Question 11.S.P.2: The [(±45/0)2]s graphite-epoxy laminate described in Sample ...
The [(±45/0)_{2}]_{s} graphite-epoxy laminate described in Sample Problem 1 is again subjected to type S4 simple supports along all four edges and a uniform transverse load q(x,y) = 30 kPa. However, the plate is now also subjected to uniform in-plane stress resultants N_{xx} = N_{yy}. Use a Ritz analysis to deter-mine the maximum out-of-plane displacement for 0 < N_{xx} = N_{yy}< 100 kN/m.
As was the case for Sample Problem 1, solutions for this prob-lem can be obtained using program SYMM (described in Sec. 6). Multiple solutions were obtained using the specified range in N_{xx} and N_{yy}, and 100 terms were used in the displacement field in all cases.
Results are summarized in Fig. 5. The maximum displacement occurs at the center of the plate (i.e., at x = 150 mm, y = 75 mm). As would be expected, the in-plane tensile stress resultants tend to reduce out-of-plane displacement. For N_{xx} = N_{yy} = 0, a maximum out-of-plane displacement of 8.03 mm is predicted. In contrast, if tensile stress resultants N_{xx} = N_{yy} = 100 kN/m are applied, the maximum out-of-plane displacement is reduced to 0.71 mm.
