“…The moisture absorption of NF reinforced polymeric composites is highly dependent on the moisture absorption of the fibers used, 27 which increases with increasing fiber volume fraction. 22,48 With the same fiber content considered in this study, the reasons for the differences in their water absorption are the variations that emerge from the differences in the chemical alteration of fiber, the fiber architecture and the fiber/matrix interface. 22,48 Figure 11.Moisture absorption of untreated and treated sisal-PET composites.…”
Section: Resultsmentioning
confidence: 99%
“…22,48 With the same fiber content considered in this study, the reasons for the differences in their water absorption are the variations that emerge from the differences in the chemical alteration of fiber, the fiber architecture and the fiber/matrix interface. 22,48 Figure 11.Moisture absorption of untreated and treated sisal-PET composites.…”
Section: Resultsmentioning
confidence: 99%
“…22,48 With the same fiber content considered in this study, the reasons for the differences in their water absorption are the variations that emerge from the differences in the chemical alteration of fiber, the fiber architecture and the fiber/matrix interface. 22,48 As indicated from Table 5, within a given immersion time, the RSC absorbs highest equilibrium moisture, M max than the Al-SC and Al-ASC ones. Several reasons are responsible for this change; the RSC contain raw sisal with more hydroxyl groups which can trap more water molecules during the composite immersion time.…”
The use of thermoplastics (TPs) for natural fiber composites is restricted to commodity ones like polypropylene and polyethylene However, using engineered TPs such as polyethylene terephthalate (PET) will benefit from its technical and economic advantages. The research aims to characterize injection molded PET composites reinforced with sisal fibers treated differently. Polyethylene terephthalate composites containing 40 wt.% of untreated, alkaline-treated, and alkali/acetylation treated sisal fibers were prepared using compounding and injection molding processes and then characterized. It has been found that production of sisal-PET composites by compounding and injection molding has been shown to be possible. Thermal damage to sisal fiber was noticed during composite production. Based on the thermogravimetric analysis analysis, a net weight loss (excluding water loss) of 11.1%–14.0% was observed at the operating temperatures of the two processes. The addition of 40 wt.% of sisal to the PET matrix improved the tensile modulus by 137%. Further improvement by 179% was observed when alkali-treated sisal fiber was used. The combined alkali/acetylation treatment of sisal yields more enhancement by 233%. This is a significant advancement because modulus is the most influential parameter during the design and service of an engineering product. Generally, compared to the raw sisal composite (RSC) the interfacial, mechanical, thermal, and water absorption properties of the alkali treated sisal composite (Al-SC) and alkali/acetylated sisal composite (Al-ASC) specimens recorded an improvement. Relative to the natural fiber reinforced thermoplastic composites that were commercialized in the automotive industry, the produced sisal–PET composites resulted in a considerable improvement of 66.6%–190% in flexural strength and by 110.5%–410.0% in flexural modulus, depending on sisal fiber treatment and the composite to be compared. Thus, the studied composites can be recommended for various parts of automobiles.
“…The moisture absorption of NF reinforced polymeric composites is highly dependent on the moisture absorption of the fibers used, 27 which increases with increasing fiber volume fraction. 22,48 With the same fiber content considered in this study, the reasons for the differences in their water absorption are the variations that emerge from the differences in the chemical alteration of fiber, the fiber architecture and the fiber/matrix interface. 22,48 Figure 11.Moisture absorption of untreated and treated sisal-PET composites.…”
Section: Resultsmentioning
confidence: 99%
“…22,48 With the same fiber content considered in this study, the reasons for the differences in their water absorption are the variations that emerge from the differences in the chemical alteration of fiber, the fiber architecture and the fiber/matrix interface. 22,48 Figure 11.Moisture absorption of untreated and treated sisal-PET composites.…”
Section: Resultsmentioning
confidence: 99%
“…22,48 With the same fiber content considered in this study, the reasons for the differences in their water absorption are the variations that emerge from the differences in the chemical alteration of fiber, the fiber architecture and the fiber/matrix interface. 22,48 As indicated from Table 5, within a given immersion time, the RSC absorbs highest equilibrium moisture, M max than the Al-SC and Al-ASC ones. Several reasons are responsible for this change; the RSC contain raw sisal with more hydroxyl groups which can trap more water molecules during the composite immersion time.…”
The use of thermoplastics (TPs) for natural fiber composites is restricted to commodity ones like polypropylene and polyethylene However, using engineered TPs such as polyethylene terephthalate (PET) will benefit from its technical and economic advantages. The research aims to characterize injection molded PET composites reinforced with sisal fibers treated differently. Polyethylene terephthalate composites containing 40 wt.% of untreated, alkaline-treated, and alkali/acetylation treated sisal fibers were prepared using compounding and injection molding processes and then characterized. It has been found that production of sisal-PET composites by compounding and injection molding has been shown to be possible. Thermal damage to sisal fiber was noticed during composite production. Based on the thermogravimetric analysis analysis, a net weight loss (excluding water loss) of 11.1%–14.0% was observed at the operating temperatures of the two processes. The addition of 40 wt.% of sisal to the PET matrix improved the tensile modulus by 137%. Further improvement by 179% was observed when alkali-treated sisal fiber was used. The combined alkali/acetylation treatment of sisal yields more enhancement by 233%. This is a significant advancement because modulus is the most influential parameter during the design and service of an engineering product. Generally, compared to the raw sisal composite (RSC) the interfacial, mechanical, thermal, and water absorption properties of the alkali treated sisal composite (Al-SC) and alkali/acetylated sisal composite (Al-ASC) specimens recorded an improvement. Relative to the natural fiber reinforced thermoplastic composites that were commercialized in the automotive industry, the produced sisal–PET composites resulted in a considerable improvement of 66.6%–190% in flexural strength and by 110.5%–410.0% in flexural modulus, depending on sisal fiber treatment and the composite to be compared. Thus, the studied composites can be recommended for various parts of automobiles.
“…This is attributed to Fick's law which assumes that when a sample comes in contact with moisture, equilibrium is instantaneously established between environmental moisture and internal moisture concentration. However, this process is gradual in reality [60,61]. This dual initial slope from the simulations can introduce some variation in how the initial slope of the weight gain curve is calculated, which can manifest as fluctuations in the calculated diffusivity values.…”
Section: Relationship Between Tortuosity and Diffusivitymentioning
Fiber reinforced polymer composite (FRPC) materials are extensively used in lightweight applications due to their high specific strength and other favorable properties including enhanced endurance and corrosion resistance. However, these materials are inevitably exposed to moisture, which is known to drastically reduce their mechanical properties caused by moisture absorption and often accompanied with plasticization, weight gain, hygrothermal swelling, and de-bonding between fiber and matrix. Hence, it is vital to understand moisture diffusion mechanics into FRPCs. The presence of fibers, especially impermeable like Carbon fibers, introduce tortuous moisture diffusion pathways through polymer matrix. In this paper, we elucidate the impact of fiber packing and morphology on moisture diffusion in FRPC materials. Computational models are developed within a finite element framework to evaluate moisture kinetics in impermeable FRPCs. We introduce a tortuosity factor for measuring the extent of deviation in moisture diffusion pathways due to impermeable fiber reinforcements. Two-dimensional micromechanical models are analyzed with varying fiber volume fractions, spatial distributions and morphology to elucidate the influence of internal micromechanical fiber architectures on tortuous diffusion pathways and corresponding diffusivities. Finally, a relationship between tortuosity and diffusivity is established such that diffusivity can be calculated using tortuosity for a given micro-architecture. Tortuosity can be easily calculated for a given architecture by solving steady state diffusion governing equations, whereas time-dependent transient diffusion equations need to be solved for calculating moisture diffusivity. Hence, tortuosity, instead of diffusivity, can be used in future composites designs, multi-scale analyses, and optimization for enabling robust structures in extreme moisture environments.
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