Reinforcement of polymer matrix with natural fiber can provide an increase in mechanical properties of the related composite. Since thermoplastics, especially bio composite materials are recyclable, they contribute to a sustainable ecosystem. In this study, 10% by weight hemp reinforced polylactic acid (PLA) matrix compounds were produced. Tensile test specimens were performed in two different infill patterns, parallel and +/- 45° cross, using the Fused Filament Fabrication (FFF) method from the developed bio composite filaments. Ultimate tensile stress increases approximately 20%. It has been observed that the geometry of the infill pattern greatly affects the tensile strength. In addition, through optical and scanning electron microscopy (SEM) the the produced composite filaments were examined. Surface interactions and homogeneous fiber distribution between PLA and hemp were investigated. As a result, hemp is used as a reinforcement material in related studies, its homogeneous distribution is very important. Although the compounds were produced by twin-screw extrusion. Weakness in the form of the surface bonding is observed. This situation affects the structural performance negatively. Addition of hemp decreases the thermal resistance and melting temperature and increases the glass transition temperature comparing to pure PLA.

In recent years, there has been an outbreak of research on natural fiber-reinforced materials to reduce non-recycled material effects and produce environmentally friendly products. In parallel with the increasing popularity of additive manufacturing, the development of new natural fiber-reinforced materials in this field has also increased to improve pure material characteristics and reduce raw materials usage. This study presents the manufacturing process of %5 waste jute-reinforced PLA filaments and the characteristics of 3D printed parts. For the production of jute-reinforced filaments, polylactic acid (PLA) granules were pulverized to increase the material surface for better bonding between materials in the composite matrix structure. The effectiveness of pulverizing PLA granules was exposed by comparing it with the production of the same composite matrix with PLA granules. Both matrices were formed into filaments to produce 3D parts in Fused Filament Fabrication technology. Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) will be presented in filament form. Besides, the mechanical properties of 3D parts will also be presented. Within the scope of the study, it is aimed to reveal the material size effect for producing natural fiber-reinforced filaments for additive manufacturing.

(1) Background: Additive manufacturing (AM), which has also become known as 3D printing, is rapidly expanding its areas of use in the marine industry. This study undertakes a historical development of AM in the marine industry. The study also criticises these developments to date and the future technological applications they will lead to, while considering the benefits for the industry and its segments. (2) Methods: This review followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the Open Science Framework. The personalized search strategy was applied to Scopus, and Web of Science databases. The core emphasis was placed on two eligibility criteria throughout the evaluation process. Firstly, Criteria 1 sought to determine the paper’s relevance to AM. Secondly, Criteria 2 aimed to assess whether the paper delves into the implementation of AM or provides valuable insights into its utilisation within the marine industry. The risk of bias was analysed using a checklist of important parameters to be considered. (3) Results: In recent years, there has been a growing trend in studies related to the application of AM in the marine industry. While AM is widespread in industries such as automotive, aviation, and healthcare, it is relatively new for the marine industry. Almost only 5% of publications related to AM are related to the marine industry. There is a need for extensive research in many areas. It has been observed that classification societies and approval institutions, which largely drive the marine industry, have not yet taken AM into consideration sufficiently. (4) Conclusions: The studies show that AM is very promising for the marine industry. However, there are new studies at the experimental and theoretical level that need to be carried out to determine the right materials and AM methods to establish the quality control methodology and the necessary classification rules. This review also emphazises AM’s pivotal role in reshaping the marine industry, addressing the potential environmental and occupational safety effects of AM.

In efforts to achieve the goal of reducing ship emissions in the fight against climate change, reducing fuel consumption by making ships lighter is stated as one of the solutions. In this study, the possibilities of making composite equivalents of propellers, which are the most complex ship elements and traditionally produced from metal materials, are investigated with the advantages of additive manufacturing, which offers a rapid production opportunity for such forms. In this way, a lighter composite propeller and, therefore, a lighter ship will be achieved, and negative environmental impacts, especially harmful emissions, will be reduced. In the study, a 1/14-scale ship propeller was produced through the material extrusion method of additive manufacturing using an HDPE composite containing long carbon fiber with a 15% weight fraction. An attempt to reduce flexibility with an epoxy-carbon fabric prepreg coating was made, as the flexibility has negative effects on the performance of the produced propeller. The propeller tunnel test showed that the applied carbon fabric epoxy prepreg helped to improve the propeller’s performance by decreasing the flexibility of the propeller and reducing the deformation at the tips. At the same time, the propeller weight was decreased by 60% compared to its metal counterparts.

In the marine industry, the search for sustainable methods, materials, and processes, from the product’s design to its end-of-life stages, is a necessity for combating the negative consequences of climate change. In this context, the lightening of products is essential in reducing their environmental impact throughout their life. In addition to lightening through design, lightweight materials, especially plastic-based composites, will need to be used in new and creative ways. The material extrusion technique, one of the additive manufacturing methods, is becoming more widespread day by day, especially in the production of objects with complex forms. This prevalence has not yet been reflected in the marine industry. In this study, the performances of plastic composite propellers produced by the material extrusion technique is investigated and discussed comparatively with the help of both hydrodynamic and structural tests carried out in a cavitation tunnel and mechanical laboratory. The cavitation tunnel test and numerical simulations were conducted at a range of advance coefficients (J) from 0.3 to 0.9. The shaft rate was kept at 16 rps. The thrust and torque data were obtained using the tunnel dynamometer. Digital pictures were taken to obtain structural deformation and cavitation dynamics. The structural performance of the propellers shows that an aluminum propeller is the most rigid, while a short carbon fiber composite propeller is the most flexible. Continuous carbon fiber composite has high strength and stiffness, while continuous glass fiber composite is more cost-effective. In terms of the hydrodynamic performance of the propellers, flexibility reduces the loading on the blade, which can result in thrust and torque reduction. Overall, the efficiency of the composite propellers was similar and less than that of the rigid aluminum propeller. In terms of weight, the composite carbon propeller containing continuous fiber, which is half the weight of the metal propeller, is considered as an alternative to metal in production. These propellers were produced from a unique composite consisting of polyamide, one of the thermoplastics that is a sustainable composite material, and glass and carbon fiber as reinforcements. The findings showed that the manufacturing method and the new composites can be highly successful for producing ship components.

Polyethylene terephthalate (PET) material, which is widely used in the packaging industry due to its thermal and mechanical properties, high chemical resistance, and low gas permeability, is among the most widely used polymer materials in the world. These properties have made their use in additive manufacturing methods widespread. Determining how some common additive manufacturing defects affect the products produced by these methods will increase the adoption of these technologies in the final product production. In this study, the investigation of the effect of layer non-joining defect called delamination on the impact strength of PET material produced by additive manufacturing method at different layer thicknesses was carried out experimentally and numerically. The effects to flexural stress on the artificially created layer adhesion defect on the middle layers of the parts produced and modeled with a layer thickness of 0.1/0.2/0.3mm were investigated. It has been observed that the increase in layer thickness decreases flexural strength. In addition, while the flexural strength of the specimens containing delamination decreased, the increase in layer thickness accelerated this decrease.