Ahmet Erkliğ

Recycled polypropylene (PP) typically exhibits insufficient mechanical strength, limiting its broader application as a polymer matrix. The effects of nanofillers—cellulose nanofibers (CNF) and halloysite nanotubes (HNTs)—and basalt fibers (BF) reinforcement on the properties of recycled PP were investigated. The morphological, mechanical, rheological, and thermal properties of the materials were characterized using scanning electron microscopy (SEM), mechanical testing, rotational rheometry, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEM analysis revealed that the incorporation of CNF led to agglomeration due to its poor compatibility with the PP matrix, which is consistent with the slight reduction in mechanical properties. In contrast, SEM images of the HNTs‐ and BF‐reinforced composites showed a nearly homogeneous dispersion within the PP matrix. The incorporation of 5 wt.% HNTs into the PP matrix had no effect on the mechanical properties. For the PP/20B5C and PP/20B5H hybrid composites and the PP/25B fiber‐reinforced composite, tensile strength increased by 50%, 62%, and 60%, while the tensile modulus increased by 148%, 150%, and 145%, respectively. The shear storage modulus at 100 rad/s for PP/20B5C, PP/20B5H, and PP/25B increased 2.3, 5.1, and 2.2 times, respectively, relative to neat PP. The crystallization temperature increased by up to 6°C, particularly for hybrid composite, compared to neat PP. The results demonstrate that sustainable nano‐ and fiber‐scale fillers can effectively enhance the performance of recycled PP, highlighting their potential to expand the reuse of recycled PP in semi‐structural applications.

This research examines the Mode I and Mode II fracture behavior of basalt/Kevlar fiber reinforced epoxy hybrid composites augmented with graphene nanoplatelets (GnP). Hybrid composites containing varying concentrations of GnP (0, 1, 2 and 3 wt%) were produced using vacuum‐assisted resin transfer molding. Mode I and Mode II fracture toughness was assessed using double cantilever beam and end‐notched flexure tests, performed in accordance with ASTM D5528 and ASTM D7905 standards, respectively. The addition of GnP markedly enhanced interlaminar fracture resistance, with the most pronounced improvements observed at GnP loadings of 1, 2 wt%. Specifically, Mode I fracture toughness increased by 51%, likely due to mechanisms such as crack deflection and bridging, whereas Mode II toughness increased by 6.2%, possibly due to improved fiber‐matrix interfacial bonding and redistribution of shear stresses. Scanning electron microscopy (SEM) analysis of the fracture surfaces revealed several toughening mechanisms, including GnP pull‐out, matrix plastic deformation and inhibition of fiber with matrix debonding. These results highlight the synergistic effects of GnP in basalt/Kevlar hybrid composites and suggest it is a viable strategy for engineering high‐performance materials with superior delamination resistance under opening and sharing loading modes. This research offers significant insights into the influence of nanofillers on the fracture behavior of hybrid composites and contributes to the development of advanced materials for engineering applications.

Hybrid composites are among the most complex systems, and simulating them presents a significant challenge. In this work, the mechanical performance of hybrid polymer composites has been comprehensively investigated using ANSYS Workbench. A range of hybrid systems, comprised of glass and jute fiber laminated configurations, were exposed to tensile loading. Furthermore, the maximum principal stress and strain patterns were utilized to study stress and strain distributions, which revealed two different failure modes: diffused ductile deformation around the nicking area and brittle failure across the grip zones. Examination of fracture propagation of samples undergoing dynamic loading revealed behavior of mixed-mode failure, accompanied by necking (which indicates ductile behavior) in some hybrid configurations on one hand, and shear and axial tension on the other hand. Stress-strain plots revealed a significant effect of hybrid configurations on strength, ductility, and stiffness. In addition, FEA predictions agreed well with previously published experimental work, with slight deviation attributed to modeling simplifications and interfacial effects. The validated models demonstrate operability for assessing hybrid composites’ conduction and predicting and controlling structural design with customized strength-to-toughness balances.

This study evaluated the buckling and tensile properties of hybrid carbon/steel mesh-reinforced epoxy composites prepared using the hand lay-up technique. It involved the fabrication of plain steel and carbon fiber laminates, as well as three symmetric hybrid laminates formed by substituting two, four, and six layers of carbon fiber with steel mesh. Test specimens were sliced from laminates according to ASTM specifications using a CNC machine to assess the effects of hybridizing steel mesh with carbon fibers on tensile properties, axial buckling, and lateral buckling. The study revealed that increasing the number of steel layers in the hybrid laminates enhances tensile strain, while showing comparable axial buckling performance compared to plain carbon laminate. In the C–S ₆ hybrid laminate (six layers of steel mesh and six layers of carbon fiber), the increments were 59.03 %, 2.17 %, and 44.44 %, respectively. Conversely, tensile strength, tensile modulus, critical lateral buckling resistance, and lateral buckling displacement decreased by 32.54 %, 33.46 %, 66.95 %, and 61.20 % at C–S ₆ hybrid laminate. These findings highlight the importance of selecting an appropriate ratio of carbon to steel mesh for composite laminates designed for various applications.

This study investigates the mechanical and impact properties of a novel class of eco‐friendly sandwich composites, combining basalt and aramid fibers with an end‐grain balsa wood core, using an epoxy polymer (MGS LR160/LH260S) as the epoxy matrix. The research focuses specifically on the critical role of fiber stacking sequence within the composite skins. Four configurations were fabricated and tested according to relevant ASTM standards. The results demonstrate that mechanical performance is highly dependent on layup stacking sequence. The Basalt/Balsa configuration achieved superior flexural properties (75 MPa strength, 80 GPa modulus), while the Aramid/Balsa configuration exhibited optimal impact resistance, absorbing 96% of the impact energy (24 J) through progressive failure mechanisms. The hybrid AB‐Balsa design showed enhanced tensile performance, achieving a strength of 17.5 MPa, which was 13% and 23% higher than the monolithic Basalt/Balsa and Aramid/Balsa configurations, respectively, underscoring the benefit of placing ductile aramid fibers in the outer layers. Conversely, the BA‐Balsa hybrid suffered from premature failure due to interfacial delamination. The balsa core universally improved damage tolerance. These findings provide critical design guidelines for lightweight structural applications requiring a blend of strength and impact resistance, such as electric vehicle battery shields, marine hulls, and protective paneling.

This study aims to investigate the effect of graphene nanoplatelets (GNP) inclusion on the mechanical properties of hybrid composites reinforced with carbon aramid fibers. Mechanical tests, including tensile and three‐point bending tests, were conducted to investigate the effect of graphene nanoparticles on the composite's mechanical behavior. Composite plates were fabricated using the vacuum‐assisted hand lay‐up method, incorporating graphene nanoplatelet particles at varying proportions (0.1, 0.25, and 0.5 wt.%) alongside a pure composite sample. The results demonstrated that 0.1 wt.% GNPs (CA01) increased tensile strength by 5.5% (571.53 MPa), while higher GNP content reduced strength due to agglomeration. Conversely, flexural strength and modulus improved significantly (27.2% and 61.6%, respectively) at 0.5 wt.% GNPs (CA05), albeit with increased brittleness. However, an increase in GNP content was accompanied by an enhancement in material stiffness and brittleness. Scanning electron microscopy (SEM) analysis revealed that the fiber‐matrix interface was strengthened, and load transfer was improved in the 0.25% and 0.5% GNP doped samples. Consequently, it was determined that the most effective nano‐graphene ratios for enhancing flexural strength and interfacial bonding were between 0.25% and 0.5%, though agglomeration risks were noted at higher loadings.

The effects of hydrothermal aging in distilled water (DW) and seawater (SW) environments on the water absorption behavior and crush characteristics of hybrid glass/carbon fiber-reinforced composite pipes with ±55° and ±70° winding angles were evaluated. Specimens were kept for 120 days at 30°C, and water absorption was analyzed experimentally and theoretically. Results revealed that distilled water-aged samples exhibited higher maximum water absorption rates (2.5% for DW55 and 2.62% for DW70) compared to seawater-aged samples (2.37% for SW55 and 2.44% for SW70), attributed to the inhibitory role of ionic components in seawater. Lower winding angles consistently showed greater water absorption due to increased microstructural voids, facilitating water diffusion. Quasi-static axial compression tests demonstrated significant degradation in crush performance after aging. Unconditioned samples with 70° winding angles achieved the highest initial peak load (56.9 kN) and specific energy absorption (28.89 J/g). However, aging reduced these values, with seawater-aged samples (SW55) showing a 12.32% decrease in specific energy absorption compared to unconditioned counterparts. Crushing force efficiency (CFE) also declined, correlating with matrix plasticization and fiber/matrix interface weakening. Notably, hybrid pipes with 55° winding angles exhibited superior energy absorption (30.44 J/g for U55), emphasizing the role of fiber orientation in load distribution.

Bu çalışmada doğal kenevir elyaf kumaş ile üretilen nano silika katkılı polimer kompozitlerin su ile yaşlandırılmasının Charpy darbe davranışına etkileri araştırılmıştır. Nano parçacık katkısının hidrofilik davranışa etkilerini gözlemlemek amacıyla nano silika parçacıkları ağırlıkça %0.5, %1.5 ve %3 oranlarında reçineye eklenerek kompozit üretimleri gerçekleştirilmiştir. Üretilen kompozitlerden ISO 179/92 standardına göre 55 x 10 mm ölçüsünde numuneler kesilmiş ve 800 saat 30℃’de çeşme suyunda yaşlandırma işlemi gerçekleştirilmiştir. Yaşlandırılan numuneler 15 J sarkaç enerjili Köger 3/70 darbe test cihazı ile test edilmiştir. Ölçülen sonuçlar hem emilen enerji hem de tokluğu gösterecek şekilde tablo haline getirilmiştir. Testler sonucunda nano katkısının tokluğu ve emilen enerjiyi düşürdüğü görülmüştür. %1.5 nano silikanın tokluğu %33.73 emilen enerjiyi ise %22,54 azalttığı gözlenmiştir. Yaşlandırma sonrasında ise darbe enerjisinde en fazla düşüş %1.5 nano oranında %33.4 olarak ölçülürken toklukta %3 nano oranında %32 olarak ölçülmüştür.

In the present study, the effects of hybridization of Basalt and Kevlar fibers in conjunction with the incorporation of Graphene nanoplatelets (GnPs) on the performance under low-velocity impact were experimentally examined. Two different hybrid structural configurations, reinforced with Basalt and Kevlar composites, were fabricated utilizing a hand lay-up technique followed by vacuum bag molding, with variations that included and excluded GnPs. The synergistic effects of hybridization coupled with the modification by GnPs on the impact characteristics of the Basalt/Kevlar hybrid composites were analyzed under an impact energy of 30 J while varying the GnPs loading. The optimal enhancement observed in the peak load and absorbed energy of the specimens was recorded as a 9.4 % and 45.7 % improvement, respectively, when Kevlar fibers were positioned in the outer layers; conversely, the specimens demonstrated enhancements of 13.35 % and 20.36 % in peak load and absorbed energy with the incorporation of 1 wt% and 3 wt% GnPs when Basalt fibers were situated in the outer layers. The increase of the impact properties of the hybrid structures was ascribed to the robust interfacial interactions established among the fibers, epoxy, and GnPs nanoparticles, which facilitated a notable enhancement in performance and optimal stress transfer from the fibers and nanoparticles to the matrix.