Soft body armor

Soft body armor has a ballistic panel having an interleaved construction of a generally vertically oriented plurality of layers of interleaved sheets or woven fiber cloth and sheets of cross plied unidirectional tape adjacently interleaved in an interleave ratio of plies of cross plied unidirectional tape to plies of woven fiber cloth within each layer of the plurality of layers, the plurality of layers forming a non-quilted array between a front face of the ballistic panel and a back face of the ballistic panel, wherein the interleave ratio of plies of cross plied unidirectional tape to plies of woven fiber cloth within each layer of the plurality of layers is between 1:1 and 4:4, and wherein the total number of the plies of cross plied unidirectional tape is equal to or greater than the total number of the plies of woven fiber cloth within the plurality of layers.

FIELD OF THE INVENTION
 This invention relates to the field of soft body armor and in particular
 soft body armor having protective elements incorporating aramid fiber
 cloth such as KEVLAR.TM. 129 aramid fiber woven cloth or SPECTRA
 SHIELD.TM. high molecular weight polyethylene filaments in a flexible
 resin matrix.
 BACKGROUND OF THE INVENTION
 Body armor typically comprises a jacket or vest which serves to hold sheets
 of typically KEVLAR.TM. 129 aramid fiber woven cloth, manufactured by E.
 I. DuPont de Nemours and Company, or other aramid fiber cloth, or SPECTRA
 SHIELD.TM. high molecular weight polyethylene filaments in a flexible
 resin matrix, manufactured by Allied Signal, close to the body so as to
 provide bullet-resistant soft body armor. Conventionally, many sheets of
 either aramid fiber cloth or SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix, sometimes as many as 55
 sheets, are overlaid and held as packets in pocket-like compartments
 within the jacket or vest. SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix, being overlaid
 synthetic fiber strands held within a resin binder, is stiffer than aramid
 fiber cloth which is a woven material of synthetic aramid fibers. SPECTRA
 SHIELD.TM. high molecular weight polyethylene filaments in a flexible
 resin matrix material is sufficiently stiff that a stack or packet of
 sheets may be inserted into pocket-like compartments in a jacket or vest
 without having to be sewn together. Aramid fiber cloth on the other hand
 is typically sewn together in the manner of quilting.
 Previously, soft body armor bas relied on individual packets of multiple
 plies of SPECTRA SHIELD.TM. high molecular weight polyethylene filaments
 in a flexible resin matrix and individual packets of multiple plies of
 aramid fiber cloth, the packets each stacked one on top of the other so as
 to intersperse packets of one between packets of the other. The packets
 arc held vertically oriented within a pocket or like vertical compartment
 in the body armor. Applicant is aware of "POINT BLANK BODY ARMOR" of
 Amity, N.Y., U.S.A. which markets soft body armor having interspersed
 packets of aramid fiber cloth and packets of SPECTRA SHIELD.TM. high
 molecular weight polyethylene filaments in a flexible resin matrix, and in
 particular having within a single vertical compartment front and back
 packets of solely aramid fiber cloth and, sandwiched in-between, a middle
 packet of solely SPECTRA SHIELD.TM. high molecular weight polyethylene
 filaments in a flexible resin matrix sleets. The front and back packets of
 aramid fiber cloth are quilted.
 Applicant is aware of U.S. Pat. No. 5,179,244 which issued on Jan. 12, 1993
 to T. Tyler Zufle for an invention entitled "Reinforced Soft and Hard Body
 Armor", U.S. Pat. No. 5,180,880 which issued on Jan. 19, 1993 to T. Tyler
 Zufle for an invention entitled "Soft Body Armor", and U.S. Pat. No.
 5,306,557 which issued on Apr. 26, 1994 to Thomas J. Madison for an
 invention entitled "Composite Tactical Hard Body Armor".
 Zufle '224 discloses body armor comprised of alternating multiple packets
 of aramid fiber cloth and SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix. Zufle '880 discloses
 body armor comprised of aramid fiber cloth outer single plies 48 and 50,
 eight plies of SPECTRA SHIELD.TM. high molecular weight polyethylene
 filament in a flexible resin matrix 52 and 54 and ten plies of aramid
 fiber cloth 56. Madison discloses body armor which includes SPECTRA
 SHIELD.TM. high molecular weight polyethylene filaments in a flexible
 resin matrix layers 4, 7 and 9 and non-woven aramid fiber layers 3 and 6.
 The object of the present invention is to provide soft body armor which
 combines the attributes of KEVLAR.TM. aramid fiber woven cloth or like
 aramid fiber cloth (hereinafter also referred to by the letter "A") and
 SPECTRA SHIELD.TM. high molecular weight polyethylene filaments in a
 flexible resin matrix (hereinafter also referred to by the letter "S") in
 an interleaved sandwich as opposed to a sandwich of packets of solely
 aramid fiber cloth and solely SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix; and in particular
 interleaved so as to alternate one and two sheets of aramid fiber cloth
 between two sheets of SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix; for example in the
 ratio of 2 sheets of SPECTRA SHIELD.TM. high molecular weight polyethylene
 filaments in a flexible resin matrix: 2 sheets of aramid fiber cloth: 2
 sheets of Spectra: 1 sheet of aramid fiber cloth and so on in a 2:1 (S:A)
 ratio, repeated for a total of 18 sheets of SPECTRA.TM. high molecular
 weight polyethylene filaments in a flexible resin matrix and 9 sheets of
 aramid fiber cloth. It has been found that this interleaved layering
 exhibits many improved characteristics over stacks of solely aramid fiber
 cloth or solely SPECTRA SHIELD.TM. high molecular weight polyethylene
 filaments in a flexible resin matrix.
 SUMMARY OF THE INVENTION
 It has been found that interleaving single plies of woven fiber cloth, as
 inhereafter defined, between sheets of cross plied unidirectional tape, as
 hereinafter defined and alternatively referred to by its acronym "CPUT",
 in a 2:1 (CPUT:woven fiber) ratio reduces the overall number of sheets
 required to provide the level of protection equivalent to threat level
 IIA, II or IIIA prior art soft body armor incorporating a greater number
 of sheets. As compared to prior art soft body armor, a typical result of
 the soft body armor according to the present invention is a 20% decease in
 weight as indicated by a decrease in areal density, a decrease in bulk, an
 increase in flexibility of the armor due to the interleaving of sheets of
 woven fiber cloth which provide friction reducing surfaces between sheets
 of cross plied unidirectional tape (which otherwise tend to stick to one
 another), a decrease in cost of manufacturing of the armor due to the
 decreased areal density, a removal of the requirement for quilting of the
 woven fiber sheets in that the cross plied unidirectional tape sheets lend
 sufficient structural rigidity to resist billowing and bunching, a
 decrease in the level of blunt trauma over purely aramid fiber body armor,
 an increase in ballistic resistance performance over purely aramid fiber
 body armor for bullets entering at an angle of for example 30 degrees, an
 increase in performance under wet conditions over purely aramid fiber body
 armor which typically loses 40 percent of its ballistic capability when
 wet, and an increase in performance over purely SPECTRA SHIELD.TM. high
 molecular weight polyethylene filaments in a flexible resin matrix body
 armor when soft body armor according to the present invention is heated
 such as by fire.
 Soft body armor incorporating the present invention has a ballistic panel
 of a multiple interleaved, generally vertical sandwich construction of
 woven fiber ("WF") sheets between sheets of cross plied unidirectional
 tape ("CPUT") The interleaved construction may be summarized as
 interleaved sheets or plies interleaved in an interleave ratio within each
 of a plurality of layers, the layers forming a non-quilted array between
 the front and back faces of the ballistic panel. Each layer will always
 have an interleave ratio between 1:1 (CPUT:WF) and 4:4 (CPUT:WF). The
 interleave ratio may be between 1:1 and 3:3, or may be between 1:1 and
 2:2. In these ratio ranges the ratio of plies of cross plied
 unidirectional tape to plies of woven fiber cloth may vary but the total
 number of plies of cross plied unidirectional tape will always be equal to
 or greater than the total number of plies of woven fiber cloth. The ratio
 of the interleaving may change from the front to the back of the ballistic
 panel, for example, 2:2:2:1 (CPUT:WF:CPUT:WF) . . . 2:1:2 (CPUT:WF:CPUT),
 ic., initially 2:2:2:1 (CPUT:WF:CPUT:WF) then repeating layers of 2:1
 (CPUT:WF), with a final backing layer of 2 sheets of cross plied
 unidirectional tape. The interleave ratio ranges within each of the layers
 may also be restricted to between 2:1 (CPUT:WF) and 4:2 (CPUT:WF), or the
 layers may have single interleave ratios of 2:1 (CPUT:WF) or 2:2
 (CPUT:WF). Threat level IIA soft body armor of the present invention will
 have at least 5 layers of interleaved sheets interleaved according to the
 interleave ratio. Threat level II and IIIA soft body armor of the present
 invention will have at least six layers interleaved in the ballistic
 panel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Ballistic fibers have several mechanical characteristics that describe how
 they react during an impact. One of these characteristics is mechanical
 impedance which is used to describe how a pressure front moves through a
 solid. It is proposed that a ballistic panel having an alternating or
 interleaved layer construction reduces blunt trauma due to the impedance
 mismatch the alternating layers present to the shock wave or energy front
 of the bullet as it impacts the ballistic panel. It is suggested that at
 the moment and point of impact the soft body armor ballistic panel
 essentially behaves as a solid laminated material block.
 It is generally accepted that the longitudinal energy wave imparted to a
 ballistic panel by the impact of a bullet is partially converted as it
 passes through the ballistic panel to a transverse energy wave front. The
 energy wave conversion transfers part of the bullet's energy transversely
 down the length of the ballistic fiber. The partial conversion of the
 longitudinal energy wave into a transverse energy wave reduces the blunt
 trauma associated with the bullet's impact.
 The ballistic fibers may be aramid fiber or SPECTRA SHIELD.TM. high
 molecular weight polyethylene filaments in a flexible resin matrix as
 described in our co-pending U.S. patent application, now (U.S. Pat. No.
 5,796,028, or may advantageously be woven high strength organic or
 inorganic fibers having improved performance, including aramid fibers such
 as poly(p-phenylene terephthalamide), eg. KEVLAR.TM. and TWARON.TM.;
 graphite fibers, nylon fibers, ceramic fibers, ultrahigh molecular weight
 polyethylene fibers such as SPECTRA.TM. and DYNEEMA.TM., glass fibers,
 liquid crystal fibers such as poly(p-phenylene-2,6-benzobisoxazole; PBO)
 and the like, hereinafter collectively referred to as woven fiber cloth.
 It is understood that "woven" includes twisted and untwisted fibers in it
 plain, basket, leno, four harness, eight harness or twill weave and the
 like. The ballistic fibers may also be a cross plied unidirectional tape
 comprised of filaments in a flexible resin matrix, eg. (SPECTRA
 SHIELD.TM., GOLD SHIELD.TM., GOLDFLEX.TM., SPECTRA 2000.TM., SPECTRA
 PLUS.TM. made by Allied Signal; DYNEEMA.TM. made by DSM), where the
 filaments can be any high strength organic or inorganic fibers including
 aramid fibers such as poly(p-phenylene terephthalamide), eg. KEVLAR.TM.
 and TWARON.TM.; graphite fibers, nylon fibers, ceramic fibers, ultrahigh
 molecular weight polyethylene fibers such as SPECTRA.TM. and DYNEEMA.TM.,
 glass fibers, liquid crystal fibers such as poly
 (p-phenylene-2,6-benzobisoxazole; PBO) and the like hereinafter referred
 to collectively as cross plied unidirectional tape.
 When an alternating, that is, interleaved, layer construction is employed
 in the ballistic panel, it is proposed that a further physical effect
 takes place that is associated with the mechanics of an energy front, When
 a longitudinal wave passes through a composite block of intimately bonded
 material and encounters an interface between layers in the material, the
 energy will pass straight through if the energy impedance of the layers
 are the same. If the energy impedance of the layers are different, energy
 is reflected proportionately to the difference in impedance. Given a block
 of material such as a ballistic panel comprised of alternating or
 interleaved layers of cross plied unidirectional tape and woven fiber
 cloth, it is suggested there is reflection of energy at every material
 interface. It is proposed that, although the ballistic panel is comprised
 of loose soft armor, at the moment and point of impact the panel's
 behavior approaches that of an intimately bonded solid layered block. This
 would explain the reduction in blunt trauma over a conventional weight of
 ballistic panel, or conversely, being able to reduce the ballistic panel
 areal density while maintaining blunt trauma with the applicable
 standards.
 Testing of the interleaved soft body armor according to the present
 invention was conducted by H. P. White Laboratory Inc. of Street, Md.,
 U.S.A. in accordance with the requirements of National Institute of
 Justice testing standard NIJ-STD-0101.03, BALLISTIC RESISTANCE OF POLICE
 BODY ARMOR, dated April 1987 and changes thereto. Results of the testing
 are tabulated below. Table 1 is a summary of the data set out in
 applicant's U.S. Pat. No. 5,796,028.
 TABLE 1
 Test Sample
 Results
 Weight Plies Ballistic Threat*
 Deform.
 Serial Testing (lbs) (**) Obliquity Caliber Shots Velocity Min.
 Penetration (mm)***
 CHT-
 1339 front dry 2.78 2:2:2:1 0 .357 Mag. 4 1451 1414
 0 44
 30 .357 Mag. 2 1433 1414
 0 na
 1339 back dry 2.97 2:2:2:1 0 9 mm. 4 1225 1212
 0 28
 30 9 mm 2 1230 1201
 0 na
 *Per NIJ-STD-0101.03, Threat Level II
 **Spectra:Kevlar:Spectra:Kevlar
 ***Deformation of clay backing. Maximum allowable: 44 mm.
 Based on the data summarized in Table 1 and theoretical and tested
 extrapolations thereof, the soft body armor according to the present
 invention satisfied the ballistic requirements of the National Institute
 of Justice Ballistic Resistance of Police Body Armor test standard for
 threat level II. The present invention applies to three National Institute
 of Justice standard threat levels; namely IIA, II, and IIIA. Threat level
 IIA is a lesser threat level than threat level II and requires lighter
 body armor in order to satisfy the test standard as compared to body armor
 satisfying the test standard for threat level II. Threat level IIIA is an
 increased threat level over that of threat level II and requires heavier
 body armor in order to satisfy the test standard as compared to body armor
 satisfying the test standard for threat level II.
 With reference to Tables 1-4, for the sake of comparison ballistic tests
 were conducted on the one hand between a ballistic sample comprised of one
 packet having 19 sheets of SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix overlaying a second
 packet having 18 sheets of KEVLAR.TM. 129 aramid fiber woven cloth
 (hereinafter collectively the "prior art sample"), and on the other hand,
 an interleaved stack of SPECTRA SHIELD.TM. high molecular weight
 polyethylene filaments in a flexible resin matrix and aramid fiber cloth
 having interleaved layers according to the present invention, each layer
 having an interleave ratio of 2:1 (Spectra:aramid) for a total of 18
 sheets of SPECTRA SHIELD.TM. high molecular weight polyethylene filaments
 in a flexible resin matrix and 9 sheets of KEVLAR.TM. 129 aramid fiber
 woven cloth in a total of nine layers.
 An example of a stack of interleaved layers according to the present
 invention is depicted in FIG. 1. It is understood threat level II and IIIA
 body armor would have an increased number of layers over that of threat
 level IIA body armor. Ballistic panel 2 has, interleaved layers 4. Each of
 interleaved layers 4 has interleaved plies of cross plied unidirectional
 tape 6 and plies of woven fiber cloth 8. The interleave ratio is the ratio
 of the number of plies of cross plied unidirectional tape 6 to the number
 of plies of woven fiber cloth 8 within an interleaved layer 4. Ballistic
 panel 2 is made up of a stack of layers 4, oriented generally vertically
 within a soft body armor vest or the like (not shown). Thus layers 4 form
 a array within ballistic panel 2, ic. a stack of layers 4 turned onto its
 side so that the array extends between a front face 10 of ballistic panel
 2 and a back face 12 of ballistic panel 2. Plies within layers 4 are
 non-quilted. Layers 4 are not quilted to each other, but rather are held
 in their generally vertically oriented array between front face 10 and
 back face 12 by being contained in a pocket or compartment within a soft
 body armor vest or the like.
 Tests were conducted according to the National Institute of Justice (NIJ)
 Standard for Threat Level II. Thus, ballistic test velocities had to fall
 between 1395 feet per second and 1445 feet per second for .357 Magnum
 caliber. Acceptable test velocities for 9 mm caliber were between 1175
 feet per second and 1275 feet per second. .357 Magnum caliber ammunition
 was jacketed soft point (JSP) with a weight of 158 grams. 9 mm caliber was
 full metal jacket (FMJ) with a weight of 124 grams. The maximum allowable
 deformation depth was 1.73 inches in a calibrated clay bed used to gauge
 blunt trauma. The prior art sample had an areal density of 0.85 pounds per
 square foot as compared to 0.72 pounds per square foot for the soft body
 amour according to the present invention. The reduced number of sheets of
 the soft body armor according to the present invention resulted in the
 soil body armor sample having a lower areal density than the prior art
 sample.
 The soft body armor according to the present invention also did not suffer
 the drawback encountered with purely aramid fiber cloth prior art soft
 body armor. In the prior art, aramid fiber sheets used in soft body armor
 usually have to be quilted, i.e. the sheets of aramid fiber cloth stitched
 together to reduce pillowing of the aramid fiber sheets upon ballistic
 impact. The soft body armor according to the present invention did not
 have to be quilted as the combination of woven fiber cloth sheets and
 cross plied unidirectional tape sheets in the aforesaid ratio reduced the
 pillowing tendency exhibited by the aramid fiber cloth. As a result of not
 having to be quilted, the soft body armor of the present invention
 exhibits improved flexibility over purely aramid fiber cloth soft body
 armor in the prior art.
 Applicant has also noted that indications of blunt trauma are reduced in
 testing of soft body armor according to the present invention over that of
 purely aramid fiber soft body armor in that the soft body armor of the
 present invention results in reduced blunt trauma characteristics more
 similar to those of purely cross plied unidirectional tape soft body
 armor. It has been observed that purely woven fiber cloth test samples
 result in more pointed and deeper deformation upon ballistic impact, that
 is, in greater indicated blunt trauma, than that of purely cross plied
 unidirectional tape samples or that of soft body armor according to the
 present invention.
 Similarly, purely cross plied unidirectional tape samples exhibit better
 deformation characteristics than do woven fiber cloth test samples when
 impacted at an angle of 30.degree. from an axis orthogonal to the test
 sample. Applicant has noted that soft body armor according to the present
 invention exhibit the improved characteristics of a purely cross plied
 unidirectional tape test sample even though woven fiber sheets arc
 regularly interleaved according to the ratio of the present invention.
 Flexibility of the soft body armor is increased by the interleaving of
 woven fiber cloth sheets because cross plied unidirectional tape sheets
 otherwise have a tendency to stick together. The woven fiber cloth sheets
 provide interleaved reduced-friction surfaces between the sheets of cross
 plied unidirectional tape.
 Applicant also notes that the improved fire-resistant characteristics of
 woven fiber cloth over those of cross plied unidirectional tape improves
 the overall protection of the soft body armor according to the present
 invention even though the interleaved soft body armor of the present
 invention includes cross plied unidirectional tape which has reduced fire
 resistant qualities. Similarly, Applicant notes that the soft body armor
 of the present invention retains the improved ballistic resistance
 characteristics of cross plied unidirectional tape when the soft body
 armor is wet even though the interleaved soft body armor of the present
 invention includes woven fiber sheets which in purely woven fiber soft
 body armor have degraded ballistic resistance characteristics when wet.
 In an alternative embodiment, the soft body armor of the present invention
 combines cross plied unidirectional tape and woven fiber cloth sheets in
 an interleaved ballistic panel comprising sheets of woven fiber cloth
 alternating between sheets of cross plied unidirectional tape in a 1:1
 ratio or in an initially 2:2:2:1 ratio (CPUT:WF:CPUT:WF) which continues
 in layers of 2:1 (CPUT:WF) so long as the total number of sheets of cross
 plied unidirectional tape is not less than the total number of sheets of
 wove fiber cloth in the ballistic panel.
 In summary, the proposed interleaved configurations improve the performance
 of a soft body armor ballistic panel as indicated by a reduction in areal
 density while maintaining National Institute of Justice performance
 standards. This increase in performance is attributed to a reduction in
 penetration of the ballistic round into the ballistic panel and a
 reduction of blunt trauma behind the ballistic panel. As the performance
 of the ballistic panel increases, plies of fabric may be removed, reducing
 the areal density while maintaining a performance capability satisfying
 NIJ Standard 0101.03. The end result therefore is NIJ Standard 0101.03
 blunt trauma performance comparable to prior art ballistic panel
 combinations, with improved comfort for the wearer through reduced weight
 (areal density), increased flexibility, reduced heat retention and
 increased moisture resistance.
 As will be apparent to those skilled in the art in the light of the
 foregoing disclosure, many alterations and modifications are possible in
 the practice of this invention without departing from the spirit or scope
 thereof. Accordingly, the scope of the invention is to be construed in
 accordance with the substance defined by the following claims.