Sijppl€iTi€nt to MECHANICAL PROPERTIES OF PLASTIC LAMINATES Original report dated 1993 Information Reviewed and Reaffirmed I960 No. 1820- A I ^dLi^'JilfJi .'7. 3. DEPOSI IUHY FOREST PRODUCTS LABORATORY MADISON 5 , WISCONSIN UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE In Cooperation with the University of Wisconsin Supplement to MECHANICAL PROPERTIES OF PLASTIC LAMINATES— By FRED WERREN, Engineer Forest Products Laboratory, — Forest Service U. S. Department of Agriculture Summary This report presents the results of tension, compression, bending, and shear tests of six parallel -laminated glass -fabric-base plastic laminates. The data supplement those of a previous report of the same title, Forest Products Laboratory Report No. 1620, in which results of tests of 14 laminates were given. Tests of the laminates were made after both normal and wet conditioning. The mechanical properties of the laminates, both dry and wet, are pre- sented in the form of tables and by average stress -strain curves. Introduction This study was made to determine the mechanical properties parallel to the orthotopic axes of six more plastic laminates, in tension, compression, bending, and shear, Five of the laminates were made with resin 2 (here- after referred to as (2) ) s which is a typical polyester resin conforming with the requirements for types I, II, and III of Military Specification MIL-R- 7575 (USAF). Laminates made with a particular glass fabric and any other 1 —This progress report is one of a series prepared and distributed by the Forest Products Laboratory under U. S. Navy, Bureau of Aeronautics No. NAer 01388 and U. S. Air Force No. 33(038) - 5 1 -4326-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. 1820-A Agriculture -Madison polyester resin conforming to these requirements may be expected to have properties similar to the comparable laminate made with (2). The sixth laminate was made with resin 8 (hereafter referred to as (8) ), a polyester resin that does not conform with the above specification requirements. The typical data reported herein supplement those of the original report. Additional combinations of fabrics and resins may be tested later. The six laminates were tested at the U. S. Forest Products Laboratory, Madison, Wis. , between March 1951 and February 1952. The study was made in cooperation with the ANC-17 Panel on Plastics. Description of Material Fabrication details are summarized briefly in table 7. Two 36- by 36- inch panels of each laminate were made at the Forest Products Laboratory. All panels were parallel-laminated, and fabrication procedures were simi- lar to those outlined in the original report. It may be noted in table 7, however, that the two panels made v/ith (8) were pressed under slightly different conditions than the panels made with (2). The 81-114 fabric was of the same weave as 181 fabric but made of a differ- ent yarn of coarser filaments. Fabric 57X-114 was a lightweight unidirec- tional fabric with the following characteristics: Thickness. ............................ 0. 006 inch Ounces per square yard. ................ 5. 37 Warp yarn. 225/i /3 Filling yarn. . 450/1/2 Count. 57 x 30 Testing All test procedures and the types of failures were the same as those des- cribed for the glass -fabric laminates in the original report except that Marten's mirror gages of 2-inch gage length were used in both dry and wet compression tests. Bending specimens of the laminates generally failed by a combination of compression and tension in both the dry and wet conditions, with the com- pression failure probably occurring first. The 181-114 laminate under Report No. 1820 -A -2- item 1-20, however, failed primarily in tension in the dry condition at angles of both 0° and 90°, but wet specimen failures were of the general type. The 57X-114 laminate failed in compres sion- shear at an angle of 0° but in tension at an angle of 90° . Panel shear tests were made as in the previous study except that no wet tests were made. Presentation of Data Table 7 indicates the fabrication methods used in making the various laminated panels and gives some information on each cured panel. Average values from tension, compression, and bending tests are given in tables 8, 9, and 10, respectively. Table 11 presents the results of individual dry shear tests, and theoretical values of ultimate shear stress based on the results of tension tests as explained in the previous report. The ratios of wet-to-dry properties for laminates are given in table 12. Average stress - strain curves in compression, tension, and shear, and average load-deflection curves in bending are shown for each laminate in figures 38 through 43. The relationship between tangent modulus and stress, in compression and shear, is shown in figures 44 through 49, based on the average stres s - strain curves for the laminates. Discussion of Results A detailed discussion of the test values is not necessary since the results are presented in the form of both tables and curves. In general, the discus- sion in the original report is also applicable to these six laminates, but a few supplementary comments follow. The effect of wet conditioning on the physical and mechanical properties of laminates made with (2) are similar to those originally reported. Wet conditioning results in small dimensional changes, but it has a substantial effect on the strength properties. The average wet-to-dry ratios for the mechanical properties of five laminates made of glass fabric and (2) are Report No. 1820-A -3- given at the bottom of table 12, and are reasonably comparable to the average values of previous laminates given in table 6. These results are typical of those obtained with the 114 finish. Finishes giving im- proved wet strengths have become available since the tests reported herein were made. Strength properties of the 181-114 laminate made with (8), item 1-17, were substantially lower than the comparable properties of a similar laminate made with (2), item 1-8 (F. P. L. Report No. 1820). The per- cent of weight increase due to wet conditioning for the 181-114, (8) laminate was about double that for the 181-114, (2) laminate. Wet con- ditioning resulted in more than average strength reduction in the tensile strength, but about the average reduction in strength in compression and bending. Since the fabrics used in both laminates were obtained from the same supplier and were considered to be identical, the differences in the mechanical properties appear to be due to the resin. The 81-114 fabric used in item 1-18 was of the same weave as the 181- 114 fabric, but it was made with a different yarn of coarser filaments and was a lower -priced fabric. The mechanical properties, however, are about the same as those of the 181-114, (2) laminate of item 1-8. Thick- ness and resin content of the 81-114 laminate were a little lower than for the 181-114 laminate, using the same fabrication conditions, but specific gravity values were higher. The percent of weight increase due to wet conditioning was about the same for each laminate. The 181-114 fabric used in item 1-20 was considered to be the same as and the equal of that used in item 1-8, but it was made by a different manufacturer. Results of dry and wet tests of laminates made from these fabrics and (2) were reasonably comparable in compressive and bending properties. Tensile strengths, however, were appreciably lower in item 1-20, especially at angles of 0° and 90 c . This observation checks with previous tests of laminates made of fabric from these manufacturers, in that the tensile strength of laminates made of fabric received from source B were somewhat lower than those made with fabric from source A. In items 1-3 and 1-13 (Report No. 1820), 128-114 fabric from these manu- facturers was made into laminates. Compressive and bending properties were comparable, but tensile values were considerably different. Another study, which included 162-114 laminates made of fabrics from the two man- ufacturers, has shown a similar relationship. No reason is offered for these differences, but it would seem that something during the manufactur- ing process of fabric furnished by supplier B has a detrimental effect on the tensile strength. Report No. 1820-A -4- Dry panel shear tests were made for each laminate, but wet tests were not included. The correlation between the observed and theoretical ulti- mate shear strengths is reasonable. Theoretical values would be ex- pected to be lower than the observed values because the panel shear specimen was tested at a lower moisture content than the related tensile specimens. These tests substantiate previous data that concluded that reasonable values of shear strength may be determined from the tension tests. Conclusions Six parallel=laminated glas s -fabric -base plastic laminates have been tested to supplement the data from 14 laminates of the original report. The mechanical properties may be seen by reference to the tables or curves presented. Results in the dry condition of the five polyester lami- nates made with (2) are considered to be typical of laminates made with the specific glass fabric and any polyester resin conforming to Military Specification MIL-R-7575(USAF) . The conclusions of the original report regarding effect of wet conditioning and initial and secondary moduli in tension were reasonably substantiated by the tests of the supplementary laminates. There is reasonable agreement between the observed and theoretical values of shear strength in the dry condition, and the theoretical wet strengths are considered to be conservative values. Although 81-114 fabric is a lower-priced product than 181-114 fabric, the mechanical properties of laminates made of these fabrics and (2) were about the same. Appendix 1 Description of Laminating Resins and Fabrics Used in Making Laminates Resin 2 -- A laminating resin of the polyester (styrene -alkyd) type. Resin 8 -- A high-temperature - setting laminating resin of the polyester (styrene -alkyd) type. Glass fabric -- All glass fabric is of the weave or type listed in table 1, and of finish 114 or its equivalent. Fabric 81 was somewhat similar to weave 181, but it was made up of coarser filaments. Fabric 57X was a lightweight unidirectional fabric. Report No. 1820-A -5 = o 'd to O U CD Jh Cd CD pp » -p I CD o CD O « o > I CD cd l ft h 8 CO w I En : 5£ P-. 1 CD : s -P » cd 1 u o CD i) ft 3 CD i u o Ph 3 CD O P s -P o G CD ! 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CO CVI OJ CV? o ■» -* -if ! 3 H rH Jt rH H 8 H H H H rH rH 1 D § H II -4. rH 1 H (4 a no CO CO H CO E"— o H H H CO H ITN ITN NO H CVI LfNNO r-co ON O O rH O O i— 1 rH H rH o o O rH OJ OJ CVI OJ CVI OJ CVI CVI OJ OJ CVI OJ CVI CVI o CO O H 6 IA H H H CVI OJ II s H 1 i— 1 H rH H H O u Ch • rC CD O b o -P aj OJ h 2 CD O ft « s o to ^ (D co > A CD CO rH -P ft Pi Pi o ft CD > -P rH cd pi >>rH CO -p +3 d ra 1i) 0) ch -h -P <+h cd CO O rH 0) -p CO a CD H o a rH -H CD -P ft °H PI CV) -H h] oj] CD B EH m| - CO CD CD rH rH b0 p! rJ H H ■rH cd cd > -p » tJ $ ■p H CD cd •H ■P ft rH rH cd H H a 1 P5 cd ft t) -P u rH d) ft cd S rH •H CD o d at ar we OJ CO al I ne -p CD H o o o rQ •H O ■h CO o° +> On CD co CD CD -d CD u U E -p o xj -P rH The cd o D9 Fai epo r 1 VO| 200 1 2 3 4 5 6 STRESS (1,000 POUNDS PER SQUARE INCH) Figure 44. - -Relationship between tangent modulus and stress in compression or shear, for laminate made of 164-114 glass fabric and resin 2. Based on curves of figure 38. Z M 91U52 F o 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 STRESS (1,000 POUNDS PER SQUARE INCH) Figure 45. - -Relationship between tangent modulus and stress in compression or shear, for laminate made of 183-114 glass fabric and resin 2. Based on curves of figure 39. DRY WET CC WPRL T SS/Oi V - e= 0° — to 15 20 25 30 -DRY- WET CC WPRL zSSIO 90°- N - e = 10 15 20 25 30 DRY SHEAR - e=o° - 1 2 3 4 5 6 STRESS (1,000 POUNDS PER SQUARE INCH) \K 91^51 F Figure 46. - -Relationship between tangent modulus and stress in compression or shear, for laminate made of 181-114 glass fabric and resin 8. Based on curves of figure 40. 2 '■ 3 4 5 6 7 STRESS (1,000 POUNDS PER SQUARE INCH ) Z M 93M8 F Figure 47. - -Relationship between tangent modulus and stress in compression or shear, for laminate made of 81-114 glass fabric and resin 2. Based on curves of figure 41. 3 4 5 6 7 STRESS (1,000 POUNDS PER SQUARE INCH) Figure 48. - -Relationship between tangent modulus and stress in compression or shear, for laminate made of 181-114 glass fabric and resin 2. Based on curves of figure 42. (The 181-114 fabric represented by this figure was made by a different manufacturer than was that for which results are given in figure 30.) 4,000 2,000 1,000 DRY WET -v \ v— \ Gl OMPR ESSIC N o° - O 8 16 24 32 40 48 56 64 1,500 1,000 500 DRY WET a rear IN i_ a- on" \ 12 16 20 24 28 32 DRY 400 SHEAR - 6= 0°- ■ Z M 91"*50 F 2 3 4 5 6 STRESS (1,000 POUNDS PER SQUARE INCH) Figure 49. - -Relationship between tangent modulus and stress in compression or shear, for laminate made of 57X-114 glass fabric and resin 2. Based on curves of figure 43. iiilllliii 3 1262 08928 6289