Note: Descriptions are shown in the official language in which they were submitted.
WO g3~10973 PCI`/US91/087~1
~".............. ^~
2123980
" ,TI, rLE
MULIILAYERED GLASS LAMINATE HA~ING
ENHANCED RESISTANCE TO PENETR~TION
- BY HIGH VELOCITY PROJECIILES
BACKGROUN~ OF THE INVE~mQN
This invention relates to glass laminates having enhanced ~:
resistance to penetration by high velocity projectiles. More particularly, the
0 invention relates to relatively thîn glass laminates which not only stop glass ~; -
from spalling whe~ impacted by small alld medium caliber bullets but also
stops penetration of the laminates by the bullets.or other small high velocity
projectiles.
Various ~pes of transparent laminated structures have been
disclosed for protecting personnel from ilying splinters and fragments of
gla~g materials which are rele~sed when a high velocity projectile strilces tbe
structure. In U.S. 3,658,636 thick plates of an amorphous polyamide are
formed into a sandwich structure with silicate glass. U.S. 2,861,021 describes -
a strucblre in which polymethyl methacrylate sheets are l~ated with
2 o polyvinyl bu~ral aIld faced with a layer of a polyamide, polyester or
regenerated cellulose sheet. Multiple plies of glass and poly~nnyl butyral are
used in combination vnth a plastic iIlterlayer as an impact absolption section
in the structure disclosed in U.S. 4,130,684.
The problem of spalling of an anti-abrasion layer which is
s applied to a laminate using polycarbonate sheets is addressed in
U.S. 4,812,359 by applying a thin polyca~bonate sheet having an
abrasion-resistant self-healing coating. A similar laminate which includes an
in~ernal elastic e~pansion core with a thin polycarbonate sheet c~vered with
an antiabrasive which can be replaced is disclosed in U.S. 4,879,183. British
3 0 Patent 828,381 discloses a five layer laminate consis~ng of two layers of glass,
two layers of polyvinyl butyrate and a central layer of polyethylene
terephthalate. Published UK Application 2 lS6 736A discloses an impact
resistant laminate comprising a number of glass sheets which are laminated
together with a rear polycarbonate sheet which is said to be resistant to
spalli~g.
WO 93/10973 PCT/US91/087~;1
2~23~ 2
A problem with most "bullet resistant" structures is that they
have a thichless in excess of that which can be accommodated in usual
glazing applications. Some structures are effective in controlling spalling but
are not effective in stopping penetration of the laminate by a projectile. Most
of the structures rely on incorporating layers of various materials in the
larninated structure. This complicates manufacture and increases costs since
different materials require different laminating techniques. -~
It has been found that by permanently bonding a very thin
composite consisting of an adhesive layer and a dimensionally stable polyester
0 film to multiple plies of glass with layers of plasticized polyvinyl butyral there
between, a glass laminate of substantially reduced thickness is provided which
is capable of resisting penetration of high velocity projectiles with little, if any, s
spalling from the inner rear face of the laminate.
SUMM~RY OF THE I~VE~TION
This invention provides a laminated glazing to which is attached
a permanent, energy absorbing thin plastic composite consisting of an
adhesive energy absorbing layer, such as polyvinyl butyral, and a strong,
dimensionally stable, chemical and abrasion resistant layer, sucb as a layer of
polyester film which may be coated with a polysiloxane or other abrasion
resistant coating. The thin plastic composite prevents spalling from the
surface of the glazing to which it has been laminated. Surprisingly, in additionto stopping glass from spalling, the composite increases the integrity and
penetration resistance of the constructions to which it is laminated when they
2 5 are impacted by bullets or other projectiles striking the opposite sur~ace. By
retaining the surface glass and holding the construction together, and by other
mechanisms not fully understood, penetration resistance is substantially
enhanced far beyond what would be expected of such a thin composite
structure.
3 o In accordance with this invention a multilayered glass laminate
consisting of at least three plies of glass is prepared by interposing layers ofplasticized polyvinyl butyral between the plies of glass. The plies of glass each
should have a thickness from about 1/8 to aboutl/4 inch (3.175 to 6.35 mm)
and the polyvinyl butyral layer should have a thickness from about 15 to about
3 5 60 mils (0.381 to 1.524 mm). A thin composite consisting of an adhesive layer
34 Rec'd PCT/PTG ~14Y 93
3 212-398~CT~lJS 9 1 / 0 8 7 5 1 -
of poly~inyl bu~rral having a thickness ~rom 15 to 60 mils (0381 to 1524 mm)
and a polyester film having a thiekness from about 3 ~o about 15 mils (0.0762 ~:
to 0381 mm) is permanently bonded to an outer l~yer of the glass. The total
thickness of the composite is not greater than about 2 mnL Anti-spalling and
s penetratioD resistant s~ructures having an overall reduc~on in thickness of
20% or morc as compared to known glass laminatcs uscd in bullct rcsistant
glazing applications a-c provided by this invcntion. Preferably, threc to seven
plies of glass adhercd together with adbesivc layers of polyvi~l butyral are
used. it is to bhe understood that the rclative ~hick~ness auld nu mb~er of plies of
lO glass of the structurcs of this invention will be dctcrmi~ed by fhe ~thrcat
levcl~,i.c. the size ~d velocity of projec~es w hicb are e~qpected to bhe -
encountered.
The polyvinyl butyral adhesive sheeting may bc sclcctcd from
thc many commercially available grades of plasticized polyvinyl bu~ral. a
particularly desirable product of thc type disclosed in Moynihan, US Patent
4,292,372 is sold by E. I. Du Pont dc Ncmours and Company undcr the
trademark Butacite. Other known adhesive material for glass laminates
such as polyurethane may also be used. The polyester film may be of the type
disclosed in Knox, US Patent 4,072,779, and may be coated witb an abrasion
2 o resistant material as disclosed in that patent. The glass may bc sclected in
accordancewith ASI'M specifications, Designation C 1172-91. Tbe glass may
bc tempcred or anncaled. Tempered glass is gencrally prefcrrcd.
Brief Descripdon of the Drawings
-FIGS. 1 and 2 are sections through the edgc of a projcctile
rcsistant laminatc according to the invendon.
Detailed Description
Refcrring to FIG. 1, a projectile resistant lan~iDate comprises
thrcc sheets l0, 12, and 14 of glass. Glass sheet 10 is positioned in a dircction
likely to receive an impact from a projectile, e.g. a bullet, on its Iace 11.
Shccts 10, 12, and 14 are bonded togethcr by interlayers of poly~inyl butyral
whicb arc from 15 to 60 mils (0.381 to 1.528 mm) thick. A polyetbylene
tercphthalatc film 24 from 3 to 15 mils (0.0762 to 0.381 mm) thick is bonded
3s to glass sheet 14 by an interlayer of polyvinyl butyral.
5UBST~T~TE SH~T
WO 93/10973 PCI'/US91/08751
~ 398' t':.~ 4~ -
FIG. 2 shows the laminate of FIG. 1 having an abrasion
resistant coating 26 adhered to the outer surface of polyethylene
terephthalate film 24. Coating 26 may be a silanol coating from 1 to 20
~ucrons thick of the type disclosed in US Pat. 4,469,743 and US Pat.
4,177,315.
The laminated structure of this invention may be prepared by
known laminating methods. Polyvinyl butyral ~llm is interleaved between
glass sheets 10, 12 and 14. ~A composite comprised of polyethylene
terephthalate film 24 and polyvinyl butyral film 22 is then positioned over the
rear face of glass sheet 14~ A coverplate is placed over the assembly, the
assembly is edge taped and placed in an airtight bag and subjected to a ~ ~-
vacuum. The evacuated assembly is then autoclaved while the bag is
maintained under reduced pressure.
The invention will be further illustrated by the following
e~amples.
EXAMPLES
Laminated glass test panels were prepared by sandwiching
polyvinyl butyral sheeting having a thickness of 30 mils (0.762 mm) between
2 o one foot (304.8 rnm)squares of nominal 100 mil (2.54 mm) thick glass .
Selected panels included a composite bonded to an outer layer of one of the
plies of Bass consisting of a layer of a Butacite~ polyvinyl butyral sheet having
a thickness of 15 mils (0.381 mm) ~nd a polyester film having a thickness of ~-
0.007 inch ~0.178 m). A Single shot from a .38 caliber handgun was fired at
the center of each panel from a distance of 15 feet (4.572 m). Spall was -
measured as grams of glass ejecting from the backside of the laminate. Spall
designated "+ + + " was not measured but was estimated to be in the range
from about 50 to 100 grams, designated "+ +" in the range from 10 to 15
grams, and "+" less than about 0.2 grams. The results of the tests are set out
3 o in the following table.
, ~ ....
WO 93/10973 PCI'/US91/08751 . ~
".~
!': i
; 1 21 2 3 9 8 0
TABLE 1
, STANDARD GLASS COMPOSITE GLASS LAI~INATE
I,AMINATE
. ._ . . ............ .. _
NO. OF THIC~CNESSPE~NEI RATE SPALLTHIC~ESS PENETRATE SPALL
PLIE~S (mm~__ - ~(l~.m2 (mm) _ . (~ml
4 11.94 YES85.1 12 45NO 0.0
~_ . -. _
4 12 95NO 0.0
~ _ _ ._
4__ 12.45NO 0.0
4 12.45YES + + +
~ ... .
15.24 NO 10.3_15.75_ NO 0.0
15.24 NO + +15.49 _ NO 0.0
15.24 YES + + + 15.49 NO 0.0
_ NO 15.is NO 0.0
Y~S +~+
._ _
_ 6 18.3 NO 13.7
6 18_ NO + + _
7 21.34 NO _ 9.5
7 21.34 NO 0.0_
7 21.84 NO + +
8_ 24.38 NO 0.29 27.94 NO +9_ 27.94 NO +
Results similar to those obtained with 4 plies of glass plus a
5 composite as shown above are obtained using 3 plies of glass plus a composite
having a total thickness of about 12.5 mm.
In TaUe 2 the data from Table 1 is condensed and reformated
to show a percentage of penetration versus sample construction,thickness and
the ratio of penetrations to the number of samples tested for each ~pe.
10 Focusing on the samples each with 4 plies of glass, the standard laminate waspenetrated, whereas the sample having the same number of plies plus the
composite shield is only penetrated 2S% of the time. In tests where the
composite was not penetrated, no spall was generated. This improvement
resulted from the addition of a polyethylene terephthalate and polyvinyl
butyral adhesive film of only 22 mils (Q559 mm) thick as compared to a glass
laminate thickness of about O.S inch (12.7 mm) (an increase of 6.4~S in
thickness). The same pattern can be seen for the samples each containing 5
plies of glass, where the number of data sets is greater. In this case, the ;
WO 93/10973 Pcr/vssl/o87~1
2~,398 ' ''
addition of the composite reduces the penetration frequen~y from 40% to O~G
with an increase of only 3.3% in thickness. It is obvious when comparing 5
plies of Standard Glass Laminate that more protection is af~orded when 4
plies of the same thiclmess of glass is used in the Composite Glass Laminate
5 of the present iIIvention. Even increasing the laminate thickness to 0.6 inch
(15.24 mm), (5 plies of laminated glass) only reduced the actual penetration
to 40% (a 27.7% increase in thiclcness).To obtain 0% penetration unth the
standard construction, 6 plies of glass were necessa~y.
TABLE 2
STANDARD GL~SS COMPOSITE GL~SS L~MINATE
I~MINATE
No.~ TH~cNss . R~no sP~ THKNSS P~N~ RAno SPALL
PLIBS (mm) TR~TE . .__ ~m) (mm)_ TRAlE (~m)
_ 4 11.94 100% 1/1 85.1 12.7 25% 1/4 0.0
. L_ _._ . .. _. .
15.24 40% _2l5 10.3 15.62 ~% 0/4 0 0 -
6 18;3 O~Yo 0/2 ~ 13.7
7- 21.59 O~o 0/3 9 5 -
. .. _ , . . _
8 24.38 0%_ 0/1 0.2
- 9~ 27.94 oo~o-- 0/1 +
11 35.56 0% 0/1 0.0
