Page 310 - Mechanics Analysis Composite Materials

Chapter 6. Failure criteria arid strength of laniinates 295

Fig. 6.21. Torsion of a drive shaft.

Using Eqs. (5.71) we can determine strains in the principal material coordinates 1, 2
of f45" layers (see Fig. 6.21)

Applying Eqs. (5.72) and the foregoing results we can express stresses in terms
of T as

The problem is to determine the ultimate torque, T,.
First, use the maximum stress criterion, Eqs. (6.2) which gives the following four
values of the ultimate torque corresponding to tensile or compressive failure of
f45" layers:

I
-t
o+ = 0, Tu =34 kNm,
_-
-
oI = oI, Kl = 30.7 kNm,
0; =at, Tu= 25.5 kNm,
c2 = o,, T,, = 23.7 kNm .
~.
The actual ultimate torque is the lowest of these values, Le., Tu = 23.7 kNm.
Now apply the polynomial criterion in Eq. (6.14), which acquires the form