Green plastics are constantly being used to minimize the negative impacts of the polymers made of fossil fuels such as petroleum. Non-renewable petroleum-based products are employed in wide range of human activities, yet plastic waste accumulation represents a serious issue for the environment (Mohd Rafee et al., 2019). On the other hand, the use of natural fibres in composite materials, such as sisal fibres, in substitution for synthetic fibres, has increased considerably. The aim of this study was to develop a low-cost manufacturing process of composites with reuse of polyethylene bags made of sugarcane ethanol (green polyethylene) reinforced with sisal fibres. The hot compression moulding (185 °C) was used to mould composite structural board. Tensile tests were conducted to evaluate the influence of the reinforcement configuration on the mechanical properties of the composites, considering two arrangements: woven fibres in (0°/90°) and randomly arranged. The results indicated that the use of woven sisal fibres in (0°/90°) as reinforcement of the green HDPE showed an increase in the tensile strength (33.30%) in contrast to the pure traditional HDPE. Randomly arranged sisal fibre-reinforced green HDPE composites showed higher modulus of elasticity than pure traditional HDPE (76.83%). Composites with woven sisal fibres showed higher values for tensile strength and ultimate strain, and lower modulus of elasticity than composites with randomly arranged sisal fibres. In addition, failure modes of the composites were observed. The results showed the viability of producing these composites by the developed equipment and the potential use of these materials as structural components.

Finite element analysis is a widely used simulation technique to analyze structural components and the mechanical behavior of materials under different loading conditions. The major steps involved in finite element simulations are the definition of the basic parameters and the discretization in elements of the component, also known as preprocessing, the analysis of the models and the post-processing by the representation and the interpretation of the obtained results. On the particular case of complex geometries obtained by fused deposition modeling, the most time consuming of these three steps is that of preprocessing, because on traditional finite element technology is require that the real geometry of the CAD model is simplified to be meshed and analyzed. Nowadays, different techniques have been proposed and developed with this objective: reduce costs in terms of time and specialized human resources because the workflow is easier and simpler. One of these methods is known as the meshless method, which do not require connection between nodes and are based on the interaction of the points of the geometry with the neighbors, so the processor analyzes the real CAD geometry and no simplifications are needed. The present work uses the meshless method based on the theory of external approximation as an alternative to the classic finite element method. In numerical simulations, the influence of core shape is evaluated on the failure mode of the 3D-printed lightweight structures. Three cell core patterns were numerically evaluated under tensile and three-point bending tests: out-of-plane hexagonal honeycomb, S-shape corrugated, and in-plane hexagonal honeycomb cores. The nucleation and propagation of cracks had more heterogeneous profiles for in-plane hexagonal honeycomb cores, showing greater unpredictability in the susceptible areas to failure. The numerical analysis with the meshless method showed a potential for a fast prediction and a low computational cost analysis.

The need for studies aiming at the selection of materials for such application is preponderant, be-cause a large increase in the focus on vehicle weight reduction by the automotive industry in recent years. In environmental and commercial terms, this reduction provides lower energy consumption and better vehicle performance, as well as limiting pollutant emissions. The present work has the objective to select the best materials in substitution of the metals and glass used in doors, hood and windows, respectively, of sports cars to decrease the weight/power ratio and consequently improvement of performance. With the aid of Ashby maps simulated through the CES EduPackTM 2018 program, maximizing the limit of tensile strength and minimizing density, it was possible to analyze that carbon fiber composites obtained values of merit index of up to eleven times greater than the value obtained by carbon steels. Already in substitution of the glass, the acrylic obtained a index of merit about three times greater. At the same time, the tensile strength, fracture toughness, density and cost of the possible materials obtained in the previous method were obtained through the Pugh matrix, the exchanges for composites of glass fiber and polycarbonate obtained outstanding responses.