Applied Mechanics and Materials Vol. 890

Abstract: In the last decades the studies on thermoplastic composites reinforced with natural fibres have been mostly focused on vegetable lignocellulosic or cellulosic fibres. These materials provide eco-sustainable solutions for a large range of applications and have been actually adopted by multiple industries. The interest on fibres of animal origin is more recent and research on composites reinforced with these fibres predominantly composed of keratin, such as wool, feathers or silk, is increasing in virtue of some advantageous properties that may overcome some of the intrinsic limitations from vegetable fibres. The combined use of vegetable and animal fibres in composites appropriate for melt blending processing is at early stages of research. After chemical treatments, the fibres of animal origin have been mostly applied as binders between vegetable fibres and polymers, not as main constituents of these composites. The use of both types of fibres simultaneously in composites of thermoplastic matrices is the subject of the present study wherein the fibres of animal origin (wool) are different kinds of residues from a textile industry and the fibres of vegetable origin (wood) are residues from carpentry activities. The chemical composition, the macro and microstructure of the fibres is analyzed, as well as that of composites that combine non-biodegradable and biodegradable polymers with diverse ratios of fibres in different conditions (wool as cards, yarns and felt cloths; wood as sawdust). The addition of coupling agents to enhance the compatibility between wool, wood and different polymers is also analysed.

Abstract: Additive manufacturing (AM) is a well-known technology for making real three dimensional objects, based on metal, ceramic and plastic material used for various applications. The aim of this review is to explore and offer an insight in to the state of the art polymer based nanocomposites in to additive manufacturing applications. In context to this, the developing efforts and trends in nanocomposites development particularly for additive manufacturing processes were studied and summed up. The scope and limitations of nanocomposites into Stereolithography, selective laser sintering and fused deposition modeling was explored and highlighted. The review highlights widely accepted nanoparticles for range of applications including mechanical, electrical, flame retardance and crossing over into more biological with the use of polymer matrices. Acquisition of functional parts with limitations in regard to printing is highlighted. Overall, the review highlights successes, limitations and opportunities that the union of AM and polymer based nanocomposites can bring to science and technology.

Abstract: The aim of this article is to develop a method in order to investigate the surface modifications of degraded polyacrylonitrile powders under microwave treatment in air. Microwave treatment of polyacrylonitrile powders in air recorded two stages of degradation firstly an exothermic reaction that started in the range of (86-117)°C. Secondly the Thermal runway here the weight loss reached a peak value between 80-90 percent with the small quantity of 0.25g polyacrylonitrile and in the ashes with a bigger quantity 1g of polyacrylonitrile. Scanning electron microscopy analysis technique revealed the morphological characteristics and the porosity of the carbon compound that may play an important role in the construction of high porosity area and so in electrochemical supercapacitor devices with high performances.

Abstract: The processing of polymers is highly complex. The study of their crystallisation assumes an important role and needs to be carefully detailed. Scattering experiments can be used to study polymer molecular organisation. However these procedures are still very multifaceted leading to the need for planning all the details in the experiments that are to be performed. This manuscript presents a finite element model developed to study the temperature variation of a T Jump System, which has been used for studying polymer behaviour with the NIMROD instrument at the ISIS Neutron and Muon Source, UK. Results show that the variation across the sample was 2oC at a maximum temperature of 70oC and 1oC at a maximum temperature of 50oC.

Abstract: We discuss the setup of a simulation on ANSYS to predict the thermal expansion of parts made of Nitinol. A simulation is justified for working conditions in which the part heating is not homogeneous originating a temperature gradient across the part section such that an analytical estimate for the part expansion cannot be calculated. We apply the simulation to the topological optimization of a square section geometry and a bullet geometry for water assisted injection molding. For the topological optimization we consider as parameter the wall thickness and consider both the cases of fast varying temperature and fast varying temperature and pressure.

Abstract: Innovation is key to firms’ competitive advantage, performance, and growth. In this paper we try to briefly link the concepts of Innovation and Entrepreneurship with the emergence of a new industrial revolution that has been labeled as “Industry 4.0”, showing that as in the past a set of innovation are the main drivers for the change of the technical and social paradigm. We summarize a number of concepts to show that the key drivers of competitiveness are Innovation and Entrepreneurship.

Abstract: Characterizing a fruit’s mechanical behavior is an important step towards reducing economic losses due to bruising. Several 3D scanning technologies allow to obtain the external geometry of a fruit, but no easily accessible tools exist for the acquisition of the geometry of internal structures such as the core. We propose a low-cost destructive method for tomographic reconstruction of a fruit from scanned slices. A method for overcoming the difficulties in registering the different images is also presented.

Abstract: The existing metallic solutions used for vertical traffic signs are associated with higher costs and environmental issues due to their manufacturing and degradation, when compared with polymeric solutions. Thus, the development of vertical signs considering the injection from polymeric materials in order to overcome problems related with sustainability, maintenance costs, and to achieve higher resistance to corrosion assumes nowadays an important role. The use of eco-friendly and innovative products considering the industrial waste combined with synthetic polymers performing the appropriate mechanical properties, can also be studied to find out new solutions that allow to solve the aforementioned problems. Additionally, these innovative vertical signs can contribute to avoid vandalism events related with theft and graffiti activities. This work presents the prior materials investigation and the structural design of vertical signs that are intended to be produced through polymer injection. Three main steps were considered: i) materials research, ii) materials characterisation through the analysis of polycarbonate resin isolated and in different sets of mixtures with different concentrations through tensile testing and static water contact angle measurements to find the optimal material composition; and iii) structural numerical simulation considering polycarbonate resin and using the current standard EN 12899-1 [1] to compute wind resistance, temporary and permanent deflections. Both experimental and numerical results led to an optimized proposal of the vertical signposting structural design.

Abstract: Dibenzylidene Sorbitol is a very effective clarification additive for isotactic polypropylene. It is not effective with polyethylene although recent studies have shown that it can act as an effective nucleating and directing agent. We employ small-angle neutron scattering measurements to more fully understand the behavior of dibenzylidene sorbitol in a polyethylene matrix. The small-aangle neutron scattering clearly shows that the disappearance of the DBS fibrils is concentration dependent and for 2% DBS the midpoint of the dissolution is at 145°C and for 1% is ~ 20°C lower

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.