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    3D-printed polylactic acid-microencapsulated phase change material composites for building thermal management
    (Pergamon-Elsevier Science Ltd, 2024) Bayram, Muhammed; Ustaoglu, Abid; Kursuncu, Bilal; Hekimoglu, Gokhan; Sari, Ahmet; Ugur, Latif Onur; Subasi, Serkan
    The integration of phase change materials (PCM) into architectural elements is an emerging strategy to enhance thermal energy storage in modern buildings. This research examines 3D-printed polylactic acid structures incorporated with microencapsulated PCM, targeting a more efficient thermoregulation in foundational architectural sections such as walls, floors, and ceilings. Through rigorous evaluations, the polylactic acid-PCM composite revealed promising thermoregulatory properties. Notably, latent heat values stood at 198.4 J/g for melting and 197.9 J/g for freezing. Real-world experiments demonstrated a distinct advantage, maintaining temperatures 3.2 degrees C-3.3 degrees C higher than standard polylactic acid at night and exhibiting a cooler range of 10.4 degrees C-13.3 degrees C during daylight. Within specific geographical contexts, like the Mediterranean and Aegean Seas coastline, 0.026 m thick polylactic acid-PCM panels stood out, registering 100 % energy savings. The findings consistently showed that an increase in panel thickness correlated with a decrease in building heating needs. Further analysis explored the carbon emissions landscape. Coal, when utilized with 0.05 m-thick polylactic acidPCM panels, was identified as particularly effective, yielding a reduction of 34 kg/m2 in annual CO2 emissions. Collectively, the findings underscore the transformative potential of polylactic acid-PCM composites, positioning them as pivotal tools for advancing architectural energy efficiency and fostering sustainable building innovations.
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    Characterisation and energy storage performance of 3D printed-photocurable resin/microencapsulated phase change material composite
    (Elsevier, 2024) Er, Yusuf; Guler, Onur; Ustaoglu, Abid; Hekimoglu, Gokhan; Sari, Ahmet; Subasi, Serkan; Gencel, Osman
    The 3D fabrication of microencapsulated phase change material (MEPCM) doped resin polymer composites enables the creation of complex shapes and customized designs, opening doors for many applications in fields. This investigation fabricated a range of resin/MEPCM (20 %, 30 %, and 40 % by volume) composites using a mechanical mixing technique. This study investigates how the addition of MEPCM impacts resin matrix composite's mechanical strength, latent heat storage characteristics, and ability to regulate temperature effectively. With a 40 % MEPCM additive ratio, a pure resin porosity value of approximately 0.4 % increased to around 17 %. Thanks to the production of homogeneously dispersed MEPCM added resins with production with stereolithography (SLA), 40 % MEPCM additive enabled characteristic FTIR peaks of both MEPCM and resin to appear and, melting and solidification enthalpy values reached 87.15 j/g and 86.25 j/g, respectively. MEPCM addition enhanced the thermoregulatory properties of resin by absorbing or releasing heat during temperature fluctuations. On hotter days, 8 mm-thick composites create temperature differences exceeding 11 C, while this difference exceeds 6 C in the room center case. The produced 3D printed MEPCM/resin composite can be a potential material to effectively regulate the temperature of electronic devices, food packets, building materials, and electronic devices and automotive components.
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    Cyclic behavior of autoclaved aerated concrete block infill walls strengthened by basalt and glass fiber composites
    (Elsevier Sci Ltd, 2021) Arslan, Mehmet Emin; Aykanat, Batuhan; Subasi, Serkan; Marasli, Muhammed
    In this study, the effects of 10 mm bilaterally applied basalt and glass fiber reinforced (BRC and GRC) cementitious plasters with different fiber content (1.0%, 2.0% and 3.0%) on the behavior of the autoclaved aerated concrete (AAC) block infill walls were investigated. For this purpose, 8 infill walls with dimensions of 150 x 150 x 20 cm were produced to examine the behavior of the infill walls under reversed cyclic loading. The load carrying capacities, stiffness degradation and energy dissipation capacities of the infill walls placed in a steel frame with hinges on all four corners were determined by using hysteretic load-displacement curves to evaluate effects of fiber reinforced cementitious plaster. The test results show that BRC and GRC plaster applications considerably increase the load carrying and energy dissipation capacities of the infill walls. However, the experimental results illustrated that the usage of BRC plasters in strengthening of the AAC block infill walls needs more attention. Having similar results for different fiber ratios in the use of GRC reveals that it may be more rational to use 1.0% fiber content for the most economical solution for strengthening. Although the results obtained in this study are valid for infill walls, the experimental results show that GRC plasters can also be used in strengthening of masonry walls. It is recommended that this method can be used quickly and effectively in strengthening of masonry structures, which occupy an important place in the existing building stock.
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    Engineering properties of hybrid polymer composites produced with different unsaturated polyesters and hybrid epoxy
    (Elsevier, 2024) Gokce, Neslihan; Eren, Sevki; Nodehi, Mehrab; Ramazanoglu, Dogu; Subasi, Serkan; Gencel, Osman; Ozbakkaloglu, Togay
    In this study, the mechanical properties of hybrid polymer composites produced with different unsaturated polyesters and hybrid epoxy resins are investigated. The composites were produced by blending unsaturated polyester resins (i.e., orthophthalic, isophthalic, and terephthalic) and bisphenol-A-based epoxy-vinyl ester resin to produce single, binary and ternary blends. In doing this, a total of 14 different combinations were produced. The results show that the binary and ternary polymer blends tend to improve almost all the tested properties of the polymer composites. Further, the fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) results confirmed that the reason for enahcned properties is due to better crosslinking and longer chains of polymers produced in binary and ternary mixtures. The absence of peaks determining the styrene polymerization character for all mixtures also demonstrates that the polymerization reaction takes place in all mixtures. It is also believed that the binary and ternary resin mixtures have developed higher energy absorption compared to single resin composites. All of the mentioned has been achieved while the gelation temperatures of the hybrid resin mixtures were not changed significantly and they began gelation at the expected temperature values. In addition to the gelation, peak exotherm temperatures, and barcol hardness values demonstrated that all mixtures achieved sufficient curing. The result of this study is significant and point to the great potential of producing high performance polymer composites through the use of binary or ternary resin mixtures.
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    Investigation of electromagnetic interference shielding performance of ultra-high-performance mortar incorporating single-walled carbon nanotubes and steel fiber
    (Elsevier, 2024) Subasi, Serkan; Seis, Muhammet; Tekin, Ilker; Kazmi, Syed Minhaj Saleem; Munir, Muhammad Junaid; Gencel, Osman; Ozbakkaloglu, Togay
    For security amenities and key infrastructure, construction materials with extraordinary mechanical, durability, and electromagnetic interference (EMI) shielding performance are essential. This study investigates the EMI shielding performance of ultra-high performance mortar (UHPM) incorporating single-walled carbon nanotubes (SWCNT) and steel fibers. Currently, no such work is present in the existing literature. Eight mixtures were prepared with varying SWCNT dosages (0%-0.03 % by weight of cement) and steel fiber additions (1.2 % of the volume of the UHPM mixture). The performance of UHPM incorporating SWCNT and steel fibers was evaluated through flow diameter, compressive strength, flexural strength, Schmidt hardness, ultrasonic pulse velocity, EMI shielding performance, and scanning electron microscopy analysis tests. It is observed that increasing the SWCNT content enhances the compressive strength, flexural strength, ultrasonic pulse velocity, and Schmidt hardness of UHPM. The addition of steel fibers further enhances compressive (up to 22 %) and flexural (up to 92 %) strengths. In terms of the transmittance behavior, the improved EMI shielding performance of UHPM with the increasing SWCNT content is observed prominently at high electromagnetic frequencies (i.e., 2500 MHz-5100 MHz). However, the improved shielding performance is observed to be quite low, limited to 10 dB. Moreover, combining steel fibers and SWCNT enhances the EMI shielding performance of UHPM in terms of the transmittance behavior. As a result, UHPM incorporating SWCNT and steel fibers behaves as an absorbent material, shielding a significant amount of energy, approximately 45 dB, at a frequency of 5000 MHz. Based on the results, UHPM incorporating SWCNT and steel fibers can be used effectively as EMI shielding material. The findings of this study will enhance the practical applications of UHPM incorporating SWCNT and steel fibers.
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    Microencapsulated phase change material incorporated light transmitting gypsum composite for thermal energy saving in buildings
    (Elsevier, 2023) Gencel, Osman; Bayram, Muhammed; Subasi, Serkan; Hekimoglu, Gokhan; Sari, Ahmet; Ustaoglu, Abid; Marasli, Muhammed
    The increased energy consumption for specific applications, including heating, cooling, air conditioning and lighting of residential and commercial buildings accelerate the research efforts concentrated on developing thermal energy storage capacity of buildings materials in recent years. Likewise, the development of light-transmitting building elements is a novel energy-saving technique that enhances lighting efficiency in build-ings. In light of these, the current study seeks to design an untried microencapsulated phase change material (MPCM) integrated glass fiber reinforced gypsum composite with sufficient light-transmitting properties and thermal energy storage capacity. In this research, a multi-scale investigation of light-transmitting gypsum composite was conducted experimentally with physical, mechanical, chemical, microstructural, thermal, light transmittance and solar thermoregulation tests. The gypsum composite is formed from alpha-gypsum, water, polymer admixture, alkali-resistant glass fiber (AR-GF), several concentrations of MPCM, and plastic optical grids to allow light to transmit through the board. Although higher fractions of MPCM yielded an apparent decrease in me-chanical strength test results, 5 wt% introduction of MPCM to the reference matrix reduced the compressive and flexural strength of specimens by 1 and 8 %, respectively. The results verified a reduction trend in thermal conductivity of composites with MPCM loading. DSC investigations revealed that the melting temperature and the regarding latent heat storage capacity of gypsum composite with 15 wt% of MCPM are 17.76 degrees C and 19.2 J/g, respectively. Light-transmitting gypsum composites showed up to similar to 10 % light transmittance, that can greatly increase the efficiency of lighting in buildings. The produced gypsum composites with MPCM kept the test room cooler during the highest temperature, while it provided a warmer room during the nighttime for an extended time. The study's findings are applicable to increase thermal comfort by reducing the significant temperature variations in buildings and improving artificial lighting efficiency, encouraging the design of sustainable building applications.
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    Physico-mechanical properties and thermal monitoring performance of thermal enhanced cement slurry-coated LWAs containing microencapsulated phase change material
    (Elsevier, 2024) Emiroglu, Mehmet; Ozguler, Alper Tunga; Nas, Memduh; Subasi, Serkan; Sari, Ahmet; Hekimoglu, Gokhan; Ustaoglu, Abid
    Over the past decade, phase change materials (PCMs) have emerged as promising solutions for thermal energy storage (TES) systems, aimed at minimizing heating and cooling energy requirements in buildings. Nevertheless, despite their potential, there are some significant challenges in effectively integrating PCMs into building components. As part of this study, lightweight aggregates (LWA) were coated with a cement slurry containing microencapsulated phase change material (MPCM) to produce lightweight concrete (LWC) with the aim of investigating its mechanical and thermal properties. The LWAs were coated with MPCM at proportions of 2.5%, 5%, and 7.5% of their weight, and an LWC-MPCM was produced using these coated aggregates. The LWC-MPCM exhibited a decrease in dry unit weight up to 1248 kg/m 3 and a reduction in thermal conductivity up to 0.60 W/ mK with negligible loss of strength. SEM examinations revealed that the cement slurry coating provided strong adhesion to the aggregates, resulting in a robust concrete-aggregate interface. The room with the LWC-MPCM experienced a decrease of approximately 0.23 degrees C in center temperature compared to the reference room during the daytime. Additionally, after sunset, the LWC-MPCM showed an increase of approximately 1 degrees C in room center temperature. These advantageous physico-mechanical and thermal properties establish LWC-MPCMs as promising and energy-efficient components for producing thermo-regulative building materials.
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    Production and assessment of UV-cured resin coated stearyl alcohol/ expanded graphite as novel shape-stable composite phase change material for thermal energy storage
    (Pergamon-Elsevier Science Ltd, 2024) Guler, Onur; Er, Yusuf; Hekimoglu, Gokhan; Ustaoglu, Abid; Sari, Ahmet; Subasi, Serkan; Marasli, Muhammed
    Expanded graphite -phase change materials (PCM) structures are reinforced to polymers with various methods to fabricate advanced thermal energy storage materials. However, these methods still suffer from processing time and product efficiency challenges. In this study, the UV-curing method was used to produce shape-stable EGPCM-reinforced resin composites with fast curing and low process temperature of the resin. The composite material, comprising UV -curable resin (30 %), stearyl alcohol (65 %), and Expanded graphite (5 %), was synthesized. This synthesis aimed to address the limitations of traditional PCMs, such as low thermal conductivity and leakage. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the materials ' phase change behavior and thermal stability. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses were conducted to elucidate the microstructure and crystallinity of composite materials. The composites, exhibiting near-perfect impermeability with leakage as minimal as 0.89 %, not only enable the attainment of cooler environments by 2 - 3 degrees C under hot air conditions but also demonstrate exceptional thermal stability up to 207 degrees C, as evidenced by TGA results. Additionally, they offer a remarkable melting enthalpy value of 153.1 J/g. These composites, with their shape-retention ability during phase transitions and high thermal energy storage capacity, are a versatile and efficient option for sustainable energy management. This research contributes to the development of innovative materials for renewable energy integration and reducing carbon emissions.