In situ monitoring of moisture uptake of flax fiber reinforced composites under humid/dry conditions

Luigi Calabrese,Elpida Piperopoulos,Vincenzo Fiore,Edoardo Proverbio,Dionisio Badagliacco,Davide Palamara,Antonino Valenza

doi:10.1002/app.51969

Luigi Calabrese, Elpida Piperopoulos + Show 5 more

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https://doi.org/10.1002/app.51969

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Abstract

AbstractThe use of green materials such as natural fiber‐reinforced composites represents an increasingly stringent prerogative in the future planning of industrial and non‐industrial production. The optimization of these materials is the main aim of the current research, focused on the evaluation of the behavior of flax fiber reinforced composites exposed to isothermal adsorption and desorption cycles, at varying the partial pressure of water vapor (P/P0). For this purpose, the moisture uptake and the morphology changes of the composite material and their constituents were in situ monitored through a measurement protocol, by using a dynamic vapor sorption (DVS) analysis, coupled with an environmental scanning electron microscopy (ESEM) visual investigation. A dependence of moisture uptake and diffusivity on the composite morphology was clearly detected. In particular, no significant variation in the morphology of the specimen is noticed at low water vapor partial pressure (i.e., P/P0 up to 5.4%) due to the limited absorption capacity (i.e., lower than 1%). On the other hand, fibers morphology changes at increasing the partial pressure up to 25.1%, showing a sensitive increase in volume. This phenomenon becomes much more relevant for high relative humidity values (i.e., ~90%), reaching more than 6% of absorption capacity.

Highlights

The continuous and wide research for advanced sustainable materials with a marked ecological footprint has led to an ever-growing interest on natural fibers reinforced composites (NFRCs).[1,2]
This implied a growing development in ever wider engineering contexts such as the automotive,[5] aeronautics,[6,7] or construction[8,9] sectors. Their widespread diffusion is limited by the low interfacial adhesion of the natural fibers with the polymeric matrix[10] and the wide heterogeneity of the natural raw materials which constrain their performance stability.[11]
Square-shaped (30 cm Â 30 cm Â 0.335 cm) flax fibers reinforced panels were manufactured through vacuumassisted resin infusion by using a two-stage vacuum pump model VE 235 D by Eurovacuum (Reeuwijk, The Netherlands)

Summary

Introduction

The continuous and wide research for advanced sustainable materials with a marked ecological footprint has led to an ever-growing interest on natural fibers reinforced composites (NFRCs).[1,2] These materials represent a promising design solution able to combine performances and environmental constrains. Production waste).[4] This implied a growing development in ever wider engineering contexts such as the automotive,[5] aeronautics,[6,7] or construction[8,9] sectors Their widespread diffusion is limited by the low interfacial adhesion of the natural fibers with the polymeric matrix[10] and the wide heterogeneity of the natural raw materials which constrain their performance stability.[11] relevant issue is the significant moisture absorption of natural fibers which negatively affects strength, stiffness, and adhesion with the hydrophobic matrix, accelerating the premature degradation of the composite material in wet or humid environments,[12,13]

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