Lamina Off-Axis Tensile Response The off-axis tension test of unidirectional composites has received consider- able attention by the composites community."Off-axis"here refers to the material axes(1-2)being rotated through an angle 0 with respect to the specimen axis and direction of loading(Figure 9.1).The off-axis specimen is typically 230 mm long and between 12.7 and 25.4 mm wide.A thickness of eight plies is common(0.127 mm ply thickness). The off-axis tension test is rarely used to determine basic ply properties. Most commonly,the purpose of this test is to verify material properties determined in tension,compression,and shear,as discussed in Chapters 5-7, using the transformed constitutive relations discussed in Chapter 2.Testing of specimens at off-axis angles between 10 and 20 produces significant shear in the principal material system.Consequently,the 10 off-axis test has been proposed as a simple way to conduct a shear test [1].The test has been used FIGURE 9.1 Geometry of the off-axis tensile coupon. ©2003 by CRC Press LLC9 Lamina Off-Axis Tensile Response The off-axis tension test of unidirectional composites has received consider￾able attention by the composites community. “Off-axis” here refers to the material axes (1-2) being rotated through an angle θ with respect to the specimen axis and direction of loading (Figure 9.1). The off-axis specimen is typically 230 mm long and between 12.7 and 25.4 mm wide. A thickness of eight plies is common (0.127 mm ply thickness). The off-axis tension test is rarely used to determine basic ply properties. Most commonly, the purpose of this test is to verify material properties determined in tension, compression, and shear, as discussed in Chapters 5–7, using the transformed constitutive relations discussed in Chapter 2. Testing of specimens at off-axis angles between 10 and 20° produces significant shear in the principal material system. Consequently, the 10° off-axis test has been proposed as a simple way to conduct a shear test [1]. The test has been used FIGURE 9.1 Geometry of the off-axis tensile coupon. w LT LT LG L I x y 2 θ TX001_ch09_Frame Page 131 Saturday, September 21, 2002 5:01 AM © 2003 by CRC Press LLC