The scope of the present work is to experimentally investigate the effect of pre‐bond contamination with de‐icing (DI) fluid and the combined effect of DI fluid and hygrothermal ageing on the fracture toughness of carbon fibre reinforced plastic bonded joints. These scenarios could occur in the implementation of an adhesively bonded patch repair in a composite aircraft structural part. To this end, mode I and mode II fracture toughness tests were conducted on contaminated specimens and mode II fracture toughness tests on contaminated/aged specimens. Three levels of contamination with a de‐icer were considered. The hygrothermal ageing conditions applied until saturation are 70°C/85% relative humidity. The experimental results reveal a detrimental effect of DI fluid on both mode I and mode II fracture toughness of the bonded joints. With increasing the contamination level, the mode I and mode II critical energy release rates decrease. Under mode I loading, the specimens failed mainly in light‐fibre‐tear mode, while under mode II loading, in adhesive failure mode. Hygrothermal ageing decreased further the mode II fracture toughness of the specimens and increased the adhesive failure mode. The present study reveals that the pre‐bond DI contamination and after‐bond ageing could critically degrade the strength of adhesively bonded patch repairs.

Multiwall carbon nanotubes (MWCNTs) and glycidyl polyhedral oligomeric silsesquioxanes (GPOSS) are common additives to enhance electrical conductivity and flame resistance of polymers, respectively. Yet, these additions may appreciably influence their mechanical behavior. In the present work, the synergistic effect of the addition of MWCNTs and GPOSS on the mechanical behavior of multifunctional polymers subjected to several types of quasi‐static loading was investigated. The results were discussed, supported by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analyses. A significant increase in the tensile strength of the polymers filled only with MWCNTs is observed as compared to the unfilled material. On the other hand, all other properties investigated, namely, compression, flexural as well as GIC fracture toughness properties were degraded. The incorporation of GPOSS into the polymer further deteriorates the mechanical behavior of the filled material. SEM analysis has revealed MWCNTs agglomerations of the order of 100 μm, while EDS analysis has revealed some areas of incomplete dissolution of the GPOSS into the resin. The results underline the sensitivity of the mechanical behavior of the multifunctional polymers on the dispersion features of the additives and the significance of both CNT agglomerates and GPOSS aggregates for the observed mechanical behavior. POLYM. ENG. SCI., 57:528–536, 2017. © 2016 Society of Plastics Engineers

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Multi walled carbon nanotubes (MWCNTs) and glycidyl polyhedral oligomeric silsesquioxanes (GPOSS) are common additives to enhance electrical conductivity and flame resistance of polymer resins, respectively. Yet, these additions may appreciably influence the mechanical behaviour of the polymers. In this work, the synergistic effect of MWCNTs and GPOSS on the fatigue behaviour of the polymer RTM6‐2 was investigated. The results were discussed supported by scanning electron microscopy and energy dispersive spectroscopy analyses. By enhancing the polymer with MWCNTs, a slight decrease in the fatigue life is observed in the range of the low stress levels; however, it tends to coincide with the reference material at fatigue limit. The incorporation of the flame retardant GPOSS into the polymer enhanced with MWCNTs seems to have a significant deteriorating effect on the fatigue life. Scanning electron microscopy and energy dispersive spectroscopy investigation revealed MWCNTs and GPOSS agglomerations; they seem to act as defects leading to a degradation of the fatigue resistance.

Purpose Over the last decades, self-healing materials based on polymers are attracting increasing interest due to their potential for detecting and “autonomically” healing damage. The use of embedded self-healing microcapsules represents one of the most popular self-healing concepts. Yet, extensive investigations are still needed to convince on the efficiency of the above concept. The paper aims to discuss these issues. Design/methodology/approach In the present work, the effect of embedded self-healing microcapsules on the ILSS behavior of carbon fiber reinforced composite materials has been studied. Moreover, the self-healing efficiency has been assessed. The results of the mechanical tests were discussed supported by scanning electron microscope (SEM) as well as by Attenuated Total Reflection–Fourier-transform infrared spectroscopy (ATR–FTIR) analyses. Findings The results indicate a general trend of a degraded mechanical behavior of the enhanced materials, as the microcapsules exhibit a non-uniform dispersion and form agglomerations which act as internal defects. A remarkable value of the self-healing efficiency has been found for materials with limited damage, e.g. matrix micro-cracks. However, for significant damage, in terms of large matrix cracks and delaminations as well as fiber breakages, the self-healing efficiency is limited. Originality/value The results obtained by SEM analysis as well as by ATR–FTIR spectroscopy constitute a strong indication that the self-healing mechanism has been activated. However, further investigation should be conducted in order to provide definite evidence.