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Self-resistance electric (SRE) heating for carbon fiber reinforced plastics (CFRP) is an alternative out-of-autoclave curing methodology that has high efficiency and low energy consumption. However, thanks to the heating mechanism of inside-out conduction, which is significantly different from that of the traditional outside-in heating process, the temperature distribution and its homogenization strategy still need further investigation. This work focuses on analyzing the affecting factors of the temperature uniformity of CFRP laminates during the SRE curing process utilizing a multi-physical numerical computation model and experimental verification. It is found that mold sizes have the most significant impact due to the non-uniform center-to-edge heat absorption of the mold. The maximum temperature difference during the untreated process could be lower than 20 K if the excess size proportion of the mold is smaller than 10%. Thermal barriers made of aerogel homogenize the temperature distribution during the dwell stage, reducing the maximum temperature difference by 84.18%. Considering that the mold size is sometimes unchangeable, the existence of auxiliary heating elements compensates the heat dissipation from the self-heated laminate and reduces the maximum temperature difference by 79.81%. Based on analysis results, a temperature homogenization strategy is proposed, where the maximum temperature difference is reduced by 86.15%.

Because of good crack growth resistance owe to the fibers between the aluminum layers, fiber metal laminates (FML) offer significant improvements compared to currently applied materials for aircraft structures. The crack resistance of different reinforced fibers, glass fiber, and carbon fiber, under stress ratio R =-1, 0.1, and 0.5, respectively, are analyzed through test data. The results showed significant scatter in the positive stress ratio and obvious difference between two outer aluminum layers. So, the failure criterions of metal materials specified in the test standard are unsuitable for the FMLs fatigue test, and it is a problem to determine the failure criterion according to the engineering applications. This study is an experimental investigations with respect to the FMLs crack resistance and a qualitative conclusions have been drawn from the data analysis.

ABSTRACT:The effects of novolac resin (NR) and modified novolac resin (MNR) on the stiffness and toughness of the carbon fiber (CF)/epoxy composites were studied when using these two kinds of modifiers with different physical and chemical performance. The results show that both NR and MNR are excellent toughening agents for the CF/epoxy composites, and the composites treated with MNR present better toughness than that of NR. However, the stiffness of the composites is almost unchanged when adding MNR. The mechanisms were analyzed by fracture studies using scanning electron microscopy and the decrease of cross-link density caused by MNR was deduced to the toughening effects. C