Dynamic-Mechanical Behaviour of Bio-composites☆

Abstract PLA-hemp bio-composites with different reinforcement content were manufactured by compression moulding process. Both flexural and impact properties were investigated and compared to the unreinforced polymer. In addition, also the creep behaviour adopting the Arrhenius theory was determined, in order to better understand the industrial application limits of PLA reinforced by natural fibres. For this purpose, DMA tests were carried out, in order to evaluate the activation energy and to apply the Time-Temperature Superposition model to the compliance curves obtained by short-time creep tests

Experimental Characterization of Metal Matrix Composite with Aluminium Matrix and Molybdenum Powders as Reinforcement

Abstract This paper is on the successful fabrication of Metal Matrix Composite (MMC) using an Aluminium plate and Molybdenum powder by Friction Stir Process (FSP). The aim was to produce a superficial MMC layer on the Al plate in order to increase the mechanical properties of the as received Al plate. A uniform dispersion of Mo particles in the Al matrix was observed from SEM observations and EDX analyses and a significant improvement in the Vickers microhardness was also detected

Comparison of tribological behaviour between natural and synthetic fibres composites

This work aims to study the wear resistance of composite materials that mainly differ in the fibre typologies used as reinforcement. In detail hemp, glass and carbon fibres in form of woven fabric were used. For the production of the composite materials, an epoxy resin was used as matrix, and the vacuum infusion process was adopted. In order to compare the tribological behaviour of the manufactured composites, a detailed experimental campaign, including tribological tests and microgeometrical measurements, was carried out. In particular, the tribological behaviour was studied through the pin-on-disk tests conducted at 210 mm/s as peripheral speed under 50 N as applied load testing both the composite and the single un-impregnated fabrics. These tests were followed by microgeometrical measurements in order to critically observe the wear tracks, evaluate their depth, width and volume and then to calculate the final less of volume. The tests results showed a good and interesting behaviour of composite materials reinforced with hemp fibres

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

Tribological Behaviour of Hemp, Glass and Carbon Fibre Composites

Lightweight composite materials are frequently used for transportation, or the interiors of furniture and boxes. Wear of the surfaces of these materials is a potential health risk affecting the respiratory system or skin. The latter can frequently occur due to human touch of uncovered synthetic fibres after wear causing dermatitis, or inflammation of the skin. Therefore, composite materials made of natural fibres as reinforcement are an interesting alternative to synthetic fibres, because they are usually less dangerous to human health. Therefore, the goal of this research is to highlight the wear resistance of hemp fibres and compare it with glass and carbon fibre composites. In this work, hemp, glass and carbon fibres in form of woven fabrics were impregnated with epoxy resin through vacuum infusion process. In order to compare the tribological behaviour of the manufactured composites, a detailed experimental campaign, including tribological tests, microgeometrical measurements and indentation tests, was carried out. The tribological behaviour was studied through the pin-on-disk tests under different conditions that mainly differ in the applied load and both the composite and the single un-impregnated fabrics were tested. The results demonstrate good wear behaviour of the laminates reinforced by hemp fibres emphasising a better wear resistance at prolonged time and under high load conditions

Influence of chemical treatments on mechanical properties of hemp fiber reinforced composites

Natural Fibers Reinforced Composites (NFRC) are finding much interest as a substitute for glass or carbon reinforced polymer composites, like for instance automobile interior linings (roof, rear wall, side panel lining), shipping pallets, construction products (i.e. composite roof tiles), furniture and household products (i.e. storage containers, window and picture frames as well as food service trays, toys and flower pots) as well as fan houses and blades. However, a notable disadvantage of lignocellulosic fibers as reinforcements is their polarity which makes it incompatible with hydrophobic thermoplastic matrix. This incompatibility results in poor interfacial bonding between the fibers and the matrix. This in turn leads to impaired mechanical properties of the composites. This defect can be remedied by chemical modification of fibers so as to make it less hydrophilic. In this paper experiments have been performed to further the development of natural fiber reinforced composites. Untreated and treated surfaces of hemp fibers were characterized using Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). Fiber-matrix adhesion was promoted by fiber surface modifications using an alkaline treatment and (3-Glycidyloxypropyl) trimethoxysilane coupling agent. The mechanical behaviour of epoxy matrix composite reinforced with woven hemp was studied and mechanical test results show that silane treatment of hemp fibers improves, both tensile and flexural properties of the composites, although no high values are obtained

A study on the sound transmission loss of a new lightweight hemp/bio-epoxy sandwich structure

Due to the increasing awareness around the environmental crisis and the depletion of petroleum resources, together with the inherent issues connected with the use of composite systems such as their disposal and recycling and the health problems associated with the use of some raw materials, new legislative rules on global scale have been promulgated to fight environmental issues and will be hoping adopted by several countries. Based on these considerations, the new generation of composite systems will have to minimize the environmental impact with a more efficient use of energy resources and materials and where possible, replace synthetic or petroleum materials with more sustainable components, like natural ones. Therefore, the aim of this paper is to investigate the sound transmission loss of a new sandwich structure in bio-composite material based on hemp fibers and bio-epoxy resin in order to further extend the application fields of natural fibers composite (NFC) materials. Measurements in the impedance tube were first used to assess the sound transmission loss at normal incidence. By using measured mechanical properties, a Finite Element Method was used to predict sound transmission loss in the same boundary condition. Finally, the so determined mechanical model has been used to predict the sound transmission loss in a diffuse field