Efficiency of Bio-Sourced Composites in Confining Recycled Aggregates Concrete

This research investigates the efficiency of using Flax Fibers reinforced bio-sourced polymer by comparison to traditional system based on Carbone Fiber Reinforced Epoxy Polymer in order to confine recycled aggregates concrete. Four concrete formulations have been formulated by incorporating recycled aggregates from demolition waste (0%, 30%, 50% and 100%). An air-entraining agent was added to the formulations to achieve the level of 4% occluded air. The main objective is to discuss and to evaluate the effectiveness of confining them using bio-sourced composite by comparison to traditional ones. To hit this target, the developed approaches are both experimental and analytical. The first part is experimental and aimed to characterize the mechanical behavior of the materials: the composites used in the confining process the unconfined concrete (effect of incorporating recycled aggregates on the overall mechanical characteristics). We establish that bio-sourced composites are efficient in strengthening recycled aggregates concrete especially if they are air-entrained. The second part of this work is dedicated to analytical modeling of mechanical behavior of confined concrete with composite under compression based on Mander’s model. The input parameters of the model were modified to consider the rate of recycled aggregates incorporation. Comparison between experimental results and the modified Mandel’s Model is satisfactory.

Flax Fibers Composite Made up by 3D Printing

This preliminary work deals with potential use of additive manufacturing to print a bio-based composite. For this, mixture of clay and flax fibers was used. First, we proceeded to the optimization of the printability conditions by ensuring that the water dosage allows a good extrusion with a continuous volume flow rate. Moreover, the yield stress obtained must allow to deposit several layers without loss of stability. This criterion was verified and then we printed a square element of 20 cm length where 4x4x16cm3 specimens were cut and used to evaluate bending strength. We have shown that under some conditions we are able to print with different layers this composite. To improve the limit height of a printed element, additional tests are necessary to increase the resistance of this type of composite. This study will be continued by Optimizing mix design using other additives and introducing of reinforcement.

DEVELOPMENT OF RESOURCE-SAVING TECHNOLOGIES FOR OBTAINING COMPOSITE MATERIALS BASED ON THE USE OF OILSEED FLAX FIBERS

The article examines the ways to solve the problem of developing a scientific basis for obtaining composite materials of different functional purposes from oilseed flax fibers. The paper covers theoretical and experimental research in the area of processing flax raw materials. The purpose of the study is to provide scientific substantiation of developing the technologies for obtaining fillers to reinforce composite materials. In order to do it, we performed modification of oilseed flax fiber and developed technologies for processing oilseed flax straw with regulated technological and performance characteristics. The article also presents the results of the research on determining causes of low wettability of oilseed flax bast. In order to find out the causes of low bast wettability, we conducted research on examining chemical composition and anatomy of straw stems. The formulation for preparing the fiber aimed to be used as a filler for reinforcement of composite materials is offered. The study suggests evaluation of the quality of composite materials produced on the basis of using modified oilseed flax fibers.

Effectiveness of Sodium Acetate Treatment on the Mechanical Properties and Morphology of Natural Fiber-Reinforced Composites

This paper aims to investigate the ability of an eco-friendly and cheap treatment based on sodium acetate solutions to improve the mechanical properties of flax fiber-reinforced composites. Flax fibers were treated for 5 days (i.e., 120 h) at 25 °C with mildly alkaline solutions at 5%, 10% and 20% weight content of the sodium salt. Quasi-static tensile and flexural tests, Charpy impact tests and dynamical mechanical thermal (DMTA) tests were carried out to evaluate the mechanical properties of the resulting composites. Fourier transform infrared analysis (FTIR) was used to evaluate the chemical modification on the fibers surface due to the proposed treatment, whereas scanning electron microscope (SEM) and helium pycnometry were used to get useful information about the morphology of composites. It was found that the treatment with 5% solution of sodium acetate leads to the best mechanical performance and morphology of flax fiber-reinforced composites. SEM analysis confirmed these findings highlighting that composites reinforced with flax fibers treated in 5% sodium acetate solution show an improved morphology compared to the untreated ones. On the contrary, detrimental effects on the morphology as well as on the mechanical performance of composites were achieved by increasing the salt concentration of the treating solution.

Influence of the hydrodynamic degumming process on the quality of decorticated flax fibers

The study explored the impact of the hydrodynamic degumming process applied for decorticated monomorphic flax on fiber quality. The experiment was designed as the first stage of research leading to the development of a method for decorticated flax fiber elementarization and cottonization; in particular, effectively dividing the fiber bundles to ensure low linear density and reducing impurities in the content, to make the fibers suitable for cotton spinning systems. The degumming process of the decorticated fibers covered hydrodynamic disposal of the gluing substances, mainly pectins from the fibers, with use of a specially designed lab-scale Model Device for Physical Degumming of the Flax Fibers. The degummed fibers were tested for linear density, length, impurity content and chemical composition by thermogravimetric analysis combined with the analysis of evolved gases (Fourier transform infrared spectroscopy) and analysis of images of fiber cross-sections and longitudinal views from a scanning electron microscope. The study outcomes allowed us to determine the optimal parameters of the degumming process applied for decorticated flax fibers, in which the obtained fibers were of the highest quality. It was found that the optimal parameters of the process were a bath temperature of 30°C and a degumming process duration of 24 hours. These lab-scale process conditions were used in further work on the degumming process of flax fiber carried out on a semi-technical scale, followed by a mechanical cottonization of the fiber, at the final stage of the technological chain.

Production of PP Composites Reinforced with Flax and Hemp Woven Mesh Fabrics via Compression Molding

Hemp and flax fibers are among the most interesting vegetable fibers that can be used to reinforce polymeric matrices. In line with the global environmental requests, the use of these fibers especially coupled with thermoforming polymers are increasing more and more in order to expand their applications and replace synthetic fibers and thermosetting plastics. However, one of the major limitations of vegetable fibers is their poor adhesion with polymeric matrices that is often overcome by fibers chemical treatments or by using coupling agents within the matrix. Aiming to produce polypropylene (PP) bio composite laminates reinforced by hemp and flax fibers without additional process steps, this paper deals on the study of their production via the compression molding technique by using woven fabrics characterized by a large mesh size able to ensure a mechanical anchoring between fibers and matrix. Two different forming strategies that differ in the time required for reaching the maximum values of compression pressure and in the dwelling time at this value were used in order to investigate how the yarn impregnation was affected by them. To expand the applications of composites under investigation, tensile, bending, Izod, heat deflection temperature (HDT) and bearing tests were carried out. The results highlighted how the use of a waiting time before the reaching of the maximum moulding pressure allowed a better matrix flow within the vegetable yarn leading to higher mechanical performances.

The Technological Process of Obtaining New Linen Dressings Did Not Cause the Loss of Their Wound-Healing Properties

Background: Linen dressings were invented a few years ago but are still being worked on. Methods: The obtained fabrics from the traditional variety of flax (Nike), two transgenic types of flax (M50 and B14) and the combination of these two flax fibers (M50 + B14) were tested in direct contact in cell cultures. Cell viability tests were performed, and the proliferation potential of cells on Balb3T3 and NHEK cell lines was checked using the Sulforhodamine-B (SRB) test. Moreover, the effect of new linen fabrics on apoptosis of THP-1 cells, as well as on the cell cycle of NHEK, HMCEV and THP-1, cells after 24 h of incubation was assessed. Results: All tested linen fabrics did not raise the number of necrotic cells. The tested fabrics caused a statistically significant decrease in the total protein content in skin cancer (except for 0.5 cm of Nike-type fabrics). The smallest cells in the apoptotic phase were in cultures treated with M50 fiber on an area of 0.5 cm. After 48 h of incubation of HEMVEC, NHEK and THP-1 cells with the tested fabrics, the growth of S-phase cells was noticed in all cases. At the same time, the greatest increase was observed with the use of B14 fabric. Necrosis is not statistically significant. Conclusions: All the obtained flax fibers in the form of flax dressings did not lose their wound-healing properties under the influence of the technological process. New dressings made of genetically modified flax are a chance to increase the effectiveness of treatment of difficult healing wounds.