The impact of fibre processing on the mechanical properties of epoxy matrix composites and wood-based particleboard reinforced with hemp (Cannabis sativa L.) fibre

Albert Hernandez-Estrada,Mark Hughes,Jörg Müssig

doi:10.1007/s10853-021-06629-z

Abstract

This work investigated the impact that the processing of hemp (C. sativa L.) fibre has on the mechanical properties of unidirectional fibre-reinforced epoxy resin composites loaded in axial tension, and particleboard reinforced with aligned fibre bundles applied to one surface of the panel. For this purpose, mechanically processed (decorticated) and un-processed hemp fibre bundles, obtained from retted and un-retted hemp stems, were utilised. The results clearly show the impact of fibre reinforcement in both materials. Epoxy composites reinforced with processed hemp exhibited 3.3 times greater tensile strength when compared to the un-reinforced polymer, while for the particleboards, the bending strength obtained in those reinforced with processed hemp was 1.7 times greater than the un-reinforced particleboards. Moreover, whether the fibre bundles were processed or un-processed also affected the mechanical performance, especially in the epoxy composites. For example, the un-processed fibre-reinforced epoxy composites exhibited 49% greater work of fracture than the composites reinforced with processed hemp. In the wood-based particleboards, however, the difference was not significant. Additionally, observations of the fracture zone of the specimens showed different failure characteristics depending on whether the composites were reinforced with processed or un-processed hemp. Both epoxy composites and wood-based particleboards reinforced with un-processed hemp exhibited fibre reinforcement apparently able to retain structural integrity after the composite’s failure. On the other hand, when processed hemp was used as reinforcement, fibre bundles showed a clear cut across the specimen, with the fibre-reinforcement mainly failing at the composite's fracture zone.

Highlights

Interest in using natural fibres to reinforce composites has resulted in the development of a range of fibre-reinforced polymers [1,2,3,4] that use fibres from plants like flax and hemp, to substitute human-made alternatives such as glass fibres (e.g. [5, 6].)
This work investigated the impact that the processing of hemp (C. sativa L.) fibre has on the mechanical properties of unidirectional fibre-reinforced epoxy resin composites loaded in axial tension, and particleboard reinforced with aligned fibre bundles applied to one surface of the panel
The results of this work confirm the superior behaviour of specimens reinforced with unprocessed hemp when compared to the specimens reinforced with processed hemp, especially for the epoxy composites that exhibit, for example, a work of fracture 49% greater in specimens reinforced with unprocessed hemp when compared to the composites reinforced with processed hemp

Summary

Introduction

Interest in using natural fibres to reinforce composites has resulted in the development of a range of fibre-reinforced polymers [1,2,3,4] that use fibres from plants like flax and hemp, to substitute human-made alternatives such as glass fibres (e.g. [5, 6].). In the form of NFRPs, the high strength and stiffness of bast fibres [12,13,14,15] can be harnessed to reinforce wood products like timber [16] and particleboard [17]. This could potentially create new application areas for wood-based products as well as developing new markets for natural fibres. The aims of the work reported in this paper were, twofold: firstly, to study how fibre damage affects the properties of NFRPs and, secondly, to explore the potential for hemp fibre to reinforce particleboard, thereby enhancing its mechanical properties and, potentially, increasing its value

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