Effect of Fungal Deterioration on Physical and Mechanical Properties of Hemp and Flax Natural Fiber Composites

Bryn Crawford,Negin Kazemian,Abbas Milani,John Klironomos,Denis Rho,Sepideh Pakpour,Karen Stoeffler,Johanne Denault

doi:10.3390/ma10111252

Abstract

The development and application of bio-sourced composites have been gaining wide attention, yet their deterioration due to the growth of ubiquitous microorganisms during storage/manufacturing/in-service phases is still not fully understood for optimum material selection and design purposes. In this study, samples of non-woven flax fibers, hemp fibers, and mats made of co-mingled randomly-oriented flax or hemp fiber (50%) and polypropylene fiber (50%) were subjected to 28 days of exposure to (i) no water-no fungi, (ii) water only and (iii) water along with the Chaetomium globosum fungus. Biocomposite samples were measured for weight loss over time, to observe the rate of fungal growth and the respiration of cellulose components in the fibers. Tensile testing was conducted to measure mechanical properties of the composite samples under different configurations. Scanning electron microscopy was employed to visualize fungal hyphal growth on the natural fibers, as well as to observe the fracture planes and failure modes of the biocomposite samples. Results showed that fungal growth significantly affects the dry mass as well as the tensile elastic modulus of the tested natural fiber mats and composites, and the effect depends on both the type and the length scale of fibers, as well as the exposure condition and time.

Highlights

Over the past decades, fiber-reinforced polymer composites (FRPC) have received increased attention in a variety of industries ranging from aerospace to ground transportation and sporting equipment [1]
North American composites industry grew at approximately 9% annually [4]. This strong growth is expected to continue in coming years, driven by factors including falling prices of carbon fiber, uptake of emerging material technologies such as natural fibers and the introduction of industry-led research and development (R&D) activities focused on innovation
The material specifications of the natural fibers in the selected mats are outlined in Table 1; it should be noted that the compositions listed do not necessarily indicate those for all hemp and flax plants in consideration as reinforcement in biocomposites, as significant batch-to-batch and breed-to-breed differences should be expected for these natural materials

Summary

Introduction

Fiber-reinforced polymer composites (FRPC) have received increased attention in a variety of industries ranging from aerospace to ground transportation and sporting equipment [1]. These materials offer desired advantages with respect to performance, for example, improved strength-to-weight and stiffness-to-weight ratios, over classical metallic materials [2]. North American composites industry grew at approximately 9% annually [4] This strong growth is expected to continue in coming years, driven by factors including falling prices of carbon fiber, uptake of emerging material technologies such as natural fibers and the introduction of industry-led research and development (R&D) activities focused on innovation. The overall Americas market for advanced composites in wind energy alone has been expected to triple to USD $25.8 billion by 2020 [4]

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Conclusion