The increasing complexity and production volume of glass-fiber-reinforced polymers (GFRP) present significant recycling challenges. This paper explores a potential use for mechanically recycled GFRP by blending it with high-density polyethylene (HDPE). This composite could be applied in products such as terrace boards, pipes, or fence posts, or as a substitute filler for wood flour and chalk. Recycled GFRP from post-consumer bus bumpers were ground and then combined with recycled HDPE in a twin-screw extruder at concentrations of 10, 20, 30, and 40 wt%. The study examined the mechanical and structural properties of the resulting composites, including the effects of aging and re-extrusion. The modulus of elasticity increased from 0.878 GPa for pure rHDPE to 1.806 GPa for composites with 40 wt% recycled GFRP, while the tensile strength ranged from 36.5 MPa to 28.7 MPa. Additionally, the porosity increased linearly from 2.65% to 7.44% for composites with 10 wt% and 40 wt% recycled GFRP, respectively. Aging and re-extrusion improved the mechanical properties, with the tensile strength of the 40 wt% GFRP composite reaching 34.1 MPa, attributed to a reduction in porosity by nearly half, reaching 3.43%.

In the present study, using a combination of theoretical discussions, practical examples, and case studies, we sought to gain a comprehensive understanding of how numerical solutions could be used to improve the design and optimize the thermal efficiency of a heat exchanger that utilizes wastewater to reduce the domestic consumption of hot water. To this end, we developed a validated numerical model. We also carried out simulations and experiments, the results of which are presented in this paper. The novelty of this work derives from our use of a new heat exchanger design for a domestic shower, and from the presented experimental–numerical evidence that proves its efficiency. We found that use of our newly designed appliance improved thermal efficiency from 14% to 27%. Moreover, we estimated that the cost of manufacturing and installing such a device did not exceed that of a widely available drain grid. Using our newly designed exchanger, a family of four living in Poland could save EUR 38 (at 2022 values) and reduce CO₂ emissions by 192 kg. An average European family could save EUR 68 and reduce CO₂ emissions by 76 kg.

In response to environmental regulations, particularly within the European Union, there is an urgent need to implement new, sustainable materials derived from recycling processes. This study investigates the potential for modifying and predicting the mechanical properties of composites made from recycled high-density polyethylene (rHDPE) and recycled glass fiber-reinforced polymer (rGFRP). Specifically, it examines tensile strength parameters and structure changes in rHDPE/rGFRP treated with three different chemical additives, including a silica-based agent (S) and maleic-anhydride polyethylene (MAH) compatibilizers; and a thermal stabilizer dedicated for the recycled polyolefins. The findings reveal that these additives do not significantly change the mechanical properties of the composite. All additives increase elastic modulus (compared to rHDPE/rGFRP for max. 3% - S), tensile strength (max. for 14%, MAH), and offset yield strength (max. 16%, MAH). Moreover, the strength of the composite can be enhanced through γ-irradiation, which was found to affect the stress-strain characteristics of the rHDPE/rGFRP blend. Notable differences were observed in the strength and elongation behavior of the composite (for rHDPE increased to 0.58 for 40 kGy and decreased for 100 kGy dose to 0.35, which is very close to the non-irradiated sample), suggesting that irradiation could be a viable method for modifying the properties of recycled composites for specific applications.

Nowadays, industries are increasingly developing advanced materials that combine high durability, sustainability, and ease of fabrication. Aramid fibers, particularly Kevlar, are widely used in engineering applications due to their excellent mechanical properties, such as high tensile strength, impact resistance, and thermal stability. At the same time, growing concerns over environmental impacts have led to increased interest in the reuse of waste materials and the development of sustainable composite systems. In this paper, we review experimental studies on Kevlar-based composites, with particular emphasis placed on composites manufactured from waste Kevlar fibers. Particular attention is given to the influence of fiber fragmentation and surface modification performed using polyvinyl butyral (PVB) on mechanical properties. We also cover material characteristics, manufacturing techniques, and the mechanical behavior of various composite systems. We primarily focus on analyzing the methodologies and research results of studies in the literature to enable future researchers to verify the quality of existing research.

This study presents a comprehensive experimental and numerical investigation of a rotating propeller using three-dimensional Digital Image Correlation (3D DIC), Computational Fluid Dynamics (CFD), and Finite Element Method (FEM) analysis. The main objective was to assess the applicability and accuracy of 3D DIC for full-field displacement and strain measurements under centrifugal loading conditions. The propeller geometry was reconstructed using 3D scanning and implemented in a numerical model with material parameters identified through mechanical testing. Experimental measurements were carried out on a dedicated test stand enabling controlled rotational speed and synchronized image acquisition. Particular attention was devoted to measurement uncertainty, including calibration errors, motion effects, and coordinate system alignment. The obtained displacement and strain fields were compared with FEM predictions after proper spatial transformation for rotational speeds 4110, 6064, and 6940 rpm. The results demonstrate good agreement between numerical and experimental data in selected regions, confirming the potential of 3D DIC for validation of rotating structures, while also highlighting limitations related to dynamic effects and optical constraints.

This study presents a comprehensive experimental and numerical investigation of a rotating propeller using three-dimensional Digital Image Correlation (3D DIC), Computational Fluid Dynamics (CFD), and Finite Element Method (FEM) analysis. The main objective was to assess the applicability and accuracy of 3D DIC for full-field displacement and strain measurements under centrifugal loading conditions. The propeller geometry was reconstructed using 3D scanning and implemented in a numerical model with material parameters identified through mechanical testing. Experimental measurements were carried out on a dedicated test stand, enabling controlled rotational speed and synchronized image acquisition. Particular attention was devoted to measurement uncertainty, including calibration errors, motion effects, and coordinate system alignment. The obtained displacement and strain fields were compared with FEM predictions after proper spatial transformation for rotational speeds of 4110, 6045, and 6940 rpm. The results demonstrate good agreement between numerical and experimental data in selected regions, confirming the potential of 3D DIC for validation of rotating structures, while also highlighting limitations related to dynamic effects and optical constraints.