The emphasis on environmental sustainability has accelerated the adoption of biocomposites as alternatives to synthetic composites. However, their low surface energy may limit adhesion in bonding applications. This study investigates the effects of cold atmospheric plasma (CAP) treatment on the adhesion of flax fiber-reinforced polypropylene (PP/flax) biocomposites. PP/flax plates were fabricated by sequential hot and cold pressing and subjected to CAP for different durations in atmospheric air. Surface modifications were characterized using contact angle measurements, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Adhesion performance was evaluated by single-lap shear tests with a structural epoxy adhesive. CAP treatment significantly improved surface wettability, reducing water contact angle from 86 degrees to 36 degrees, while surface free energy reached a maximum after 150 s. Single-lap shear strength increased from 0.54 MPa to 1.90 MPa at 150 s. Failure mode changed from adhesive failure in reference specimens to substrate failure in CAP-treated joints. AFM indicated plasma etching increased nanoscale roughness, while XPS and ATR-FTIR confirmed formation of polar functional groups and oxidation. Improvements beyond 150 s diminished, showing an optimal treatment range. These findings demonstrate that controlled CAP treatment effectively enhances the adhesive bonding of PP/flax.

This study investigates the development of sustainable polymer composites for structural strengthening by incorporating waste glass fibers and natural fibers (flax and hemp) into an epoxy matrix, in response to the growing environmental concerns. Mechanical, thermal, and durability-related properties were evaluated through tensile testing, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), water absorption, and water immersion aging tests. Results showed that incorporating waste glass fibers enhanced the tensile strength and thermal decomposition temperature by 88% and 5.4%, respectively, compared to composites reinforced with solely natural fibers. Water absorption tests indicated that waste glass fiber-reinforced hybrid composites exhibited lower water uptake than flax and hemp fiber-reinforced composites. After water immersion, the tensile strength loss was recorded as 22, 25, and 8.5% for the composites reinforced with hemp, flax, and waste glass fiber, respectively. The findings confirm that incorporating waste glass fibers into natural fiber composites effectively mitigates moisture sensitivity and improves mechanical performance. Hybridizing flax and hemp fibers with waste glass fibers provides a practical and sustainable approach to enhancing composite performance, making them a viable alternative for strengthening reinforced concrete structures requiring long-term resistance. The recycled waste glass fibers employed in this study offered comparable mechanical performance while drastically lowering raw material consumption and environmental impact, in contrast to virgin glass fibers frequently used in earlier investigations. This demonstrates how recycling-oriented composite design can provide both sustainability and performance benefits.

In recent years, polypropylene has become one of the most popular thermoplastic polymers due to its excellent properties, chemical resistance, affordability, and easy processing. When reinforced with glass fibers, wood fibers, or mineral fillers, polypropylene composites exhibit enhanced mechanical strength, stiffness, and durability. This makes them suitable for applications where high performance and specific mechanical properties are required, such as in automotive interior parts, building materials, and consumer goods. This research analyzes the effects of wood fibers as an organic filler and wollastonite mineral as an inorganic filler on the mechanical and viscoelastic properties of polypropylene. Various weight ratios of these fillers were added into polypropylene to produce hybrid biocomposites using a laboratory-type high-speed thermokinetic mixer and a heated-cooled hydraulic press. The mechanical properties were determined by tensile and three-point bending tests, and viscoelastic properties were analyzed using dynamic mechanical analysis. The test results indicated that the polypropylene composite sample containing 7% by weight of silane-treated wollastonite and 3% by weight of wood fibers showed the best results among all samples. The storage and loss moduli of the sample are approximately 25% and 22% higher than those of the polypropylene, respectively. Overall, hybrid biocomposites filled with silane-treated wollastonite exhibited enhanced mechanical and viscoelastic properties compared to those filled with untreated wollastonite, as supported by the experimental data.

Lignocellulosic fillers derived from pruned cherry tree branches were studied relative to the mechanical and viscoelastic properties of polypropylene (PP) composites. Tree branches were collected from the orchard after pruning and the wood and bark parts were separated from each other. Both materials were processed into particles of different sizes (below 100 µm and between 100 and 250 µm) and filled into PP at different weight percentages (5%, 10%, 15%, and 20%). The mechanical performances of the biocomposites were evaluated through tensile tests, while their viscoelastic behavior was analyzed using dynamic mechanical analysis (DMA). Results revealed a decline in tensile strength with increasing filler content, which was attributed to poor interfacial adhesion between the PP matrix and fillers. However, tensile modulus increased with increasing filler content, with the highest values were observed at 20% filler loadings. The DMA showed enhanced storage and loss moduli, indicating improved stiffness and energy dissipation. Scanning electron microscopy (SEM) confirmed the presence of voids and filler agglomeration, further explaining the mechanical property reductions. These results demonstrate the potential of cherry tree pruning waste as a bio-filler for sustainable biocomposites with improved stiffness.

The objective of this study was to obtain new composites containing polylactic acid (PLA) with artichoke stem (AP) at concentrations of 1

Polymer composites are becoming more and more involved in many industries such as aerospace, automotive, transportation and sports. As usage increases in the commercial market, the polymer industry provides materials to almost every area of technology and industry, allowing the production of materials or new materials to be produced and the development or orientation of new types of needs. In the last 10 years, the use of polymer composites has become the new materials needed in electronic technology. The aim of this study is to investigate the effects of polypropylene (PP) on mechanical and conductivity properties by using mica (M) as an inorganic filler and carbon nano tube (CNT) as an organic filler. Before hybrid composite materials were produced, polypropylene (PP) and M-PP composites were produced and composite with the best mechanical properties were selected. PP-M composites were produced by using a thermokincetic mixer with the addition of mica in 10%, 20%, and 30% weight ratios. Hybrid composites were manufactured using CNT addition into PP-20M with %1, %3, %5, and %7 weight ratios. Mechanical properties of the composite materials produced using tensile and bending tests and viscoelastic properties by dynamic mechanical analysis (DMA), thermal properties by differential scanning calorimeter (DSC) and thermogravimetric (TGA) analyses and morphological structures by scanning electron microscopy (SEM) were investigated

This study investigates the mechanical and thermal properties of polypropylene (PP) composites incorporating pumice, a naturally occurring porous volcanic rock with high SiO2 content, sourced from three regions in Türkiye (Nevşehir, Alaçatı, and Kütahya). Pumice was processed to particle sizes below 10 microns to maximize nucleating effectiveness, and composites were fabricated by melt compounding. The distinct mineralogical composition, porosity, and surface chemistry of the pumice samples enabled systematic evaluation of how regional variations influence crystallization and mechanical performance. A multi-analytical characterization approach, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and standardized mechanical tests (tensile, flexural, and impact), was applied. Results revealed that Alaçatı pumice at 0.1 wt% increased the impact strength of PP by about 11%, while maintaining stiffness. This demonstrates that pumice, unlike conventional fillers, can simultaneously enhance toughness and rigidity. Thermal analysis confirmed improved stability, with higher degradation onset and maximum decomposition temperatures observed in pumice-filled PP. DSC results indicated that certain pumice loadings promoted nucleation and increased crystallinity, while excessive amounts disrupted chain packing. SEM examinations confirmed uniform dispersion at low loadings, with agglomeration at higher levels reducing impact resistance. This work provides the first systematic demonstration of pumice powders as effective nucleating agents in PP, combining regional mineralogical diversity with measurable performance benefits. These findings indicate that pumice can serve as a sustainable, low-cost alternative to conventional nucleating agents, with potential applications in polymer components requiring improved toughness and thermal stability.

The objective of this study is to investigate the effect of air (dielectric barrier discharge) DBD plasma treatment on the bonding strength of adhesively bonded glass fiber-reinforced epoxy composite-aluminum lap joints. The bonding performance of lap joints produced by the plasma treatment was compared with that of untreated and peel-ply surface treatments. Water contact angles of the substrates were measured for untreated, peel-ply, and plasma surface-treated substrates. Experimental results showed that plasma-treated aluminum and GFRP substrates increased the wettability properties and thus shear strength of adhesively bonded GFRP-Al joints increased. After the shear tests, the fracture surfaces of the substrates were visually examined and three different damage modes were observed, including light fiber tear failure, adhesive failure, and thin layer cohesive failure modes.

The growing global demand for sustainable and environmentally friendly polymer materials is driving interest in cellulose-based materials. In response to this need, lignocellulosic fillers (LF) were extracted from pruning waste of bing cherry tree (Prunus Avium L.) branches as an alternative source of filler materials. The extracted LF were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Their chemical composition, density and particle size distribution (PSD) were also analyzed. In the second part of the study, biocomposites were prepared by incorporating fillers with particle sizes below 100 microns into an epoxy matrix at concentrations of 5%, 10% and 15% by weight. These biocomposites were then characterized by tensile test, three-point bending test and SEM analyze to determine their mechanical and morphological properties. Among the biocomposites, the one with 5% wood filler showed the best properties with a tensile strength of 45 MPa, tensile modulus of 1883 MPa, flexural strength of 74 MPa and flexural modulus of 2559 MPa. The results demonstrate the effectiveness of lignocellulosic particles in improving polymer matrices and suggest their potential for use in non-structural applications in the automotive and marine industries, such as interior panels.

In this study, air dielectric barrier discharge (DBD) plasma treatment was applied at various voltages and treatment durations to improve the bonding strength of glass fiber reinforced epoxy composites (GF/EP). In addition, single lap shear and three-point bending strengths of adhesively bonded joints were compared between untreated and surface-treated (sanding, peel ply, and plasma) samples. Surface properties of GF/EP composites were examined using contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Atomic Force Microscopy (AFM). Then, mechanical tests (single lap shear and three point bending) were performed and the damage modes were determined. Surface analyses revealed that wettability and polar functional groups increased on the GF/EP surface after plasma treatment. From the mechanical test results, it was observed that the plasma treatment applied to GF/EP composites increased both single lap shear and flexural strength compared to untreated, sanding and peel ply surface treatments. After both single lap shear and 3-point bending tests, adhesive, and light fiber tear failure modes were observed.

Polylactic acid (PLA) was modified with three types of MVOs, which are the epoxidized soybean oil (ESBO), maleinized sunflower oil (MSO) and maleinized olive oil (MOO), at different weight fractions. A co-rotating twin screw extruder was used to produce composite materials by melt mixing process. The effect of MVOs content, from 2.5% to 10%, on the morphology, mechanical properties, density and water absorption were investigated in detail. Addition of ESBO and maleinized vegetable oils leads to a slight decrease in density of PLA from 1.252 to 1.231 g/cm3. As the concentration of MVO in PLA increases, the amount of water absorption also increased and the highest water absorption value was observed in P10MSO. In general, the elastic modulus (EM) was slightly changed by the addition of MVO to PLA, while the tensile strength (TS) decreased. Due to the plasticizing effect of MVOs, an increase in the Izod impact strength was obtained.

Effusion cooling is one of the significant cooling technologies in combustor liners in terms of cooling efficiency and weight reduction. However, effusion cooling technology is difficult to manufacture. In fact this technology requires laser-drilling of thousands of tiny holes with shallow angles on a sheet metal with a thickness generally varying between 0.5 to 1.5 mm. In addition, the use of thermal barrier coating is common in gas turbine engines and is one more challenge for the drilling process. In order to obtain more efficient gas turbine engines, the inlet temperature keeps increasing in the last decades, which induces the combustion chamber to operate in a hotter environment. Therefore, efficient cooling technology is needed, even if it is hard to manufacture. For laser drilling, several parameters have to be explored to obtain acceptable holes. This study includes the microstructure investigations of the holes produced with different laser parameters and the optimal laser parameters determined according to the microstructure of six different effusion cooling hole configurations. The results show that laser process differences affect the metal substrate microstructure and thermal barrier coating structure. Drilling method, peak power, number of pulses, gas type and pressure value have a significant effect on the hole geometry and its microstructure.

The purpose of this research is to improve the dynamic-mechanical properties of the polypropylene filled by artichoke stem (AS) particles and wollastonite (W) in different weight fractions. The effect of weight ratios of fillers in polypropylene was mathematically modeled using the data obtained as a result of the experimental work. In the modeling phase, multiple nonlinear neuro-regression analysis was used. In this context, proposed linear and nonlinear models have been examined by performing R2training, R2adjusted, R2testing, and boundedness check. The models that satisfy these four criteria were selected as the objective functions for the optimization phase. Finally, Modified Differential Evolution Algorithm was used to obtain maximum storage modulus and loss modulus by adjusting weight percent ratio of artichoke stem particle and wollastonite. The experimental results and the modeling optimization results showed that when the polypropylene-artichoke stem particle-wollastonite hybrid polymer composite was used instead of other non-hybrid polymer composite, the storage modulus and the loss modulus improved by approximately 40%.

In this study, ground wastes of Nettle (Urtica dioica L.) fiber (GWN), which contains cellulose of 52.2 wt%, hemicellulose of 28.9 wt%, and lignin of 18.9 wt%, filled polypropylene (PP) composites were fabricated by using a high-speed kinetic mixer. The effect of filling GWN into PP at different weight fractions on density, crystallization behavior, coefficient of thermal expansion, and thermal stability was investigated. In addition, tensile and flexural tests were performed to determine how the mechanical properties of PP were affected. Morphological observations were conducted using scanning electron microscopy (SEM). The flexural strength values of PP increased by 10%, 15%, and 31% with the addition of 7 wt%, 14 wt%, and 21 wt% GWN, respectively. However tensile strength value of PP decreased slightly with the addition of GWN. 21 wt% GWN addition into PP led to a considerable decrease (about 29%) in the thermal expansion coefficient of PP. The degree of crystallinity of PP was not affected by the addition of GWN.

In this study, the performance of sandalwood (SW), as an efficient potential filler material for high-density polyethylene (HDPE), was investigated in detail. Firstly, the characterization of SW was conducted by the determination of chemical composition with chemical and thermal analysis methods. The distribution of SW particles, which were used in composite fabrication, was obtained by using a dynamic light scattering analyzer. Then, the composites of SW, whose weight fractions varied from 5% to 20%, with HDPE were produced in a high-speed thermokinetic mixer. The detailed characterization of composites was made by using thermogravimetric analysis, scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, dynamic mechanical analysis (DMA), Fourier transform infrared, thermal conductivity measurements, and tensile and three-point bending tests. From DMA, storage modulus and loss modulus values of the HDPE matrix increased with increasing the weight fraction of SW. It is clearly seen that SW incorporation into HDPE at weight fractions of 5% and 20% exhibited the best improvement in terms of tensile and flexural strengths, respectively. It can be noted that the reinforcement effect of SW for HDPE is more prominent at high temperatures.

In this research, artichoke stem particles (AS) and wollastonite (W) were used as an organic and inorganic fillers in order to improve the mechanical properties of polypropylene (PP). In this regard, PP-matrix composites containing AS and W were produced as non-hybrid and hybrid using a high speed thermo-kinetic mixer. Mechanical properties of polymer composites were investigated by the tensile test. Experimental results reveal that the highest modulus of elasticity was obtained in PP-W and the highest tensile strength was obtained in raw PP while the lowest ultimate strain value was obtained in PP-W-AS. Then, multiple-nonlinear regression analysis was employed to determine the effect of weight ratios of W and AS in PP on modulus of elasticity, tensile strength and ultimate strain. Experimental results were expressed with polynomial, rational and trigonometric models. The results show that the proposed models have well fitted with the experimental results. The coefficient of determination (R2) values were found between 0.95 and 1 in all models. Also, boundedness check control of the proposed models which gives information about whether models are realistic or not was carried out by calculating the maximum and minimum values produced by the relevant model.

Today, plant-fiber-filled polymer composites are used in many applications because of their favorable properties such as low price, renewability, biodegradability and non-toxic characteristics. However, usage of these composites is limited due to their insufficient thermal properties. To overcome this situation, plant fibers can be combined with mineral fillers that improve the thermal performance in polymer composites. In this study, the effect of wollastonite hybridization with artichoke was analyzed. Artichoke and wollastonite particles were used as an organic and an inorganic filler, respectively. Artichoke-polypropylene (PP) composites containing 10, 20 and 30wt% artichoke particles were manufactured using a high-speed thermokinetic mixer. Based on mechanical results, PP-based hybrid composites containing artichoke and wollastonite particles were fabricated to see the effect of wollastonite hybridization; 3, 5 and 7wt% wollastonite were added into the artichoke-PP matrix to compare with artichoke-PP composites containing 10 wt% artichoke particles. The storage modulus of artichoke-PP composites increased with increasing artichoke content. The hybrid composites had a higher storage modulus compared with composites containing 10 wt% artichoke. The hybrid composite PP-7A-3W (containing 7 wt% of artichoke and 3 wt% wollastonite) showed the highest storage modulus value. The initial decomposition temperature of PP-3A-7W had the highest value among all composites.

The aim of this study is to investigate the reinforcing effect of Ceratonia siliqua (CS) powder as a novel natural filler for polypropylene (PP) based composites. CS powder up to 20 wt% was filled into PP matrix by using high speed thermo kinetic mixer. Mechanical and thermal properties of CS filled PP based composites were investigated by tensile and three point bending test, dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry analysis, fourier transform infrared analysis, and thermomechanical analysis. Morphology of the composites was also investigated by scanning electron microscopy. By filling 5% and 10% of CS into PP, tensile strength and flexural strength of PP increased by about 32 and 23%, respectively. This indicates that CS has a great potential to be used as reinforcing filler for PP composites. CS filling into PP led to lower coefficient of thermal expansion values which could help preventing the thermal expansion.

Bu çalışmada silika-esaslı partiküller (SP), tetra etoksi silan (TEOS) kullanarak sol-jel yöntemi ile üretilmiştir. Üretilen silika-esaslı partiküller ile poliüretanın (PU) ısıl iletkenliğinin düşürülmesi amaçlanmıştır. Bu parçacıklar farklı oranlarda (ağırlıkça %0,5, 1, ve 2) poliüretanın içine ilave edilerek kompozit plakalar elde edilmiştir. Bu plakaların yapılan ısıl iletkenlik ölçümlerinde poliüretana %0,5 SP eklenmesi ile ısıl iletkenlik değerinin %16 civarında azaldığı görülmüştür. Bunun yanısıra basma dayanımında ise %6’lik bir azalma gerçekleşmiştir. Daha yüksek SP’nin PU’ya eklenmesiyle ısıl iletkenlikte azalma oranı düşerken basma dayanımındaki bozulma artmıştır. SP eklenmesi poliüretanın kimyasal yapısını, ısıl stabilitesini çok fazla değiştirmezken, ısıl genleşme katsayısını ise düşürmüştür. Poliüretan kompozitlerin içerisindeki SP parçacıkların dağılımı da taramalı elektron mikroskop analizleri ile incelenmiştir.