FR2544656A1 - Armoured material mfg. - Google Patents

Abstract

At least one single-thread filament is coated with a heat stting resin to give a cladded filament, to be wound on a core. The filaments are used to build up a number of layers, with the filament axis of each layer at an angle to the filaments of the proceding layers on the core. The filaments are then converted into a blank for insertion into a moulding press to hold them in their orientation and shape, while the resin is set, until it is fully set.

Description

 The invention relates to materials suitable for application to armor or armor.

 The invention also relates to a process for shaping a breastplate material which stops projectiles and uses resins and monofilament fibers.

 Currently, protective helmets for military personnel are made using a woven fabric impregnated with resin. The impregnated woven fabric is cut into rectangular strips or in other shapes which are then laid in a certain configuration in which the edges of the strips overlap to form a preformed structure. The preform is carried out by manual application of the strips on a # mandrel. The operation of hand shaping and overlapping of the various strips of material makes it difficult to form a uniform material and the resulting finished product exhibited a very variable impact resistance from one location to another. These variations in impact resistance and the resulting weaknesses of the helmet are obviously undesirable.

 In addition, the woven fibrous materials are expensive, in equal quantity, compared to the monofilament fibers and the operation of impregnating the woven material with resin results in a significant additional cost. Therefore, the resin-impregnated woven material is an expensive raw material for use in making previously shaped shapes.

 Cutting an impregnated woven material into strips results in significant material loss and further increases processing costs. Wastage is even greater when the impregnated woven material is cut into non-rectangular sections.

 Briefly described, the invention relates to a process by which a monofilament fiber is used in combination with a resin for the production of a preform suitable for an additional treatment which consists in bringing the resin to maturation in order to obtain a thermoset material. The method allows significant flexibility with respect to the configuration of the preform and, since the monofilament material is distributed uniformly in the finished product, the resulting product is substantially uniform.

 During the implementation of the process of the invention, a monofilament fiber is coated with an uncured resin, after which the coated fiber is wound on a mandrel so as to form several layers. The filaments of each of the successive layers are arranged so as to form an angle with the filaments of the preceding layer, thus producing a large number of superimposed crossings of filaments. The fibers are arranged on the mandrel according to the configuration of a desired preform and they are coated with enough resins to bond and consolidate into a homogeneous body when the resin is hardened. The preform obtained is placed in a mold and heat and pressure are applied to consolidate it.

 The improved battleship article produced by the process of the invention is a battleship material having a large number of fibrous layers, each of the successive layers being arranged so as to form an angle with the layer which immediately precedes it. The fibers are consolidated by a thermoset resin, the power of which adheres to the fiber is less than the tensile strength of the fiber. The resulting armor material does not show a line of weakness due to the presence of cut edges.

The invention will be described in more detail with reference to the attached drawing by way of non-limiting example and in which
- Figure 1 is a partial schematic elevation of a process for coating a monofilament fiber and there to arrange on a mandrel to achieve a preform
- Figure 1A is a perspective view of a preform thus obtained
- Figure 2 is a schematic cross section of a tool suitable for the maturation of the preform; and
- Figure 3 is a schematic perspective view of a mandrel for winding a cylinder of fibrous material.

 The drawing, in which the same reference numerals designate the same elements, and in particular FIG. 1, shows a roll of monofilament fiber 10 to be coated.

The fiber is slowly unwound under tension from a spool 12 so as to pass through a bath 14 of liquid resin contained in a reservoir 16. The monofilament fiber 10 passes under a tension roller 18 and is drawn continuously from the resinous material.

 The resin-coated fiber 20 passes over a roller 22 and arrives on a rotary mandrel 24 mounted on a spindle 26. The winding of the fiber is a known shaping technique making it possible to distribute numerous layers of fibers on a mandrel in order to produce a preform 27 comprising a large number of layers. The fibers are wound tightly on the mandrel. They form a large number of crossing points at which the fibers of one layer pass over the fibers of several previous layers by crossing them. The control device making it possible to produce a mass of fibers distributed uniformly is not shown, but it is known to the specialist in the winding of fibers. As shown, a helmet preform is wound on an egg-shaped or egg-shaped mandrel. When the winding is completed, the preform can be cut transversely into two halves, along a line 29, so that two preforms are obtained cup-shaped suitable for pressing to form a finished helmet.

 As shown in Figure 2, after the resin-coated monofilament fiber 20 has been wound on the mandrel 24 and the preform has been cut to form two cups 28, the latter can be matured using a press 30. After the cup 28 has been placed on a lower die 32 mounted on the base 34 of the press, a complementary upper mold 36 having a cavity is mounted on the upper frame 38 of the press, above the tool 32, and is brought into position in order to apply a pressure of the order of 3500- # 4000 kPa to the preform. The mold frames 34 and 38 are movable vertically along support columns 40 which are mounted using conventional techniques in the mold frames. Pressure can be applied by the use of conventional hydraulic technology ( not shown), as is common in the field of molding and maturing thermosetting resins reinforced with fibers. From a functional point of view, the amplitude of the pressure applied by the molds 32 and 36 to the preform 28 is sufficient to compress and consolidate the fibers responding to the maturation of the resin until a thermoset material.

 Means are associated with. molds 32 and 36 for applying heat to the preforms during pressing in order to bring the resin to maturation. Suitable sources of heat include live steam, heated oil, radio frequency radiation, or electric resistance heaters. The amount of heating is generally adjusted so that the resin hardens uniformly in the shortest time acceptable from an industrial point of view. The temperature at which the preform is matured or cured depends on the resin used to consolidate the fibers. The duration of the maturation time also varies depending on the resin and the temperature. Determination of the desired temperature and time for maturation is within the skill of the art and will not be described in further detail.

 In general, the fibers useful for the implementation of the invention are monofilament fibers.

The expression "monofilament fiber" used in the present specification designates fibers having a certain length on the order of several decimeters up to several hundred meters. These fibers are produced by various manufacturers using known techniques for forming fibers. The fibers are available in different diameters and they are made of different materials.

 One type of fiber useful for implementing the invention comprises polyamide fibers. A commercially available polyamide fiber is sold under the name "Kevlar", which is a polyamide monofilament available from E.I. DuPont Company. Polyamide fibers have excellent impact resistance, since they tend to absorb and dissipate impact forces along their longitudinal axis when they are not rigidly held, and also from one bundle of fibers to another at the points crossing.

 Glass monofilament fibers constitute a second type of monofilament useful for implementing the invention. Glass fibers also have good impact resistance and are capable of forming a healthy armor material when properly oriented and consolidated with a compatible thermosetting resin.

 An advantage of the process of the invention is that the successive layers can be formed using different fibrous materials. Using conventional production techniques, any variation in the type of fibers in the woven material results in a substantial change in the properties of the structure to the point where the material used changes from a type of fiber, for example a polyamide fiber, to a second type of fiber, for example a glass fiber. Using the techniques of the invention, one or more layers consisting of a fiber can be placed on the mandrel and other successive layers, consisting of a second fiber, can be applied to the previous ones. Obviously, if this is desired, a number of fibrous layers can be placed on the mandrel in order to obtain a finished product having the desired properties. For example, an extremely hard, impact-resistant material could be placed on the outer layer of the armor material in order to absorb a substantial part of the impact when a projectile comes into contact with the armor material, the successive layers of which of a more flexible material, are designed to slow down further and absorb the shock of the projectile when it penetrates.

Since the layers are arranged one after the other, no discontinuity appears in each of these individual layers.

 Before being wound on the mandrel, the monofilament is coated or coated with a resinous material suitable for consolidating and holding the fibers in a resin matrix. The function of the resin is to consolidate or join and hold the fibers firmly so that the intersecting layers form a three-dimensional network.

In general, the resin used in the present invention has an adhesive power on the fibers that is less than the tensile strength of these fibers.

In other words, under the effect of a shock, the fibers are free to transmit the force of the shock along their longitudinal axis, which requires that the resin does not keep the fibers rigidly on their surface, but that it allows a small longitudinal displacement of the surface of the fibers inside the resin. It is obvious that the resin must oppose a certain resistance to the movement of the fibers so that the structure resists and that the fibers deviate, transverse to their axis, only in a limited way under the impact of a projectile.

 One type of resins useful for implementing the invention consists of polyester resins. These unsaturated polyester resins have active hydroxyl and carboxyl groups contained in the resin and they can have average molecular weights between 800 and 5000 or more. A small amount of a free radical catalyst is added to the resinous material, which promotes maturation or hardening under the effect of the application of heat to the liquid resin. A polyester resin useful for implementing the invention may be the resin of the glycol maleate type. These resins are obtained from maleic acid or anhydride with the desired glycol, in the presence of an esterification catalyst. Resins of the glycol maleate phthalate type using glycol, maleic anhydride and phthalic or isophthalic acid, with glycol, form another type of polyester resin useful for the implementation of the invention. These resins are produced by conventional techniques and can be modified by the addition of other compatible resinous materials to obtain a resin having desired properties.

 Another type of resin useful for the implementation of the invention consists of phenolic resins.

These are inexpensive, provide good consolidation, can be manipulated by the use of conventional techniques and do not bind too firmly to "Kevlar'1. Moisture must be removed from phenolic resins in phase" B "during a processing step.

 Another advantageous type of resin is vinyl ester resins, suitable for filament winding techniques, without the need to pass the resin through the "B" phase. Another type of resin which may be useful, depending on the The use which is made of the armor consists of the well known urethane resins which are the reaction product of an isocyanate with a polyol. These urethanes are well known in the art for their flexibility and resistance to degradation. The urethanes can be modified by the use of other known organic reaction products, such as isocyanurate bonds in resins, such isocyanurate also increasing. resistance to heat and giving a resin with a spatial configuration trimerized at the molecular level, giving additional mechanical strength and rigidity to the urethane resin.

As shown in the drawing, the monofilament fiber passes through a liquid bath before being placed on the mandrel. Coating with liquid resins is a conventional technique and this coating technique ensures a complete and total coating of the surface of the fiber with a liquid resin which flows along the fiber and thus forms a uniform coating. The coating techniques are well developed and it is possible to ensure the formation of a liquid resin coating of substantially uniform thickness over the entire length of the fiber when it arrives on the mandrel. It is also part of the invention to coat the fibrous material with a solid thermosetting resin which can form a uniform consolidated matrix obtained by maturation under the application of heat and pressure. One such technique consists in heating the fiber and passing it through a fluidized bed of thermosetting material solidified in phase
B, the heated monofilament containing sufficient heat to melt a small part of the thermosetting resin particles which adhere to the monofilament and thus entrain them on the mandrel. These fluidized bed coating techniques are well known in the prior art. Under the effect of the additional application of heat, the B-phase resin liquefies enough to fill any adjacent gaps, which results in a uniform resin matrix holding the monofilament in position.

 Another resin-solid coating technique is to apply a small amount of pressure-sensitive adhesive to the monofilament fiber before passing the latter through a solidified thermosetting resin. The pressure sensitive adhesive retains solid resin particles on the surface of the monofilament. The monofilaments coated by this process are essentially dry and are easy to handle. The monofilaments thus obtained can be coated and rewound on a reel for later use, since the coating of solid thermosetting resin makes it possible to obtain a dry fiber, easy to handle, which can be stored in the form of a reel and used at a As thermosetting resins do not react before the application of heat and pressure significantly higher than normal ambient heat and pressure, the monofilament maintains the fiber in an unconsolidated state until the time of maturation. .

As indicated above, the resin of the material according to the invention is designed to maintain the successive layers of fibrous material in a spatial arrangement such that the axes of the fibers of the successive layers of material form angles between 30 and approximately 900, these laminated materials having significant resistance to tearing under the impact of a projectile
Since a laminate thus produced, in accordance with the invention, is designed to dissipate the energy of an impact along the length of the fibers and from one bundle of fibers to another, by a certain longitudinal movement of the fibers, it is desirable to keep the resin at the minimum level necessary for maintaining the fibers in the appropriate arrangement and consolidation or assembly. The amount of resin present corresponds to the amount necessary to consolidate or assemble the fibers which constitute 50 to 85% the volume of the breastplate.

The amounts of resin may be sufficient to maintain the fibers in a firm spatial configuration, but less than those necessary to bind the fibers rigidly. If the amount of resin is significantly increased above the desired amount, the resin matrix eventually forms a significant part of the volume of the breastplate, which weakens the material. Significantly less amounts of resin than specified result in a material in which the fibers are not adequately consolidated or maintained in the required spatial arrangement, so that, under impact, the fibers tend to separate and allowing the projectile to pass through the material before the fibers have absorbed the maximum force of the projectile that they can support along their longitudinal axes.

 When desired, a primer or other coating may be applied to the fibers prior to their treatment with the resinous material to ensure that the adhesion between the fiber and the resin is of the desired value for it to occur sufficient movement of the fiber in the resin matrix under the effect of the impact of a projectile.

 During the shaping, the constitution of the layers by means of monofilament fibers aims to obtain layers of minimum thickness - and of a maximum number of crossing points of the axes of the fibers forming the various layers. The superimposed crossings have various angles and the successive layers form a three-dimensional network.

 The foregoing detailed description relating to the production of the preform relates to a three-dimensional, shaped article, such as the well-known infantry helmet. However, there is a great need for a light armor material in sheet form. Such sheets can be used in vehicles, ships or on portable equipment in order to protect sophisticated electronic devices which are more and more common in such applications.

 A flat sheet of material can be formed by the fiber winding techniques described above, the fibers being applied to a cylinder as shown in Figure 3. The resin coated fiber 20 is wound on a cylindrical mandrel 42 so that the 'We obtain a sleeve 44 of fibers having a large number of superimposed crossing points. When using fiber winding techniques, the fibers that are wound on the mandrel in a given pass are spaced from each other. The successive layers fill the spaces and create additional crossing points. The fibers of each of the successive layers form overlapping crossing points with the fibers of more than one previous layer, thus giving the wound preform a three-dimensional network of crossing points. from different angles.

After the fibers have been wound tightly over the mandrel, the resulting sleeve can be removed from the latter by forming a cylindrical mast of fibrous material.

The fibrous cylinder can either be compressed between flat platens to form a flat sheet, or the cylinder can be cut longitudinally and opened to form a larger flat sheet. The sheet is then subjected to heat and pressure so as to form a consolidated sheet of breastplate. It is obviously possible to form the sheet between trays shaped during molding so as to obtain slightly curved surfaces. Such forming must not significantly modify the orientation of the fibers nor cause, by displacement, a close alignment of the fiber bundles. Where possible, the fibers should be spaced so that the same layer does not contain multiple fibers in axial alignment and close together.

The flat sheet resulting from the implementation of the invention makes it possible to obtain a light breastplate which can be used in mobile applications, while providing a degree of protection against the penetration of particles. Possible applications include the protection of vehicles based ashore, ships and electronic equipment
It goes without saying that many modifications can be made to the process and to the armor material described and represented without departing from the scope of the invention.

Claims (15)

 1. A method of producing a breastplate material capable of withstanding a significant impact before breaking, characterized in that it consists in coating at least one monofilament fiber 110) with a thermosetting resin (lo) in order to form a coated monofilament fiber (20), to apply this coated monofilament fiber on a mandrel (24) to form several layers, the axis of the filament of the second layer and of each of the successive layers placed on the mandrel forming an angle with the axis filament from the immediately preceding layer, the monofilament being wound onto the mandrel in the configuration of a desired preform (27), the method also comprising placing the preform in a mold (32, 36) and applying sufficient pressure to this preform to maintain the fibers in their spatial and angular arrangement during the maturation of the resin until a fully cured state.  2. Method according to claim 2, characterized in that the monofilament fiber is a polyamide fiber.  3. Method according to claim 1, characterized in that first and second monofilament fibers formed of different materials are coated with resin and are applied to the mandrel by forming alternating layers so as to obtain successive alternating layers consisting of different fibrous materials.  4. Method according to claim 1, characterized in that the preform is of cylindrical configuration and is split longitudinally before maturation so that a sheet is obtained and the resulting breastplate consists of a sheet.  5. Method according to claim 1, characterized in that the resin is chosen from the group comprising polyester, phenolic or vinyl ester resins.  6. Method according to claim 1, characterized in that the coating step consists of heating the monofilament fiber and passing the heated monofilament fiber through a bed of solid resinous material, the heat of the fiber having the effect of making attach the resin to the monofilament fiber to form a coated fiber.  7. Armor material capable of withstanding significant impacts, characterized in that it comprises at least one monofilament fiber (10) disposed in this material and forming successive layers, the axes of the fibers of adjacent layers forming between them a certain angle so as to constitute a large number of crossing points, a resinous material (14) surrounding and consolidating the fibers by forming a three-dimensional structure, the adhesion of the resin to the fibers being less than the cohesive strength of said fibers so that, when A force is applied to the armor material, a substantial part of the impact force is absorbed longitudinally by the fibers.  8. Armor material according to claim 7, characterized in that the monofilament fiber is made of polyamide.  9. Armor material according to claim 7, characterized in that the monofilament fiber is glass.  10. Armor material according to claim 7, characterized in that the resin matrix consists of a material of the thermoset polyester type.  11. Armor material according to claim 7, characterized in that alternating layers of monofilament fibers are made of different materials.  12. Material according to claim 7, characterized in that said alternating layers consist of polyamide and glass fibers.  13. Armor material according to claim 7, characterized in that the fibrous material constitutes approximately 50 to 80% of the volume of the total material.  14. Method according to claim 1, characterized in that the preform is of cylindrical configuration and in that the application of pressure is carried out between substantially flat plates in order to form a sheet of breastplate.  15. The method of claim 14, characterized in that it further comprises cutting the cylindrical preform longitudinally and opening the cylinder before the application of pressure to form a sheet preform.