Supplement to MECHANICAL PROPERTIES CIF CROSS4AMINATED AND COMPOSITE GLASS-FACIRIC-13ASE PLASTIC LAMINATES March 1953 INFORMATION REVIEWED AND REAFFIRMED 1959 LO COPY masse • rot.ota to: Wood Engineering Ker*earcit !Crest Product* Laboratory 53705 giscorAl ilk This Report is One of a Series issued In Cooperation !with the AIR FORCE-NAVY-CIVIL SUCCOMMIITEE on AIRCRAFT DESIGN CRITERIA Under the Supervision of the AIRCRAFT COMMITTEE of the MUNITIONS BOARD No. 1821-A uNrrED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY Madison 5, Wisconsin In Cooperation with the University of Wisconsin SUPPLEMENT TO MECHANICAL PROPERTIES OF CROSS-LAMINATED AND COMPOSITE GLASS-FABRIC-BASE PLASTIC LAMINATES! By ALAN D. FREAS, Engineer and FRED WERREN, Engineer 2 Forest Service Forest Products Laboratory, — U. S. Department of Agriculture Abstract Methods of predicting the properties of cross laminates and composite parallel laminates were presented in Forest Products Laboratory Report No. 1821. Reported herein are the results of tests on additional composite parallel laminates, together with the results of application of the computation methods previously presented. The conclusions of the original report are reasonably confirmed by the results of the present study. Introduction It was the purpose of this study to supplement the data of the original report h.y tests on composite parallel laminates of a different type than that originally studied. In this study, facings of from 1 to 11 plies of a fine-weave fabric were applied to a core of a coarser-weave fabric. This type of construction might be employed where it was desired to impart a relatively smooth surface to a. laminate made primarily of a coarse-weave fabric. -This —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 01338 and U. S. Air Force No. USAF-(33-038)51-4 2 26-E, Amend. 2 (53-131), Results here reported are preliminary and may be revised as additional data become available. ?Maintained at Madison, Wis. , in cooperation with the University of Wisconsin. Report No. 1821-A Agriculture -Madison -1- Material One 1/4-inch-thick panel of each of three constructions was tested in this study. All panels were made with a core of 162-114 fabric with 1, 6, or 11 plies of 112-114 fabric on each face. The panels were laminated with resin 2, a laminating resin of the polyester (styrene-alkyd) type conforming with the requirements of types I, II, and III of U. S. Air Force Specification 12049. For al] panels, the resin was catalyzed with 0. 8 percent of benzoyl peroxide by weight. Fabrication procedures were as described in the original report. Information on the make-up and physical properties of the various panels is given in table 11. Before the composite panels were fabricated, an attempt was made to obtain 162-114 fabric from manufacturer A, who furnished the 162414 fabric for the earlier panels.! The manufacturer did not have the fabric available at that time, so the material was purchased from manufacturer B. Both manufacturers stated that the 114 finishes were identical and that the fabrics, as obtained from either source, were considered to be the same. Subsequent tests, however showed that this was not so. Therefore, a 162-114 control laminate was fabricated by using fabric from the same roll as that used in the composite laminates. Fabrication procedures were the same as those used for the composite laminates. Testing All test procedures were the same as those described in the original report Presentation and Discussion of Results Average miscellaneous data and test results are given in tables 11, 12, 13, 14, and 15. Control data for the 112-114 laminate and for the shear properties of the 162-114 laminate are from earlier tests of another study. 3 Tension, compression, and bending properties of the 162-114 laminate are from the control laminate made of the same fabric used in the composite laminate. Comparisons of test results with computed results are shown in tables 16 through 20. 3 --Werren, Fred. Mechanical Properties of Plastic Laminates. Forest Products Laboratory Report No. 1820. February 1951. Report No. 1821-A -2- Methods of computing the various properties of the composite laminates from the properties of the components are described in the original report and will not be repeated herein except for the equations. Tension and Compression Modulus of elasticity. --Modulus of elasticity of composite laminates may be computed from the equation: =n > E a = (It) E1A1 i=1 where E a = modulus of elasticity of the composite laminate A = cross-sectional area of the composite laminate Ei = modulus of elasticity of the ith ply in the direction of stress A i = cross-sectional area of the ith ply. Values of E i were taken from the data for parallel laminates, tables 12 and 13. A compariMn of computed and test results is shown in tables 16 and 17. Computed and test values for modulus of elasticity in tension and in compression generally agree within 10 percent. Strength properties. --Three possible procedures for computing the tensile and compressive strength properties of composite laminates from those of the CQMponent materials are represented by the equations: Method 1 Sa - A [A l 4 Ez A2 (2) Method 2 _ Report No. 1821-A 52 [ E A Ez A1 -3- + Az] (3) Method 3 Sa= 1 i =n S•A. (4) i =1 where Sa = strength property of composite laminate S / = strength property of type 1 layers parallel to direction of stress S 2 = strength property of type 2 layers parallel to direction of stress Si = strength property of the ith ply parallel to stress E l = modulus of elasticity of type 1 layers parallel to direction of stress modulus of elasticity of type 2 layers parallel to direction of stress E 2 = A / = total cross-sectional area of type 1 layers A2 = total cross-sectional area of type 2 layers Ai = cross-sectional area of the ith ply A = total cross-sectional area. In method 1, the computations were based on the properties of the 112 laminate; that is, Sl equals the strength of the 112 laminate. In method 2, the computations were based on the strength of the 162 laminate. Ratios of strength values computed by all three methods to strength values obtained by test are shown in tables 16 and ]7. As was to be expected from the results given in the original report, neither method 1 nor method 2 gives good correlation between computed and test values. By using method 3, there is reasonably good correIation between the tensile values. Compression values are also in reasonable agreement except for the composite laminate with facings of one ply of 112-114 fabric. Properties in tension at a 45° angle. --Two methods of predicting the tensile properties of composite laminates at an angle of 45° to the warp direction were discussed in the original report. The first involved the use of the formulas of Report No. 1821-A -4- Forest Products Laboratory Reports Nos. 1803 and 1803-A, with the tensile and shear properties of the composite laminates at angles of 0° and 90°. The second was based on using the weighted average of the 45° properties of the component parallel laminates. Parallel-laminate properties were weighted according to the proportion of the area occupied in the composite laminate. Results of both methods of computation are shown in table 20. Both methods, except for stress at proportional limit, give reasonable correlation between computed and test results in tension, with the second method being somewhat better. The lack of correlation for stress at proportional limit may be attributed largely to difficulties in accurately locating the proportional limit. Discussion of tensile properties. --Previous discussion has mentioned that a new panel of 162-114 fabric, parallel-laminated, was made to furnish control values for tension, compression, and bending tests. This was necessary because the laminates made from the 162-114 fabric from manufacturer B were appreciably lower in tensile properties than comparable laminates made with similar fabric from manufacturer A. Other mechanical properties were reasonably comparable. In two other instances in tests of plastic laminates, laminates made with fabric from manufacturer B were appreciably lower in tensile properties than those made with fabric from manufacturer A. This may be seen by a comparison of items 1-3 and 1-13 (128-114 laminates) and items 1-8 and 1-20 (181-114 laminates) in Forest Products Laboratory Reports Nos. 18202 and 1820-A. it Examination of the data will also show that laminates made with fabric from manufacturer A were thinner, had a higher specific gravity, and had a lower resin content. Analysis of these data indicates that there is apparently some difference between 114 finish fabrics furnished by the two manufacturers, even though the materials are supposed to be identical. This difference or variation, which might be in :he finish, substantially affects the tensile properties of the laminate. Some differences might also be noted in tensile tests of the fabric, as are shown in the results of tests of 162-114 fabric, table 21. Static Bending Modulus of elasticity. --The modulus of elasticity in static bending may be computed from 4 —Werren, Fred. Supplement to Mechanical Properties of Plastic Laminates_ Forest Products Laboratory Report No. 1820-A. February 1953. Report No. 1821-A -5- EiIi (5) where E a = modulus of elasticity of the composite laminate Ei = modulus of elasticity of the ith ply parallel to span Ti = moment of inertia of the ith ply about the neutral plane of the laminate = moment of inertia of the laminate about its neutral plane. A comparison of computed with test values is shown in table 18. --Three possible methods of computing the static-bendingstrength properties of the composite laminates from the strength_properties of the component materials are represented by the equations: Strength properties. Method 1 1 E [11 (6) +1 2 a Method 2 f 1 E 2 12 Er 2tf [1 a (7) Method 3 =n f a = 1 I fiIi i = Report No. 1821-A 1 -6- (8) where fa = strength property of the composite laminate f 1 = strength property of the type 1 layers parallel to span f2 = strength property of the type 2 layers parallel to span fi = strength property of the ith ply parallel to span = sum of moments of inertia of the layers of type 1 about the neutral plane of the laminate 1 = sum of moments of inertia of the layers of type 2 about the 2 neutral plane of the laminate Ii = moment of inertia of the ith ply about the neutral plane of the laminate I = moment of inertia of the composite laminate about its neutral plane E 1 = modulus of elasticity of the layers of type 1 parallel to span E 2 modulus of elasticity of the layers of type 2 parallel to span tf d = ratio of thickness of surface layer to total thickness of laminate. In method 1, computations were based on the strength of the 112 laminate; that is, f 2 equals the strength of the 112 laminate. In method 2, computations were bas7F on the strength of the 162 laminate. The value of tf was taken as the total thickness of each 112 facing. Results of computations birThese methods are shown in table 18. As was found in the original report, methods 1 and 2 do not give consistently good correlation between computed and test results. Method 3, however, gives generally good correlation except for stress at proportional limit. Shear The original report showed that reasonably good correlation between computed and test results in shear could be expected by use of the following equation: =n FiAi Fa = 1 =I Report No. 1821-A -7- (9) where F a = property of composite laminate A = total cross-sectional area of composite laminate F 1 = property of ith ply A 1 = cross-sectional area of ith ply. A comparison of computed and test results is given in table 19. In view of the small number of tests (two per laminate), the correlation is considered satisfactory. Conclusions The results of tests of three composite laminates made of 112-114 and 162-114 glass fabrics confirm reasonably well the conclusions of the original report.. The conclusions of the original report were: (a) The properties of composite or cross laminates stressed in tension or compression parallel or perpendicular to the warp direction may be taken a s the average of the properties of the component layers, parallel to stress, weighted according to the proportion of the area they occupy. (b) 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. (c) 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 parallel laminates. (d) The properties of cross laminates or composite laminates stressed in tension at 45° 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. (e) 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-A -8- Table 11.--Miscellaneous data relative to composite parallel laminates made of 112-114 and 162-114 fabrics and resin 2 Panel : Number of plies1 :Specific: Resin : Barcol : gravity: content: hardness No. : :Total:112-114:162-114: : tabri2:-fObr12: : : :Percent : : Thickness : : : : In. 69 : 69 : 0.250 .250 112-114 Control Laminates 5 6 : : 84 : 44 • 84 : 284 .... • 1.71 : 43.5 : 1.70 : 43.4 : 162-114 Laminates--for Shear Controls 52 53 17 • • • 17 2 17 : 1.76 : 37.7 : 217 : 1.76 : 38.2 : 62 : .252 62 : .254 63 : .257 69 : .262 69 69 : : .264 162-114 Laminate--for Tension, Compression, and Bending Controls 223 : 16 • ° 316 : 1.72 : 41.0 : Composite Laminates 217 218 212 219 : 18 : : 26: : : 34 : E 2 : 216 : 1.73 : 41.1 : 214 : 1.71 : 42.0 : 222 : 212 : 1.71 : 42.0 : .260 1 –Layers of 112-114 fabric formed a facing on a core of 162-114 fabric. One-half the number of plies of 112-114 fabric shown above at each face. Fabric from manufacturer A. Fabric from manufacturer B. Report No. 1821-A Table 12.--Results of tension tests of parallel laminates made of 112-114 and 162-114 fabrics and resin 2 Stress at -°. Fabric :Layers of: Direc- : Modulus of :----- --------------- ------ ----: 112-114 :tion of: elasticity :fabric at: test :------ ----------- :Proportional limit: Ultimate : :Initial:Secondary: :each face: :Initial :Secondary: : : 2 6 --------g --------- :66-66-..---: ------- g...... ...... : : : :Degrees : 1,000: 1,000 : P.s.i. : P.s.i. : P.s.i. : No. : : 2:ILtit : 2.i. : . Controls - Parallel-laminated 112-114 g.........: . : 0 45 90 : 2,690 : 2,390 : 11,800 : 29,500 : 42,700 :.......: 1,540 : ----- ...: 3,760 : 20,550 : 2,640 : 2 ) 240 : 9,800 : 27,050 : 38,650 0 45 90 : 2,760 : 2,440 : 7,940 : 19,750 : 37,600 :e... .e: 1,360 :........: 3,460 : 16,350 : 1,960 : 1,520 : 4,560 : 10,200 : 20,600 . °. 162-114 :.........: . °. : °. Composite Laminates - Parallel-laminated 112-114 8 : 162-114: : : 112-114;: 162-114: : : 112-11482 162-114: : 1 : : : 0 45 90 0 6 11 Report No. 1821-A : : : : : : : 0 45 90 0 45 90 : 2,760 : 2,370 : 6,400 : 18,500 : 35,600 0 . 1,450 :.. ------ : 2,580 : 16,000 : 2,040 : 1,380 : 4,330 : 11,750 : 19,900 0 . : : .. : 2,670 : 2,250 : 8,120 : 20,950 : 36,050 ° 2,580 : 16)400 ° 1,350 : ° : 1,960: 1,400 : 4,660 : 12,850 : 22)400 . : : : . : 2,690 : 2,240 : 8,490 : 24,500 : 37,900 ° 2,380 : 16,200 :.......: 1,530 ° : 2,000 : 1,490 : 5,520 : 14,750 : 24,300 Table 13.--Results of compression tests of parallel laminates made of 112-114 and 162-114 fabrics and resin 2 Fabric :Layers of: Direc- : Modulus of : 112-114 :tion of: elasticity :fabric at: test : :. :each face: : No. :Degrees : 1,000 Stress at -: : :Proportional: 0.2 percent: Ultimate : offset : limit : : P.s.i. : P.s.i. : P.s.i. ' • Controls - Parallel-laminated 0 90 : : 162 .. 114 :MO000090: 0 : : 90 : 112-114 :70000000.: . 2,820 2,630 23,250 21,600 : : 36,850 32,900 : 36,850 : 32,900 2,850 2,100 11,250 10,200 : : 19,100 18,300 : 19,100 : 18,300 Composite Laminates - Parallel-laminated 112-114;: 162-114: 1 112-114j: 162-114: 6 112-114;: 162-114: 11 Report No. 1821-A : 0 90 : : 2,810 1,900 : : 0 90 : : 2,660 2,020 : 0 90 : : 2,810 2,050 e 0 : 0 16,950 15,700 : : 23,900 21,750 16,450 17,300 : : 22,100 21,450 16,750 17,800 23)400 23,250 : 23,900 : 21,750 22,100 : 21,450 t 23,400 23,250 Table 14.--Results of static-bending tests of parallel laminates made of 112-114 and 162-114 fabrics and resin 2 :Modulus Stress at -- Fabric :Layers of: Direc- Modulus of : : of 112-114 :tion of: elasticity : :Proportional: 0.2 percent :rupture :fabric at: test : : offset : limit : :each face: : : : : P.s.i. P.s.i. : P.s.i. :Degrees : 1,000 No. .. : p.s.i. : Controls - Parallel-laminated 112-114 ..... 0 90 162-114 ..... o 90 : : 2,590 2,400 : : 31,000 26,450 : 58,250 48,350 : : 58,250 48,350 17,200 11,300 : : 32,550 22,850 : : 35,000 26,900 • 2,470 1,720 : : Composite Laminates - Parallel-laminated 112-1148: 162-114: 1 : 0 90 112-114,1: 162-114: 6 : : 0 90 112-114:: 162-114: 11 : : 0 90 Report No. 1821-A 2,690 2,000 24,550 12,200 : : 2,680 2,110 24,050 15,250 : : 2,730 2,270 28,200 14,950 • : 38,600 26,250 : 38,800 28,800 43,750 33,750 : 54,65o 36,800 : 43,750 33,750 55,050 37,800 Table 15.--Results of panel shear tests of parallel laminates made of 112-114 and 162-114 fabrics and resin 2 Stress at -Fabric :Plies of : Modulus : 112-114 : of :fabric at: rigidity : Proportional : 0.2 percent : Ultimate offset : : limit :each face: : 12--- 000 No. ° P.s.i. P.s.i. P.s.i. Controls - Parallel-laminated 112-114 :.........: 660 1,920 : : 162-114 :.........: 580 2,220 : : : 4,070 : : 13)600 4,810 : 11,700 : 10,300 Composite Laminates - Parallel-laminated 112-114)': 162-114: . 112-114;: : 2,240 570 : : : 6 : 2,160 : : 4,580 •. 10,850 2)540 : : 4,850 : 10,900 560 : 162-114: 112-114;: 4,930 1 11 162-114: Report No. 1821-A : 510 : . : : M .0 -14H 4) 0 0 S 0Y30 S HH 1-1 00 0 O • • HH © 0 • 00 • • •• •• al 0) c*. 4) .4. CC) 00 (7\• H (C\ 00 0• ri 8-1 id 0 .1:1 4-) k.0 00 Oo 00 oo •0 00 00 & D. 0 • o• 0• H q CU ...* al0 tr‘0 H H 18 .0 -P 4) 00 00 t3 00 •0 WO oo 00 OD CO 0 00ON0 H 4) 00 0-4 (1) Ra +2 4-1 0 4) 0 0 rig .L:1 0 CO 0 4, A0 40 P4 0 qg .s:1 4--' ID X 000.- 0 00 K\ 8 ▪45 1:11. 4) X 00 0. N 00 .. 4) C) cps .44 •. Prl at if\ .0 0\. CO. c.) 43 izi .. o 'a& • .--1. tr\. 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OLJ X 00 00 00 0 CA 0 a 0 • 000, Sri 1 0 II .H X 00 I ' al 00 00 +3 Q3 0-1 id co co 0 -P (1) •rl (1) k3 +k3 Z00 CA 0 H P4 0 '8 k 43 0 FJ O Qi 4 O 0 Pi Pre .1 0 01 a) k vi A Report No. 1821-A •• •• 0 I-I • • H r-I 00 00 H 00 00 r-1 0\ .--1 lc\ e a H r1 nt-- H ,-1 a 00 94 0 co a) ..-i J-4 1..• /11 EA it-(7, • • r -I 00 00 .-i p H \O 0\ ..../0n0• 0 0 0 00 XI +3 0 00 00 00 00 a o PI o + 3 ori CO 00 0-1 0 0 4-1 H O 9-1 43 ,8 0 : QI H 0 E-4 a 00 00 0 00 00 00 0 fi te\ .0. a: CU H • 0 .-I H H a) • • ..-4 F-. ,0 moo __I- 00 00 • •0 in \O At an 44 -4 H L— ,. 0 +3430 +3 r14 If \ ..0 MD %%0 re\ a 1-1 0 , • . a) • 0\ -ICO • 0 • 00 00 0• 00 00 00 H 0\ al • n• n al al•-4* • 00 L— 0 n H H r-I H 0. 00 00 •0 P V ,e al Ct\ c9\ c0 . • 0 -4- st 0\• 0\ • o‘o\ • •• 00 00 00 0\ 00 0\ H H .. 00 0:1 00 k AO u E. 00 0\ •• KN..* • • 110 Table 19.--Ratios of computed shear properties to properties obtained from test Ratios : Construction Stress at -:Modulus : : of :rigidity:Proportional:0.2 percent: Ultimate : : offset limit : : : : : 1.02 : 1 ply of 112-114 fabric on each face 0.99 •. : 0.97 : 1.14 1.01 : : 1.03 : : 1.10 .84 : .95 : 1.12 6 plies of 112-114 fabric : : : 1.05 : : 11 plies of 112-114 fabric : :. on each face : 1.18 : on each face Table 20.--Ratios of pro pe rties, properties obtained in test Construction 1 ply of 112-114 fabric on each face Stress at : Proportional : Ultimate lim limit : :Method 1:Method 2: :Method 1:Method 2:Method 1:Method 2 Modulus of elasticity •. : 0.99 plies of 112-114 fabric on each face 1.06 11 plies of 112-114 fabric on each face .89 6 Report No. 1821-A : . • : . • : •. : : 1.74 1.03 : 1.67 .92 : 2.13 0.94 .• •. : 1.34 °. 1.11 : : 1.03 •. •. : : : : .• :. : 1.36 : 1.15 : 1.03 1.49 : : 1.19 .° : 1.08 Table 21.--Physical properties of 162-114 glass fabric from two different manufacturers) Properties Samples from : Manufacturer A : Manufacturer B Breaking strength (pounds per inch) (Grab method) Warp Fill : : •. 459 277 398 Elongation (percent) Warp Fill • : : 8.0 4.0 7.3 4.5 Breaking strength of thread (pounds) Warp Fill : : : 17.0 18.1 17.5 15.9 Elongation of thread (percent) Warp Fill : : 1.7 1.7 Thread count per inch Warp Fill • : : 28.5 16.5 Yarn ply Warp Fill : : 5 5 : 5 (2) : (2) : 253.4 1.87 1.49 • Weave Twist per inch (yarn) Warp Fill 28.5 16.5 4.5 4.6 4.1 4.2 -'Properties based on tests at the Wright Air Development Center, Wright-Patterson Air Force Base, Ohio. Plain, 1 up and 1 down. Report No. 1821-A 5