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NATIONAL ADVISORY COMMITTEEFOR AERONAUTICS

TECHNICAL NOTE ..-.. .-

—.

Ho. 1054..-........ ....

IMPACT STRENGTH AND FLEXURAL PROPERTIES OF..-,,, -.

LAMINATED PLASTICS AT HIGH-AND Low T2W?ERA’YJR@s —

By J. J. Lamb, Isabelle AIbrecht; and B. M. ixilro~National Bureau of Standards

.-

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.

=a!!L=’‘ WashingtonAugust 1946

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tAr.?&Y*4ti.19RmeF. .; _.LAWXWK)RY ,,’ -.

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NATIONAL ADVISORY COMMITTEE F@R AERONAUTICS

TECHNIC.4L NOTE No. 1054

IMPACT STRENGTH AND FLEXURAL PROPERTIES OF

LAMINATED PLASTICS AT HIGH AND LOW TZJfPERATURES

By J. J. Lamb, Isabelle Alhrecht, and B. M. Axilrod

SUMMARY

The Izod-inpact strengths and flexural ~roperties of sev-eral types of plastic laminates, whioh are either in use orhave potential application in aircraft structures and pails,were determined at different temperatures in th-e range of-700 to2000. F.

The materials investigated were unsat?lrated-polyesterlaminates rei~foroed with glass fabric and phenolic laminates

4 reinforced with asbestos fabric, high-strength paper, rayonfabrio , and cotton fabric. Both high-pressure and low-pressuretypes of cotton-fabric phenolic laminates were included.

●

The impact strength of specimens tested flatwise at ’770 Fwas 4 to 7 foot-pounds per inch of notch for all the laminatesexcept the glass fabric and ray~n fabric laminates. These twomaterials had impact strengths of 31 and 17 foot-pounds,respectively, a% 77° l?. The high-strength-paper, rayon-fabric,and asbestos-fabric phenolic laminates showed SBall changes inimpact strength between -700 and 2000 F. Cotton-fabric pheno-lic laminates showed pronounced decreases in iQpact strengthat the low temperature and small changes between 77-G arid 200°F. The glass-fabric unsaturated-polyester laminates had in-creased impact strengths at the IGW temperature. .—

The flexural strengths and moduli of elasticity of allthe materials increased with change in the test temperaturefrom 77° to -700 F. Under exposure to a 2000 F temperature,all materials except the asbestos-fabric laminate lost 30 to40 percent of their flexural strength at 770 F and the moduli

# of elasticity of all the materials, except the asbestos-fabricand one cotton-cloth phenolic laminate, decreased about 20percent.

%

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NA(lA TN NO. 1054 2

}

Tests made at room temperature after heating the materi-. als at 2000 F for 24 hours indicate that prolonged heating

* with consequent loss of moisture content and further cure ofthe resin may offset the effect of high temperature alone. Inflexural tests made at 1500 3’ and 90 percent relative humiditytwo laminates showed considerable 10SS in strength.

A knowledge of the effect of temperature on the strengthproperties of plastics is of considerable importance in ap-plication of the materials for aircraft structural purposes.Results obtained by various investigators (references 1, 2,and 3) on plastic materials indicate that considerable varia-tion may be expected.

Oberg, Schwartz, and Shinn (reference 2) reported varia-tions of 10 to 30 percent in the tensile and flexural proper-

A ties of grades C, L, and XX Phenolic laminates for the range-380 to 78t) F. Data on resin-bonded plywood and compreg alsoare included.

b

Norelli and Gard (reference 3) reported data for tensile,compressive, and shear strengths and tensile moduli of elas-ticity for various phenoli~ laminates for temperatures rang-ing from -670 F to as high as 392~ T in some instances. Theyconcluded that the percentage change in strength foroellulose-filled plastics is greater than for the mineral-filled plastics.

-.

Meyer and Erickson (reference 4) determined the mechani-cal properties of high-strength paper-%ase phenolic laminatesfor temperatures from -690 to 2000 F. E’or this temperaturerange they found large variations in tensile, compressive, andflexural strengths and somewhat smaller variations in modulusof elasticity. The strength and modulus-of-elasticity valuesdiminished with increasing temperature.

In recent investigations by the Naval Air Experimental● Station (reference 5) considerable data has been obtained at

77° and 1600 F on the mechanical properties of a variety ofplastic laminates. The ultimate strength and modulus-of-

k elasticity values were generally lower at the higher tempera-ture but the percentage changes varied greatlY for the .different materials.

—

Izod-impact test data reported by Fuller (reference 6)for grades L and XX phenolic laminates and for a glass-cotton-fabric phenolio laminate indicate an increase in Izod-impact ‘–

—

strength with temperature for the cellulose-filled resin andan opposite trend for the glass -cotton-fabric laminate for therange -670 to 1580 E. Shinn (reference 7) found that theIzod-impact strength of payer and cotton-fabric phenolic lami-nates increased with temperature over the temperature range-67° to 158° F and a similar trend was observed for paper andcotton-fabric allyl laminates between -67° and 77° ~,

The present investigation was undertaken to obtain the*mpact , flexural, tensile, and compressive strength propertiesof representative laminates in the temperature range -70° to2000 F. Since testing at these temperature condit:o:S_pre- _sents many problems not net in testing at room temperature, amajor part of the project was concerned with the developmentof apparatus and techniques. This report summarizes the re-sults of Izod-impact and flexural tests on the selected mate-rials . Both flexural strength and flexural~modulus-of-elasticity data were obtained in the flexural tests.

This investigation, conducted at the National Bureau ofStandards, was sponsored by and conducted with the financialassistance of the National Advisory Committee for Aeronautics.

The courtesy of the Army Air Forces, Bakelite Corporation,consolidated Water Power and paper company, 3or~iCa lnSLllationCompany, Plaskon Division of the Ittbbey-Owens-Ford Glasscompany, and the Synthane Corporation in furnishing materialsfor use in this invest~gation is gratefully acknowledged. Thecooperation of Il. JA Kaiser, R. W. Thiebeau~ G, E. Brenner,and P. Pfaff of the National Bureau of Standards InstrumentShop in the design and construction of the flexural apparatusand the preparation of the test specimens also is appreciated.

MATERIALS

The materials selected for testing included commercial

●grades of high- and low-pressure cotton-fabric phenolio lami-nates, an asbestos-fabric grade AA phenolic laminate, a high-strength-paper phenolic lamtnate, a rayon- fabric phenolic

● laminate, two experimental phenolic laminates made-with highpressure and low pressure, respectively, using the same gradeC cotton fabric as filler, and two glass-$abria laminatesbonded with the same unsaturated polyester resin. The

—

NAC.4 TN No. 1054 4

}materials were supplied in nominal 1/8- and l/2-inch thiclc-nesses. A detailed description of the materials is contained

‘+ in table I.

DEFINITIONS

Izod-impact strength:

Energy to break the specimens divided by the dimensionalong the notch of the specimen

Flexural properties for beam of rectangular cross section sub-jected to a concentrated load P at midspan:

Extreme fiber stress (at midspan)~

, P load

L span or distance between supports

b breadth of beam

d depth of beam

Flexural strength:

where I?m is maximum load and other quantities are as definedpreviously

Flexural modulus of elasticity:

L3 PE=—-

4bd3 X

.—

where x is the defle~tion at mi~span and the other quantitiesare ae defined previously

NAC.4 TN No. 1054 5

?Initial mod Ulus of elasticity Mi is obtained when the

initial slope of the load-deflection curve is used for P/x.●

Secant Iuodulus of elast ictt?r for the stress range O toS1 is obtained from the above formula for E, using thevalue of Pl corresponding to SI and obtaining the corre-sponding deflection xl from the load-deflection curve.

Specific flexural strength:

S=

(Specific gravity)2

Specific modulus of elasticity:

E

(Specific gravity)3●

where the specific gravity ie taken as equal numerically tos the density in grams per cubic centimeter.

Statistical terms:

Mean value:

The arithmetic mean of a get of measurements

Standard error of the mean (usually called the ‘tstandarderror” if no other statistic is referred to at thesame time):

[

rla+ r2a + r=e + . . . + ri2+ , . . + rn2S.E. =

n(n-1)

where

ri the difference between the i= measurement and the mean.value

a n the number of measurements

NACA TN NO. 1054

Standard error for the difference of two means:

1 (s*E. l)a2

S.E.D = + (S.E*2)

where

S.E.I standard error for first mean

S.E.2 standard error for second mean

Criterion for significant difference between two means(as for example when comparing the mean of a group oftreated specimens with the mean of a sinilar group ofuntreated specimens):

If the difference of the two means exceeds threetimes S.E.D, the difference is considered signifi-cant .

M?PARATUS AND TEST PROCEDURE

The testing procedures outlined in Federal SpecificationL-P-406a (reference S) were followed as closely cs possible.The specimens, however, were not polished with fine emery p&-per after machining. The flexure specimens of one glass- -filled laminate U2 were cut with a diamond abrasive- sati~

-.——

The impact and flexure specimens of the other glass-filledlaminate A32 were machined with carbide-tipped tools. Spec-imens of all other materials were machined with high-speedsteel tools which gave a finish considered satisfactory.

Specimens tested at 77° F and 50 percent relative humid-ity were conditioned at least 96 hours prior to test. Speci-mens tested at other temperatures were first conditioned thesame as the 77° F specimens and then were kept at the testingtemperature for 24 + 2 hours prior to test.

.Impact Strength

& The impact tests were made according to Method 1071 inFederal Specification L-P-406a, using a Baldwin-Southwark~endulum-type Izod-impact machine which had ranges of 2, 8,

NACA TN No. 1054 ?

and 16 foot-pounds. The specimens were centered and the notchlocated properly with alinement jigs.

The tests were made at temperatures of -700, Oo, 77°, and200°F. The relative humidity was controlled at 50 percent Intesting at 770 F and was not controlled at the othe~ tempera-

—

tures. The tests at Oo and 770 F were made in rooms controlled-..

at these temperatures, For the -700 and 2000 F tests, theimpact machine was housed in an insulated cabinet shown infigure 1. The air in the cabinet was circulated by a fan ex-cept during the impact tests. Dry ice was used to cool theair; heating was done with electric heaters. Tke specimenswere kept in a conditioning cabinet at the test temperaturefor about 20 hours and were then placecl in the testing cabinet2 to 4 hours prior to testing.

In testing conducted in the insulated cabinet the opera-tor kept his hands, which were protected with woolen gloves,inside the cabinet for periods of about 15 minutes at a time.This iS sufficient for testing about 5 to 10 epecimens.

The materials in the l/2-inch thickngss were tested flat-wise and edgewise for both the lengthwise and crosswise orien-tations. Since the Izod-impact machine had a limited capacity(16 ft-lb), the epecimens of the glass-filled laminate testedflatwise were made only 0.25 to 0.30 inch wide. Edgewisetests were made on specimens of the l/8-inch-thick sheets ofthe materials for both lengthwise and crosswise orientations.

Flexural Properties

The flexural tests were made according to Method 1031 ofFederal Specification L-P-406a, using a 2400-pound-capaoityBaldwin-Southwark hydraulic universal testing machine whichhad ranges of 240, ~20Q, and 2400 pounds. This machine waslocated in a room in which the atmosphere was controlled at77° F and 50 percent relative humidity. Tests to obtainflexural strength and load-deflection graphs were made at-700, 770, and 2000 3’. For the low- and high-temperature teststhe specimen, the flexural jig, and the deflection indicatorwere enclosed in a temperature-controlled cabinet equippedwith a blower. The arrangement of the flexur~l apparatus forthe low- and high-temperature tests is shown in figures 2 and3. ln fi~re 2 the insulated cabinet has been removed to showthe pressure piece, flexural jig, and attachments.

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The flexural jig is initially centered and alined relative

NACA TN No. 1054●

8

to the pressure piece in the following way. The alfnement

●plate (L) having parallel V-grooves is used to locate theflexural jig relative to the pressure piece (E’)after thespan has been set appropriately. This is done with the con-tact edge of the pressure piece in the central V-groove in(L) under a light load. The stand is clamped to the magneticchuck and the latter is energized. As the right- and left-hand sections of the calibrated screw (J) have right- andleft-hand threads, respectively, the flexural jig is now self-centering. Subsequent changes in the span mereiy requireloosening the cap screws, setting the screw (J), and tighten-ing the cap screws again. --—

,- _.

The deflection of the specimen at the center of the spanrelative to the supports is indicated by an equal-arm lever(N) actuating a gage shown in figure 3. The gage, aSouthwark-E’eters plastics extensometer, Type PS-6 or p5-7, iSattached to the aluminum alloy brackets (P) which have groovesto locate the knife-edges of the gage. Load-deflection graphsare obtained with this gage coupled to the renorder on the.testing machine. The high-magnification gage, Ftodel F’S-6, hasa range of 0.23 inah and the low-magnification gage, ModelE’S-7,, a range o: 1 inch.

In figure 3 the flexural apparatus is shown with a speci-men in place and the front of the cabinet removed. Triple-paned windows in the front and side, armholes, and lights in-side the cabinet facilitate the manipulation of the specimenand equipment.

Little difficulty was encountered in the high-temperaturetesting with this equipment. At low temperatures, frost onthe electrical contacts of the gage was washed off with eth”ylalcohol. Rusting of the flex~ral jig an& gage upon removalfrom the cabinet was avoided by immersing them in alcohol un-til they attained room temperature. They were then disassem-bled and dried thoroughly and the flex~ra~ jig re-oiled.

The span of the flex~ral jig is adjustable from 1.6 to 9inohes and the screw is graduated to 0.002 inch, Ehe comhina-”tion of recording gage and lever is acaurate to about 5 percent

. in the measurement of deflections over 0.01 inch with the PS-6gage and to about 3 percent for deflections over 0.1 inch withthe PS-7 gage. The percentage error diminishes as the deflec-.tion increases. Calibrations were made only at 77° F.

The flexural properties were determined only for the0.5-inch-thj.ck laminates. Each material was tested four ways,

NACA TN MO. 1054

*flatwise and edgewise for specimens cut both lengthwise andcrosswise. At least five specimens were tested for each

● material for all orientations. The only deviation fromMethod 1031 of Federal Specification L-P-406a was the use Ofa span-depth ratio of 8:1 instead of 16:1 in order to con-serve materials. However, for comparative purposes flexuretests were made also at 77° F with a span-depth ratio of16:1.

RESULTS AND DISCUSSION

Impact Strength

The data for Izod-impact strength of the various lami-nates at temperatures of -70°, Oo, 77°, and 200° F are pre-sented in table II. The variation in impact strength withtemperature is shown graphically in figures 4a and 4b forlengthwise specimens of the 0.5-inch-thick materials testedflatwise. Figures 5 to 8 show the variation of impact.strength of paper, cotton-fabric and rayon-cotton-fabric phe-nolic laminates with temperature for the various orientations

. of specimen and direction of load.

The Izod-impaot strengths at 77 0 F for the phenolic andglass-fabrio laminates tested flatwise are approximatelya.s follows :

Type of Laminate Izod-Impact Strength(ft-lh/in. of note h~

Grade C phenolic, high-pressureand low-pressure 4-7

High-strength-paper phenolic 4

Asbestos-fabric phenolic 2- 4*

Rayon-cotton-fabrio phenolic 17

Glass-fabric unsaturated-polyester 30

The paper and asbestos laminates showed less than 25percent variation in impact strength over the range of temper-ature and orientations of speoimen and loading investigated.

NAC.k TN No, 1054 10

,

The vari.atioa in impact strength was less than 10 percent forthe 0.5-inch-thick paper laminate tested flatwise.

.

The temperature-impact strength trend for high-strengthpaper laminate agrees quite well with Shinnls data (reference7) for flatwise tests where a very slight increase in strengthwith temperature was found for the range -67° to 158° Y. Meyerand Erickson (reference 4) reported that the impact strengthsfor ‘lPapregttat the extremes of temperature were slightly lessthan the normal temperature values, a trend found in this lab-oratory only for the 0.5-inch sheets tested edgewise. Intheir impact tests at 158° and 200° F Meyer and Mrlckson stated(reference 4) that the specimen was I!\ested at room tempera-

ture within 15 to 30 seconds after removal from the condition-ing medium”; this test condition is believed to introduce someuncertainty into the results.

All the cotton-fabric laminates exhibited a steady de-crease in impact strength as the temperature was reduced from77° to -700 y. For materials 12, L2, and V2, the impact

. strength at -700 F was between 55 and 65 percent of the 77° Fvalue for all orientations of specimen and directions of loademployed. The corresponding range for W2 high-pressure

. grade C laminate, was 73 to 77 percent. L~ttle change in im-pact strength at 200° F compared to 77° F was observed for thecotton-fabric laminates with the exception of the 12 mate-rial. The latter laminate showed a steady increase in impactstrength with temperature up to 200° E’. These results are ingood agreement with values reported for grade-C material byShinn (reference 7),who found that in flatwise tests impactstrengths at -67° and 1580 F were 66 and 113 percent, respec-tively, of the value at 77° F.

Directional properties were observed for the parallel-plylaminates, 12 and K2. The asbeetos-fabric material, K2,for which the effect was greatest, exhibited an impactstrength in the crosswise direction less than half of the cor-responding value in the lengthwise direction.

The rayon and glass-fabric laminates had much higherimpact strengths than the other materials and also show dif-ferent impact-strength versus temperature trends (figs. 4a and4b). When tested edgewise, the rayon laminate in both the”

..——

l/8- and l/2-inch thicknesses showed a slight but steady de-crease in impact strength,as the temperature was varied from-70° to 200° F. The glass-fabric laminate, AB2, shows aconstant trend toward higher impact strength at low

NACA TN No. 1054 11

temperatures. This agrees with, data on glass-fabric laminatesgiven by both Yield (reference 2) and filler (reference 6).

The approximate values for the changes in ~zod-~mpactstrength at -70° and 2000 F are as follows:

Change in

Type of laminateTzod-impact strength_700 F 200~ F

(percent) (percent)— ——

Grade C phenolic, low-pressure -40 oto5

Grade C phenolic, high-pressure -25 tO -40 +10 to +35

Asbestos-fabric-phenolic -15 “10

High-strength paper phenolio o to -20 +5 to -20

Ra~~on-fabric phenolic o to +35 o to -lo.

Glass-fabric unsaturated-, polyester +45 -5 to -15

The impact strength for specimens struck edgewise waslower than that of specimens of the same material tested flat-wise. For a given orientation of specimens in the sheet, theratio of edgewise to the flatwise impact strength was verynearly constant for a given material over the range of temper-ature employed. These ratios are given in table III for thedata in table II. The mean value of this ratio was 0.5 to 0.6for the cotton-fabric la~inates, 0,2 for the paper laminate,0.8 for the asbestos-fabric laminate, and about 0.4 for therayon-fabric laminate. The data of Meyer and Erickson (refer-ence 4) for cross-ply high-strength paper laminate give avalue of 0.19 for this ratio at the various test temperatures.

In the tests at 200° l? the materials may have lost somemoisture as compared to those tested at the ~OWC~ temperaturesand may have undergone further cure as a result of the heating,TO obtain information relatfve to these effects, Izod-im:act.specimens were tested at 770 F after being ,he~ted at 200 Ffor 24 hours and cooled to room temperature for 1 to 2 hours

, over calcium chloride in a desiccator. The results of thesetests are shown in table IV. The low-pressure cotton-fabricmaterials , L2 and V2, were about 10 percent weaker and theglass-fabric laminate about 10 percent stronger after the 200°F

UACA TN No. 1054 12

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heating. A decrease of 10 percent was noted for the rayonlaminate, but this was not significant according t? th.g_sta- .... .tistical criterion. (See section on definitions. ) NO defi-nite effect of the heating on the strength of the othermaterials was noted.

Flexural Properties

The results of the flexural tests of the laminates attemperatures of -70° to 200° F are shown in table V for an8:1 span-depth ratio. Values reported include flexuralstrength, specific flexural strength, initial and secantmoduli of elasticity, and specific modulus of elasticity. Thepercentage changes in strength of the materials from the 77°Fvalues under exposure to the high and low temperatures arealso shown in table V. The variations with temperature of

flexural strength, specific flexural strength, initial flex-ural modulus of elasticity, and specific initial flexuralmodulus of elasticity of the materials are shown in figures “9,10, 11, and 12, respectively, for the lengthwise-flatwise ___tests.

A typical load-deflection curve obtained at -70° F withthe recorder is shown in figure 13. Average curves of extremefiber stress versus deflection at midspan are shown in figure14 for the different materials at 77° F. Similar stress-deflection curves are shown in figures 15 through 23 for thenine laminates at -700, 770, and 2000 F. Figures 24 and 25represent the average strese-deflection curves for the fourdirections of testing at 77° F of the asbestos-fabric laminateand the glass-fabric laminate, U2, respectively. Averagestress-deflection curves for specimens taken lengthwise,crosswise, and on the diagonal from the rayon laminate, 22,and the glass laminate, AB2, are shown in figures 26 and 27,respectively, The experimental stress-deflection data wereadjusted for the thickness of the material by multiplying themess-ured deflection at midspan by the ratio of standard thick-ness to the actual thickness; the curves shown in figures 14through 27 were calculated for a standard thickness of 0.50inch.

—

—

.

NACA TN No. 1054 13

‘The flatwise flexural properties of some of the laminatesat 77° F were approximately as follows :

InitialFlexural

Type of laminateflexural

“streng:th modulus ofelasticity

(lo” psi) (lOs psi)

Grade C phenolio,low-pressure 16 0.80

Grade C phenolic,high-pressure 18 to 22 1.0 to 1.1

Asbestos-fabric phenolic 9(C) and 16(L) 1.O(C) and 1.2(L)

High-strength-paper phenolic 33 2.4

Rayon-cotton-fabric phenollc 34 1.6

Glass-fabric unsaturated-polyester 45(C) and 55(L) 2.5 to 2.9

(c) - Crosswise (L) - Lengthwise

The four cotton-fabric phenolic laminates, 12, L2, V2,and W2, exhibit quite similar properties. For a given ma-terial the properties were generally equal to within 15 per-cent for the various orientations of specimen and load. Theflexural strength of these cotton-fabric laminates increasedabout 10 to 30 percent at -700 F and decreased very nearlY30 percent at 200° F, compared to the 77° F va~ues. Correeeponding changes for the initial modulus of elasticity were

-.

increases of 40 to 80 percent at -70°F and moderate decreasesup to about 25 percent at 200° T. The variations of secantmodulus values with temperature are greater than for the ini-tial modulus of elasticity.

These results are in fair agreement with data for gradeC phenolic laminate given by Oberg, Schwartz, and Shinn (ref-erence 2). They observed increases in flexural strength andflexural modulus of elasticity of about 17 percent at -38° H’oompared to values at 78° F and 40 percent relative humidity.

The asbestos-fabric laminate, K2, of parallel-ply con-struction showed directional effects, especially in regard to

NACA TN No. 1054 14

.

,

.

the flexural strength. (See table V. ) The variation of thestrength properties of this material with temperature was””lessthan that of the cotton-fabric .laminates and the trend is dif-ferent. Most of the change in flexural properties of theasbestos-fabric laminate occurred between ’77° and -70° I’; theflexural strength and initial modulus of elasticity increased ‘roughly 20 and 35 percent, respectively, at -70° F. The aver-age change in flexural properties at 2000 F was not over 5percent. The stress-deflection curves for this material (fig.16:)indicate the similarity between the properties at 77° and200° F.

.The flexural strength and initial flexural modulus of

elasticity of the paper phenolic. laminate, S2, varied withtemperature in a manner similar to the values for the co-tton-fabric laminates except that the initial modulus of elasticityincreased only 20 percent between 77° and -700 F.

.

Meyer and Xrickson (reference 4) reported that the flex-ural strength and flexural modulus of elasticity for high-strength-paper phenolic laminate decreased at elevated tern- “-peratures and increased at subnormal temperatures. The mag-nitudes of the changes which they recorded agree fairly wellwith the data given in this report. Their material was CIUit@’similar to that ‘tested at this laboratory, being,made with thesame resin under approximately the same molding conditions andwith a similar type of paper. In tests at the”~av&l””A~ ‘----”’‘-Experimental Station (reference 5) on a phenolic mater-i-al lam-inated with a spruce sulfite paper, probably of the high-strength type, it was noted that the flexural strength andflexural modulus of elasticity at 160° F were about a thirdless than at 77° E’. From a comparison 0~ the data obtainedby various investigators it is concluded that, while theflexure-property temperature trend iS definite, the magnitudesof the changes must be determined on each sample.

The two glass-fabric laminates, U2 and A32, showedthe came trend in c~ange of flexural strength and mo&ulus ofelasticity with temperature (figs. 9 and 11). The flexural ““” -strength increased about one-third at -70° 1? and decreasedabout one-third at 200° F. The flexural strengths of the twomaterials did not differ significantly. The AB2 laminatewas superior to the U2 material in flexural modulus of elas-” ““ -ticitr, having greater values ~t all temperatures and for alldirections of testing. The percentage decrease in modulus ofelasticity at 200° F was less for the AB 2 than for the U2-- , ._laminate.

NACA TN No. 1054 15

For both glass-fabric laminates the stress-deflection di-agrams were less curved than for any other materials tested.In the lengthwise and crosswise directions the secant modulusof elasticity for the range O to 25,000 psi showed a decreaseof less than 10 percent from the initial modulus of elasticityat all the temperatures.

The approximate values for the changes in flexuralstrength and flexural modulus of elasticity at -70° and 200° Ffor the lengthwise and crosswise directions of the laminatesinvestigated may be summarized as follows:

change inchange in

flexural strengthinitial flexural

uodulr- “Type of laminate

Ua of elasticity-7(30 ~ 200° F -700 F 2000 F

(percent) (percent) (percent) (percent)—

Grade C phenolic 10 to 30 -30 40 to 80 -8 to -25

As5estos-fabricphenolic 20 -5 35 0

High-strength-paperphenolic 25 -40 20 -18

Rayon-cotton-fabricphenolic 30 -25 40 -30

Glass-fabric unsat-urated-polyester 30 -30 to -35 lG to 15 15 to -25

Four of the nine materials tested, the two glass-fabriclaminates , the asbestos-fabric laminate, and the grade C lam-inate, 12, were of parallel-ply construction. The mostpronounced difference in strength properties between specinenstaken from the principal directions of the sheet was observedin the asbestos-fabric laminate, K2. Its crosswise impactand flexural strengths were only half of those for the length-wise direction. The lengthwise flexural properties of the two

. glass-fabric laminates differ less than 15 percent from thecorresponding crosswise flexural properties. The differencesbetween the flexural properties for the l~ngthwise and cro6s-.wise directions for the grade C parallel-ply laiuinate, 12,were smalZ and were of the same order of magnitude as the cor-responding difference for the three cross-ply cotton-fabriclaminates. The flexural -properties of the AB2 glass-fabric—” ““

NACA. TN No. 1054 16

.

and of the rayon-fa-oric laminate are greatly reduced for the45° direction. ‘I!heflexural strength and initial flexural.modulus of elasticity values for the 45* direction for theglass-fabric laminate are two-thirds and for the rayon-fabriclaminate are one-half of the average values for the two prin-cipal directions.

When the density is considered in evaluating the flexuralproperties of the materials, the cellulose-filled laminates,with lower densities than the mineral-filled laminates, com-pare more favorably with the latter materials and are superiorin some instances. This may be seen by com~aring figures 9and 10 or 11 and 12. The specific flexural strength valuesare in the ratios of 18:17:16 for the rayon-fabric, paper, andglass-fabric laminates, respectively. The specific initialflerural modulus of elasticity values are in the ratios of9:6:5 for the paper, rayon-fabric, and glass-fabric laminates.These graphs also show that there is no difference in specificstrength properties between the low-pressure and high-pressurelaminates, V2 and W2, made with the same grade C fabric.

.

Flexural tests were also made at 77° F on specimensheated at 200° F for 24 hours to determine whether changes in

. the strength properties occurred in the 200° F tests, Suchchanges may be brought about by (a) additional cure of theresin, (b) loss of moisture, (c) deterioration of the fillerif organic, or (d) a combination of these factors. The re-sults of these tests and of tests on unheated specimens areshown in table VI. The flexural strength values showed anaverage decrease of about 8 to 13 percent for the cotton-fabricand paper laminates. The changes in the flexural moduli ofelasticity were small and not consistent except for the 10w-pressure material, 112, which exhibited increases of 10 per-cent after heating. The glass-fabric laminate, U2, exhibitedaverage increases of 11 and 4 percent, respectively, in flex-ural strength and moduli of elasticity on heating. Theasbestos-fabric la~tnate, K2, also exhibited higher flexuralproperties after heating, the increases in flexural strengthand moduli of elasticity bsing about ‘7and 12 percent, respec-tively.

It seems reasonable that the strength and modulus Ofelasticity values of these organic plastios should diminishwith increase in temperature if no change in composition or

. structure ta’kes place, If heating a laminate at 200° F for.—.._

24 hours causes an increase in the strength properties due toa change in composition or structure, then in the flexuraltests at 200° F (table V) the effects of prolonged heating and

.

--

NhCA TN No. 1054 ..17

of an elevated test temperature may oppose one another. Thismay explain the very small differences between the flexureproperties at 77° and 200° F (table V) for the asbestos-fabriclaminate which had increased flexura”l properties at 77° Y aft-er heating (table VI). The effect of prolonged heating onthe flexural strength of laminates was investigated byHausmann, Parkinson, and Matns (reference 9). They found thatthe flexural strength of grades C, X, and XXX phenolic lami-nates at 90° C increased with the length of time the specim’e,nswere at the test temperature. (See table I, reference 9.)For the grade XXX laminate the flexural strength values at90° C after a month of heating were nearly equal to the 25° Cvalues on unheated specimens.

Plexural strength tests were made on’ six laminates at150° F and 90 percent relative humidity after 24 hours condi-tioning at the “test temperature, combining the effects ofelevated temperature, and high relative humidity. The resultsof these tests are given in table VIII together ti”i%hcorre- “--spending data from table V for the 77° and 200° F tests.

.

The deleterious effect of these extreme conditions wasmost pronounced for the paper laminate, S2, and the low-pressure grade C laminate, V2.. The other four materials werenot so greatly affected by these conditions as they were by 24hours at 200° F and a low relative humidity. The effect ofmoisture content on the strength properties of high-strength-paper laminate was studied by Erickson and Mackin (referencelo). They tested specimens from. a series of panels condi-tioned 100 days at 80° F at various relative htimidities. Theyfound decreases in ultimate strength in tension, compression,and fle’xure of 25 percent or more and decreases of about 35percent in modulus of elasticity as the relative humidity wasvaried from 30 percent to 97 percent, corresponding to mois-ture contents ranging from 0.2 to 9.5 percent.

———

The above results and the results obtained in this labora-tory indicate the necessity for studying the effect of relativehumidity as well as temperature on the strength properties of .-laminates , especially those with cellulosic fillers.

The results of tests made at 770 F using span-depth ra-. ttos of 16tl and-8:1 are given in table VII, The flexural

strength obtained with a 16:1 span-&eptb ratio was slightlyless for all uatdrials, the decreases rangihg fro-m about 2

.percent for the glass-fabric laminate, U2, to about 7 percentfor the cotton-fahrio phenolic laminates. The initial “flexuralmodulus of elasticity values were usually a little greater for

?

/..-

NACA TN No. 1054 18

the tests with the larger span-depth ratio. The 12 material,a high-pressure phenolic grade C laminate, showed significantchanges in both flexural strength and initial modulus of elas-ticity with the change in span-depth ratio. Significantchanges in only one of the two properties occurred for therest of the materials listed in table VII.

CONCLUSIONS

1. The Izod-impact strength-temperature trend of thelaminated plastics is different for the various types of mate-rial. The glass-fabric laminates decreased steadily in impactstrength with increasing temperature, the value at 200° F be-ing about 70 percent of the -70° value. The asbestos-fabric,rayon-fabric, and high=strength-paper phenolics showed littlevariation $n impact strength between -700 and 200° F. Thecotton-fabric phenolics exhibited increasing impact strengthwith temperature, roughly doubling their impact strength be-tween -700 and 200° F.

2. The Izod-impact strength values for the rayon-fabricand the glass-fabria laminates are much greater than for theother materials.

3. The ratio of edgewise to flatwise impact strength forthe l/2-inch-thick phenolic laminates tested is nearly con-stant over the range of temperatures, -70° to 200° F.

4. An increase in flexural properties occurred for allmaterials at low temperature, and at high temperature a de-crease occurred for all materials except the asbestos-fabriclaminate, which showed no change.

5. The high-strength-paper and two glass-fabric laminateBare outstanding in flexural properties. When the materialeare compared on the basis of specific st,rength values, th-epaper and rayon-fabric laminates are superior to the others.

6. The low-pressure grade-C phenolic laminate, V2, com-pared favorably in flexural strength properties w$th the high--pressure laminate made with the same filler, especially whenthe comparison was made in terms of specific strength proper-ties.

7. The flexural properties of plastic laminates at hightemperature are not a function of temperature alone, but may

NACA TN No. 1054 19

be affected by further cure of the resin and loss of moisturecontent.

8. The effect of high humidity in addition to an elevatedtemperature may be much different from the effect of the ele-vated temperature alone. A severe loss in strength was notedfor the high-strength-paper and one low-pressure cotton-fabricphenolic laminate at 150° F and 90 percent relative humidity.

National Bureau of Standards,Washington, D. C,, December 29, 1945.

N~CA TN NO. 1054 20

REFERENCES

1. Field, Philip M.: Basic Physical Properties of Laminates.Modern Plastics, vol. 20, Aug. 1943, pp. 91-102, 126,128, 130.

2. Oberg, T. T., Schwartz, R. T., and Shinn, Donald A. : Me-chanical Properties of Plastic Materials at Normal andSubnormal Temperatures. Air Corps Tech. Rep. No, 4648,June 6, 1941; Modern Plastics, vol. 20, April 1943, pp.87-100, 122, 124, 126, 128.

3. Norelli, F.,and Gard, W. H.: Temperature Effect onStrength of Laminates. Ind. Eng. Chem. , vol. 37, June1945, pp. 580-585.

4. Xeyer, H. R., and Erickson, B. c. O. : Factors Affectingthe Strength of Papreg. Some Strength Properties atElevated and Subnormal Temperatures. Rep. NO. 1521,

Forest Products Laboratory, U. S. Dept. of Agriculture,Madison, Wis., Jan. 1945.

5. Renwick, Wm. C.: Properties of Plastic Laminates, Part VI.Naval Air Exp. Sta. Rep. TED NAM 25217.0, June 3, 1944.

6. Fuller, Forke$t B. : Engineering Properties of Plastics.Modern Plastics, vol. 20, June 1943, pp. 95-97, 130.

7. Shinn, D. A.: Impact Data for Plastic Materials at VariousTemperatures . Air Corps Tech;Rep. Iio. 5C12,Aug. 9, 1943; Modern Plastics, vol. 22, July 1945, pp.145-152, 184-186.

8. Federal Specification L-P-406a: Plastics, Organic; GeneralSpecifications, Test Methods; Jan. 24, 1944. GovernmentPrinting Office, Washington 25, D. C.

9. Hausmann, E. O., Parkinson, A. E., and Mains, G, H. : HeatResistance of Laminated Plastics. Modern Plastics, vol.22, Nov. 1944, pp. 151-154, 190, 192, 194, 196, 198.

.

10. Erickson, E. C. O., and Mackin, G. E,: Properties andDevelopment of ?apreg - A High-Strength Laminated I’aperPlastic. Trans . A.S.M.E. , vol. 67, May 1945, pp. 267-277.

. .

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Table III.- Ratio of Edgewise Impaat Strength to FlatWiseImpact Strength fr L~minated Plastics at

Various Temperatures.

Orientation Ratio at Test Temperature of

Uatierial DesignationMean Ratio

of Specimen -70° F 0° F 77° F 200° F All Tem~.

12, Grade C Phenolic kngthF!iBe 0.62 0. $z

0.53 ;.g 0.59Crocewi~e 0.60 0. 1 0.58! .

K2, Asbestos-Fabrio Phenolic Lengthwise 0.77 0.80 o.t14 0.62 O.goCrosswise o.g2 0.73 0.60 O.gb

IL?, Lcw-Pressure Lengtdiviee 0.57 ‘“ 0.56 0.54 0.54 0.55

Cot’ton-Fabric Phenolic CrosswiEe 0,56 O.bg 0.52 0.55

S2, High-S&en@h-Paper Lengthwise 0.17 0.17 0.20 0.16 O.lg

Phenoll.coT08eWi813 0.17 O.lg 0.21 0.15

V2, Low-Pre8sure Lengthwise 0.46 0.50 0.50 0.’51

Grade C Phenolic 0rosswi6e 0.51 0.53 0,56

W2, High-Pressure Lengthwise 0.51 0.47 ;.;: 0.52Orosswise

0.55

Grade C Phenolic0.63 0.57 . 0.60

Lengthwise ().F3 ::;~ ::g ;:;: 0.3922, Rayon-Cotton-Fabric CroOBwise

Phenclic0.$1

Lengthwise 0.32!IB2, Glass-Fabric CroBswise 0.32

Unsaturated-Polyester

I

.

Material DesW.n tlon

12,

X2,

u?,

S2,

w!,

W2,

22,

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Range ofUaohine

LzHL

Wade c Phenolio

Aebecitos-FabricPhenolic

Low-PreseureCotton-FabrioPhanollo

=ll#~~en@-Paper

bw-Pressure(tradeC Phenoltc

El@@reEsureMade C Phenolio

~n.cottotiabrlo-.Phenozlo

AB2, Glaa*Fabrlcu~aturated-Polyester

Orient atIonof Speo imen

Len@hwieeOrosmiae

LengthwiseCmsswine

klgthwieaOrostmiee

Lengthwi~eOroeewiee

Lengthwise(!rosswide

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Lengthwise

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?latviee?latwiee

?latwiee

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Flaiwise

No Heat”ing”;ft-ib/in. of netoh)

~.: :0.14-0.05

3.&142 0.031.60t 0.05

3.22 t 0.083.09 2 0.01

4.iEi”2 O.1o4.17 20.14

6.5 ? o.lki6.2 :0.18

5.27i 0.37

17.6 t 0.617.4 20.7

31.5 :0.6

6i4

g?4

i!8

.5’s

gLI

6

1616

16

!r@h-

Heated at 20+30Fdft-lb/in. of notoh)

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s.c!6: 0.061.48 : 0.03

2.!36: 0.04’2.ql2 0.02

4.02 ! 0.i13 y4.29 t 0.20

5.95~ o.~5.55~ o.~

4.93 ? 0.12

16.0 2 0.4lp.g : 1.0

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a.

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d.

The teetB ware made in aooordanoe with Method 1071, Federal Speoifioetian -kP-W)6n.Meen value for nine to twelve apeoimene for all materials except gl.aae-fabriolaminate AB2, for whioh 20 to 25 epeoimens were tested. The aocompau’1.ngplu6 or minue mlue is the standard er or.Specimen6 conditioned and tested at $F ml SC@ relative humidity.

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45.1 t 0.742.6:0.5

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2.55 :0.012.52t 0.03

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an g:l span-dapth ratio. Emb TSIIM in the tnble rapretenta the man for five machoenn.

Datn f mu table ti ; qaoirnanc oonditionod nnd teatod’ at fi and 50% relntiva @idi ty.

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B, Lw——!lrad4 o momllo

W,. 2g0J.-0M-2wlo

,

9.0 * 0.1

16.5 z O.e

1 .320.1?1 .0 : 0.s

1 .e t 0.221 .8 : 0.,1

52.1 :0.5

57.9 :0.8

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‘1

-

!

I

NACA TN NO. 1054 30

.

.

TABLE VIII.- FLEXtTIUilLSTRENGTH OF LA311NAT S AT VARIOUSdTEMPERATURES AND RELATIV33 IIU161DITI .

I

12,

S2,

V2 ,

W2,

Z2 ,

Grade C Phenolic

=gh-Strength-PaperPhenoliO

Low-PressureGrade C Phenolio

High-PressureGrade C Phenolio

Rayon-Cotton-FabricPhenolio

22.2’2 0.3

33.2 t 0.4

34*4 : 0.5

AB2, Glass-Fabric 53.2 t 0.1Unsaturated-Polyester

FlexUral StrMO°F90~ R.H.=

(1031b/in2)

19.8 t 0.2

13.2 2 0.6

7.0 $ 0.1

15.4 ~ 0.3

26.0 ~ 0.3

34,7 ~ 0.4

a. Lengthwise specimens tested flatwise..

b.

co

d.

uth200% .

e 6X R.H.C(1031b/in2)

14.5 2 O*1

19.4 2 0,2

11.4 : 0.2

13.3 ~ 0.2

25.8 2 0,5

33.8 ~ O*8

Tests were m&de in accordance with Method1031, Federal Speciflcati,onL-P-406a,using an S:1 span-depth ratio~ Each valuein the table represents the mean for fivespecimens●

Data from table V; specimens conditionedand tested at 77°F and 50j%relativehumidity.

Specimens tested at 15001? and 9@ relativehumidity after”24 hours at the testconditions.

Data from table V; specimens tested at2000F and less than 6% relativehumidity after 24 hours at the testconditions.

NACA

.

.

.

.

.

.

.

TN No. 1054 Fig. ””1 “-““‘ ““--”””,.l..= .

— .-. ——---—— x-n—. —s =.= ..= -. ....= . .

-. .. .. .. . a .,=...—. . .. . ...: . .

s

r---- .-. -.-,

-

‘<..=-. .: -:- -

. -.. ,- .~.i-- .—.- --.

Figure l;- Izod impact maohine in insulatedwith front panel removed.

oabinet# —

..-.

.

.

..

,.

NACA TN NO. 1054 Fii?.2-.

i

—

—

,

.... ..... ..

,..,.;_- ;--:,..-,-,-~— !.

y_

~+

*+

G mm!P

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,. ”.,

-

... -_ . . . -.

‘ /“-?’: ~

Figure 2.- Adjustable-span flexural jig used for high-and low-temperature testing.

..

i.

,,.,

Figure 3,- FlexUral apparatusln insulated cabinet with front panel removed;a mecimen ie in Dlace.

q,

CK.cd

NACA

40

30

20

10

0

TN NO. 1054 Fig. 4a

TYPE OF LAMINATEI GRAOE C PHENOLIC

K ASSESTOS-FABRIC PHENOLICL LOW-PRESSURE COTTON-FABRIC PHENOLICs HIGH-STRENGTH-PAPER PHENOLICv LOW-PRESSURE GRADE C PHENOLICw HIGH-PRESSURE GRADE C PHENOLIC

RAYON-COTTON-FMRIC PHENOLIC2 GLASS-FABRIC UNSATURATED-POLYESTER

*

.

~

I I I-. ---70 u 77 zOO

TEMPERATURE. 0 F

Fi@re 4a.- Variation of lzod impact strength withtemperature for l/2-inch-thick laminates.

.

Lengthwise specimens tested flatwise.

,. . . .. .. -.. —._ .. ..__

NACA

2!

?iI

t

6

a

4

3<

a

i,

TN-No. 1054 Fig. 4b

v

V&

L

.—

tTYPE OF LAMINATE

I GRADEC PHENOLICK ASSESTOS-Fq PHENOLICL W-PRESSURE COTTON-F=IC PHENOUCs HIGH-STRENGTH-- PRENOLIC

——

v KMN-~SURE GJ?AUZ C PHENOLICW HIGH-PRESWRE GRM C PHENOLIC

I I I I-A . . . . . .

-Iv w 6 vu

TEMPERATURE. 0 F

Figure 4b.- V6mlation of Izod”irnpti–t–streng~” “~ithtemperature for l/2-inch-thick laminates.

Lengthwise speoimens tested flatwise.

.

w

S2CF’x——.—~0

S2LF

w

MO %.

M+LE-----0.70*

TSICE——. —*——.—: .—— ——— ——— .— _

0.%0x

SILE

~1 = SH~ l/8.INCH T~OK

S2 = BEEET l/2-llUIH THICKLF = LIWGTH%ISE SPEOIMENS TESTED FLATWISELE = LENGTHWISE SPEOIMENS TESTED EIKUKISE:: = OROSSWISE SPECIMENS TESTED FLATWISE

= OROSSWISE SPECIMENS TESTED EDGEWISE

I I I.fi . v. .-

-#u u

TEMPERATURE, i

CuJ

Figure 5.- Variation of Izod impact atrength with temperature forhigh-strength-paper phenolio laminate.

I

I

ol

I

.

NACA TN No. 1054 Fig. 6.

.

.

7

e

5

.

—— ---- .—. ..+ _— ..-= — -. . .._

T#/-..

F“

V1 = SHEET l/8-INCH THIOK~: = SHEET l/2-INOH THICK

= LENGTHWISE SPECIMENS TESTED FLATWISE‘LE= LENGTHWISE SPEOIMENS TESTED EDGEWISE

OF = CROSSWISE SPEOIMENS TESTED FLATWISEOE = CROSSWISE SPECIMENS TESTED EDGEWISE

I I I. 7n n 77 *M,“ ,, .-

TEMPERATURE, OF

Figure 6.- Variation of Izod impaot strength withtemperature for low-pressure grade C cotton-

fabric phenolio laminate. Mean value * st=dard erroris indicated by $ or ~. .

—.——

. —

.

.

NACA TN No. 1054 Fig. 7

●

●

3.0

- W2CE~——- W2LE

w.

SHEET l/8-INOH THICKSHEET l/2-INCH THICKLENGTHWISE SPEOIMENS TESTED FLATWISELENGTHWISE SPECIMENS TESTED EDGEWISECROSSWISE SPECIMENS TESTED FLATWISECROSSWISE SPECIMENS TESTED EDGEWISE

TEMPERATURE, ‘F

.

Figure i’.-Variation of Izotiimpact strength withtemperature for high-pressure grade C cotton-

fabric phenolic laminate. Mean value * standard erroris indicated by $ or ~. .—

... ._____

I

‘

.

l?ACATN NO. 1054

.

15.0

10.0

5.0

0

Fig. 8

-ee.x--

. . .

,-----

Z2LFLECFCE

SHEET V2- INCH THICKLENGTHWISE SPECIMENS TESTED FLATWISELENGTHWISE SPECIMENS TESTED EDGEWISECROSSWISE SPECIMENS TESTED FLATWISECROSSWISE SPECIMENS TESTED EDGEWISE

1

-70 0 77 ““-“-2

TEMPERATURE, ‘F

Figure 8.- Variation of Izod impact strength with -temperature for rayon-cotton-fabric

p~enolic lainate<

NACA TN NO. 1054 Fig. 9 -

,

●

.

.

..

.

~?:!::::.~LOW-PRESSURE COTTON-FABRIC PHENOLIC

GLASS-FABRIC UNSATURATED-POLYESTERLOW-PRESSURE GRADE C PHENOLICHIGH-PRESSURE GRADE C PHENOLIC I

RAYON-COTTON-FABRIC PHENOLIC

GLASS-FmRIC UNSA~RATED- POLYESTER

s

w

K

10

0 -70 77 200

TEMPERATURE, ‘F

Figure 9.- Variation of flexural strength with temperaturefor l/2-inch thick laminates. Lengthwise

specimens tested-flatwise. Span-depth ratio 8:1.

. . , .

TYPE OF LAtvllNA~ ‘

1 GRAOE C PHEMOLtC

K A~FASfUCFtl~lX “

L~ cOTTON-EMRIC PHEN3LIC

S HIGH-STREWTH- PAPER PHEMLIC

i

U GLASS-FABRK lNSATURATEO-~YESTER—

—

—

—

V LOW—~ EJiAOE C PHENCLIC

W HIGH-PRESSURE GRAOE C PHEMNJC

Z RAWM-COTTCN-FABRIC PHEMOLIC

Ml GMSS-~ lNSMIJRA~

1

i

q,

Is.,(-2r i i

—

—o

-700F 770F. 200°FLgure 10.- Comparison of specific flexural stren~h of l/2-inch-thiok

ldnatee at three temperatures. Len@’hwise specimens ~tested flatwise. Span-depth ratio 8<1.

,,I

NACA TN No. 1054

-.— -.

Fig. 11 .

.

.

.

.

3.00

2.50

2.00

l.so

1000

IK

suv

r’

w

z

TYPE OF LAMINATEGRADE C PHENOLICASBESTOS-F~RIC PHENOLICLOW-PRESSURE COTTON-F~RIC PHENOLICHIGH-STRENGTH-PAPER PHENOLICGLASS-FMRIC UNSA~RATED-POIYESTERLOW-PRESSURE GRADE C PHENOLICHIGH-PRESSURE GRADE C PHENOUCRAYON- COTTON-FASRIC PHENOLIC

I AB GL’ASS- F=RIC UNSA~RATED-POCfESTER

V

vI

.50

I

0 -70 77 200

TEMPERATURE, 0 F

Figure 11.- Variation of initial flexural modulus ofelasticity with temperature for l/2-inch- “

thick laainates. Lengthwise specimens tested flatwise.Span-depth ratio 8:1.

—

. . I

TYPE OF LAMINA~

I

K

L

s

u

v

w

G

GRAOE C PHENOLIC

~OS-FA8RiC PNENOIJC

~RE COTIUN-FABRIC PNENIXK

HIGN-STRENGTH-PMER PHENOLJC

G&FMIC UWATURATEO- ~ER

LtW-P~SSURE GRAOE c wmalc

14GH ‘PRESSURE GRAM C PM340LIC

RAYON-COTTON-FM.RkZ PNENOLIC

GMss-mmc uwmJRATEo-PoLYEsTER

●

>iii

—

.

—

—i i

—i

—

—

—

—

vij

8

Vw

770)? 200°F

Figure” 12.-”Comparison of specific flexural modulus of elasticity ofl/2-inc&tnl.ck laminates at three temperatures. Len@hwlee

-7(M’

specmenE tee~ed flatmi~e. Span-deptn ratio 8:1.’

, . . .I

9-21-449a4ca lbFlexureU2-7CJV.05 Ln.jmin701760

24@l lbIII38J.J.Lamb

Deflection

pi~e 13. - ‘lypioel flexural loaUAefleotion curveB at -700F obtalnecl with automaticstress-strain reoorde,r. OroBewise specimens of .rjlam-fabrio laminate, U2,

te~ted flatwise. Spe.n-depth ratio 8:1.

,.,,,

I ::

NACA TN NO. 1054 Fig. 14

TYPE OF LAMINATE

w

5k W

I GRADE C PHENOLICK ASSESTOS-~lC PFIENOLICL W-PRESSURE COTTON-FASRIC PHENOLICs HIGH-STRENGTH-PAPER PHENOLICu GLASS-FASRIC UNSATURATED-POL~ERv N-PRESSURE GRADE C PHENOLICw HIGH-PRESSURE GRADE C PHENO\lCz RMON-COTTON-MBRIC PHENOLIC

As GLASS-F~lC UNSATURATED-PWESTER

I u I IAB

/ /

o .0s .10 ● .20 .25

tXFLEC170N AT MID-SPAN, IN.

Figure 14.- Flexural stz!ess-deflectioncurves for l/2-tnch-thick laminates at 770F. Len@htise

specimens tested flatwise. Span-depth ratio 8;1.●

NACA TN No. 1054 Fig. 15

.

.

.

.2s

4

.

*

Is

la

5

0

/

7

INITIAL MODULUS OF ELASTICITY

1,600,000 PSI770F: 1,080,000 PSI

2000F: 860,000 PSI

Ae- .--.Vau .Iw .150 .200

DEFLECTION AT MID-SPAN> IN.

Figure 15.- Flexural stress-deflection curves for gradeC cotton-fabric phenolic laminate, 12.

Lengthwise specimens tested flatwise. Span-depth rati~ 8:1.

NACA TN MO. 1054 Fig; “16

●

.

.

20

1(

o .025 .050 .075 JOO

. DEFLECTION AT MID-SPAN, IN.

.

.

770E

./

●

INITIAL MODULUS OF ELASTICITY

-7(30~: 1,640,000 PSI770F: 1,200,000 PSI

200°F: 1,220,000 PSI

Figure lti.-Flexural stress-deflection curves for gradeAA asbestos-fabric phenolic laminate, K2.

Lengthwise specimens tested flatwise. $pan-deptk ratio 8:1,

.

.

. .

●2O

15

F

Ic }

5

,.

0JMo

/ I INITIAL MODULUS OF ELASTICITY

7-;’:’~ ,1,370,000 PSI”

800,000 PSI -20WF: 750,000 PSI

Joo ,200 .

DEFLECTKN AT Ml D-WAN, IN.

. .I

I

.250

I

Figure 17.- Flexural stressdeflection ourves for low-pressure cotton-1 fabric phenolic laminate, L2. Lengthwisespeclznenstested

Ifla~wise.Span-depthratio 8:1.

P-a

NACA TN

b

.,

No. 10!54 Fig. 18

/’40 - I , -7cfF

/ 77*E

30 - /

20

.

.

[0

I1?ITIALMODULUS OF ELASTICITY

2,890,000 PSI _770F: 2,420,000 PSI

2000F: 1,950,000 PSI

o -025 .050 .075 .100

DEFLECTION AT MID-SPAN, IN.

.—

Figure 113.-Flexural stress-deflection curves for high-strength-paper phenolic laminate, S2.

Lengthwise specimens tested flatwise. Span-clepthratio 8:1.a. ,●

NAOA TN No. 1054 Fi~, 1S

70

60

50

40

30

20

10 -

0

INITIAL MODULUS OF ELASTICITY

-700~: 2,870,000 PSI770FZ 2,590,000 PSI -200°F: 1,890,000 PSI

.0!50 JOO .150 .200

DEFLECTION AT MID-SPAN, IN.

Figure 19.- Flexural stress-deflection cwrves for glas8-fabric laminate bonded with unsaturated

polyester resin, U2. Lengthwise specimens tested flatwiseSpan-depth ratio 8:1.

.-.

. . I

I

2a

Is

Ic

5

. .0

n%

.—

/ 2WE

/ ///. // ~

INITIALMODULUSOF ELASTICITY

-;$;: 1,220,000PSI820,000PSI

aooOF ; 710,000 P81

—

1 I

J350 Jm J50 200 250 3(

WFLKTMMJ AT Ml D-SW, IN.

Figure 20.- Flexuial stress-deflection curvee for low-pressure gralie Ocotton-fabric phenolic laminate, V2. Lengthwise specimens

teate~ flatwise. Span-depthratio 8:1. t

1.

NACA TN NO. 1054 Fig. 21 “

A

,

20

15

10

5

0

/ // 4-70 “E

77°K

INITIAL MODULUS OF ELASTICITY,

1,310,000 PSI770F: 960,000 PSI

2000F: 800,000 PSI

-—- ---.050. dm .150 200

DEFLECTION AT MID-SPAN, IN. - ‘“

Figure 21.- FlexureJ.stress-deflection ourves for high--pressuregrade C cotton-fabric phenolic

laminate, _W2.Lengthwise specimen tested flatwise, 8pan-depth ratio 8:1.

.

.. . .. .. .. . . .

NACA TN No. 1054 Fig. 22

(u.

z

s-1

40

35

30 9

2s

20

El

10INITIAL FLEXURAL FLEXURAL

/ MODULUS OF ELASTICITY STRENGTH DEFLECTION

WIN? WINS IN.

-70. F a, 340,000 43,700 0.165

77*F I,*o*” ““34,400 0.25

200” F 1,100,000 25,800 0.23

I Io .02 .04 .06 .02 JO .12 A4

DEFLECTION AT MID-SR4N , IN. .

Figure ”22.- Flexural stress-deflection curves for rayon-cotton-fabric p’henolic laminate, Z2.

Lengthwise specimens tested flatwise at three temperatures.Span-depth ratio 8:1.

-.. ,-. ,,

I?ACIATN No. 1054 Fig. 23.- —

b

. .

70

m

50

7

1

INITIAL FLE%uRAL FLEXURk 1

MODULUS OF ELASTICITY ST=NGTH DEl

z--l WIN? WIN?

=TION

IN. -

DEFLECTION AT MlD-SFAN, IN.

Figure 23.- Flexural stress-deflection curves for glass-fabric laminate, AB2. Lengthwise specimens

tested flatwise. Spaa-depth ratio 8:1.

-, I

LF . L~QT~IsE

SPEOIMEUSTESTEDFLATWISE

LE = L~GT~ISE

SPEOIMENSTESTEDEDGEWISE

OF = CROSSWISESPECIMENSTESTEDF’LATWISE

(jE= ~RoS~IgE

SPEOIMEWTESTEUEDGEWISK

a

:

K

1—050 ---i

DEFLECTION AT MI D-SPAN, IN.

Figure 24. - Flexural stress-deflection cumes for asbestos-fabricphenolic leminat e, K2, at 770F. Span-depth ratio 8:1.

I. . —

. ,.

. .

(

I

. w

1 --- 1~a”----l

DEFLECTlOl AT MI D-SPAN, ‘ IN.

Figure 25.- Flexural stress-deflection ourves for glass-fabriclamlnat e bonded with unsaturated polyester resin, U2,

at 77°#. Spen-depth ratio 8:1.

1

I

q

&.alCJl

NJiC3ATN No. 1054 Fig. 26

35

‘g “25

20

R’ u.

10

5

0

-++’

I&r”INITIAL FLEXURAL FLEXURAL TOTAL

MODULUS OF IELASTICITY STRENGTH DEFLECTIONLSAN8 WIN? IN.

LENGTHWISE 4-- =.- 0.25

CROSSWISE WxWOO 32,%0 0.25

// I 45” DIAGONAL 7- W,900 . 0.28

1“ I I I.05 m ●le .20 .2s .30

DEFLECTION AT MID -SPAN, IN.

Figure 26.- Flexural stress-deflection curves for rayon-ootton-fabric ptienolicl-inate, 22, tested

flatwise at 770F. Span-depth ratio 8:1.

NACA TN No. 1054

.

60

so

40

30

20

10

0

Fig. 27

.

lNITIAL FLEXURAL FLEXURAL TOTAL

MODU UJS OF ELASTICITY STRENGTH DEF-TION

L2AN: L2AN? IN.

LENGTHWISE 2,a80,000 53@oo 0.11

CROSSWISE 2,s40@03 46,000 0.10

4S” DIAGONAL l#lo,ooo 35,700 a3s

,

/

.

/

.02 .04 .0s .08 10 32 34

DEFLECTION AT MID-SPAN, IN.

Figure 2?.- Flexural stress-”deflection curves for glass-fabric laminate, AB2, tested flatwise at 77°F.

Span-depth ratio 8:1.