Calcium sulphoaluminate cement (CSA) has been recognized for its rapid hardening, high early strength, strong chloride resistance, and low carbon emissions. This study developed a CSA-based foam concrete using a physical foaming method, incorporating industrial by-products—fly ash (FA) and ground granulated blast-furnace slag (GGBS)—at replacement ratios of 0%–30% to reduce costs and modify properties. Key properties assessed were flowability, dry shrinkage, density, compressive strength, and thermal conductivity. Results showed that FA and GGBS enhance flowability, reduce dry shrinkage and density, and diminish compressive strength, with dosage-dependent effects. The optimal replacement ratio of FA was 15%, yielding the lowest thermal conductivity at 0.0638 W/m·K, with only a minor strength reduction relative to the pure CSA foam concrete. The findings enable tailored design of sustainable, cost-effective CSA foam concrete using industrial by-products.

<abstract> <p>Ultra-thin flexible glass with thicknesses of 100 µm or below is a substrate in the fields of optics, electronics, and semiconductors. Its brittleness is challenging in production processes like physical vapor deposition processes, especially in roll-to-roll production. In many cases, multiple geometric deformations take place and each step, like coating or cutting, influences the glass strength. By now, the relation between the strength of ultra-thin glass under quasi-static conditions and its strength under cyclic load has not been studied. Moreover, the effect of coatings has not been investigated. Both aspects are crucial to design reliable production processes. Therefore, the strength of ultra-thin glass under cyclic load was studied for uncoated and coated substrates. Two coating types were investigated: a single indium tin oxide film and a seven-layer antireflective layer stack. The coatings significantly influence the strength of the underlying glass in both test modes. The barrier properties, thin film stress, and the morphology/crystalline structure are identified as the major characteristics influencing the strength.</p> </abstract>

<abstract> <p>This study explores the characteristics and potential engineering applications of Cu-Al-Mn and Cu-Al-Be-Mn shape memory alloys (SMAs). The research investigates the chemical composition, transformation temperatures, and mechanical properties of these SMAs when incorporated into Al metal matrix composites. It was found that the addition of Mn and Be has a significant impact on the performance of Cu-Al alloys. Among Cu-Al-Mn SMAs, SMA 1, with a composition of Cu-80.94%, Al-10.54%, and Mn-8.52%, exhibited superior strain recovery, super elasticity (SE), and improved mechanical properties compared to other compositions. The study also demonstrates that the inclusion of SMA fibers in Al composites enhances residual strength, energy absorption capacity, and the ability to close fissures, contributing to a more robust and resilient material. In the case of Cu-Al-Be-Mn SMA (SMA 6) with Cu-87.42%, Al-11.8%, Be-0.48%, and Mn-0.3%, displayed improved properties, outperforming other compositions in terms of strain recovery, residual strength, energy absorption capacity, and crack-closing ability. These findings suggest that Cu-Al-Be-Mn SMAs hold promise for various engineering applications. The study provides valuable insights into the potential of these SMAs to enhance the performance of structural materials, offering increased strength, ductility, and resilience. This research contributes to a deeper understanding of the applications and advantages of SMAs in the field of engineering.</p> </abstract>

<p>This paper studied the mechanical properties of carbon fiber-reinforced polylactic acid (CF-PLA) samples manufactured with three different 3D-printed patterns: gyroid, tri-hexagon, and triangular. Filler content was generated in the samples at infill ratios of 30%, 60%, and 90%. Conventional tensile, flexural, impact, and fatigue tests were conducted to investigate the mechanical properties. It was found that the gyroid infill pattern enhanced performance, exhibiting tensile strength and modulus of elasticity up to 63% and 13% greater, respectively, than the tri-hexagon pattern at a 90% infill ratio. The fatigue life improvement was 113% compared with the tri-hexagon pattern. The tensile strength and modulus of elasticity increased up to 35% and 40% after including carbon fibers. The increase in flexural modulus was 30% compared to the triangular pattern, whereas impact energy absorption reached the best result with the triangular pattern, up to 89% more than the gyroid pattern. These results elucidate the optimization of infill patterns and ratios together with carbon fiber reinforcement for the development of CF-PLA components as a high-performance 3D printing solution for a wide range of engineering applications.</p>

<abstract> <p>Phononic crystals (PnCs) possessing desired bandgaps find many potential applications for elastic wave manipulation. Considering the propagating essence of three-dimensional (3D) elastic waves and the interface influence of multiphase material, the bandgap design of 3D single-phase PnCs is crucial and appealing. Currently, the main approaches for designing 3D single-phase PnCs rely on less efficient trial-and-error approaches, which are heavily dependent on researchers' empirical knowledge. In comparison, topology optimization offers a dominant advantage by transcending the restriction of predefined microstructures and obtaining topologies with desired performance. This work targeted the exploration of various novel microstructures with exceptional performance by geometric-constrained topology optimization. To deal with high-dimensional design variables in topology optimization, the unit cell structure of a PnC was confined by pyramid symmetry to maximumly deduct the variable number of the unit cell. More importantly, to alleviate mesh dependence inherent in conventional topology optimization, node-to-node and edge-to-edge connection strategies were adopted, supplemented by the insertion of cylinders to ensure the stability of these connections. Finally, unstable PnC structures were filtered out using extra geometric constraints. Leveraging the proposed framework for the optimization of 3D single-phase PnCs, various novel structures were obtained. Particularly, our results demonstrate that PnC structures with only one type of mass lump exhibit significant potential to possess outstanding performance, and geometric configurations of the ultimately optimized structures are intricately linked to the particular sequence of the bandgaps.</p> </abstract>

<p>The aim of this study was to characterize a Sn-Ti solder alloy containing 6 wt.% SiC nanoparticles and evaluate its use for direct soldering of SiC ceramics to a copper (Cu) substrate. Soldering was performed with direct ultrasound activation. The average tensile strength of the solder alloy was 17.1 MPa. Differential Thermal Analysis (DTA) analysis revealed an apparent transition at 234 ℃, corresponding to a eutectic reaction within the Sn-Ti binary system, indicating structural changes in the solder. The solder matrix consisted primarily of pure tin, while titanium combined with SiC nanoparticles to form a TiC phase. The existence of this phase was confirmed by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis of the solder. The bond at the interface between the SiC ceramic substrate and the solder was formed through diffusion and chemical reactions. The XRD analysis of the fractured surface from the SiC side confirmed the formation of phases such as TiC, Ti<sub>2</sub>Sn, CTi<sub>2</sub>, CuSn, SiC, and Cu<sub>6</sub>Sn<sub>5</sub>; the TiC and CTi<sub>2</sub> phases resulted from the interaction of active Ti in the solder with the SiC ceramic surface. The bond at the Cu substrate interface formed due to the high solubility of tin in the solder and the formation of probable CuSnTi and CuSnTi3<sub>5</sub> phases, along with a mixture of Sn + η Cu<sub>6</sub>Sn<sub>5</sub> solid solution. The average shear strength of the SiC/Cu joint, fabricated using SnTi3 solder with 6 wt.% SiC nanoparticles, was 21.5 MPa.</p>

<abstract> <p>In this work, a novel method for a more sustainable recycling and cost-efficient manufacturing technique of polyether ketone ketone (PEKK) based thermoplastic composite materials is proposed to recover and reprocess waste and end-of-life materials in the aerospace industry. For the recycling of carbon fiber reinforced thermoplastics (CFrTP), an innovative scrapping process based on mechanical cutting was developed and the properties of the obtained scrap and the recycled panel were analyzed. Thus, a cutting tool was developed for the delamination of the input material so that long fibers can be retained in the resulting scrap. Different processing approaches of material scrapping were evaluated, aiming to obtain manageable scrap that can be subsequently used for a compression molding process. Additionally, an automatic process was evaluated to manage the scrap and perform the corresponding lay-up to manufacture high-quality thermoplastic composite products with recycled materials.</p> </abstract>

<abstract> <p>Ordinary Portland Cement (OPC) is a crucial building component and a valuable strategic resource. The production of cement accounts for 5% to 10% of global carbon dioxide (CO<sub>2</sub>) emissions. Over the years, many researchers have been studying ways to reduce the amount of CO<sub>2</sub> in the atmosphere caused by cement production. Due to its properties, biochar is found to be an interesting material to be utilised in the construction industry due to its effectiveness in CO<sub>2</sub> sequestration. Biochar is a solid residue created by the thermal breakdown of biomass at moderate temperatures (350–700 ℃) without oxygen or with a small amount of oxygen, sometimes known as bio-carbon. Biochar has a wide range of uses, including those for heating and electricity generation, cleaning flue gases, metallurgy, animal husbandry, agriculture, construction materials, and even medicine. The objective of this paper is to review the potential of biochar as a cementitious material by evaluating its physical, chemical, mechanical, and durability properties. Using biochar as a cementitious material makes it possible to conclude that cement production will be reduced over time by partial replacement, which will also promote and encourage sustainable development in the future.</p> </abstract>

<abstract> <p>A functionally graded material (FGM) was prepared using epoxy resin reinforced with silicon dioxide with a particle size of 100 μm and weight percentages of 0, 20, 40, 60, and 80 wt%. In a gravity-molding process using the hand layup technique, specimens with international standard (ASTM)-calculated dimensions were created in a mold of poly(methyl methacrylate), which is also known as acrylic. Tensile, flexural, impact, infrared wave, and thermal conductivity tests, and X-ray diffraction (XRD) were conducted on specimens of the five layers of the FGM. The XRD and infrared spectroscopy demonstrated that the compositions of the silica particles and epoxy had a strong association with their physical structures. The findings of experimental tests indicated that increasing the ratio of silicon dioxide enhanced the mechanical properties, and the increase in modulus of elasticity was directly related to the weight percentage of the reinforcement material. The composite with 80% silica had a 526.88% higher modulus of elasticity than the pure epoxy specimen. Both tensile and flexural strengths of the composite material were maximal when 40 wt% of the particle silicon dioxide was utilized, which were 68.5% and 67.8% higher than those of the neat epoxy, respectively. The test results also revealed that the impact resistance of the FGM increased when the silica proportion increased, with a maximum value of 60 wt% silica particle content, which was an increase of 76.98% compared to pure epoxy. In addition, the thermal properties of epoxy resin improved when SiO<sub>2</sub> was added to the mixture. Thus, the addition of silica filler to composite materials directly proportionally increased their thermal conductivity to the weight ratio of the reinforcement material, which was 32.68–383.66%. FGM composed of up to 80% silica particles had the highest thermal conductivity.</p> </abstract>