panel of any preceding claim, wherein the peg diameter is 4mm to 4.5mm.

14. The flexible armour panel of any preceding claim, wherein a central scale thickness, along a central longitudinal axis of each scale, is between 2.5mm and 2.75mm.

15. The flexible armour panel of claim 1 , wherein each layer of the fibre pack comprises a plurality of plies of unidirectional fibres.

16. The flexible armour panel of claim 15, wherein there are two plies per layer, arranged in a 0 / 90 degree fibre orientation.

17. The flexible armour panel of any preceding claim, wherein the scale pack is formed by an additive manufacturing method in an assembled condition and the scalepack is configured to require destruction of a coupling between scales to remove a scale from the scale pack.

18. The flexible armour panel of any preceding claim, wherein the scale pack comprises or consists of nylon / polyamide, for example consists of PA11.

19. The flexible armour panel of any preceding claim, wherein the scale pack comprises a variable scale size, with a central region of the scale pack comprises scales with a first size, and a peripheral region of the scale pack comprises scales with a second size, smaller than the first size, and at least some of the scales in the peripheral region are not edge scales.

20. A method of producing a flexible armour panel with a defined ballistic protection and a defined stab protection, comprising: determining a scale pack thickness required to provide a defined stab protection, wherein the scale pack comprises a plurality of articulating imbricated rigid scales, wherein each scale of the plurality of articulating imbricated scales is coupled directly to at least one adjacent scale of the plurality of articulating imbricated scales; obtaining a fibre based pack comprising a plurality of layers of a fibre reinforced polymer matrix, the fibre based pack capable of providing a defined level of ballistic protection; determining a reduced scale pack thickness by reducing the scale pack thickness by at least 20%; producing a flexible armour panel comprising a scale pack with the reduced scale pack thickness, sandwiched between the plurality of layers of the fibre based pack.

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