PSI - Issue 25

J.M. Parente et al. / Procedia Structural Integrity 25 (2020) 282–293 J.M. Parente/ Structural Integrity Procedia 00 (2019) 000 – 000

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Table 3 Articles on fatigue behaviour in reinforced composites published since 2010 with matrix and nanoparticle used.

Author/ year

Matrix

Nanoparticle

Type of fatigue test Tensile/ flexural

Glass fibre/ epoxy

Graphene

Yavari et al. (2010) Kim et al. (2012) Shen et al. (2013) Knoll et al. (2014)

Carbon nanotube aerogel Graphene nanoplatelet

Tensile Tensile Tensile Bending Tensile Tensile Bending

Carbon fibre/ epoxy Carbon fibre/ epoxy

Graphene nanoplatelets

Graphene nanoplatelets/ carbon nanotube

Iron

Graphene oxide

Lin et al. (2014)

Si 3 N 4 /PEN

Graphene Graphene Graphene

Paradee et al. (2015)

Kumar and Xavior (2016) Aluminium

Copper

Hwang et al. (2017) Bourchak et al. (2018) Leopold et al. (2019) Zhang et al. (2019)

Glass fibre/ epoxy Carbon fibre/ epoxy Graphene aerogel

Carbon nanotubes/ graphene nanoplatelets Tensile

Graphene nanoplatelets

Tensile Bending

-

lowest stress levels. Different nano-reinforcements were also compared by these authors for the same content (0.2 wt.%), and, dependently on the applied stress, graphene platelets promoted fatigue lives about 1-2 orders of magnitude higher than those observed with single walled carbon nanotube and multiwalled carbon nanotubes. Finally, these authors also carried out fatigue tests in uniaxial tensile mode, and they found improvements relatively modest (3-5 times higher depending on the stress level) relatively to the bending fatigue results, when composites with neat resin were compared with nano-enhanced by 0.2 wt.% of graphene platelets. The benefits observed in the bending mode are explained by the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling under compressive stress. On the other hand, in terms of tensile fatigue the interface is less important because the fibres are more effective than the matrix in carrying tensile loads. Shen et al. (2013) studied the static properties, in tensile and bending mode, of a carbon fibre/epoxy laminate reinforced by different contents of graphene nanoplatelets. The benefits obtained in terms of fatigue strength were evaluated only for 0,25 wt.% of graphene nanoplatelets, and the tests were carried out only in tensile mode at 5 Hz and at R=0.1. Compared to composite laminates with neat resin, they found fatigue lives around 1.2 to 5.4 times and 15.3 to 37.1 times longer for higher and lower stress levels, when 0.25 wt.% of graphene nanoplatelets was added to the epoxy resin. Simultaneously, the fatigue life of the neat laminate was more sensitive to applied stress levels compared to the composite laminate with nano-enhanced resin. From the fracture morphologies, it was possible to conclude that adding graphene nanoplates to the resin suppresses the formation of micro cracks during cyclic loading and prevents crack expansion, which weakens the effects of delamination, minimizes fractures and, consequently, improves the fatigue life. In fact, when graphene nanoplates are present, they improve significantly the adhesion between carbon fibres/epoxy resin, which explains the delamination decreasing and the reduction of cracks expansion. Knoll et al. (2014) investigated the effect of different types of carbon nanoparticles (0.3 wt.% multiwall carbon nanotubes and 0.3 wt.% few layered graphene) on the fatigue behaviour of carbon fibre laminates. The carbon fibre was impregnated with nano-enhanced epoxy resin. Fatigue tests were performed in tensile mode at R = 0.1, frequency of 6 Hz and at three load levels (80%, 70% and 65% of mean tensile strength). The variation of stiffness was monitored as an indicator for material degradation as well as the specimen surface temperature was monitored by an infrared camera. Finally, the fracture surfaces were analysed by scanning electron microscopy (SEM) to reveal the nanoparticles influence on the fatigue damage. These authors found an increase on the fatigue life with the presence of carbon nanoparticles, but much more pronounced for few layered graphene. For example, at the highest load level (80% of mean tensile strength) the average fatigue life is 5 and 15 times longer when multiwall carbon nanotubes and few layered graphene were added, respectively. On the other hand, at the lowest load level (65% of mean tensile strength) these values are 2 and 1.9 times longer, respectively. The stiffness degradation was analysed and, regardless of the differences observed, all composite laminates presented the three typical stages. The unmodified laminates exhibit a significantly larger initial degradation (stage I) compared to the nano-reinforced laminates. In stage II, the degradation of the unmodified laminates proceeds faster, and the stage III occurs earlier (for a shorter number of fatigue cycles). The stiffness degradation of the laminates with nano-enhanced resin proceeds more slowly and at a