Page 321 - Mechanics Analysis Composite Materials

306 Meclicmics und unnlwis of coniposite niaterials

Fig. 7.3. A composite section of a space telescope. Courtesy of CRISM

0 ?qb$ angle-ply carbon-poxy external skin with the following parameters:
@s = 20", hE = 3.5 mm, ET = 120 GPa,
= = 0.27,
E; = 11 GPd, qz 5.5 GPa, 19;~
= 1 W/m K, 2; = 0.6 W/m K,
I - - -0.3 x 10 l/OC, = 34 x 10 ' 1/"C,
0 carbon-poxy lattice laye; (see Fig. 4.90) formed by a system of &4, helical ribs
with
4, = 26", h, = 9 mm, 6,. = 4 mm, a,. = 52 mm, E, = 80 GPa,
I., = 0.9 W/m K, E, = -1 x lop6 1/"C,
0 internal skin made of aramid fabric with
h: = 1 mm, E: = E: = 34 GPa, G:, = 5.6 GPa,
v:, = = 0.15, A: = A: = 0.13 Wjm K,
a: = a: = 0.8 x lop6 l/OC (x and 1' are the axial and the circumferential
coordinates of the cylinder),
0 internal layer of aluminum foil with
hf = 0.02 mm, Ef = 70 GPa, vf = 0.3,
I,t = 210 W/m K, cq = 22.3 x 10 I/OC.
Apparent thermal conductivity of the cylinder wall can be found with the aid of
Eqs. (7.10), (7.1 1) and the continuum model of the lattice layer described in Section
4.7 as

Calculating yields A., = 0.64 W/m K. Thermal resistance of a unit length of this
structure is

1 K
rlr = - -
.
36.8
=
Dh Wm