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
• • 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

Definitions

• This invention relates to a ballistic structure which provides improved ballistic protection due to use of a particularly specified para-aramid yarn having a combination of high tenacity and moderate linear density.
• a ballistic protective fabric comprising yarn of at least 28 grams per denier (gpd) tenacity with a linear density of from 300 to 750 denier, which, when tested for V50 in accordance with MIL-STD- 662e using 9mm full metal jacket hand-gun bullets weighing 124 grains, in layers to yield an areal density of 3.4 kilograms per square meter (0.7 pounds per square foot) , exhibits a V50 of greater than 442 meters per second (1450 feet per second) .
• gpd grams per denier
• the fabric is made using yarn of poly (p-phenylene terephthalate) having a tenacity of at least 28 gpd (25 cN/dtex) which can be made by a process comprising the steps of: (a) extruding filaments of an acid solution containing at least 30 grams per 100 milliliters of acid of poly (p-phenylene terephthalamide) having an inherent viscosity of at least 4, out of a spinneret and through a layer of inert noncoagulating fluid into a coagulating bath and then through a spin tube along with overflowing coagulating liquid; (b) jetting additional coagulating liquid symmetrically about the filaments in a downward direction forming an angle of 0° to 85° with respect to the filaments within about 2.0 milliseconds from the time the filaments enter the spin tube, (i) maintaining a ratio of the mass flow rate of combined overflowing and jetted coagulating liquid to mass flow rate of the filaments of greater than about 250, (ii)
• P-aramid fibers are extremely strong on a weight basis and provide good ballistic protection with a relatively high degree of comfort .
• There has been great effort expended in developing yarns and fabrics with improved ballistic performance because even small improvements save the lives of users of ballistic garments. Each improvement is hard-won and highly significant.
• the present invention represents an improvement in ballistic performance, measured by V50.
• the physical parameters which have been believed to be important for ballistic performance in aramid yarns are tenacity, modulus, and elongation to break. While those parameters are still held to be important, this inventor has discovered that yarns of especially high tenacity -- greater than 28 grams per denier -- used in a linear density range of about 300 to 750, preferably 400 to 600 denier, will provide surprising improvement in ballistic performance. It has been discovered that the performance of ballistic fabrics is at an optimum in the yarn denier range of about 300 to 750 and is highest in the denier range of 400 to 600. It is believed, for reasons that are not fully understood, that ballistic fabrics having yarns of less than 300 denier and more than 750 denier exhibit ballistic performance lower than the performance of fabrics made from yarns inside that range.
• ballistic performance is believed to- be improved by using yarns exhibiting increased tenacity; and the inventor has discovered that ballistic fabrics made from yarns with tenacity of 28 to 32 or as much as 33 grams per denier yield the high ballistic performance of this invention.
• the yarns of this invention can be made from individual filaments which have a relatively wide range of denier per filament of less than one to more than two. Yarns with filaments having a denier of 1.5 or less have been found to be softer and more comfortable when used in protective garments.
• Ballistic fabrics of this invention are made with yarns which are woven or laid into fabrics; and the fabrics are formed into garments or other structures for ballistics protection.
• the kind of fabric, whether woven or not, and, if woven, of whatever weave customarily used in ballistics applications, to which the yarn is applied is not important to realize the benefit of the invention. That is, for any fabric, ballistic performance obtained using the yarn of this invention will be improved over that obtained using a similar yarn having a lower tenacity or a linear density outside the specified range.
• Body armor using ballistic protective fabrics is usually made with several layers laid or sewn together to yield a laminated structure.
• the laminated structure can include additional layers of other materials, such as decorative or moisture resistant covering fabrics or other shock absorbing materials.
• the form of the laminated structure and whether or not it includes additional layers of other materials is not important to realization of the improved ballistic performance of this invention.
• Yarns of the present invention have a tenacity of at least 28 gpd. These yarns can be made, generally, in accordance with a process as disclosed in United States Patents No.
• PPD-T poly (p-phenylene terephthalamide) having an inherent viscosity of at least 4.0 dissolved in sulfuric acid having a concentration of at least 98%.
• a PPD-T solution is extruded from a spinneret, through an air gap and into a coagulating bath.
• the spinneret has capillaries with a diameter of 0.051 millimeter (2.0 mils) or less. It has been found that capillaries of more than 0.051 millimeter (2 mils) yield fiber filaments which are believed to have less molecular orientation resulting in decreased strength and, therefore, not as strong as filaments which are made using capillaries of smaller diameter. As a practical matter, capillaries of less than about 0.025 millimeter (1 mil) are difficult to use and may not yield fibers of acceptable quality.
• Water alone or combinations of water and alkaline solutions can be used for fiber washing.
• a convenient method for washing is to spray the threadline, as it leaves the coagulating bath on rolls with aqueous alkaline solutions (e.g. saturated NaHC ⁇ 3 or 0.05 N NaOH) , to reduce the acid content to about 0.01% (on a dry fiber basis) .
• the fibers can conveniently be dried on heated rolls (e.g. 160°C) .
• the preferred washing method is to wash the fibers with a spray and pass them continuously to dryer rolls maintained at about 150 °C. It is preferred that the fibers be conducted directly from the washing to the drying without subjecting the fibers to any dewatering processes.
• Drying tensions of less than 3.0 gpd result in fibers which have reduced molecular orientation resulting in reduced strength and drying tensions of greater than 7.0 gpd cause excessive threadline breakage and related operational difficulties. Drying tensions of about 3.5 to 6.0 gpd are particularly preferred.
• Ballistic tests of the composite samples are conducted to determine the ballistic limit (V50) in accordance with MIL-STD-662e, except in the selection of projectiles, as follows: A lay-up to be tested is placed in a sample mount to hold the lay-up taut and perpendicular to the path of test projectiles.
• the projectiles are 9mm full metal jacket hand-gun bullets weighing 124 grains, and are propelled from a test barrel capable of firing the projectiles at different velocities.
• the first firing for each lay-up is for a projectile velocity estimated to be the likely ballistic limit (V50) .
• the next firing is for a projectile velocity of about 50 feet per second less in order to obtain a partial penetration of the lay-up.
• the next firing is for a velocity of about 50 feet per second more in order to obtain a complete penetration.
• subsequent velocity increases or decreases of about 50 feet per second are used until enough firings are made to determine the ballistic limit (V50) for that lay-up.
• the ballistic limit (V50) is calculated by finding the arithmetic mean of an equal number of five of the highest partial penetration impact velocities and five of the lowest complete penetration impact velocities, provided that there is not more than 125 feet per second between the highest and lowest individual impact velocities.
• Tenacity is reported as breaking stress divided by linear density. Modulus is reported as the slope of the initial stress/strain curve converted to the same units as tenacity. Elongation is the percent increase in length at break. Both tenacity and modulus are first computed in g/denier units which, when multiplied by
• Denier is the weight, in grams, of 9000 meters and dtex is the weight, in grams, of 10,000 meters of yarn or filament.
• Tensile properties for yarns are measured at 24°C and 55% relative humidity after conditioning under the test conditions for a minimum of 14 hours. Before testing, each yarn is twisted to a 1.1 twist multiplier (for example, nominal 1500 denier yarn is twisted about 0.8 turn/centimeter). Each twisted specimen has a test length of 25.4 cm and is elongated 50% per minute (based on the original unstretched length) using a typical recording stress/strain device.
• the twist multiplier (TM) of a yarn is defined as :
• poly (para-phyenylene terephthalamide) (PPD-T) having an inherent viscosity of about 6.3 dL/g before solutioning and about 5.5 dL/g in fiber form was spun into apparatus as illustrated in U.S. Patent No. 4,340,559 using tray G.
• the diameter of the spin tube was 0.76 cm (0.3 inch) and jets of 0.21 and 0.42 millimeters (8 and 16 mils) were employed with an angle of 30 degrees between the jetted stream and the threadline.
• the solvent employed in making spin dope was about 100.1% sulfuric acid and the concentration of polymer in the spin dope of about 19.4 wt . % .
• the spinnerets of 0.051 and 0.064 millimeters (2.0 and 2.5 mils) were employed.
• the number of capillaries of spinnerets employed included 133, 266, 400, 500, 560 and 666 capillaries.
• the air-gap, i.e., the distance of filament travel from the exit face of the spinneret to the first contact with coagulating liquid, was about 0.635 cm (0.25 inch) .
• the coagulating liquid was maintained at about
• Examples of the invention utilized spinnerets with capillaries of 0.051 millimeter.
• the yarns were dried under tension of greater than 3 grams per denier and the yarns had linear densities of 400 to 600 denier.
• Comparative examples utilized the same polymer and the same spinning apparatus under substantially the same conditions, except that the drying tensions and the spinneret capillary sizes were different as shown in TABLE I.
• the yarns made herein were woven into fabrics and the fabrics were assembled, using multiple layers as indicated in TABLE II, into ballistic test panels.
• the fabrics were all plain weave and had a variety of weave counts as, also, indicated in TABLE II.
• the number of fabric plies in each sample was selected to yield an areal density as near as possible to 3.42 Kgrams per square meter (0.7 pounds per square foot) and the plies were sewn together to form unitary structures for the ballistics V50 testing. Results are shown in TABLE II and, graphically, in the Figure.
• V so for yarn deniers of less than 300 and more than 750 are lower than for yarn deniers within that range and V 50 for yarn tenacities less than 28 gpd are lower than for yarn tenacities above that value.
• the yarn denier and yarn tenacity limits for the ballistic protective fabric of this invention are graphically reproduced in the Figure.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
• Woven Fabrics (AREA)
• Artificial Filaments (AREA)
• Professional, Industrial, Or Sporting Protective Garments (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Reinforced Plastic Materials (AREA)

Applications Claiming Priority (5)

Publications (1)

Family

ID=26704958

Family Applications (1)

Country Status (9)

Families Citing this family (4)

Family Cites Families (11)

• 1997
  • 1997-10-22 CN CN97199150A patent/CN1234862A/zh active Pending
  • 1997-10-22 JP JP52057898A patent/JP2001504556A/ja not_active Ceased
  • 1997-10-22 KR KR1019990703606A patent/KR20000052792A/ko not_active Ceased
  • 1997-10-22 WO PCT/US1997/019150 patent/WO1998019131A1/en not_active Ceased
  • 1997-10-22 CA CA002267624A patent/CA2267624A1/en not_active Abandoned
  • 1997-10-22 EA EA199900407A patent/EA000934B1/ru not_active IP Right Cessation
  • 1997-10-22 EP EP97913740A patent/EP0932812A1/de not_active Withdrawn
  • 1997-10-22 BR BR9712438-9A patent/BR9712438A/pt not_active Application Discontinuation
  • 1997-10-22 BR BR9712433-8A patent/BR9712433A/pt not_active IP Right Cessation
  • 1997-10-22 AU AU50859/98A patent/AU5085998A/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events