Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41H—ARMOUR; ARMOURED TURRETS; ARMOURED OR ARMED VEHICLES; MEANS OF ATTACK OR DEFENCE, e.g. CAMOUFLAGE, IN GENERAL
  • F41H5/00—Armour; Armour plates
  • F41H5/02—Plate construction
  • F41H5/04—Plate construction composed of more than one layer
  • F41H5/0471—Layered armour containing fibre- or fabric-reinforced layers
  • F41H5/0485—Layered armour containing fibre- or fabric-reinforced layers all the layers being only fibre- or fabric-reinforced layers

Definitions

• the invention relates to a ballistic-resistant moulded article containing a compressed stack of monolayers, with each monolayer containing unidirectionally oriented reinforcing fibres and a polymer as matrix, the fibre direction in each monolayer being rotated with respect to the fibre direction in an adjacent monolayer.
• a moulded article is called a UD-composite.
• the invention also relates to a process for manufacturing the moulded article.
• a moulded article of this kind is described in US-A-4,623,574, in which the matrix consists of an elastomer.
• a disadvantage of this structure is that the structural stiffness and dimensional stability of these moulded articles are unacceptably low for many applications.
• US-A-4,623,574 also describes moulded articles with a high structural stiffness but these have an unacceptably low protection level and an unacceptably high backface deformation upon the impact of a projectile. On account of the high backface deformation their application for body protection is out of the question because of the risk of injury (trauma effect).
• the object of the invention is therefore to provide a ballistic-resistant moulded article which on the one hand has a high structural stiffness and dimensional stability and on the other hand offers a high protection level and a low trauma effect.
• the reinforcing fibers being aramid fibers, the matrix polymer having a modulus of elasticity of more than 200 MPa, the monolayer having a fiber content of between 20 and 145 g/m 2 and the monolayer having a matrix content of at most 25 wt.%.
• a further advantage of the moulded article according to the invention is that the moulded article retains its good ballistic-resistant properties at high temperatures (for example above 90°C) and does not delaminate upon repeated exposure to high temperatures because it is dimensionally stable. Because of these properties the moulded article is very suitable for protecting non-living objects (off-the-body armour), for example as a structural member of military vehicles, helicopters and the like.
• the fibre content in the monolayer in the ballistic-resistant moulded article according to the invention is preferably between 20 and 120 g/m 2 . More preferably, the fibre content in the monolayer is at most 100 g/m 2 and most preferably at most 75 g/m 2 .
• the advantage of a lower fibre content is that, in combination with the use of the specified matrix material, a lower matrix content may suffice to achieve sufficient fibre bonding as a result of which the advantages of the invention are even more pronounced.
• a fibre content of less than 20 g/m 2 is unattractive from an economic point of view. In view of obtaining even better anti-ballistic properties the matrix content of the ballistic resistant moulded article is preferably choosen as low as possible.
• the matrix content of the ballistic-resistant moulded article according to the invention is preferably at most 15 wt% and more preferably at most 10 wt%.
• the matrix in the moulded article consists of a polymer with a modulus of elasticity higher than 200 MPa.
• the modulus of elasticity of the matrix material is determined to ASTM D638. It has been found that very good results are obtained if the matrix polymer in the ballistic-resistant moulded article contains a vinyl ester.
• the monolayer can be manufactured by known methods, for example as described in US-A-4.623.574. Preferably by pulling a number of fibres, preferably in the form of continuous multifilament yarns, from a fibre bobbin frame over a comb, causing them to be parallelly oriented in one plane. Preferably, before or after being parallelly oriented in one plane the fibres are coated with a quantity of a liquid substance which contains the matrix material or a precursor which at a later stage in the manufacture of the moulded article reacts to form the polymeric matrix material with the required modulus of elasticity. Precursor is here understood to be a monomer, an oligomer or a crosslinkable polymer. The liquid substance may be a solution, a dispersion or a melt.
• the moulded article is manufactured by stacking a number of monolayers crosswise in a known manner, preferably at an angle of about 90°, and forming the stack into a consolidated structure via an increase in temperature and/or pressure.
• the moulded article is preferably manufactured by compressing monolayers onto each other at a compressive pressure of at least 1 MPa, preferably at least 2.5 and most preferably at least 5 MPa at a temperature of more than 100°C and subsequently cooling without pressure.
• the great advantage of this method is a much shorter cycle time, leading to a substantial reduction in production costs.
• the monolayer is preferably manufactured by wetting continuous multifilament yarns with a solution of the matrix material.
• the viscosity of the solution is preferably lower than 500 mPa.s.
• the advantage of this is that it enables the required low matrix percentage in the moulded article according to the invention to be achieved more easily while a good fibre bond, which is required in view of the objective of the invention, is maintained.
• good wetting of the filaments in the yarns is achieved on account of the low viscosity, despite the small total amount of matrix material applied.
• the viscosity of the solution of the matrix material is measured with the aid of a Brookfield viscometer according to ASTM D2393-68.
• the yarn titre is preferably at least 800 denier, more preferably at least 1,200 and most preferably at least 1,500 denier.
• the ballistic-resistant moulded article according to the invention obtainable according to the method described above preferably has an SEA of at least 25 Jm 2 /kg, more preferably at least 28, even more preferably at least 30 and most preferably at least 32 Jm 2 /kg.
• Backface deformation is preferably at most 20 mm, more preferably at most 15 mm. SEA and backface deformation are defined in the example.
• a monolayer was manufactured using the method and apparatus described in WO 95/00318.
• As matrix material a vinyl ester polymer based on Adlac 580/05® mixed with Dispercol KA 8584® in combination with Trigonox C® as curing agent was used. The modulus of elasticity of the matrix material was 3800 MPa.
• the matrix material was dissolved in styrene.
• the viscosity of the solution was 200 mPas. The solution was applied by passing the fibres through the solution.
• a flat moulded article (30x30 cm.) was made by compressing 160 monolayers of 55.5 g/m 2 at 120°C for 20 minutes at a pressure of 10 bar, after which the moulded article was cooled without pressure.
• the specific energy absorption (SEA) was determined according to the STANAG 2920 test, in which .22 calibre FSPs (Fragment Simulating Projectile), hereinafter referred to as fragments, with a weight of 1.1 g (to US MIL-P-46593), are fired at the ballistic structure in a defined manner.
• the energy absorption (EA) is calculated from the kinetic energy of a fragment having the V 50 velocity.
• the V 50 is the velocity at which the probability of bullets penetrating the ballistic structure is 50%.
• the specific energy absorption (SEA) is calculated by dividing the energy absorption EA by the areal density AD of the moulded article.
• the trauma effect is measured by placing the ballistic-resistant moulded article against a clay background and measuring the depth of the backface deformation upon impact.
• the V 50 was 707 m/s
• the SEA was 31 Jm 2 /kg
• backface deformation was 15 mm.
• the stiffness was high, which means that the moulded article proves to be suitable for use in structural mouldings.

Landscapes

• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
• Reinforced Plastic Materials (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=19761700

Family Applications (1)

Country Status (4)

Cited By (7)

Citations (8)

Family Cites Families (1)

• 1995
  • 1995-10-13 NL NL1001415A patent/NL1001415C2/nl not_active IP Right Cessation
• 1996
  • 1996-10-04 DE DE69611587T patent/DE69611587T2/de not_active Expired - Lifetime
  • 1996-10-04 EP EP96202774A patent/EP0768507B1/fr not_active Expired - Lifetime
  • 1996-10-11 IL IL11941196A patent/IL119411A/en not_active IP Right Cessation

Patent Citations (8)

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