May 6, 2008 by Victor Cortez
I was reviewing the homework assignment for session #4, and I was confused on how the values for Qxx, Qyy, Qxy and Qss were obtained. How is it known to select the T300/N5208 values? The problem did not specify this, or did I miss something. Can someone explain?
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For this particular
For this particular assignment, the material used was T300/N5208. You are right, it is not clearly given in the assignment. Generally, unless otherwise stated, the material we consider is T300/N5208.
Professor Tsai has pointed out that the stiffness values (Q) are given in Table 3.2 from row 13 to 16 onwards in the book "Theory of Composites Design". The other way to find Q values would be to use Mic-Mac. If you go to, say Mic-Mac In-Plane, then choose T300/5208 and then Mic-Mac will automatically calculate the Q values for you.
Pranav Dhoj Shah, PhD
The on-axis stiffness matrix
The on-axis stiffness matrix (Qxx, Qyy, Qxy and Qss) can be
obtained from the Engineering Constants of the material (Ex,
Ey, Es, nux) using the Equations 2.22. For the material T300/
5208, Equations 2.29 show the on-axis stiffness matrix and
compliance matrix elements.
However, in the assignment for session 4, the values of Qxx,
Qyy, Qxy and Qss were not required for Problems 1, 2, 3, 5
and 6. Problem 1 asked for a transformation matrix. In problem
2, the off-axis elements of the stiffness matrix should be expressed
in terms of the Ui's. In problem 3, the values for the C[0] were given
(it mentions, however, T300/5208) and the elements for the C[45]
transformed matrix were asked. Problems 5 and 6 are independent
of the material.
The only problem that required the on-axis stiffness matrix elements
was Problem 4. However, it is shown on the graph that the lower
bound material is AS/3501 and the upper bound material is T300/
5208.
Carlos A. Cimini Jr.
Visiting Scholar
Aero & Astro
Stanford University