New Journal of Glass and Ceramics, 2011, 1, 40-48
doi:10.4236/njgc.2011.12007 Published Online July 2011 (http://www.SciRP.org/journal/njgc)
The Effect of Glass Plate Thickness and Type and
Thickness of the Bonding Interlayer on the
Mechanical Behavior of Laminated Glass
Issam S. Jalham1, Omar Alsaed1
1Industrial Engineering Department, Univers ity of Jordan, Amman, Jordan.
Received March 8th, 2011; revised April 5th, 2011; accepted April 12th, 2011.
ABSTRACT
In this work the effect of the type of the bonding interlayer (polyvinyl butyral (PVB) or Ethyl Vinyl Acetate (EVA)),
number of bonding layers, and the position and the thickness of the Glass plates on the maximum load capacity and
absorbed energy by laminated glass. Further more, this investigation presents a mathematical model that relates the
maximum force capacity of the glass laminated structure to the glass plate thickness, type and thickness of the interlay-
er regardless the position of the fixed glass plate. Both practical work results and the theoretical model indicate that the
maximum load capacity of laminated glass bonded with either PVB or EVA decreases as the interlayer thickness in-
creases. Moreover, the maximum load capacity for the glasses bonded with EVA is greater than those for the PVB
bonded ones under the same conditions. On the other hand, it was observed that that laminated glass absorbed energy
increases with the increase of the interlayer thickness and the increase of glass plate thickness.
Keywords: Laminated Glass, Polyvinyl Buty ral (PVB), Ethyl Vinyl Ace tate (EVA), Layer, Load Capacity
1. Introduction
Ceramics and glasses, which have strong ionic-covalent
chemical bonds, are very strong and stiff. They are also
resistant to high te mperatures and corrosion, but are brit-
tle and prone to failure at ambient temperatures. In con-
trast, thermoplastic polymers such as polyvinyl butyral,
which have weak secondary bonds between long chain
molecules, exhibit low strength, low stiffness, and a sus-
ceptibility to creep at ambient temperatures. These po-
lymers, ho wever, tend to b e extremely ductile a t ambient
temperatures. When combine glass and polymer to form
a laminated glass, some change in the maximum load
capacity will occur, which depends on both the glass and
polymer type. This led to investigate how the glass
thic kness a nd t he type and n umber of la minate d int erlay-
er affect the maximum load capacity of laminated glass
as well as their effect on the absorbed energy.
2. Literatu re Rev iew
Laminated glass consists of two or more glass plies
bonded together with an elastomeric interlayer, usually
polyvinyl butyral (PVB) or Ethyl Vinyl Acetate (EVA).
Afte r breakage, the interlayer holds the resultant glass
shards in place and, in most cases, the glass remains in
the frame when laminated glass fractures. This post-
breakage characteristic of laminated glass has made it
desirable for use in vehicle windshields for decades be-
cause it makes the occupant safer from glass shards than
other glazing materials.
The shea r modulus st ud ie s we r e c ar r ied o ut by Que net t
[1] and Hooper [2]. Quenett [1] noticed that when the
interlayer thickness decreases, shear modulus increases
and reported that the condition of the interlayer is a con-
trolling factor in static bending and dynamic impact re-
sistance. Hoo per [2] confir med the results of Quenett [1] .
He stated that after testing glass beams in four points
loading with varying temperatures and interlayer hard-
ness, he found that t he shear modul us of the interla yer is
inversely prop ortional to the interla yer thickness and a lso
mentioned that plasticizer contents, ambient tempera-
tures, and load durations are the primary factors control-
ling bending resistance of laminated glass. He attributed
this behavior to the “thermoplastic” nature of the inter-
layer, stating the decreased bending stiffness was the

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Interlayer on the Mechanical
Behavio r of Laminated Glass
41
primary disadvantage to a r c hitectural laminated glas s.
Strength of the monolithic and laminated glasses tak-
ing in to ac count the geo metr y and thi ckne ss of t he te sted
plates was studied by several researchers. For example,
Pilkington Ltd. [ 3] co mpared monolit hic glas s stre ngth to
the strength of laminated glass specimens made of sheet
and float glass. They found that, at normal temperature,
laminated glass specimens exhibit the same strength as
monolithic glass specimens having the same rectangular
dimensions and glass thicknesses. On the other hand,
Linden et al. [4] conducted a non-destructive test on
monolithic, layered, and laminated glass specimens in-
strumented with strain gages. They concluded that lami-
nated glass strength and monolithic glass strength ap-
peared to be equivalent at normal temperatures; and the
strength of la minated gla ss specimens approached that of
layered glass specimens at elevated temperatures. In ad-
dition, Norville [5] tested two laminated glass specimen
of sizes 38 x 76 and 66 x 66 in. destructively. His de-
structive experimentation also showed that the strength
of laminated glass specimens is the same or greater than
that of monolithic specimens having the same rectangular
dimensions and nominal thicknesses under similar load
conditions.
Keller [6] used novel method to measure the delami-
nating energy in laminated glass in the rele vant dynamic
range. He found that increasing the interlayer thickness
improves the penetration resistance of laminated glass
because more energy can be absorbed in the high speed
delimitation process since the interlayer is simply less
like to tear.
In contrast to the results of the above mentioned re-
searches contradiction was reported in Nagalla et al. [7] ;
Minor and Reznik [8]. Nagalla et al. [7] in their ad-
vanced theoretical work compared layered glass to mo-
nolithic. They discovered that some aspect ratios of the
layered glass experienced lower principal stresses than
monolit hic glass subje cted to unifor m, transver se loading
in some ranges of the loading. They concluded that the
strength factor of 0.6 used by some building codes for
laminated glass may be too low for many window geo-
metries and design pressures.
Minor and Reznik [8] destructively tested three sizes
of laminated glass specimens (33 x 66, 38 x 76, and 66 x
66 in.) with an 0.030 in. interlayer, and compared the
resulting failure pressures to those from tests on mono-
lithic glass specimens having the same rectangular di-
mensions and nominal glass thicknesses. They intro-
duced four variables, which are: glass thickness, glass
type, temperature, and damage to one plate of glass (i.e.,
damage to tension or compression side) . Their te sting led
to the following geral conclusi ons:
1) Laminated glass specimens tested at room tempera-
ture have approximately the same failure pressure as
monolithic glass specimens having the same rectangular
dimensions and nominal glas s thicknesses;
2) As temperature increases laminated glass behavior
migrates towards the layered glass model;
3) Laminated glass specimens having twice the no-
minal glass thickness of monolithic specimens display
strength greater than or equa l to twice t he strengt h of the
monol ithi c specimens.
Some researchers investigated the effect of tempera-
ture on the properties of glass. Linden et al. [9] con-
ducted non-destructive testing on two different plate
geometries. First, they tested the same plate geometry
(60 x 96 x 1/4 in.) as used in the parent report to study
load duration and temperature effects. Second, they
tested a different geometry (55-1/8 x 57-1/8 x 3/8 in.)
with two interlayer thicknesses (0.030 and 0.060 in.) to
study the effects of interlayer thickness on strength and
deflection. They conducted destructive tests on one plate
geometry (60 x 96 x 1/4 in.) at room temperature and at
170°F. Perusal of their data indicates that while load du-
ration and elevated temperatures acting individually re-
duce the s tr uctural rigidity of the laminated glass, the two
factors do not interact, producing a greater combined
reduction in laminated glass strength. Weller [10], Used
experimental study to compare different interlayer mate-
rials in laminated glass in respect to their structural be-
haviour. The material properties above the verification
temperature clearly showed the temperature dependency.
The relaxation times fall with increasing temperature and
the shear stress gets smaller.
Theoretical modeling of the glass behavior was also
carried out by many researchers. Linden et al. [4 ] derived
theoretical results through the finite difference solution
and compared experimental and theoretical results. They
concluded that the theoretical finite difference model for
monolithic and layered glass appeared to be acceptable
for the one glass plate geometry tested. Moreover, Behr
and Kremr [11] used experimental validation of a me-
chanics-based finite element model for architectural la-
minated glass units subjected to low velocity and two
gram projectile impacts. The impact situation models a
scenario commonly observed during severe windstorms.
This study confirmed the ability of an analytical finite
element model to predict accurately the peak strains in
representative architectural laminated glass units as a
function of impact velocity. Correlations between peak
radial strains computed using finite element analysis and
those measured experimentally were close, with the av-
erage difference between analytical predictions and ex-
perimental data being 7.7%.

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Int er layer on the Mechanical
Behavio r of Laminated Glass
42
Zang et a l. [12] investigation focused on the use of the
3D discrete element method to study the impact fracture
problem of laminated glass. The glass and the (PVB) of
laminated glass plane are discretized to uniform rigid
spherical elements. This investigation showed that the
accuracy of the 3D model and numerical analysis code
are more validated in the elastic range by comparing with
FEM.
Recently, Belies [13] compared (PV B) with st iffe r and
stronger interlayer Sentry Glass Plus (SGP). After brea-
kage of both glass sheets the load decreased to a rela-
tively low level (typically between 2 kN and 3 kN) be-
fore the broken glass pieces and interlayer started again
to buil d up co mpres si ve a nd tensile stre sse s, respe ctively.
Subsequently, the load slightly increased again and after
reaching the maximum, it decreased significantly (to less
then 0. 3 kN). When s ubje cted to in-plane b endi ng (buc k-
ling prevented), the post breakage residual resistance is
relatively poor for both interlayers, as illustrated above.
The residual load-bearing capacity was very limited and
far below the initial glass strength.
It is clear from the above review that the research work
focused on the comparison between the strength of mo-
nolithic and laminated glases and did not take into con-
sideration the bonding interlayer thickness, and the posi-
tion and thickness of the glass plates. Furthermore, the
main bonding material in these studies is PVB. This in-
vesti gatio n d iffe rs fr o m the ab o ve me ntio ned one s in that
it concentrates on how the glass thickness and the type
and number of laminated interlayer affect the maximum
load capacity of laminated glass as well as their effect on
the absorbed energy.
Details for the preparation of the mullite ceramic tile
(900 mm × 1800 mm × 5.5 mm) were reported in [4].
The raw materials were as follows: 50 wt% - 55 wt% fly
ash, 30 wt% - 35 wt% pyrophyllite, 10 wt% - 15 wt%
bauxite and 4 wt% AlF3.
Microcrystal glass was a sort of borosilicate glass and
the composition is sho wn in Table 1.
High purity silica, reagent grade boric acid, zinc oxide,
sodium carbonate and yttrium oxide were used as source
materials and mixed in the above ratios, ball milled and
dri ed. Then, the mixture was gro und in a p latinum cr uci-
ble and kept it at 1500˚C for 3 h. The molten glass trans-
formed from the mixture at high temperature and under-
went water quenching and a course of drying and ball
milling to produce a glass power with an average size
about 1 - 3 μm. These glass powder was distributed un-
iformly by distributor on the surface of mullite ceramic
tile and its thickness was kept at 1.2 mm. Next, the cov-
ered tile was placed in a furnace for a second sintering at
1000˚C - 1200˚C, causing the glass powder to remelt,
nucleate, crystallize and combinesolidly with the ceramic
base. After cooling down to the room temperature, the
large-size ultra-thin mullite glass ceramic tile was pre-
pared finally.
3. Materials, Equipment, and Experimental
Procedure
3.1. Material
The materials used in this investigation are float glass
plates, and Polyvinyl Butyral (PVB) and Ethylene Vinyl
Acetate (EVA) as interlayer materials. The maximum
force capacity and the amount of the absorbed energy of
the laminated glass were determined for the input va-
riables that are summarized in Tables 1 -4 below. Figure
1 shows the schematic diagram for the assembly of the
glass plates and interlayer.
3.2. Equipment
Equipment used in this investigation are Glass cutting
machine of BSJ-NL3725 type, Bend testing machine of
OUTOGRAPH AG—1S type, and Charpy testing ma-
chine.
3.3. Experim enta l Pro ced ure
Testing procedure can be summarized as follows:
1) Cutting plates of 40 cm x 30 cm from glass panels
of 4 mm, 6 mm , 8 mm, 10 mm, 12 mm thicknesses. The
sharp cut edges have been broken off or beveled with a
grind ing tool ;
2) Manufacturing of PVB-laminated glass. It compris-
es the washing and drying of individual glass sheets,
laying the PVB film between the two glass sheets by
usin g roller process, and heati ng and pres sing the a ssem-
bly.
An assembly full- surface bond is created in an autoc-
lave using temperatures of about 140°C and pressure of
about 150 psi. The interlayer becomes a viscous at this
temperature and pressure, and any remaining air dis-
solves into the la minate layer;
3) M anufactur ing of EV A laminated glass. It compris-
es the washing and drying of individual glass sheets,
laying the EVA film between the two glass sheets by
using roller process, and the assembly is headed in single
stage lamination process (vacuum with integrated heating
and cooling in the same apparatus);
4) Cutting of the manufactured laminated glass to the
required size by using the cutting machine. For point
bend test, the rectangular sheets dimension is 80 mm x
300 mm while for Charpy test, the rectangular sheets di-

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Interlayer on the Mechanical
Behavio r of Laminated Glass
43
Table 1. PVB samples for be nding and C ha rpy impact tests (the outer plates and interlaye r thickne ss c hang eable) .
One inter l ayer Four int erlayers Si x int erlayers
Inner plate (mm) Outer plat e (mm) Inner plate (mm) Outer plat e ( mm) Inner plate (mm) Outer plate (mm)
4 4 4 4 4 4
4 6 4 6 4 6
4 8 4 8 4 8
4 10 4 10 4 10
4 12 4 12 4 12
Table 2. PVB sampl es for bending a nd C ha rpy impact tests (the inner plates and interlaye r thickne ss c hang eable) .
One inter l ayer
Four interlayers
Six int erlayer s
Inner plate (mm)
Outer p late (mm)
Inner plate (mm)
Inner plate (mm)
Outer p late (mm)
Inner plate (mm)
4
4
4
4
4
4
6
4
6
4
6
4
8 4 8 4 8 4
10
4
10
4
10
4
12
4
12
4
12
4
Table 3. EVA samples for bending and C ha rpy impact tests (the out er plates and interlayer thicknes s changeable).
One inter l ayer One int erlayer One interla y er
Inner plate (mm) Inner plate (mm) Inner plate (mm) Inner plate (mm) Inner plate (mm) Inner plate (mm)
4
4
4
4
4
4
4
6
4
6
4
6
4
8
4
8
4
8
4
10
4
10
4
10
4
12
4
12
4
12
Table 4. EVA samples for bendi ng an d Charpy impact tests (the inner plates and interlayer thickness changeable).
One inter l ayer
One inter l ayer
One inter l ayer
Inner plate (mm)
Inner plate (mm)
Inner plate (mm)
Inner plate (mm)
Inner plate (mm)
Inner plate (mm)
4
4
4
4
4
4
6
4
6
4
6
4
8
4
8
4
8
4
10 4 10 4 10 4
12
4
12
4
12
4
mension is 80 mm x 300 mm.
4. Results and Discussion
As stated before, the maximum force capacity and the
amount of the absorbed energy of the laminated glass
were determined for the input variables that are summa-
rized in Tables 1-4 for the assembly shown in Figure1.
The outer surface is the one in contact with the force
while the inner surface is that locates on the other side
from the force. Results and discussions of the investiga-
tion will be br ie fed in the following sections.
4.1. Load Capacity (Force) and Absorbed
Energy
It is clear from Figure 2 that the higher the thickness
(number) of interlayer, the less the maximum load capac-

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Int er layer on the Mechanical
Behavio r of Laminated Glass
44
Figure 1. Schematic diagram for the assembly of the glass plates and interlayer. Outer glass is the one in contact with the
applied force.
Glass thickness [ mm]
46810 12
Force [N]
0
400
800
1200
1600
2000
2 INTE RL AYERS
6 INTE RL AYERS
4INTE RL AYERS
Figure 2. Testing the maximum force on (PVB) laminated
glass where the thickness of inner plate was fixed and the
outer plate was fixed and the outer plate and interlayer
were change able.
Glass thickness[mm]
46810 12
Force [N]
0
400
800
1200
1600
2000
2 INTERLAYERS
6 INERLAYERS
4 INTE RL AYERS
Figure 3. Testing the maximum force on (PVB) laminated
glass where the thickness of outer plate was fixed and the
inner plate was fixed and the inner plate and interlayer
were changeable.
Glass thi c kn e ss [mm]
46810 12
Force [N]
0
500
1000
1500
2000
2500
2 INTERLAYERS
4 INTERLAYERS
6 INTERLAYERS
Figure 4. Testing the maximum force on (EVA) laminated
glass where the thickness of inner plate was fixed and the
oute r plate an d interlayer were changeable.
Glass thi c kn ess [mm]
46810 12
Force [N]
0
500
1000
1500
2000
2500
2 INTERLAYERS
4 INTERLAYERS
6 INTERLAYERS
Figure 5. Testing the maximum force on (EVA) laminated
glass where the thickness of outer plate was fixed and the
oute r plate an d interlayer were changeable.
ity of the laminated glass bonded with PVB material for
the fixed thickness of the inner glass plate. This load ca-
pacity is a characteristic strength from Weibull strength
distribution. The same behavior can be observed for the
laminated glass bonded with the same material although
the fixed thickness is the thickness of the outer glass
plate (Figure 3). The same trends also can be observed
for the laminated glass bonded with EVA (Figures 4 and
5). The trend of these results is in agreement with the
shear modulus results reported by Quentt [1], Hooper [2],
and the predictions of Zang et al. [12]. On the other
hand, they contradict with the results of Minor and Rez-
nik [8 ].
Figure 6 shows that the position of the plate of the
fixed thickness does not affect the maximum load capac-
ity and the maximum load capacity for laminated glasses
bonded with EVA is greater than that for the ones
bonded with PVB provided that the same conditions are
maintained.
The absorbed energy shows an opposite effect. For
example, Figure 7 shows that the higher the thickness
(number) of bonding interla yer, the higher the amount o f
the absorbed energy. Moreover, the laminated glass
which is bonded with PVB absorbs more energy than
those bonded with EVA. The trends in these results are in
agreement wit h the results of K e lle r [6].
An int er es ti n g b ehavio r is s hown i n Figure 2 whe n t he
outer thickness of the outer glass is 6 mm. In this case,
the maximum load capacity for the 4 interlayer is less
Plate Thickness
Interlayer Thickness
Outer (Upp e r ) Glass plate
Inner (Lower) Glass plate
Plate Thickness

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Interlayer on the Mechanical
Behavio r of Laminated Glass
45
than that for the laminated glass bonded with 6 interlay-
Glass thickness[ mm]
46810 12
Force [N]
0
500
1000
1500
2000
2500
PVB, OUTER FI X ED THICKNE SS
PVB, INNER F I X ED THICKNE SS
EVA, INNER FIX ED THICKNE SS
EVA, OUT ER FIXED THICKNESS
Figure 6. Comparison of the ma x i mu m load c apacit y for the
2 or fixed interlayer thickness, variable bonding material,
and different positio ns of gl ass thicknesses.
Glass thickness [mm]
46810 12
Absorbed energy until fracture [J]
0
10
20
30
40
6 INTERLAYERS, PVB
4 INTERLAYERS, PVB
2 INTERLAYERS, PVB
2 INTERLAYERS, EVA
4 INTERLAYERS, EVA
6 INTERLAYERS, EVA
Figure 7. Abso rbed energ y unti l fracture by Char py impact
test when the inner thickness is variable and the bonding
material is PVB and EVA.
ers. Furthermore, the amount of absorbed energy the la-
minated glass of 4 mm thickness and 6 bonding inter
layer of EVA is greater than that for 4 interlayers boded
with PVB for the same thickness. These interactions
worth more investigations in the future.
4.2. Modeling of the Maximum Load Capacity
(Force) and the Absorbed Energy
The maximum load capacity of glass and its absorbed
energy are very important in real life applications. For
example, high rise buildings or some open areas are ex-
posed to a high impact wind forces. To be able to find the
suitable glass to resist the forces and help in absorbing
higher energy, it is of a great importance to select the
suitable glass. As it was noticed before, there is a contra-
dict ion in the result s whe n compar ing the maxi mum loa d
capacity and the amount of absorbed energy. To over-
come this, the modeling took place for the maximum
load capacity and the amount of absorbed energy sepa-
rately depending on the thickness of glass and the thick-
ness of the bonding interlayer regardless the position of
glass plates. The modeling of the interaction of the
maximum load capacity and the amount of absorbed
energ y will be consid ere d in our future invest igation.
The modeling tool used in this investigation was mul-
tiple regressions with the help of minitab software. Four
relationships were determined because the measured re-
sults of failure strength and absorbed energy till failure
upon impact is different due t o the visco -elastic damping
of interlayer. These are:
1) The maximum load capacity as a dependent varia-
ble and thickness of glass and the thickness of the PVB
bonding interlayer as independent variables.
2) The amount of absorbed energy as a dependent va-
riable and thickness of glass and the thickness of the
PVB bonding interlayer as independ ent variab les.
3) The maximum load capacity as a dependent varia-
ble and thickness of glass and the thickness of the EVA
bonding interlayer as independent variables.
4) The amount of absorbed energy as a dependent va-
riable and thickness of glass and the thickness of the
EVA bonding inter layer a s independe nt variables.
The multiple linear regression assumes that the varia-
ble response is a linear function of the model parameters
and there are more than one independent variable in the
model.
The general form of the developed model may be
written:
y xx
αβ γ
=++
12
(1)
where
y: is dependent variable (Max bending force or Max
absorbed energy);
α, β, γ: are regression coefficients;
x1, x2: are the thickness of glass and the interlayer gl ass
thicknes s es resp ectively.
After running the minitab software, the results can be
summarized as follows:
1) The equation that relates the maximum load capac-
it y ( y) as a dependent variable and thic kness of glas s (x1)
and the thickness of the PVB bonding interlayer (x2) as
independent variables is:
12
Maximum load capacity(PVC)34817458.3xx=−+ −
(2)
The observations, which were described by this rela-
tionship, are independent random variable as can be seen
on Figure 8(a) as this figure presents the normal percent
prob ability of the resid uals and the p lot points lie a long a
straight line. So, the h ypothesi zed distrib ution ade qua tely
describe data and the model is appropriate. Furthermore,
the model explains about 91.5% of the variability of the
process because the adjusted R-sq = 91.5%. The analysis

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Int er layer on the Mechanical
Behavio r of Laminated Glass
46
of variance of the process shows that the results are ex-
tre mely si gni fic ant a s t he P -value is about zero. T he ben-
efits of this equation can be seen clearly when applied to
real life cases. To find the suitable laminated glass with
dependent variables x1(thickness of glass) and x2 (the
thickness of the PVB bonding interlayer) that can resist
the external force (wind force as an example), the varia-
ble x1 can be changed as it is the onl y variable that has a
positive sig n.
2) The equation that relates the amount of absorbed
energy as a dependent variable and thickness of glass (x1)
and the thickness of the PVB bonding interlayer (x2) as
independent variables is:
12
Amountofabsorbedenergy(PVB)=17.45.121.74
xx
−+ +
(3)
Figure 8 (b) presents the normal per cent probability of
the residuals and shows that the observations are inde-
pendent rando m variable and follow the normal distribu-
tion. Moreover, the model explains about 90.3% of the
Residual
Percent
4003002001000-100-200-300-400
99
95
90
80
70
60
50
40
30
20
10
5
1
Normal Probability Plot of the Residuals
(response is MAX PVB1)
(a)
Residual
Percent
86420-2-4-6-8
99
95
90
80
70
60
50
40
30
20
10
5
1
Normal Probability Plot of the Residuals
(response is MAX PVB 2)
(b)
Figure 8. Normal probability plot of residuals of (a) the
maximum load capacity relationship and (b) amount of
absorbed energy for PVB bonding material.
Residual
Percent
3002001000-100-200-300
99
95
90
80
70
60
50
40
30
20
10
5
1
Normal Probability Plot of the Residuals
(response is MAX EVA 1)
(a)
Residual
Percent
210-1-2
99
95
90
80
70
60
50
40
30
20
10
5
1
Normal Probability Plot of the Residuals
(response is MAX EVA 2)
(b)
Figure 9. Normal probability plot of residuals of (a) the
maximum load capacity relationship and (b) amount of
absorbed energy for EVA bonding material.
variability of the process because the adjusted R-sq =
90.3%. The analysis of variance of the process shows
that the results are extremely significant as the P-value i s
about zero. To find the suitable laminated glass with de-
pendent variables x1 (thickness of glass) and x2 (the
thic kness of t he PVB b onding interla yer) t hat can a bsorb
the highes t amount of energy unt il fra cture, t he variab les
x1and x2 can be changed.
3) The equation that relates the maximum load capac-
ity as a dependent variable and thickness of glass (x1) and
the thickness of the EVA bonding interlayer (x2) as in-
dependent variables is:
12
Maximum load capacity (EVA)8818568.3
xx
=−+ −
(4)
Figure 9(a) presents the normal percent probability of
the residuals and shoes that the observations are drawn
from independent variables and the standard deviation
and the variance of both populations are equal as the plot

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Interlayer on the Mechanical
Behavio r of Laminated Glass
47
points shows that the data follows a normal distribution. Also the model explains about 94.7% of the variability of
Figure 1 0. Failure observed aft er bendi ng test (side view).
Figure 11. Failure obser ved after bending test (top view).
Figure 1 2. Failure after Charpy t es t .
the process because the adjusted R-sq = 94.7%. The
analysis of variance of the process shows that the results
are extremely significant as the P-value is about zero.
4) The equation that relates the amount of absorbed
energy as a dependent variable and thickness of glass (x1)
and the thickness of the EVA bonding interlayer (x2) as
independent variables is:
12
Amountofabsorbedenergy(EVA)6.712.740.620xx=−+ +
(5)
Figure 9(b) presents the normal percent probability of
the residuals. The plot points show that the process data
followed a normal distribution and the observations are
independent random variable. Moreover, the model ex-
plains about 95.7% of the variability of the process be-
cause the adjusted R-sq = 95.7%. The analysis of vari-
ance of the process shows that the results are extremely
significant as the P-value is about zero.
4.3. Failure Observation
Bending test took place until fracture. Then the fractured
surface was analyzed. It was found that the propagation
of fracture was linear within the glass plate and non li-
near within the bondi ng po lymer a s seen in t he side view
(Figure 10). This difference may be due to the thermop-
lastic nature of the bonding material which was described
by Hooper [2]. The top view in Figure 11 shows the li-
near nature of propagation within the brittle glass AND
Figure 12 shows the failure after Charpy test.
5. Conclusions
Linear
Linear
Non-linear
Outer gla ss plate
Inner glass plate
Binding material

The Effect of Glass Plate Thickness and Type and thickness of the Bonding Int er layer on the Mechanical
Behavio r of Laminated Glass
48
The conclusions that can be drawn from this investiga-
tion are:
1) The higher the thickness of interlayer, the less the
maximum load capacity of the laminated glass bonded
whether wit h PVB or E V A bo nd ing material for the fixed
thicknes s of t he inner glas s plate
2) The position of the plate of the fixed thickness does
not affect the maximum load capacity and the maximum
load capacity for laminated glasses bonded with EVA is
grea ter than t hat for the o nes bo nded with P VB pro vided
that the same conditions are maintained
3) The higher the thickness of bonding interlayer, the
higher the amount of the absorbed energy whether the
laminated glass bonded with PVB or EVA bonding ma-
terial. Moreover, the laminated glass which is bonded
with PVB absorbs more energy than those bonded with
EVA
4) Regression models were developed to calculate the
maximum load capacity and the amount of absorbed
energy separately depending on the thickness of glass
and the thick ness o f the bo nding i nterl ayer regard less the
position of glass plates. Positive variables are taken into
consi deration during calcula t io ns .
5) The propagation of fracture was linear within the
glas s plate and non linear within the bonding polymer
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