Under specific couplings of the elastic constants of orthotropic media, a very important family of orthotropic materials degenerates into the class of either transversely isotropic or isotropic media. Most of the engineering composites, especially fiber-reinforced, are of transversely isotropic media. Hence, for different composites, the norms are calculated for each material (Radwan, 1991) in Table 3. From the table, it can be clearly concluded that B(4)/N5505 has the strongest stiffness effect among the five composites. From Table 4, the most isotropic composite is E-glass/epoxy, and the most anisotropic composite is T300/5208. From the latter table, it was possible to measure the degree of anisotropy for several composites.
Materials |
Cu |
C v_22 |
C v_12 |
C v-23 |
C ‘-44 |
C55 |
Norm |
T300/5208 |
184.60 |
13.94 |
5.88 |
7.06 |
3.44 |
7.17 |
174.06 |
B (4)/N5505 |
208.08 |
25.04 |
95.72 |
12.70 |
6.17 |
5.59 |
284.62 |
AS/H3501 |
141.80 |
12.20 |
85.08 |
6.21 |
3.00 |
7.10 |
222.11 |
E-lass/Epoxy |
41.12 |
11.57 |
21.38 |
6.04 |
2.77 |
4.14 |
62.58 |
Kev 9/Epoxy |
78.66 |
7.53 |
53.49 |
3.86 |
1.83 |
2.30 |
132.92 |
Table 3. Elastic constants and norms for transversely isotropic materials, GPa |
Material |
N iso |
N. aniso |
N |
N iso N |
N. anis N |
T300/5208 |
99.67 |
142.64 |
174.06 |
0.56 |
0.82 |
B (4)/N5505 |
223.39 |
176.37 |
284.62 |
0.78 |
0.62 |
AS/H3501 |
173.04 |
139.24 |
222.11 |
0.78 |
0.63 |
E-glass/Epoxy |
55.01 |
29.84 |
62.58 |
0.88 |
0.48 |
Kev 49/Epoxy |
105.13 |
81.34 |
132.92 |
0.79 |
0.61 |
Table 4. The Norm ratios for transversely isotropic materials, GPa