Environmental effects creep behavior

Additional factors which must be taken into account are environmental effects (thermal as well as chemical), effects of defects, statistical variability of the material, long-term behavior, and cyclic versus static loading effects. Assessment of these effects requires the end user to conduct a large series of tests using multiple specimens. A typical series will examine a unidirectional material in tension in the 0, 90, and cross-ply directions 0, 90, and cross-ply in compression and 1-2, 1-3, and 2-3 shear at different temperatures ranging from —54°C to the expected service temperature creep rupture at temperatures up to the expected service temperature and fatigue at room and elevated temperature. This series of tests, shown in Table 12.1, may require over 400 specimens. 

A comprehensive analytical model for predicting long term durability of resins and of fibre reinforced plastics (FRP) taking into account viscoelastic/viscoplastic creep, hygrothermal effects and the effects of physical and chemical aging on polymer response has been presented. An analytical tool consisting of a specialized test-bed finite element code, NOVA-3D, was used for the solution of complex stress analysis problems, including interactions between non-linear material constitutive behavior and environmental effects. 

Chevali, V.S., Dean, D.R., Janowski, G.M. Effect of environmental weathering on flexural creep behavior of long fiber-reinforced thermoplastic composites. Polym. Degrad. Stab. 95, 2628-2640 (2010)... 

Harada, Y., Suzuki, T., Hirano, K., Nakagawa, N., Waku, Y. (2005). Environmental effects on ultra-high temperature creep behavior of directionally solidified oxide eutectic ceramics. Journal of the European Ceramic Society, 25(8 SPEC. ISS.), 1275-1283. 

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