Stress Effects on Fluid Ingress and Its Relation to Damage

9 Stress Effects on Fluid Ingress and Its Relation to Damage 

Weight-gain data were collected on uni-directionally reinforced AS4/3502 graphic/ epoxy composite coupons loaded transversely to the fiber direction as well as on neat 3502 samples. All specimens were exposed to RH = 98% and T = 40°C, with different samples loaded in tension at 0, 15, 30, and 45% of the dry epoxy failure stress of 52 MPa. 

Results for the epoxy specimens are shown in Figs. 4.20-4.24. These results show that nioo increases monotonically with the stress a suggesting the relation rrioo Aa that tallies with the model presented in Sect. 6.3, while D increases with a during absorption and decreases during desorption. In addition. Fig. 4.16 demonstrates the presence of a hystersis loop in the absorption/desorption data for sufficiently high levels of stress (Fig. 4.25). 

Note that the weight gain data follow curve A in Fig. 4.2 rather than the Fickian model. At least for the case of cr = 0 this suggests the presence of a two phase diffusion process. 

Credit Regester, R. F. (1969). Behaviour of fibre reinforced plastic materials in chemical service. Corrosion 25, pp. 157-167. Reprinted by permission of NACE international 

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