Appendix C Sample Laboratory Report Lamina Tensile Response The lamina tensile response of a carbon-fiber,epoxy-matrix composite was examined experimentally to establish the intrinsic mechanical properties. The test specimen geometries were chosen according to the outline presented in Chapter 5,in accordance with ASTM standards.The specimens were loaded to failure in a tensile testing machine utilizing serrated wedge grips. Average test results and standard deviations were as follows: Elastic modulus in the fiber direction E1=126±2GPa Elastic modulus transverse to the fiber direction E2=10.2±0.4GPa Poisson's ratios:Major v2=0.30±0.01 Minor V2a-0.024 Ultimate tensile stress in the fiber direction XT=2037±85MPa Ultimate tensile stress in the transverse direction Xg-53±8MPa Ultimate tensile strain in the fiber direction e=0.015 Ultimate tensile strain in the transverse direction e1-0.0057 Procedure The procedure for this experiment is detailed in Chapter 5.Briefly,unidirec- tional panels were configured for achieving test specimens with 0 and 900 orientation as shown in Appendix B.After the edges of the panels were trimmed,tabs made from a glass-fabric epoxy laminate were adhesively bonded to both surfaces at two opposite edges of the panels.Four specimens of each orientation were machined to the appropriate widths using proce- dures detailed in Chapter 4.The 0 specimens were nominally 12.7 mm wide, whereas the 90 specimens were 25.4 mm wide.The 0 specimens were 8 plies thick,whereas the 90 specimens were 16 plies thick.To establish the axial stiffness(E),Poisson's ratio (v2),and the overall stress-strain response of the 0 specimens,a bidirectional(0/90)strain gage rosette was bonded at the geometric center on one surface of each specimen.In addition,an axial gage was bonded on the opposite surface of the specimen.For the 90 ©2003 by CRC Press LLC
Appendix C Sample Laboratory Report Lamina Tensile Response The lamina tensile response of a carbon–fiber, epoxy–matrix composite was examined experimentally to establish the intrinsic mechanical properties. The test specimen geometries were chosen according to the outline presented in Chapter 5, in accordance with ASTM standards. The specimens were loaded to failure in a tensile testing machine utilizing serrated wedge grips. Average test results and standard deviations were as follows: Procedure The procedure for this experiment is detailed in Chapter 5. Briefly, unidirectional panels were configured for achieving test specimens with 0 and 90° orientation as shown in Appendix B. After the edges of the panels were trimmed, tabs made from a glass–fabric epoxy laminate were adhesively bonded to both surfaces at two opposite edges of the panels. Four specimens of each orientation were machined to the appropriate widths using procedures detailed in Chapter 4. The 0° specimens were nominally 12.7 mm wide, whereas the 90° specimens were 25.4 mm wide. The 0° specimens were 8 plies thick, whereas the 90° specimens were 16 plies thick. To establish the axial stiffness (E1), Poisson’s ratio (ν12), and the overall stress–strain response of the 0° specimens, a bidirectional (0°/90°) strain gage rosette was bonded at the geometric center on one surface of each specimen. In addition, an axial gage was bonded on the opposite surface of the specimen. For the 90° Elastic modulus in the fiber direction E1 = 126 ± 2 GPa Elastic modulus transverse to the fiber direction E2 = 10.2 ± 0.4 GPa Poisson’s ratios: Major ν12 = 0.30 ± 0.01 Minor ν21 = 0.024 Ultimate tensile stress in the fiber direction X 1 T = 2037 ± 85 MPa Ultimate tensile stress in the transverse direction X 2 T = 53 ± 8 MPa Ultimate tensile strain in the fiber direction e 1 T = 0.015 Ultimate tensile strain in the transverse direction e 2 T = 0.0057 TX001_AppC_Frame Page 227 Saturday, September 21, 2002 5:14 AM © 2003 by CRC Press LLC
specimens,a single-element strain gage oriented along the length of the specimen was bonded to each surface of the specimen in the gage section to determine the axial stress-strain response.No strain gages transverse to the specimen loading axis were used because the minor Poisson's ratio(v2) may be determined from E,E2,and vi2.Each specimen was tested in a general-purpose testing machine at a crosshead rate of 2 mm/min.Specimen load and strains were sampled throughout the test using a PC-driven data acquisition system.The specimens were loaded to failure. Specimen Dimensions Specimen cross-sectional dimensions were recorded as follows: Specimen Orientation(deg)Width(w)(mm) Thickness (t)(mm) 1 0 12.78 1.067 3 0 12.78 1.067 3 0 12.65 1.067 0 12.75 1.067 90 25.40 2.184 6 90 25.35 2.185 7 90 25.45 2.134 8 90 25.53 2.236 Stress-Strain Data The load readings were converted to axial stress readings using the cross- sectional dimensions reported above.Examples of stress and strain data recorded using the data acquisition system are tabulated below. Stress-Strain Data for Specimen 2 ([0]s)(Reduced Set from Original Record) The last two columns are strain readings from the same strain gage rosette. C:(MPa) E(ustrain) E(ustrain) -e2(ustrain) 0 0 10 0 36 310 320 120 72 590 600 200 108 860 870 280 144 1,140 1160 340 180 1,420 1440 420 252 2,010 2,000 570 395 3,050 3,030 880 647 4,900 4850 1380 1.006 7,490 7,430 2.040 1,294 9,470 9.420 2540 1,617 11,640 11590 3,070 1,9772 14,060 13.990 3,610 a Ultimate stress. ©2003 by CRC Press LLC
specimens, a single-element strain gage oriented along the length of the specimen was bonded to each surface of the specimen in the gage section to determine the axial stress–strain response. No strain gages transverse to the specimen loading axis were used because the minor Poisson’s ratio (ν21) may be determined from E1, E2, and ν12. Each specimen was tested in a general-purpose testing machine at a crosshead rate of 2 mm/min. Specimen load and strains were sampled throughout the test using a PC-driven data acquisition system. The specimens were loaded to failure. Specimen Dimensions Specimen cross-sectional dimensions were recorded as follows: Stress–Strain Data The load readings were converted to axial stress readings using the crosssectional dimensions reported above. Examples of stress and strain data recorded using the data acquisition system are tabulated below. Specimen Orientation (deg) Width (w) (mm) Thickness (t) (mm) 1 0 12.78 1.067 2 0 12.78 1.067 3 0 12.65 1.067 4 0 12.75 1.067 5 90 25.40 2.184 6 90 25.35 2.185 7 90 25.45 2.134 8 90 25.53 2.236 Stress-Strain Data for Specimen 2 ([0]8) (Reduced Set from Original Record) The last two columns are strain readings from the same strain gage rosette. σ1 (MPa) ε1 (µstrain) ε1 (µstrain) –ε2 (µstrain) 0 0 10 0 36 310 320 120 72 590 600 200 108 860 870 280 144 1,140 1,160 340 180 1,420 1,440 420 252 2,010 2,000 570 395 3,050 3,030 880 647 4,900 4,850 1,380 1,006 7,490 7,430 2,040 1,294 9,470 9,420 2,540 1,617 11,640 11,590 3,070 1,977a 14,060 13,990 3,610 a Ultimate stress. TX001_AppC_Frame Page 228 Saturday, September 21, 2002 5:14 AM © 2003 by CRC Press LLC
Stress-Strain Data for Specimen 6([90]16) (Reduced Set from Original Record) G2 (MPa) E2(ustrain) 2(ustrain) 0 0 1.77 180 200 3.54 350 380 5.31 520 550 10.6 1040 1120 17.7 1750 1860 23.0 2290 2410 30.1 2990 3130 35.4 3520 3690 40.7 4120 4330 49.6 5050 5280 60.2 6220 6510 63. 6580 6879 Ultimate stress. Test Results Test results for three representative 0 test specimens are presented in graph- ical form in Figures C.1-C.3.The linear response region in the fiber direction is bounded by a strain of about 0.004.It is noteworthy that the stress-strain response exhibits strain hardening characteristics-a reflection of the strain hardening behavior of carbon fibers.Results for three representative 900 specimens are shown in Figures C.4-C.6.Here only a modest nonlinearity in the stress-strain response is observed.The strain softening is due to the nonlinear response of the epoxy matrix. Reduced Data The mechanical properties were reduced from the measured data using procedures and equations provided in Chapter 5.The following equations were employed: (C.1) E1 2s (C.2) E XT=G (C.3) 59 (C.4) E2 X=o2 (C.5) ©2003 by CRC Press LLC
Test Results Test results for three representative 0° test specimens are presented in graphical form in Figures C.1–C.3. The linear response region in the fiber direction is bounded by a strain of about 0.004. It is noteworthy that the stress–strain response exhibits strain hardening characteristics — a reflection of the strain hardening behavior of carbon fibers. Results for three representative 90° specimens are shown in Figures C.4–C.6. Here only a modest nonlinearity in the stress–strain response is observed. The strain softening is due to the nonlinear response of the epoxy matrix. Reduced Data The mechanical properties were reduced from the measured data using procedures and equations provided in Chapter 5. The following equations were employed: (C.1) (C.2) (C.3) (C.4) (C.5) Stress-Strain Data for Specimen 6 ([90]16) (Reduced Set from Original Record) σ2 (MPa) ε2 (µstrain) ε2 (µstrain) 00 0 1.77 180 200 3.54 350 380 5.31 520 550 10.6 1040 1120 17.7 1750 1860 23.0 2290 2410 30.1 2990 3130 35.4 3520 3690 40.7 4120 4330 49.6 5050 5280 60.2 6220 6510 63.4a 6580 6879 a Ultimate stress. E1 1 1 = σ ε υ ε ε 12 2 1 = − XT ult 1 1 = σ E2 2 2 = σ ε XT ult 2 2 = σ TX001_AppC_Frame Page 229 Saturday, September 21, 2002 5:14 AM © 2003 by CRC Press LLC
Carbon/Epoxy,[0]a 2000 -2 1500 00000 1000 500 0000000 0 ,2 .4 .681.0 1.2 1.4 76 Strain, FIGURE C.1 Stress-strain results for specimen 1(0). Carbon/Epoxy,[0]8 2000 -82 E1 1500 1000 500 0 6 .81.0 1.2 1.4 1.6 Strain,% FIGURE C.2 Stress-strain results for specimen 2(0). Carbon/Epoxy,[0] -82 E1 2000 1500 1000 500 0 .4 .6.81.0 1.2 1.4 1.6 Strain,% FIGURE C.3 Stress-strain results for specimen 3(0). ©2003 by CRC Press LLC
FIGURE C.1 Stress–strain results for specimen 1 (0°). FIGURE C.2 Stress–strain results for specimen 2 (0°). FIGURE C.3 Stress–strain results for specimen 3 (0°). TX001_AppC_Frame Page 230 Saturday, September 21, 2002 5:14 AM © 2003 by CRC Press LLC
Carbon/Epoxy,[9011s o 50 40 30 20 10 0 .2 .3.4 .5 .6 ,7 ,8 Strain (2),% FIGURE C.4 Stress-strain results for specimen 5(90). Carbon/Epoxy,[90]1 60 50 40 30 20 10 0 2 3 .4.5 .6 7 .8 Strain (), FIGURE C.5 Stress-strain results for specimen 6(90). 50 Carbon/Epoxy,[9011s 40 00 0 生四 0000-00-0-0-0000-0-0-000-0-00 20 10 0 1 2 3 5 .6 Strain (2)% FIGURE C.6 Stress-strain results for specimen 7(90). ©2003 by CRC Press LLC
FIGURE C.4 Stress–strain results for specimen 5 (90°). FIGURE C.5 Stress–strain results for specimen 6 (90°). FIGURE C.6 Stress–strain results for specimen 7 (90°). TX001_AppC_Frame Page 231 Saturday, September 21, 2002 5:14 AM © 2003 by CRC Press LLC