Alain Bourmaud

Université Bretagne Sud | UBS · IRDL – Institut de Recherche Dupuy de Lôme

Limiting plant fibre damage during industrial processing is challenging for biobased composite development due to plant cell wall sensitivity to temperature and shear. This study developed an innovative fluorophore grafting method to indirectly monitor flax fibre morphological damage during twin-screw extrusion in a poly-(caprolactone) matrix. Resu...

The diversity of the plant biomass available on earth makes plants an exceptional resource for replacing fossil resources in green chemistry, bioenergy and biobased materials. For numerous applications, and especially the high-tech ones (building block molecules, high-power bioenergy, additive manufacturing of biobased materials), the macrostructur...

In the present work, an innovative range of foams based on flax gum-filled epoxy resin was developed, reinforced or not by flax fibers. Foams and composites with different gum and epoxy resin contents were produced and their mechanical and thermal performances were characterized. To enhance the organic flax gum filler’s cross-linking, we exploited...

Residual shives have a major impact on the quality and performance of flax textile and composite preforms. Quantifying the content of shives in batches of scutched flax fibres is a time-consuming and operator-dependent process. Although the shive content can be estimated from the chemical composition, our aim here is to explore a series of effectiv...

In the present work, an innovative range of foams, based on flax gum-filled epoxy resin was developed, reinforced or not by flax fibers. Foams and composites with different gum and epoxy resin contents were produced and characterized for mechanical and thermal performances. To enhance the organic flax gum filler's cross-linking, we exploited the ox...

In ancient time, life elements, like plants and animals, and unanimated forces of nature were usually associated with specific meanings related to deities and sacred rituals. In Roman archeology, the strong symbolic value of plants represented in wall paintings and artifacts was proved by several contributions, but this topic is often neglected. In...

The present work describes the use of novel flax preforms reinforcement as substitution of glass fibres in complex composite stackings made of polyurethane foam impregnated with methylene diphenyl 4, 4′-diisocyanate (MDI), for automotive headliner parts manufacturing. Headliner structure, cohesion and mechanical performances are highly dependant of...

This study aims at better understanding the damage and fracture kinetics in flax fibre elements at both the unitary and bundle scales, using an experimental setup allowing optical observation at high recording rate in the course of tensile loading. Defects and issues from flax unitary fibre extraction are quantitated using polarized light microscop...

This study aims at better understanding the damage and fracture kinetics in flax fibres elements at both the unitary and bundle scales using an experimental setup allowing optical observation at high recording rate in the course of tensile loading. Defects issues from flax unitary fibre extraction are quantitated using polarized light microscopy. T...

Flax fibres are valuable reinforcements for tomorrow's composites. However, defects called kink-bands, which mainly appear on fibres during the extraction and transformation phases, might affect their mechanical properties. Defects induced pores, within the kink-band are investigated in this work. They were morphologically explored using synchrotro...

This study focuses on the use of tomato (Solanum lycopersicum L.) by-product biomass from industrial plants as reinforcement for designing a range of new degradable and biobased thermoplastic materials. As a novel technique, this fully circular approach enables a promising up-cycling of tomato wastes. After an in-depth morphological study of the de...

The microdroplet test is commonly used to determine the apparent interfacial shear strength (IFSS) of fibre-reinforced microcomposites. A deeper analysis of the test outcome can provide meaningful information about the fibre / matrix interface behaviour if a predictive approach is adopted. In this study, this predictive approach was used to investi...

Lignocellulosic powders have a chemical composition that makes them explosive under certain conditions. In the form of ultrafine particles, they can be directly used as fuel in combustion devices to...

Tensile properties of elementary flax fibres were investigated through in situ Synchrotron X-ray diffraction in order to understand the effect of tensile loading, on the internal reorganisation of crystalline cellulose; for the first time, these experiments were conducted for different RH conditions. Synchrotron radiation experiments were considere...

The creation and ultrastructure of kink-bands in flax fibres are key issues for developing more and more performing biobased composite materials. Nevertheless, despite many hypotheses and structural characterisation, the exact origin of kink-bands and the moment they appear remain unexplained. Here, by using cutting-edge techniques such as microtom...

Currently, the effects of global warming are one of the most important topics on the agendas of all governments and international economic and scientific organisations on the planet. Temperatures and rainfall will be especially subjected to increasing deregulation, and thus crop yields will be affected according to geographic location. Cellulosic m...

Verticillium wilt is a disease caused by the fungus Verticillium dahliae (V. dahliae) which is widespread in flax (Linum usitatissimum L.) cultures. V. dahliae negatively impacts the fibre yield with up to 60% loss at the scutching step of fibre transformation. Yet, little is known about the consequences of V. dahliae on the mechanical properties o...

The cellulose microfibril realignment of unitary flax fibres with contrasted density of structural defects, which are also known as dislocations and defined as zones of microstructure heterogeneities, was investigated upon tensile testing by means of X-ray diffraction performed on SWING beamline at synchrotron SOLEIL. The in situ continuous tensile...

The external shape and internal lumen of flax fibres are investigated using X-ray microtomography (µ-CT) and finite element (FE) modelling. µ-CT reveals an intricate flax fibre and lumen morphology, with mean porosity contents between 0 and 7.2%. The FE model is based on 3D volumes obtained by X-ray µ-CT and tensile testing in the elastic domain. N...

The creation and ultrastructure of kink-bands in flax fibres are key issues for developing more and more performing biobased composite materials. Nevertheless, despite many hypotheses and structural characterization, the exact origin of kink-bands and the moment they appear remain unexplained. Here, by using cutting-edge techniques such as microtom...

Flax fibres have been used by humans for approximately 10,000 years. With time, the geographic area of production and cultivation has changed, as have the applications of flax fibres; from clothing to sails and paintings from antiquity, to automotive, fashion, and design applications in the contemporary era. The degradation process of flax fibres i...

Fibre bundles are groups of elementary fibres glued together thanks to the middle lamella, and are the main fraction in plant fibre composites. In this study, relationship between the mechanical properties of flax fibre bundles, chemical composition and cellulose structure were investigated. To do so, a sequential biopolymer extraction was implemen...

Flax fibres are widely used in the automotive sector to reinforce polyolefins, such as for dashboard and interior door panels. A promising option is poly-(lactid) (PLA), as it leads to higher mechanical properties and offers an additional end-of-life scenario following recycling: industrial composting. However, like other composite systems such as...

Flax (Linum usitatissimum) lodging is an issue of great interest for industrial producers due to its economic impact; despite a strong varietal selection over around one century, this plant remains sensitive to lodging which represents a main technico-economic issue. To better understand lodging effects at the cell wall and stem scale, the cell wal...

A variety of techniques were used to investigate flax yarns sampled from four selected Italian paintings on canvas dated between the 17th and 18th centuries and compare them with a modern flax yarn. The goal was to establish their state of preservation and highlight the critical issues thanks to a combined approach that used SEM, atomic force micro...

Flax/Poly-(lactide) non-woven composites are an alternative to conventional glass/poly-(propylene), offering a potentially lower environmental impact solution for the automotive industry. To understand this complex material, its detailed architecture and void distribution are examined through 3D microtomography. Anisotropy in fibre orientation is a...

Incorporation of unused agricultural by-products into materials is a relevant strategy in developing biosourced and economically competitive products that limits the environmental impacts of plastics. Development of 3D printing techniques offers the possibility to design such biomaterials while bringing new functionalities, however, it is critical...

Injection moulded composite materials reinforced with wood fibres or particles can offer a credible alternative to other plant-derived fibres, particularly from an economic and environmental point of view. In this study, we compared the recycling behaviour of poly-(propylene) composites reinforced with ground wood particles versus wood and flax fib...

Flax has a long and fascinating history. This plant was domesticated around 8,000 bce1 in the Fertile Crescent area2, first for its seeds and then for its fibres1,3. Although its uses existed long before domestication, residues of flax yarn dated 30,000 years ago have been found in the Caucasus area4. However, Ancient Egypt laid the foundations for...

Pre-treatments for plant fibres are very popular for increasing the fineness of bundles, promoting individualisation of fibres, modifying the fibre-matrix interface or reducing water uptake. Most pre-treatments are based on the use of chemicals and raise concerns about possible harmful effects on the environment. In this study, we used physical pre...

PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden com-posting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that flax fibres prefer...

Flax shives have been proven to be relevant injection-moulded reinforcement materials with a stiffness that reaches 90% of that obtained with cut flax fibres. Nevertheless, little is known of the reinforcing mechanisms of this material. In this study, deeper insight is sought on the mechanical properties of flax shives, which originate mainly from...

Prompted by environmental legislation and citizens’ awareness induced by global warming effects, the market for plant-fibre reinforced composites has been growing steadily for the past 10-20 years, as observed by the substantial increase in academic and industrial research developments. However, the transition to larger production still requires se...

Flax lodging is an issue of great interest for producers due to its economic impact. To better understand its effects at the cell wall and stem scale, new knowledge regarding the cell wall composition dynamics during cell wall development and after a 90° tilt bending stress is reported. Deep-Ultra Violet fluorescence emission (DUV) dynamics recorde...

Plant fibres and especially flax can be distinguished from most synthetic fibres by their intricate shape and intrinsic porosity called lumen, which is usually assumed to be tubular. However, the real shape appears more complex and thus might induce stress concentrations influencing the fibre performance. This study proposes a novel representation...

Retting of fibrous plants such as flax is an essential step in the extraction of fibre bundles and their transformation into textiles and reinforcement fabrics for use in garments and composites. Dew-retting is traditionally performed from Northwest France to the Netherlands, as the climate is highly favourable for this process. Hemp is a plant tha...

Fibres from annual plants are a sustainable alternative to glass fibres in composite manufacturing. However, both synthetic fibres, such as carbon fibres, and cellulosic fibres exhibit heterogeneities along their lengths, which appear as localised morphological misorientations known as kink-bands. In plant fibres, kink-bands occur due to growing co...

The last 80 years have seen significant changes in industrial technologies, with the development of composite materials being particularly striking. These were hardly present before the Second World War but were made possible by the availability of new polymers, fibre reinforcements and innovative manufacturing techniques. In parallel, the traditio...

Replacing glass fibres with flax fibres is a first step in reducing the ecological impact of thermoset composite materials, and employing a biodegradable thermoplastic matrix opens up recycling and composting as end-of-life routes. Here, a range of flax fibre reinforced biodegradable thermoplastics were investigated: poly-(hydroxy alkanoate) (PHA),...

To design new eco-composites, a wide range of plant fibers can be used to reinforce polymers. This article, intended for specialists of materials, aims to classify them and understand the origin of their performances. Through 3 specific models of plant fibers, considered as references, the complex multi-scale architecture of plant cell walls is exp...

Liquid composite moulding (LCM) of plant fibre composites has gained much attention for the development of structural biobased composites. To produce quality composites, better understanding of the resin impregnation process and flow behaviour in plant fibre reinforcements is vital. By reviewing the literature, we aim to identify key plant fibre re...

Over the last decades, bio-based composite materials have been developed as an ecological alternative to synthetic fibre-reinforced composites, and flax fibres are one of the most commonly used fibres for this purpose. The secondary cell wall (S2) and the microfibril angle (MFA) of plant fibres are the main factors responsible for the mechanical be...

The use of biomass in injection moulded or extruded thermoplastic composites is an important issue, especially when trying to add value to low-cost co-products. The objective of this work was to conduct a complete study on the morphological characterisation and carbohydrate analysis of a range of co-products obtained during the processing of flax s...

Over the past decades, the use of plant fibre reinforced composites has increased significantly due to their many attractive attributes such as high specific strength and modulus, wide availability, low cost and high environmental credibility compared to their synthetic counterparts. These attributes are especially attractive for lightweight applic...

Fibre orientation is an essential factor governing the mechanical properties of composite materials. This study proposes an original method based on gray-level granulometry to analyse the fibre orientation distribution (FOD) of synthetic and natural fibre reinforcements aiming composite applications. An orientation maps is computed from SEM images...

Given the vast amount of available research in the area of natural fibre composites, a significant step forward in the development of next-generation plant fibre-based products would be to devise a framework for rational design. The authors use a top-down approach, starting with an example final product to define the product specifications for high...

Understanding the mechanical behavior of carbon fiber reinforced polymers requires knowledge on the deformation behavior of carbon fibers, they are highly anisotropic and heterogeneous. Nanoindentation is an efficient method for determining the mechanical properties in small volumes of materials. For isotropic materials, a single nanoindentation te...

Flax shives (FS) represent approximately 50 % in weight of dry flax stems, making it the main by-product of the flax scutching industry. Being an available and low-added value lignocellulosic resource, flax shives are an interesting candidate for thermoplastic composite reinforcement. In this study, raw flax shives were fragmented by knife milling...

Non-woven composites reinforced with plant fibers are widely used in the automotive and construction sectors. The vast majority is composed of petroleum-based, non-compostable polyolefins, which are no longer a viable solution in an environmental context where the end-of-life management of industrial products is becoming a major societal issue. Her...

Today, plant fibers are considered as an important new renewable resource that can compete with some synthetic fibers, such as glass, in fiber-reinforced composites. In previous works, it was noted that the pectin-enriched middle lamella (ML) is a weak point in the fiber bundles for plant fiber-reinforced composites. ML is strongly bonded to the pr...

The automotive and aeronautic industries have become strategic sectors for North African countries. However, the future growth of these sectors will likely depend on the availability of raw materials such as plant fibres to reinforce polymers. In the framework of this paper, we reviewed the research that focused on alfa fibres, which are deemed to...

Whatever in pulp or biocomposite sectors, the elements called fines coming from plant fibres have generally a length lesser than 200 μm. Their mechanical impact has long been debated in short plant fibre thermoplastic composites. Are they solely a filling agent or on the contrary, have they a potential of reinforcement in such composites depending...

The use of composite materials reinforced by flax fibres has been increasing steadily over the last 20 years. These fibres show attractive mechanical properties but also some particularities (naturally limited length, presence of a lumen, fibres grouped in bundles in the plant, complex surface properties and composition). An analysis of the availab...

Flax fibres are a promising reinforcement in the development of biocomposites and are finding new applications in transport structures. However, there is a perceived problem with plant fibres related to the variability of the properties of these natural materials. This paper describes the factors which affect variability, from plant growth conditio...

Ultrasound-assisted synthesis of diglycidyl ethers of isosorbide (DGEI) with different epoxy equivalent weight (EEW) with isophorone diamine (IPD) hardener have been performed. Interestingly, it was found that one specific epoxy formulation exhibits high reactivity with amine hardener inducing high glass transition and indentation stiffness. Associ...

In recent years, lignocellulosic biomass has been increasingly used in various applications. While for many of them the plant materials require coarse milling, some new applications for green chemistry, bio-energy and bio-packaging necessitate comminution to obtain very finely calibrated particles (below 200 μm in size). This milling step is not in...

L'étude des propriétés thermomécaniques des matériaux composites permet une meilleure compréhension de leur comportement sous sollicitations multi-physiques. Ces composites présentent également des comportements non linéaires avec des dépendances à la vitesse de déformation et à la température. Afin d'obtenir les propriétés effectives du composite,...

Les propriétés non linéaires des composites bio-sourcés sous un chargement thermomécanique sont étudiées dans ce travail. L'approche, basée sur un formalisme micromécanique, dérive les propriétés thermoélastiques du bio-composite. Elle prend également en compte l'anisotropie du matériau par les textures morphologique et topologique de la microstruc...