Question

3. A [0/90]s graphite/epoxy laminate is subjected to a tensile normal load of 1N/m in the x- direction (the direction parallel to the fibers in the 0° ply). Assume the thickness of each ply is 5 mm and use properties of unidirectional graphite/epoxy lamina from the table. a) Calculate the resultant strains of the laminate b) Calculate the global stresses in the laminate c) Calculate the principal stresses (stresses in material directions) of the top layer. Typical Mechanical Properties of a Unidirectional Lamina (SI System of Units) Glass/ Boron/ Graphite/ Property Symbol Units epoxy epoxy epoxy Fiber volume fraction Longitudinal elastic modulus Transverse elastic modulus Major Poisson's ratio Shear modulus Ultimate longitudinal tensile (o 0.45 38.6 0.50 0.70 GPa GPa 181 204 8.27 0.26 4.14 18.50 0.23 5.59 10.30 0.28 7.17 12 GPa MPa 12 1500 1500 40 246 1062 610 31 118 72 1260 1ult strength Ultimate longitudinal (MPa compressive strength Ultimate transverse tensile MPa MPa MPa um/m/oC um/m/°C m/m/kg/kg m/m/kg/kg 61 202 67 σ2'ult strength Ultimate transverse (o), compressive strength Ultimate in-plane shear strength Longitudinal coefficient of 8.6 0.02 thermal expansion Transverse coefficient of 22.1 30.3 thermal expansion Longitudinal coefficient of 0.00 0.00 0.00 moisture expansion Transverse coefficient of 0.60 0.60 0.60 moisture expansion Source: Tsai, S.W. and Hahn, H.T., Introduction to Composite Materials, CRC Press, Boca Raton, FL, Table 1.7, p. 19; Table 7.1, p. 292; Table 8.3, p. 344. Reprinted with permission.

Answer 1

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