MECHANICAL PROPERTIES Of
CROSS-LAMINATED ANC,
COMPOSITE GLASS-FABRIC-BASE
PLASTIC LAMINATES
Information Reviewed and Reaffirmed
July 1961
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No. 1821
Wood Engineering Research
borato
Forest Products
Lary
Madison, Wisconsin 53705
UNITED STATES DEPARTMENT OF AGRICULTURE
FOREST PRODUCTS LABORATORY
MADISON 5, WISCONSIN FOREST SERVICE
In Cooperation with the University of Wisconsin
MECHANICAL PROPERTIES OF CROSS-LAMINATED AND COMPOSITE
GLASS-FABRIC-BASE PLASTIC LAMINATES'
By
ALAN D. FREAS, Engineer
and
FRED WERREN, Engineer
2
Forest Products Laboratory, - Forest Service
U.S. Department of Agriculture
Abstract
The properties of glass-fabric laminates may be varied by varying the
orientation of the laminations or by combining laminations of differing
properties. Reported herein are the results of tests of cross laminates
of three fabrics varying in strength parallel and perpendicular to their
warp. Also tested was a parallel laminate combining two of these fabrics
in alternate laminations. Methods are given for predicting the properties of
the laminates tested, based on properties of parallel laminates.
Introduction
One of the advantages of laminates lies in the fact that the strength
properties may be varied by varying the orientation of the laminations, or by
combining laminations of differing properties in the same laminated panel.
This report presents the results of tests on three cross-laminated panels,
each made of a different fabric, and one composite panel, parallel-laminated,
with alternate laminations of two different fabrics.
-This progress report is one of a series prepared and distributed by the
Forest Products Laboratory under U.S. Navy, Bureau of Aeronautics Order
No. NAer 01044 and U.S. Air Force No. USAF-(33-038) 51-4066-E. Results
here reported are preliminary and may be revised as'additional data become
available. Original report published in February 1951.
2
-Maintained at Madison, Wis., in cooperation with the University of Wisconsin.
Report No. 1821
The fabrics tested are typical of the range used in aircraft.
Relationships developed from this study, therefore, should be applicable
to other glass fabrics now being used for airo1aft latinateb,
MAteti41
One panel of each of four laminates was tested in this study.
Three of the panels were cross - laminated (warp direction of adjacent
plies at right angles) of 112-114, 116 - 114, or 145 - 114 fabric. The fourth
panel was parallel-laminated with alternate plies of 112-114 and 143-114
fabric. All panels were laminated with resin 2, a high-temperaturesetting, low-viscosity laminating resin of the polyester (styrene-alkyd)
type conforming with the requirements for Types I, II, and III of U. S.
Air Force Specification 12049. For all panels, the resin was catalyzed
with 0.8 percent of benzoyl peroxide by weight.
The fabric and resin were laid up between cellophane-covered cauls.
Immediately after impregnation and lay-up, the panel was cured at a pressure of 14 pounds per square inch for 1 hour and 40 minutes in a press at
a temperature gradually increasing from 220° to 250° F. Pressure was
controlled by means of an oil-filled steel bladder located on the bottom
plate of the press. Information on the make-up and physical properties
of the various panels is given in table 1.
Testing
All specimens were, prior to test, conditioned to approximately
constant weight at 75° F. and 50 percent relative humidity. The tests
were conducted under uncontrolled conditions of temperature and relative
humidity, but the specimens were exposed to these conditions for as short
a time as possible. Six specimens of each material were tested in
tension, compression, and bending, and two or three of each material in
shear.
Tension Tests
The tensile specimens used were 16 inches long and of the thickness of the laminate. The maximum sections at the ends were 1-1/2 inches
wide and 2-7/8 inches long. The minimum section at the center was 0.8
inch wide and 2-1/2 inches long. The maximum and minimum sections were
connected by circular arcs of 20-inch radius tangent to the minimum
section.
Specimens were cut parallel to and at 45 degrees to the two warp
directions of the cross laminates and parallel, perpendicular, and at
45 degrees to the warp direction of the parallel laminate.
Report No. 1821
-2-
The specimens were held in Templin-type grips, and load was applied
at a head speed of 0.035 inch per minute. Strains were measured across a
2-inch gage length with a pair of Marten's mirrors reading to 0.00001 inch;
load-deformation readings were taken to failure.
Compression Tests
Compression test specimens were 1 inch wide, 4 inches long, and of
the thickness of the laminate. They were cut parallel to the two warp
directions of the cross laminates. The parallel laminate was cut parallel
and perpendicular to the warp direction. The specimens were loaded on
their ends and were restrained from buckling by an apparatus similar to
that shown in figure 2 of A.S,T.M. Standard Designation D805-47. Load
was applied at a head spee6 of 0.012 inch per minute.
Bending Tests
Bending specimens were 1/2 inch wide, 6 inches long, and of the
thickness of the laminate. They were cut parallel to the two warp
directions of the cross laminates. The parallel laminate was cut parallel
and perpendicular to the warp direction. Specimens were tested under
center loading over a 4-inch span. Load was applied at a head speed of
0.078 inch per minute. Deflections were measured by means of a dial gage
supported in such a manner that the spindle touched the bottom of the
specimen at the center of the length. Load-deflection readings were taken
to failure.
The directional orientation of bending specimens is determined by
the direction of the top ply when the specimen is in the test apparatus.
For the 0° specimen, the top ply is parallel to the span.
Panel Shear Tests
Shear specimens were cut somewhat to the shape of a formee cross,
the outline of which is that of figure 1. The part of the specimen common
to the four arms of the cross was 3 inches square. The specimens were
cut so that the edges of the 3-inch square were parallel to the two warp
directions in the cross-laminated material. For the parallel laminate,
the edges were parallel and perpendicular to the warp direction. Four
pairs of machined steel plates (fig. 2) having the shape of the arms of
the cross, excluding the 3-inch square at the center, were bonded to the
arms, with one plate on each side of each arm. Each plate was alined to
its mate, during the bonding process, by two pins. Upon completion of
bonding, machine bolts were added. Thus, when the bolts were tightened,
the specimen was clamped between two plates. A specimen to which the
plates have been cemented and bolted is shown in figure 1, with the
rollers and roller pins in place.
Report NO, 1821
-3-
The load was applied to the rollers through triangular steel pieces
that direct the load along the edges of the 3-inch-square central section
of the specimen. Thus, a condition of approximately pure shear stress
was obtained in this section., The apparatus is shown, set up ready for
test in figure 3.
The load wale applied At a head speed of approximately 0.01 inch
per minute. Load and compressive strain readings were taken at regular
intervals of load. Compressive strains were measured by Tuckerman strain
gages of 1-inch gage length mounted on the two faces of the specimen.
Metalectric strain gages, as used in other tests ) are shown on figure 3
rather than the Tuckerman gages used in this study.
Presentation and Discussion of Results
Average test results are given in tables 2, 3, 4, and 5. The
control data shown are from parallel-laminated panels tested in other
similar research. Comparisons of test results with computed results are
shown in tables 6, 7, 8, 9, and 10.
Tension and Compression
Modulus of elasticity.--In studying the elastic properties of
plywood, it has been found that the modulus of elasticity of plywood was
equal to the average, weighted according to the volume occupied, of the
moduli of elasticity of the individual plies in the appropriate direction.
It is reasonable to assume that laminates of the types tested have similar
relations. For the laminates, this would be expressed as follows:
1 i= n
E
—
Ea
A >
EiA.
(1)
• =
Where: Ea = modulus of elasticity of the cross-laminated or composite
panel.
A = cross-sectional area of the laminate.
Ei = modulus of elasticity of the ith ply in the direction of stress.
Ai = cross-sectional area of ith ply.
In computing values of modulus of elasticity for comparison with
test results, values of Ei were taken from the data for parallel laminates,
tables 2 and 3. A comparison of the values of modulus of elasticity computed
by equation (1) with those from test is shown in tables 6 and 7. In general,
the values agree within 10 percent.
2"Msohanical Properties of Plastic Laminates" by Fred Werren. FEL Report
No. 1820, February 1951.
Report No. 1821
Strength properties.--The total load which can be carried by a
composite material equals the sum of the loads carried by the parts. That
is, P = P1 + P2 = S1A1 + S2A2 . Also, S 1 = Elea. and S2 = E2e2 . Since
the strains (e l and e2) must be equal, Si/El = S2/E2 and S1/S2 = El/E2.
Therefore, P S 2A1E1/E2 + S2A2 SiAl + S1A2E2 /E1l and the over-all
stress in the laminate may be calculated from:
-
S1
A
1 +E2 A2
El
or
(2)
(3)
where: Sa = strength property of cross laminate or composite laminate.
S1 = strength property of type 1 layers parallel to direction of
stress.
S2 = strength property of type 2 layers parallel to direction of
stress.
El = modulus of elasticity of type 1 layers parallel to direction
of stress.
E2 = modulus of elasticity of type 2 layers parallel to direction
of stress.
A l = total cross-sectional area of type 1 layers.
A2 = total cross-sectional area of type 2 layers.
A = total cross-sectional area.
Strictly, the relations of equations (2) and (3) apply only
within the elastic range of the material; experience with other materials,
however, has indicated that they may be expected to give reasonable
approximations even beyond this range.
Computations based on the relations shown in equations (2) and
(3) have been made, and comparisons between computed and test results are
shown in tables 6 and 7. The computed stress is based on the control
values from the parallel laminate, tables 2 and 3. For the cross-laminated
material, the 90° values are used for method 1, and the 0° values are used
for method 2. For the composite material, the appropriate stress of the
143-114 laminate is used in method 1 and the stress of the 112-114 laminate
is used in method 2.
In the majority of instances, agreement between computed and test
values is reasonable. In some of the parallel laminates, strain at
failure was , different for the 0° and 90° directions. It was considered
possible that better accuracy could be obtained by basing computations
on the strength corresponding to the smaller failure strain or by averaging
the stresses at the smaller failure strain. A check of these procedures
indicated no improvement over the methods of equations (2) and (3).
Report No. 1821 -5-
It is possible that the layers which fail at the smaller strain
when parallel-laminated are supported, in the cross-laminated or composite
form, by the other layers to the extent that they support their stress at
failure (as determined from tests of parallel-laminated material) even
for additional strain. If this be true, the strength of the cross laminates
or the composite laminates would be represented by the average strength of
the component layers (as determined from tests of parallel laminates)
weighted according to the area occupied. That is:
Sa
=n
A > i = 1
SiAi
(4)
Where: Sa = property of the cross laminate or composite laminate.
A = cross-sectional area of the laminate.
Si = property of the ith ply parallel to stress,
Ai = cross-sectional area of the ith ply.
Computations on this basis have been made and ratios of computed
to test values are shown in tables 6 and 7 as method 3. On the whole,
agreement between computed and test values is better by this method than
by the other two. Agreement between computed and test values for stress
at proportional limit is poor for a number of cases, regardless of method.
At least in part, this may be attributed to the difficulty of accurately
locating the proportional limit.
The Properties for the cross laminates tested in the two directions are, for all except a few cases, essentially the same. This is to
be expected, since the same proportions of material are loaded parallel
and perpendicular to the warp direction regardless of direction of test.
It is not clear why the test results at 0.2 percent offset and ultimate
in compression for the 143-114 cross laminate are so different in the
two directions. The large differences in proportional limit for the
112-114 and 116-114 cross laminates in the two directions are probably
due in part to difficulty in accurately locating the proportional limit.
Properties in tension at 42_Segrees.--Previous reporta— have
developed relations between properties of parallel laminates at different
angles to the warp direction. Similar relationships would be expected to
hold for the cross-laminated or composite materials tested for this
report, since these materials are also considered to be orthotropic. The
check, however, will be limited because values are available only at
45 degrees in tension.
—Herren, Fred and Norris, C. B. Directional Properties of Glass-fabric-
base Plastic Laminate Panels of Sizes that do not Buckle. Forest
Products Laboratory Report 1803, 1949, and Report 1803-A, 1950, Supplement to Report 18030
Report No. 1821
I
-6-
The formulas given on pages 11 and 12 of Forest Products Laboratory
Report No. 1803 4 were used for calculation based on the values derived
from tests of cross laminates and the composite laminate at 0° and 90°.
Values of Poisson's ratio for use in the equation for modulus of elasticity were not available. Approximate values based on those given in
Reports 1803 and 1803-A. were used. In any event, the term involving this
property does not enter importantly into the calculations, so that small
errors will not seriously affect the results.
A comparison of computed with test results based on these calculations is shown in table 10 as method 1. Computed and test values for
modulus of elasticity agree within 10 percent, but agreement for other
properties is not so good. In each case, the properties derived from
shear tests are important factors in the calculations, but shear values
are based on only two or three tests and are thus somewhat less reliable
than the other values.
Forest Products Laboratory Report No. 1816 2 proposes relations
between ultimate strength along the orthotropic axes and ultimate strength
at various angles to these axes. The report shows good agreement between
computed and test results for parallel-laminated glass-fabric laminates.
For tension, the relation between properties and test direction is
slightly modified from that given in Reports Nos. 1803 and 1803-A. The
modified relation (equation 13, Report No. 1816) gives no better agreement
than does that of Report No. 1803.
At least for the fabrics whose parallel-laminate properties are
about the same both parallel and perpendicular to the warp direction, it
would seem that the 45-degree properties should be the same as for the
parallel laminates, since each layer is being stressed in the same manner
as in the parallel laminate. Some interaction between layers because of
differing properties may be expected, but it should be small. For a
laminate made of the 143-114 fabric, however, such agreement would not
be expected because of the difference in properties in the two directions.
A comparison on this basis is shown in table 10 as method 2. For the
composite laminate, the 45-degree values from the 112-114 and the 143-114
parallel laminates are weighted according to their areas. In general, the
computed and test values agree within 10 percent except for the 143-114
cross laminate at ultimate. Agreement is better than for the computations
based on the equations of Report No. 1803.4
Forest Products Laboratory Report No. 1803 discusses the difficulty
of making satisfactory shear tests and suggests that shear properties can
be better determined by computations based on tensile and compressive
properties. This would indicate the improbability of being able satisfactorily to predict tensile properties at an angle to the warp direction when
it is necessary to base the computations on shear properties derived from test.
N orris, C. B. Strength of Orthotropic Materials Subjected to Combined
Stresses. Forest Products Laboratory Report 1816, July 1950.
Report No. 1821 -7-
Static Bending
Modulus of elasticity.--In plywood, it has'been found that modulus
of elasticity in bending was equal to the average, weighted in accordance
with the moment of inertia, of the moduli of elasticity ok the individual
plies parallel to the span. A similar relation, for the laminates studied,
would be:
Ea .
1
> EiIi
n
(5)
1
Where: Ea = the modulus of elasticity
panel.
Ei = modulus of elasticity of
I i = moment of inertia of the
the laminate.
I = moment of inertia of the
of the cross-laminated or composite
the ith ply parallel to span.
ith ply about the neutral plane of
laminate about its neutral plane.
Computations based on this equation were made using, as values Of,
Ei , values from the parallel-laminate data of table 4. Good agreement
between computed and test values is shown in table 8.
Strength properties.--Theoretical considerations indicate that the
resisting moment of a laminate consisting of layers differing in modulus
of elasticity may be computed from:
M = f1
(6)
c
or
-r
M = f2
-7
1 r
2
(7)
Where: M = resisting moment of the laminate.
I/c = section modulus based on the over-all dimensions of the laminate.
I = moment of inertia of the laminate about the neutral plane.
I l = sum of the moments of inertia of the layers of type 1.
12 . sum of the moments of inertia of the layers of type 2; type 2
layers assumed to be on surface of laminate.
fl strength, in the parallel-to-span direction, of the type 1 layers.
f2 = strength, in the parallel-to-span direction, of the type 2 layers.
r = E1/E2.
El modulus of elasticity of type 1 layers in the parallel-to-span
direction.
E2 = modulus of elasticity of type 2 layers in the parallel-to-span
direction.
tf/d = ratio of thickness of surface layer to total thickness of
laminate.
Report No. 1821
-8-
From this it may be seen that:
a
or
f
a
2 4.
T
[--1 1 12
[1
=f
1 t
T.- 7. f
2
[I 1 r
(8)
2
(9)
where f is the strength of the laminate as computedfrom the usual equaa
tion
a = Mc/I.
These equations are based on the assumption of elastic behavior and
thus are not strictly applicable beyond the proportional limit. In studies
of plywood, however, similar relations have been found to be applicable
even to modulus of rupture.
Equation (9) is applicable when it is assumed that the strength of
the outer layers controls the strength of the laminate; and equation (8),
when it is assumed that the layer adjacent to the outer layer controls.
In the case of the cross laminates, which had an even number of plies, the
warp directions of the surface layers on the two surfaces were opposed. In
calculating strength, therefore, it was necessary to use equation (9),
assuming, in one case, that the outer layer having the warp direction at
90° to the span controlled and in the other case, that the outer layer
having the warp direction at 0° to the span controlled. For the composite
laminate, made with an even number of plies and parallel-laminated, both
equations applied.
For the cases studied and for most cases involving more than a
few plies, the factor (1 - 2ff) will be nearly unity and can thus be
d
generally disregarded. For the composite laminate tested, for example,
the factor had a value of 0.975.
Computations based on equations (8) and (9) were made. A comparison
of computed with test results is shown in table 8. For the cross laminates,
all computations were made using equation (9) in the manner indicated
earlier. Method 1 designates values based on the strength properties of
the parallel laminates at 90°. Method 2 designates values based on the
strength properties of the parallel laminates at 0°. For the composite
laminate, method 1 designates values computed from equation (9) and thus
based on the properties of,the 112-114 parallel laminate. Method 2
designates values computed from equation (8) and thus based on the properties
of the 143-114 parallel laminate.
For the 112-114 and 116-114 laminates whose properties are similar
in the two directions, agreement between computed and test values is good.
For the other two laminates, agreement is poor in many instances. In each
case of poor agreement, it may be noted that the computed value is lower
than the test value when the computation is based on the property of the
weaker laminations. In general, the reverse is true for computations based
on the stronger laminations.
Report No. 1821
-9-
This is probably explainable on the following basis. Take, for
example, the case of the 143-114 cross laminate. The strength properties
of the 143-114 parallel laminate at 90° to the warp direction are from
about 1/5 to 1/16 those at 0°. The 90° layer on the outer surface would,
therefore, be expected to fail at a relatively low load. The adjoining
layer, however, is relatively strong and the remaining portion of the
laminate, after failure of the weak outer layer, might be strong enough
to carry additional load. The actual strength, therefore, would be higher
than that predicted on the basis of the strength of the outer layer at 90°.
Calculations based on the assumption that the outer 90° layer is
ineffective and that the laminate is one lamination thinner than it
actually is give reasonable checks with test values Computations for
the same cross laminate based on the strength of the outer 0° layer are
considerably higher than the test values because the early failure of the
opposite surface is not taken into account. For cross laminates of this
type, therefore, better predictions of strength can be made if the weaker
of the two outer layers is assumed to be ineffective and the strength computed as if the laminate were one lamination thinner.
It appears, therefore, that the procedures outlined above can be
expected to give reasonable estimates of strength properties when the
component plies have properties not differing greatly. When the properties
are significantly different, the procedures are not adequate. The data
are not sufficient to define the limiting ratio of properties at which
the procedures fail.
Since, for tension and compression, a weighted average of properties
of the two types of layers had proved a reasonable basis for calculation,
a similar method was considered for the bending properties. The weighting,
however, was in accordance with the moments of inertia of the two sets of
layers. That is:
Fa1
I
i=n
Fi
(10)
i =1
Where: Fa = strength property
I = moment of inertia
Fi = strength property
direction.
I i = moment of inertia
the laminate.
of the laminate.
of the laminate about its neutral plane.
of the ith ply in the parallel-to-span
of the ith ply about the neutral plane of
Computations on this basis have been made, and a comparison of
computed with test values is shown in table 8 as method 3. In general,
the agreement is better than for the other two methods.
Report No. 1821
-10-
Shear
Panel shear tests of plywood, where the stresses were applied along
two of the orthotropic axes, have indicated that the direction of the plies
(either parallel or crops plies) does not affect the properties so long as
the plies are the same._ This is to be expected since shear forces are
applied both parallel and perpendicular to the grain and each ply is stressed
in the same manner regardless of its grain orientation with respect to its .
neighbors. Similar relations are to be expected with glass-fabric laminates.
Where layers differing in properties are combined, their effects would be in
proportion to the area occupied. That is:
Fa = —A--
1 n
>
FiAl
i
Where: Fa = property of cross laminate or composite laminate.
A = area of cross laminate or composite laminate.
Fi = property of ith ply.
Ai = area of ith ply.
Computations based on this equation have been made, using the
properties determined from tests of parallel laminates for Fi. For the
cross laminates, of course, the properties would be the same as for the
parallel laminates.
Table . 9 presents a comparison of computed with test results.
Agreement is generally good, with a few exceptions. Better agreement can
probably not be expected in view of the small number of tests.
Conclusions
Glass-fabric laminates may be made with various combinations of
fabrics or fabric orientation. The laminates tested for this report include
three cross-laminated panels made from each of three fabrics, and a parallellaminated composite panel made from two fabrics. Based on the limited
number of combinations tested, reasonable estimates of their properties may
be found.
The properties of cross laminates or composite laminates stressed
in tension or compression parallel or perpendicular to the warp direction
may be taken as the average of the properties of the component layers,
parallel to stress, weighted according to the proportion of the area they
occupy.
Norris, C. B., Werren, Fred, and McKinnen, P. F. The Effect of Yeteer
Thickness and Grain Direction on the Shear Strength of Plywood. Forest
Products Laboratory Report 1801, July 1948.
Report No. 1821
-11-
The properties of cross laminates or composite laminates stressed in
bending parallel or perpendicular to the warp direction may be taken as the
average of the properties of the component layers, parallel to span, weighted
according to the proportion they contribute to the moment of inertia of the
laminate.
The properties of cross laminates or composite laminates stressed in
shear with the shear loads applied parallel and perpendicular to the warp
direction may be taken as the average of the properties of the component
plies when loaded in the same way, weighted according to the proportion of
the area they occupy. For cross laminates, the properties are the same as for
the parallel laminates.
The properties of cross laminates or composite laminates stressed in
tension at 45 degrees to the warp direction may be taken as the average of
the properties of the component layers, parallel to stress, weighted according
to the proportion of the area they occupy. For cross laminates, the properties are the same as for the parallel laminates.
Since the laminates tested involve fabrics having a range of relative
strength parallel and perpendicular to warp typical of the range used in
aircraft applications, the relations developed should be applicable to any
other glass fabrics now being used for aircraft laminates.
Report No. 1821
-12-
.4-28
Table 1.--Miscellaneous data relative to laminates made
with resin 21
•
: Barcol
Panel : Fabric :Direction : Total : Specific : Resin : number : gravity : content : hardness
of
No. :
:
.
:
of
:
plies
:
plies?:
Percent :
10 : 112-114; : Parallel : 41
: 143-114 :
: 1.84
34.6
:
72
26 : 143-114 : Cross
: 26
: 1.85
: 31.3
:
70
29 : 112-114 : Cross
: 84
: 1.70
: 44.9
:
69
62 : 116-114 : Cross
: 70
: 1.83
36.0
:
71
=Resin 2 is a high-temperature-setting, low-viscosity, laminating
resin of the polyester (styrene-alkyd) type.
?Panel 10 was parallel-laminated with alternate plies of 112-114
(21 plies) and 143-114 (20 plies) fabric. All other panels were
cross-laminated (adjacent plies at right angles).
Report No. 1821
Table 2.--Results of tension tests of glass-fabric cross laminates
and a composite lsnInate
_
.•..
:
Fabric :Direc- : Modulus of
Stress at
: tion :
e1astioity
t: Proportional licit : Ultimate
: of :
: test : Initial Second- :
ary : Initial :Secondary :
:Degrees: I.
!
1 1,000
f p.s.i. :
P.s.i. : P.s.i. : P.s.i.
Contrp1S Parallel-laminated
112-114 :
0
: 45
: go
: 2,690 : 2,390 : 11,800 : 29,500 : 42,700
3,76o : 20,60o•
•
• 1,540 •
9,800 : 27,000 : 38,700
: 2,640 : 2,240 :
116-114 :
0
: 45
: 90
: 3,570 : 3,010 :
:......-.: 1,830
: 2,950 : 2,640 :
6,820 : 29,300 : 47,000
3,740 : 22,800
8,200 : 33,100 : 46,700
143-114 :
:.........: 5,690 .... 1,66o
: 1,690 :
44o
• 61,700 : 89,850
....
3 1 890 : 14,000
8,46o : 10,750
2,650 :
0
45
: 90
Cross-laminated
112-114 :
0
: 45
: 90
: 2,450 : 2,120 : 10,700 : 23,700 : 39,150
•
3,250 : 21,050
• 1,460
9,500 : 25,050 : 39,50o
: 2,66o : 2,25o :
116-114
3,060 : 2,76o :
:.........: 1 1 690 •
: 3,170 : 2,780 :
91 860 : 29,250 : 45,30o
3,560 : 22,350
•
9,35o : 29,400 : 44,750
: 3,100 : 2,820 :
7,110 : 30,200 : 51,200
3,850 : 18,800
.....
7,250 : 27,350 : 51,050
o
: 45
: 90
143-114 :
o
: 45
: 90
1,700
: 3,000 : 2,750 :
:...,.....:
112-114, 143-114 Fabric Alternated; Parallel-laminated
112-114;:
Report 1821
5,070 :...... .... : 59,600 : 79,950
1,680 :,....,....:
3,560 : 16,500
2,190 :
990 :
3,130 : 14,350 : 18,650
•
0
143-114 : 45
: 90
Table 3.--Results of compression tests of glass-fabric cross
laminates and a composite laminate
Stress at -Fabric : Direc- : Modulus of :
: tion of : elasticity : : Proportional : 0.2 percent : Ultimate
test :
:
:
offset
limit
:
:
P.s.i.
: Degrees :1,000 p,s.i.:
P.s.i.
Controls Parallel-laminated
112-114 :
116-114 :
143-114 :
36,850
32,900
: 36,850
: 32,900
28,900
26,450
• 28,900
26,450
52,000
20,650
52,000
21,900
23,350
38,600
18,250
37,050
38,600
37,050
28,900
29,200
28,900
: 28,900
0
2,820
23,250
90
2,630
21,600
0
90
3,200
3,120
:
:
17,950
17,650
:
0
90
5,180
:
36,700
:
1,590
:
11,450
:
Cross-laminated
112-114 :
116-114 :
143-114 :
0
2,830
90
2,890
0
3,370
14,550
:
90
3,220
:
19,300
:
3,330
t
19,500
33,250
: 34,050
3,480
:
21,800
40,850
: 41,050
0
•
90
:
112-114, 143-114 Fabric Alternated; Parallel-laminated
112-114;:
143-114 :
0
90
Report No. 1821
:
:
4,630
1,960
39,000
14,300
50,100
24,200
: 50,100
• 24,450
Table 4.--Results of static bending tests of glass-fabric cross
laminates and a composite laminate
•
•
Fabric : Direc: tion of
: test
:
: Modulus of :
Stress at --
: elasticity : :
: Proportional : 0.2 percent
:
:
limit
:
offset
: Degrees :1,000 p.s.i.:
: Modulus
:
of
: rupture
:
P.s.i.
:
31,000
26,450
58,250
: 58,250
48,35o
: 48,350
.
P.s.i.
P.s.i.
Controls Parallel-laminated
112-114 :
:
0
90
:
116-114 :
2,590
2,400
:
:
0
:
2,860
28,650
43,800
: 43,800
:
90
.
2,690
:
26,300
38,55o
: 38,800
143-114 :
:
0
90
4,75o
1,44o
:
83,300
93,550
10,30o
: 93,550
: 18,10o
29,950
27,300
51,450
51,450
: 51,450
: 51,500
5,62o
Cross-laminated
112-114 :
:
0
90
:
:
2,510
2,530
116-114 :
:
o
:
90
:
2,86o
2,86o
31,10o
27,65o
43,20o
41,150
: 43,200
: 41,150
143-114 :
0
:
2,910
32,450
:
go
:
3,160
34,000
51,400
60,400
: 54,650
: 61,100
:
112-114, 143-114 Fabric Alternated; Parallel-laminated
112-114;:
0
:
4,320
75,200
143-114 :
90
:
1,760
8,340
Report 1821
86,400
17,150
: 86,400
: 28,000
Table 5.--Results of panel shear tests of glass-fabric cross
laminates and a composite laminate
:
.
Fabric : Modulus :
Stress at -.
of
:
: rigidity: Proportional : 0.2 percent : :
:
limit
offset
:
•
:
1z 000 •p.s.i. :
P.s.i.
:
:
P.s.i.
Ultimate
P.s.i.
Controls Parallel-laminated
112-114 :
116-114 :
143-114 :
660
570
760
:
:
:
1,920
1,660
:
2,520
4,070
3,420
4,600
13,600
11,450
12,150
Cross-laminated
112-114 :
116-114 :
570
620
143-114 :
630
:
2,380
:
4,520
14,450
1,640
2,570
:
:
3,550
4,900
11,300
14,100
112-114, 143-114 Fabrics Alternated; Parallel-laminated
112-114;:
143-114 :
670
Report No. 1821
:
2,380
4,740
11,700
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Table 9.--Ratios of computed shear properties to properties
obtained from test
Laminates
Ratios
Modulus
Stress at -of
:
: rigidity : Proportional : 0.2 percent : Ultimate
limit
:
offset
:
112-114 fabric,
cross-laminated
1.16
116-114 fabric,
cross-laminated
:
:
,92
143-114 fabric,
cross-laminated
:
:
1.21
112-114, 143-114
:
fabrics alternated, :
parallel-laminated :
1.10
Report No. 1821
:
0.80
0.90
:
0.94
1.02
.96
:
1.01
.98
.94
:
.86
.99
.94
:
1.07
:
:
:
Table 10.--Ratios of computed tensile properties at 45 degrees to
warp direction to properties obtained in test
Laminate
.
.
ModUlus of
elasticity
patio
!
stress at --
: Proportional :
Ultimate
limit
: Method : Method :---• : 1
: 2
: Method : Method : Method : Method
•
1
•
:
2
:
1
:
2
•
▪
•
•
cross-laminated: 1.08 : 1.06 : 1.46 : 1.16 : 1.22 : 0.98
112-114 fabric,:
fabric,:
•
cross-laminated: 1.07 : 1.08 ;
116-114
143-114 fabric,:
•
cross-laminated: 1.09 :
112-114,
143-114 fabrics:
alternated, :
parallellaminated
•
Report No. 1821
•
•
.92 : 1.05 :
•
•
.98 : 1.34 : 1.01 : 1.40 :
:
-.
.•
.•
-
:
:
•.
.-
•
:
•.
.•
•.
•
.91 :
1.02
•
.95 :
.97 : 1.34 : 1.08 : 1.19 :
.74
.95
Figure 1. --Panel shear apparatus used in testing glass-fabriclaminate specimen.
ZM 80082 F
Report No. 1821
Figure 3 . -- Method of testing panel shear specimens of glass-fabriclaminate. Strain measurements can be made with metalectric gages
(shown) or with mechanical gages.
ZM 80083 F
Report No. 1821
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