tension in the 00 direction at cryogenic temperatures. The nominal specimen thickness

and width were 2.2 mm and 15 mm. The mechanical loads corresponding to matrix

cracks (Table 4-1) were extracted from Figure 5 in Aoki et al. (2000). The strain

transverse to the fiber direction, 82, iS assumed to be the strain that induces matrix-

cracking in the laminate. Based on the load condition and the configuration of the

laminate, the transverse strain 82 in the 900 plies is the most critical strain in the laminate.



 0.012

 0.010

 0.008
 -4 Epsilon1 -5 Epsilon2 -A Gammal2
 0.006

 c* 0.004

 0.002

 0.000

 -0.00 ) 40 -0 0 0

 -0.004

 -0.000

 Temperature (aF


 Figure 4-2. Polynomials fit to coefficients of thermal expansion: a1 and u2

 Normally, strain allowables are calculated by loading laminates at room

temperatures. However, for micro-cracking, the residual stresses are of primary

importance, so all strains are calculated from the stress-free temperature, assumed to be

300 oF. The calculations are made by integrating the thermal strains from the stress free

temperature to the operational temperature as described in the next section.