MIL-HDBK-17-3F Volume 3.Chapter 10 Thick-Section Composites Inclusion and treatment of environmental effects Data acquisition and analysis Multiaxial yield and failure criteria Size effect and scaling law Edge effects treatment Static and dynamic testing,including fatigue and impact loadings Sensitivity to stress concentrations -NDE of damage 10.2.3.1 Uniaxial tests The type of common tests conducted on the unidirectional laminate to obtain the conventional 2-D in-plane tensile,compressive,and shear stiffness,as well as failure strength and strains are summarized in Figures 10.2.3.1(a)through 10.2.3.1(c).These tests are also discussed in detail in Volume 1,Section 6.8.The additional unidirectional laminate design property tests needed when a 3-D (thick-section) analysis is required are summarized in Figure 10.2.3.1(d)and described in detail in Figures 10.2.3.1(e) and 10.2.3.1(f).Test methods available to obtain these properties are summarized in Table 10.2.3.1(a). Further test method development is needed for tension and compression testing in the 3 or through-thickness direction. For oriented laminates,the additional design properties tests needed in addition to the 2-D tests for a 3-D analysis are summarized in Figure 10.2.3.1(g).The 3-D through the thickness stiffnesses can also be predicted from the unidirectional lamina stiffnesses by the methods discussed in Section 10.2.4(Theoreti- cal Property Determination).Table 10.2.3.1(b)summarizes the test methods available for determining 3-D properties for an oriented laminate.Furthermore,test method development is also needed for tension and compression testing in the z-thickness direction similar to the need for unidirectional laminate testing. An example of representative thick-section composite properties for an intermediate modulus car- bon/epoxy material system are presented in Tables 10.2.3.1(c)and(d)for the unidirectional lamina and [0/90]oriented laminate.The lamina properties were taken from Reference 10.2.3.1(a)and the [0/90]data were obtained by a Hercules test program from an 80-ply (t=0.59 in.,15mm)fiber-placed,auto- clave-cured laminate(Reference 10.2.3.1(b)). Tables 10.2.3.1(a)and (b)identify three uniaxial compressive test methods for testing composites greater than 0.250 inches(6.35 mm)in thickness.Both the David Taylor Research Center(DTRC)and the Alliant Techsystems testing fixtures,which are shown in Figures 10.2.3.1(h)and 10.2.3.1(i),respec- tively (see References 10.2.3.1(a)and 10.2.3.1(c),respectively),were developed for uniaxial compres- sion testing of thick prismatic columnar shaped composite material specimens.The US Army Research Laboratory-Materials Directorate (ARL)(Reference 10.2.3.1(d))test method utilizes a cubic specimen loaded directly between two steel platens with no associated fixturing.The development of compression data relative to the different material orientations identified in Tables 10.2.3.1(a)and(b)is accomplished through independent,successive uniaxial load applications.Successive uniaxial compression tests,that consist of one-directional load applications per material orientation,can be undertaken with conventional, medium-to-high capacity load frames.With proper care and specimen fixturing,these tests may also be used for determining unidirectional compressive material strengths and failure characteristics. The primary feature that both the DTRC and the Alliant Techsystems test fixtures provide is that they have been developed for maintaining proper gripping and alignment of the test specimens as well as pro- viding constraints to minimize any potential specimen end brooming (specimen splitting)under compres- sive load applications.Any potential onset of apparent,specimen end splitting and fixture-induced test specimen material cracking,may cause significant material strength reductions.Special tabbing as well as associated specimen-tabbing connection detail may be required for some uniaxial compression testing of thick composites. 10-6
MIL-HDBK-17-3F Volume 3, Chapter 10 Thick-Section Composites 10-6 − Inclusion and treatment of environmental effects − Data acquisition and analysis − Multiaxial yield and failure criteria − Size effect and scaling law − Edge effects treatment − Static and dynamic testing, including fatigue and impact loadings − Sensitivity to stress concentrations − NDE of damage 10.2.3.1 Uniaxial tests The type of common tests conducted on the unidirectional laminate to obtain the conventional 2-D in-plane tensile, compressive, and shear stiffness, as well as failure strength and strains are summarized in Figures 10.2.3.1(a) through 10.2.3.1(c). These tests are also discussed in detail in Volume 1, Section 6.8. The additional unidirectional laminate design property tests needed when a 3-D (thick-section) analysis is required are summarized in Figure 10.2.3.1(d) and described in detail in Figures 10.2.3.1(e) and 10.2.3.1(f). Test methods available to obtain these properties are summarized in Table 10.2.3.1(a). Further test method development is needed for tension and compression testing in the 3 or through-thickness direction. For oriented laminates, the additional design properties tests needed in addition to the 2-D tests for a 3-D analysis are summarized in Figure 10.2.3.1(g). The 3-D through the thickness stiffnesses can also be predicted from the unidirectional lamina stiffnesses by the methods discussed in Section 10.2.4 (Theoretical Property Determination). Table 10.2.3.1(b) summarizes the test methods available for determining 3-D properties for an oriented laminate. Furthermore, test method development is also needed for tension and compression testing in the z-thickness direction similar to the need for unidirectional laminate testing. An example of representative thick-section composite properties for an intermediate modulus carbon/epoxy material system are presented in Tables 10.2.3.1(c) and (d) for the unidirectional lamina and [0/90] oriented laminate. The lamina properties were taken from Reference 10.2.3.1(a) and the [0/90] data were obtained by a Hercules test program from an 80-ply (t=0.59 in., 15mm) fiber-placed, autoclave-cured laminate (Reference 10.2.3.1(b)). Tables 10.2.3.1(a) and (b) identify three uniaxial compressive test methods for testing composites greater than 0.250 inches (6.35 mm) in thickness. Both the David Taylor Research Center (DTRC) and the Alliant Techsystems testing fixtures, which are shown in Figures 10.2.3.1(h) and 10.2.3.1(i), respectively (see References 10.2.3.1(a) and 10.2.3.1(c), respectively), were developed for uniaxial compression testing of thick prismatic columnar shaped composite material specimens. The US Army Research Laboratory - Materials Directorate (ARL) (Reference 10.2.3.1(d)) test method utilizes a cubic specimen loaded directly between two steel platens with no associated fixturing. The development of compression data relative to the different material orientations identified in Tables 10.2.3.1(a) and (b) is accomplished through independent, successive uniaxial load applications. Successive uniaxial compression tests, that consist of one-directional load applications per material orientation, can be undertaken with conventional, medium-to-high capacity load frames. With proper care and specimen fixturing, these tests may also be used for determining unidirectional compressive material strengths and failure characteristics. The primary feature that both the DTRC and the Alliant Techsystems test fixtures provide is that they have been developed for maintaining proper gripping and alignment of the test specimens as well as providing constraints to minimize any potential specimen end brooming (specimen splitting) under compressive load applications. Any potential onset of apparent, specimen end splitting and fixture-induced test specimen material cracking, may cause significant material strength reductions. Special tabbing as well as associated specimen-tabbing connection detail may be required for some uniaxial compression testing of thick composites
MIL-HDBK-17-3F Volume 3,Chapter 10 Thick-Section Composites F 2 Design Data ●●●●●●●● 2 tu ● Design Data E 心 号 FIGURE 10.2.3.1(a)Unidirectional laminate in-plane tensile design properties. E3 2 Design Data ●●●●●● 3 ●●●●●1●●●● 2 13 ●●●●00●●0 2 3 Design Data F E E1 v-32 哈 e FIGURE 10.2.3.1(b)Unidirectional laminate in-plane compressive design properties. 10-7
MIL-HDBK-17-3F Volume 3, Chapter 10 Thick-Section Composites 10-7 FIGURE 10.2.3.1(a) Unidirectional laminate in-plane tensile design properties. FIGURE 10.2.3.1(b) Unidirectional laminate in-plane compressive design properties
MIL-HDBK-17-3F Volume 3,Chapter 10 Thick-Section Composites 3 ●●●●●●●● ●●●●●Q●● Alternate Test Method (IOSIPESCU) Design Data 2a12g +45° Ey ※ L→ex※ ±45°Layup Y12"-y Y12=45-e+45 Es G12T2 FIGURE 10.2.3.1(c)Unidirectional laminate in-plane shear design properties. F =Stress(psi) YE=Strain (in./in.) E=Extensional modulus(psi) G =Shear modulus (psi) Poisson's ratio 43 ·Ftu。tu 33, 3 31 32 c 3,e3 32 13 13 ·FSu su 29Y2gC20 2 23 FIGURE 10.2.3.1(d)Unidirectional laminate thickness direction design properties. 10-8
MIL-HDBK-17-3F Volume 3, Chapter 10 Thick-Section Composites 10-8 FIGURE 10.2.3.1(c) Unidirectional laminate in-plane shear design properties. FIGURE 10.2.3.1(d) Unidirectional laminate thickness direction design properties
MIL-HDBK-17-3F Volume 3,Chapter 10 Thick-Section Composites 3 3 Design Data F Tig.Qia IOSIPESCU Test Specimen Design Data +45° 23Y230 23 Yi3E-45-e+45 Y23845-45 3 23 +45D FIGURE 10.2.3.1(e)Unidirectional laminate design properties for shear thickness direction. 3 Design Data ●● 2 V32 Var ●●●● ●●● Design Data 31 23 v 2 31- FIGURE 10.2.3.1(f)Unidirectional laminate tensile and compressive design properties in thickness direction. 10-9
MIL-HDBK-17-3F Volume 3, Chapter 10 Thick-Section Composites 10-9 FIGURE 10.2.3.1(e) Unidirectional laminate design properties for shear thickness direction. FIGURE 10.2.3.1(f) Unidirectional laminate tensile and compressive design properties in thickness direction
MIL-HDBK-17-3F Volume 3,Chapter 10 Thick-Section Composites TABLE 10.2.3.1(a)Test methods available for determining 3-D laminate properties. Loading Inplane Test Loading Out-of-plane Test Property Method Property Method 1-Ten 12 、 ASTM D3039 3-Ten 3 To Be SACMA SRM-4 Developed V32 1-Comp ASTM D3410 3-Comp ECU SACMA SRM-1 3 3 ECU To Be ALLIANT TECHSYSTEMS Developed 始 DTRC ARL 2-Ten ASTM D3039 13-Shear 2 ASTM D2344 「2eu E1 SACMA SRM-4 c SACMA SRM-8 IOSIPESCU 2-Comp ASTM D3410 23-Shear 12 ea SACMA SRM-1 13 23 ALLIANT 贸 TECHSYSTEMS 6少 ic DTRC IOSIPESCU ARL 12-Shear ASTM D3518 Notes: 12 02 SACMA SRM-7 10-10
MIL-HDBK-17-3F Volume 3, Chapter 10 Thick-Section Composites 10-10 TABLE 10.2.3.1(a) Test methods available for determining 3-D laminate properties