This paper investigates the mechanical behavior of polylactic acid (PLA), polycarbonate (PC) and carbon fiber-reinforced high-temperature polyamide (PAHT-CF) specimens fabricated by fused deposition modeling (FDM). PC and PAHT-CF are considered engineering grade materials that exhibit good mechanical properties, suitable for rapid prototypes and functional parts fabrication. PLA, a popular, commonly used FDM material, has been included in this work for comparison purposes. The purpose of the present study is to provide comprehensive experimental data on the materials’ critical properties since limited data is available in the existing literature and there is a lack of comparative analysis regarding the three materials. Mechanical characterization has been carried out on the basis of tensile, three-point bending, impact and creep tests. Measurements of hardness, density and porosity were conducted, and the specimens’ morphology was examined through microscopy. The results showed that the highest strength and flexural modulus of elasticity were observed for the PAHT-CF specimens followed by PC and PLA. PC specimens exhibited the highest impact resistance followed by PAHT-CF and PLA. The highest stage II creep resistance was achieved by PAHT-CF followed by PC and PLA. The optical and scanning electron microscopy images revealed that specimens’ quality depends on the printing parameters.

The increased use of fossil fuels in transportation is considered a major cause of environmental pollution and climate change on a global scale. In international shipping, regulations and strict measures have been introduced by the International Maritime Organization to achieve the goal of a 40% reduction in greenhouse gas (GHG) emissions by 2030, with the envisage to reach net-zero GHG emissions close to 2050. Renewable energy sources, such as solar photovoltaic (PV) systems, can be implemented on new-build or existing marine vessels as an effective alternative source for auxiliary power generation, reducing the dependency on fossil fuels and contributing to decarbonization. In the present paper, a sustainable retrofit design using PV panels on an existing Ro-Ro vessel is analyzed for its feasibility. The proposed system is used for energy production during ship cargo operations and takes advantage of the large space area on the upper deck and its continuous exposure to sunlight during its voyage. To investigate the effectiveness of the PV system as an alternative to fossil fuel consumption, an environmental and economic evaluation is performed. According to the results obtained, the solar PV system can provide approximately 88% of the required energy annually for lighting during ship cargo operations, with the corresponding fuel savings and emission reductions, making the investment economically feasible, with a high potential to contribute to environmental sustainability.

Material extrusion is a widely employed additive manufacturing technique with the functional capability of fabricating solid objects or cellular structures by depositing molten thermoplastic material in successive layers according to the designed path of deposition beads. Carbon fiber sandwich composites are advanced structures, ideal in applications that require high strength and stiffness, and low weight. In the present work, sandwich composites consisting of a carbon fiber-reinforced polyamide core—3D printed with a cubic pattern at 50% infill density—and carbon fiber fabric (CFF) skin, were fabricated using the hand lay-up method and experimentally investigated. The results showed that the tensile, flexural and impact strength of the sandwich composites increased by 64.5%, 24.5% and 69.0%, respectively, compared to unreinforced 3D printed specimens with 50% infill density, and by 24.3%, 18.8% and 56.3%, respectively, compared to unreinforced 3D printed specimens with 100% infill density. In addition, a reduction in the water absorption and the density of the sandwich composites was observed. Similar results were obtained for sandwich composites with one additional internal CFF layer. This work demonstrates that this specific combination of materials and manufacturing processes can be successfully employed for lightweight, water-resistant carbon fiber sandwich structures with improved mechanical strength.

Material extrusion is a widely employed additive manufacturing technique with the functional capability of fabricating solid objects or cellular structures by depositing molten thermoplastic material in successive layers according to the designed path of deposition beads. Carbon fiber sandwich composites are advanced structures, ideal in applications that require high strength and stiffness, and low weight. In the present work, sandwich composites consisting of a carbon fiber-reinforced polyamide core—3D printed with a cubic pattern at 50% infill density—and carbon fiber fabric skin, were fabricated using the hand lay-up method and experimentally investigated. The results showed that the tensile, flexural and impact strength of the sandwich composites increased by 64.5%, 24.5% and 69.0% respectively, compared to unreinforced 3D printed specimens with 50% infill density, and by 24.3%, 18.8% and 56.3% respectively, compared to unreinforced 3D printed specimens with 100% infill density. In addition, a reduction in the water absorption and the density of the sandwich composites was observed. Similar results were obtained for sandwich composites with one additional internal CFF layer. This work demonstrates that this specific combination of materials and manufacturing processes can be successfully employed for lightweight, water-resistant carbon fiber sandwich structures with improved mechanical strength.

This work presents a novel approach that integrates naval architecture and traditional shipbuilding. It is an innovative solution that bridges the two sectors, offering a novel perspective to the traditional shipbuilding industry and, concomitantly, underscoring methods to integrate novel technologies into traditional shipbuilding. This integration of novel technologies into traditional shipbuilding is a crucial step in the broader decarbonization process of shipping. The paper delineates the fundamental design parameters of a traditional yacht. The vessel is distinguished by a “karavoskaro” bow and a “barkalas” stern. Initially, the lines plan of the traditional vessel was mapped in 3D ship design software, followed by the calculation of the basic hydrostatic and hydrodynamic quantities. Subsequently, a three-dimensional model was designed to scale, and a physical prototype of the hull was constructed using three-dimensional printing technology. The latter was then used as a mold for the construction of the glass reinforced polyester hull of the traditional vessel using the hand lay-up technique. The objective of this study is to establish a methodology for integrating traditional shipbuilding expertise with contemporary naval architecture science and technology, with a focus on the blue economy and the decarbonization of shipping. The integration of traditional shipbuilding art, a cornerstone of the development of the Greek maritime state, which has evolved and persisted throughout the ages, with innovative technologies, holds the potential to serve as a crucial mechanism in the establishment of a lightweight fleet that aligns with the demands of sustainable, decarbonized maritime transportation within the Greek maritime domain.

As circular economy is a key driver for the transition to product sustainability with certain economic, social, and environmental benefits, scientists and engineers are focusing on the development and integration of sustainable manufacturing processes and materials in a wide range of industries. In the field of industrial engineering, there is a growing interest in substituting metal components with advanced thermoplastics to produce lightweight products and reduce environmental impact. Material extrusion additive manufacturing is a rapidly evolving technology with sustainable and competitive features, such as fabrication of functional products with complex geometry, on-demand and in-situ production, and material savings. This chapter endorses the industry trend towards using sustainable recycled materials for 3D printing applications and presents recent developments in polymer recycling for a wide range of thermoplastics, including commodity polymers (i.e., ABS, PP, PLA), engineering polymers (i.e., PETG, PA, PC, PMMA, POM), and high performance polymers (i.e., PVDF, PPS, PSU, PEEK, PEKK, PEI). The challenges associated with the filament extrusion and remanufacturing process are highlighted, as well as the effect of process parameters on the mechanical properties of 3D printed samples. Future research directions are suggested to provide systematic and validated information on the performance of remanufactured parts from recycled feedstock.