Influence of nanoclays on water uptake and flexural strength of glass–polyester composites

Abstract

Fiber-reinforced polyester composites have received significant attention in a variety of applications due to their considerable potential due to such characteristics as high strength, stiffness, and modulus. However, one of the most important concerns about polymeric composites is their sensitivity to moisture attack. This work has been conducted to investigate the effects of nanoclay addition on reinforcing glass/polyester composites against water absorption and the resultant deterioration of flexural strength. Therefore, chopped strand mat and woven fiberglass polyester specimens were fabricated by using the hand lay-up technique with varying weight percentages of Cloisite 20A nanoclays (0, 1.5, and 3 wt%) and immersion in water for a time duration of 21 days. The specimens were weighed for the water absorption test. The results showed a remarkable drop in water absorption of the composite samples with the increase of nanoclay content. Moreover, although all the pure and nanocomposite specimens underwent degradation in flexural strength due to the water absorption, the strength was found to significantly increase with increasing the percentage of nanoclay at all immersion periods. The experimental results were confirmed by scanning electron microscopy (SEM). SEM images indicated that the presence of nanoclay protected the fiber/matrix interfaces.

Development of epoxy-based sandwich composite panel with hollow glass microspheres/clay hybrid core and banana fiber facesheet for structural applications

“…From the graph, it is clear that the sandwich composites with HGM cores absorb water at a considerably higher rate than the sandwich composite with hybrid cores which is because water invades the interface layer of HGM and epoxy resin of HGM and the pores, this may cause damage to the HGM at higher concentration. A maximum of 4.54 % absorption is measured in the sandwich composites with the hybrid core while 8.61 % is observed in the sandwich composites with HGM core due to the presence of nanoclay in the hybrid core which provides moisture resistance to the sandwich composites because clay contains silicon-oxygen (SiO 4 ) tetrahedron bilayers with deep-rooted octahedral layers of aluminum and iron which can resist moisture and this is similar to result reported by Nemati Giv et al [ 68 ] on water absorption behavior of composites filled with nanoclay.

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Durability prediction analysis on mechanical properties of GFRP upon immersion in water at ambient temperature

“…As presented in Table 2 and Figure 5, the flexural strength of all the three glass fiber weight percentage composites decreased upon immersion in water at ambient temperature. A considerable reduction in flexural strength of composite samples with the increase in immersion time can be noted, and a similar trend is reported by Nemati Giv et al, (Nemati Giv et al, 2020). Increasing glass fiber weight percentage declined the reduction of flexural strength from 16% at 30 wt.% of glass fiber to 14 and 09% at 40 and 50 wt.% of glass fiber, respectively, for an immersion period of 180 days.…”

“…However, the rates of water absorption declined over time. The weight percentage of composite has reduced as a result of chemical interaction between polyester and water molecules in the composite at the end stages of longer immersion duration (Nemati Giv et al, 2020). The moisture absorption is observed with polyester only because of the "no moistureabsorption property" of glass fiber (Chaichanawong et al, 2016).…”