Papers by Keyword: Cork

Abstract: In several sports, such as martial arts, point scoring depends on applied impact. Embedded sensors in wearable protection devices help to quantify the impact intensity. In parallel, there is a growing interest in developing products with a reduced ecological footprint, using natural materials such as cork. Considered a light, resilient, flexible, and hypo-allergenic material, cork has been proving to be a material with interesting impact absorption properties to be integrated into personal protection, as is the case with helmets and vests. Silicon rubber has also been proposed as an alternative elastomer material with adequate sealing and electrical isolation properties, while resistant to ageing and impact. Since injuries occur more frequently in lower extremities, presented work is part of a project that aims to explore the interest of replacing foams and synthetic leathers usually applied in foot protections with smaller CO₂ footprint materials while increasing their impact absorption properties. At this stage, a part of a protection prototype consisting of a plate made from natural cork, coated with silicone rubber protection containing embedded force sensors, was studied. The objective is to explore the potential of such materials to replace those conventionally applied in commercial foot protections. Firstly, the adhesion between imprinted silicon and cork was confirmed through peeling tests. Then, considering the opportunity of inserting sensors within the additive manufacturing of the parts, different silicone coating configurations and sensor placements were tested regarding their impact performance. Comparison between impact absorption performance was carried out using an impact test device, assessing sandwich composite performance and force sensing reading accuracy. Silicone printability during the robocasting extrusion technique demonstrated to facilitate the sensor placement without requiring deposition path modification. It showed to be an easy way to manipulate the sensor position within the composite layers and, by that, to modify its impact performance. This is an important contribution to the main goal of the undergoing project, which is to completely replace commercial materials with this new sandwich composite.

Abstract: The building sector is one of the biggest consumers of energy in the world and it is pushing the scientific community to find various alternative solutions to solve the problem of thermal insulation of buildings. Therefore, the selection of appropriate building materials is a major challenge for improving the thermal comfort and energy performance of buildings. In this scenario, the interest of plaster-based composites as insulating materials increases, in particular for new applications, as insulators for the building envelope, and this deserves to be studied. In this investigation, new plaster-based composites with cork were produced and tested at lab scale, in order to obtain cheap solutions with improved thermo-physical and acoustic performance. The results show that it is possible to improve the thermal, mechanical, and acoustic performance of construction biomaterials by using plaster as a binder and cork as a natural reinforcement: thermal conductivity was equal to 0.097 W/m.K, the compressive strength to about 2.30 MPa, and the transmission loss to about 40 dB. Keywords: Plaster-Gypsum; Cork; Thermal, Mechanical and Acoustic Properties.

Abstract: The objective of our work is to study the influence of nature and the shape of the insulating materials on the mechanical performance of composites based on plaster. The study aims to increase the thermal performance of the building envelope and the same time maintains sufficient mechanical properties of the composites studied. Plaster was combined with two additives (alpha fiber and granular cork). A physical and mechanical characterization of the composites plaster-fiber alpha and plaster-cork was carried on. Authors obtained an important gain in term of lightness 27 % concerning the composite plaster-fiber alpha, however for the composite plaster-cork, the value is 34 %. Concerning the mechanical properties, authors found a decrease in flexural strength of 60 % for the plaster-cork, and an increase of 33 % for the plaster-alpha fiber. For the compressive strength, a reduce of 87 % for the plaster-alpha fiber and 80% for the plaster-cork was observed. Those finding are justified by the scanning microscopic electron tests which show the distribution of the two insulators and adhesion within the plaster matrix.

Abstract: This work focuses on studying the possibility of 3D printing of composite materials composed by cork and a polymer matrix (CPC). Initially the cork was mixed with two types of polymers (HDPE and PP) in different proportions and later processed using extrusion and injection. The composites were tested to study the physical, chemical and mechanical properties. The material was then tested on a large-scale 3D printer to study its feasibility and the ability to produce new products through 3D printing. Attention was focused on the use of pure cork, varying the concentration of cork and coupling agent in thermoplastic matrix composites of PP and HDPE. It was demonstrated that the increase of 5wt.% of coupling agent in the two types of polymers significantly improved the mechanical properties and adhesion between the phases but the increase in cork concentration decreased mechanical properties and crystallinity. The CPCs with PP showed to have better mechanical properties, better aesthetic and internal structural quality, and easier processability than those with HDPE matrix. Nevertheless, the HDPE CPCs showed a high degree of crystallization. Concerning 3D printing, with the filament obtained was demonstrated the possibility of making new products based on natural cork fibers, showing promising results, although additional research is still needed to optimize the process.

Abstract: Jute fabric is well-known reinforcing material in composite science, however, there is a necessity to treat these fabrics to reduce moisture uptake and improve properties. Nevertheless, every modification increases the cost and reduces the possible applications. Presented research deals with an investigation of possibility to use untreated jute in various fabric weight as a reinforcing material in sandwich structures facings. Untreated jute reinforcements and two types of cork cores were saturated in one step during vacuum infusion creating a lightweight sandwich composite. All samples were mechanically tested in three-point bending test. Experimental results showed the most appropriate material combination and produced sandwich structure are proposed for design applications.

Abstract: Knowledge of acoustical properties of granular and fibrous sustainable materials has been stimulated thanks to their rather easy handling and durability. In this work direct measurements of the normal incidence sound absorption coefficient of three non consolidated materials (esparto fibers, cork and perlite) have been carried out using the so-called transfer function method. These materials are plentiful in Morocco and they require low amounts of energy for processing, which makes them attractive as either thermal insulating or sound absorbing materials. Results show that the acoustical efficiency of studied materials is comparable to traditional materials. In addition, an inverse estimation of non acoustical parameters (flow resistivity, tortuosity and porosity) of these materials has been performed introducing a new predictability approach. This is based on Global Sensitivity Analysis combined with Global Numerical Optimization Techniques, regarding most usual mathematical models.

Abstract: All components of a huge machine tool need to work together perfectly to ensure not only a quality finished product, but operator safety. One of those many components is the material of support panels and moving parts in the machine construction. Mechanical structure of the machine, in most cases does not reach the technical level of regulatory techniques or electric drives and potential increase in dynamics, speed or accuracy of the machines remain unused. Used classic construction materials, steel or light alloy then zoom in to limit their physical capabilities. Designers have machine tools or robots are forced to solve the formidable task in the form of reducing the weight of the moving parts while maintaining or even increasing stiffness with respect to the thermal stability or damping. Laminates are for construction of production machines, robots and manipulators of crucial importance. One big advantage is the high rigidity while maintaining low specific weight. The presented paper is focused on the investigation of composite sandwich construction produced by prepreg technology, which is the suitable production choose for construction of machine tools parts. First of all, the production of sandwich structures with cork core, honeycomb core and foam cores are compared and described. In terms of the production process it is a method very friendly to the environment, since there are no leaks styrene vapours into the air. Since it is important from the perspective of a manufacturer of transport or machine industry manufactured from environmentally friendly materials, so naturally from materials that are from the perspective of safety of passengers (operators of machine tools or robots) at a high level, when any accident was lowest possible hazard due to fire (burn materials used) and terms of the strength of composite materials. This is one of the major scientific articles and to find the most ideal surveyed composite sandwich materials that would be the greatest possible extent fulfils the required properties. In the experimental part of the article are compared and investigated the mechanical characteristics of composite sandwich structures with regard to varying number of layers of predimpregnated skin materials due to the different types of core materials suitable for use in the machine industry. In addition, these characteristics are an important part of the article research because described the influence number of layers to values of the bending stiffness those composite structures.

Abstract: The main aim of this work is the mechanical characterization of a composite material resulting from the combination of three by-products coming from industry, namely, flue gas desulfurization (FGD) gypsum, granulated cork and textile fibers from tire recycling. The material is considered as a green material as the raw material are considered by-products and it is intended to be used as a building material for non-structural purposes in civil engineering construction. The mechanical characterization includes uniaxial compressive tests and bending tests for characterization of the fracture behavior. Additionally, ultrasonic pulse velocity is measured to evaluate its variation with time of curing.

Abstract: The influence of humidity content on the electrical and dielectric properties of a composite made from recycled TetraPak® containers and granulated cork was studied. The material components have been dried before preparation and after the composite was conditioned by keeping the samples in a dry environment (desiccator) or in an oven at high temperature (70°C in air). The differences observed in electrical properties (investigated by isothermal charge and discharge current measurement) and dielectric properties (measured using dielectric relaxation spectroscopy) show that the thermal treatment at high temperature is more efficient on removing water and slows down the re-absorption rate.

Abstract: Ethylene-propylene diene ter-monomer (EPDM) filled with asbestos are widely used as thermal insulation in space vehicles because of its low specific gravity, low temperature flexibility, high ozone and oxygen resistant, superior thermal and ablation characteristics. However, asbestos has been banned worldwide because of its carcinogenic nature. This study was aimed to replace asbestos by environmental friendly and low specific gravity filler, cork in thermal insulation for space vehicles. Various batches of cork filled EPDM were obtained by compounding 0, 10, 20, 40, 50, 60, 70 and 100Phr (parts per hundred parts of rubber) of cork powder with EPDM in Two-roll-mill in presence of other necessary compounding ingredients. The resulted vulcanizates were characterized for mechanical, thermal and ablation performances. It was observed that cork loadings significantly enhanced tensile strength and hardness of EPDM. However, elongation at break of EPDM decreased with the increase of cork concentration. Moreover, no significant reduction in density of EPDM was obtained instead of compounding with lower specific gravity cork powder. Temperatures cures in Thermo-gravimetric analysis shifted to lower temperature with increasing of cork percentage in the formulation. Furthermore, char formation of the EPDM composites decreased with the increase of cork Phr in the composition which was the indication of degrading thermal stability of EPDM by cork powders. It can be concluded that on the basis of mechanical properties asbestos can be replaced by cork powder however, cork filled EPDM exhibited inferior thermal properties as compared to asbestos filled EPDM.