Effective Young's Modulus Estimation of Natural Fibers through Micromechanical Models: The Case of Henequen Fibers Reinforced-PP Composites.

Ferran Serra-Parareda,Quim Tarrés,Marc Delgado-Aguilar,Francesc X Espinach,Roberto Aguado,Fabiola Vilaseca

doi:10.3390/polym13223947

Abstract

In this study, Young’s modulus of henequen fibers was estimated through micromechanical modeling of polypropylene (PP)-based composites, and further corroborated through a single filament tensile test after applying a correction method. PP and henequen strands, chopped to 1 mm length, were mixed in the presence of maleic anhydride grafted polypropylene (MAPP). A 4 wt.% of MAPP showed an effective enhancement of the interfacial adhesion. The composites were mold-injected into dog-bone specimens and tensile tested. The Young’s modulus of the composites increased steadily and linearly up to 50 wt.% of fiber content from 1.5 to 6.4 GPa, corresponding to a 327% increase. Certainly, henequen fibers showed a comparable stiffening capacity of PP composites than glass fibers. The intrinsic Young’s modulus of the fibers was predicted through well established models such as Hirsch or Tsai-Pagano, yielding average values of 30.5 and 34.6 GPa, respectively. The single filament test performed to henequen strands resulted in values between 16 and 27 GPa depending on the gauge length, although, after applying a correction method, a Young’s modulus of 33.3 GPa was obtained. Overall, the present work presents the great potential for henequen fibers as PP reinforcement. Moreover, relationships between micromechanics models and filament testing to estimate Young’s modulus of the fibers were explored.

Highlights

In recent years, natural fibers have experienced growing demand as plastic reinforcement/filler as a result of the growing environmental consciousness in our society and the need amongst manufacturers for eco-friendly materials [1,2]
The inherent incompatibility between henequen fibers and polypropylene (PP) may inevitably lead to weak interfacial adhesion, scarce stress-transfer capacity, creation of void spaces, and poor water barrier properties. Such issues can be avoided, or at least mitigated, by incorporating maleic anhydride grafted polypropylene (MAPP) into the composites, which may act as a bridge between the lignocellulosic and polymeric phases
Henequen strands were chopped to 1 mm length and melt-extruded with polypropylene for the development of composite materials

Summary

Introduction

Natural fibers have experienced growing demand as plastic reinforcement/filler as a result of the growing environmental consciousness in our society and the need amongst manufacturers for eco-friendly materials [1,2]. The incorporation of natural fibers in thermoplastic matrices has shown a reasonable enhancement of the mechanical properties in terms of stiffness and rigidity. The strength improvement is more reliant on the fiber-matrix interfacial characteristics [7]. These characteristics shown by natural fiber polymer composites have made them suitable for use in various fields such as automotive and building and construction, their use being especially attractive for applications demanding low-density materials [8,9]

Methods

Results

Conclusion