Browsing by Subject "Tensile strength"

Now showing 1 - 4 of 4

Open Access
Effects of thermoplastic coating on interfacial interactions in advanced engineering composites for aerospace applications
(2023-05-03) Yavuz, Zelal; Khaligh, Aisan; Öz, Y.; Tuncel, Dönüş
Delamination due to an inferior adhesion between reinforcement material and matrix in carbon fiber-reinforced thermoplastic (CFRTP) composites is a crucial problem to be solved. To this end, this study aims to overcome poor wettability between reinforcing phase, i.e., carbon fiber (CF), and thermoplastic matrix, i.e., polyetherether ketone (PEEK). Herein, CF’s surface was tailored by application of different polymeric sizing agents which have different chemical structures. Morphology and topology analyses were performed by Scanning Electron Microscope and 3D laser scanning, respectively. Later, a variety of wettability results were obtained by the sessile drop method used in Contact Angle (CA) measurements for CFs throughout application of each sizing agent applied by dip coating. Sizing materials were designed such that the chemical structure of CF’s surface could exhibit compatibility with the matrix itself. Consequently, complete wettability (CA: 0°) was achieved for CFs sized by HPEEK (CF/hydroxylated PEEK (HPEEK)) and the surface free energy (SFE) of CF was enhanced from 5.43 to 72.8 mJ/m2 while the SFE of the PEEK matrix is 40.1 mJ/m2. Moreover, sizing by HPEEK improved the average surface roughness of CF by 32% which enables optimized adhesion. Afterward, repetitive tensile tests were carried out to observe effects of improved interfacial interlocking on the mechanical properties of the final CFRTP composite. Stress–strain curves revealed that the tensile strength of CFRTP improved from 473 to 508 MPa through the sizing of CF by HPEEK whereas pristine PEEK has a much smaller tensile strength (98 MPa) than the aforementioned CF-reinforced composites.
Open Access
Fabrication of cellulose acetate/polybenzoxazine cross-linked electrospun nanofibrous membrane for water treatment
(Elsevier, 2017-12) Ertaş, Yelda; Uyar, Tamer
Herein, polybenzoxazine based cross-linked cellulose acetate nanofibrous membrane exhibiting enhanced thermal/mechanical properties and improved adsorption efficiency was successfully produced via electrospinning and thermal curing. Initially, suitable solution composition was determined by varying the amount of the benzoxazine (BA-a) resin, cellulose acetate (CA) and citric acid (CTR) to obtain uniform nanofibrous membrane via electrospinning. Subsequently, thermal curing was performed by step-wise at 150, 175, 200 and 225 °C to obtain cross-linked composite nanofibrous membranes. SEM images and solubility experiments demonstrated that most favorable result was obtained from the 10% (w/v) CA, 5% (w/v) BA-a and 1% (w/v) CTR composition and cross-linked nanofibrous membrane (CA10/PolyBA-a5/CTR1) was obtained after the thermal curing. Chemical structural changes (ring opening) occurred by thermal curing revealed successful cross-linking of BA-a in the composite nanofibrous membrane. Thermal, mechanical and adsorption performance of pristine CA and CA10/PolyBA-a5/CTR1 nanofibrous membranes were studied. Char yield of the pristine CA nanofibrous membrane has increased notably from 12 to 24.7% for composite CA10/PolyBA-a5/CTR1 membrane. When compared to pristine CA membrane, CA10/PolyBA-a5/CTR1 nanofibrous membrane has shown superior mechanical properties having tensile strength and Young's modulus of 8.64 ± 0.63 MPa and 213.87 ± 30.79 MPa, respectively. Finally, adsorption performance of pristine CA and CA10/PolyBA-a5/CTR1 nanofibrous membranes was examined by a model polycyclic aromatic hydrocarbon (PAH) compound (i.e. phenanthrene) in aqueous solution, in which CA10/PolyBA-a5/CTR1 nanofibrous membrane has shown better removal efficiency (98.5%) and adsorption capacity (592 μg/g).
Open Access
Fracture of femoral neck: Analysis of new implant models with a slit and without a slit by the finite element method
(WHO Office in Azerbaijan, 2017) Jafarov, A. A.; Ozer, Z.; Alizadeh, Ch. A.; Mammadov, A. M.
During fractures of the neck of the femur (PBHB) for the completion of postoperative fusion, there is a need for stable fixation - interfragmental immobility. The stability of used implants in a living person is difficult to calculate. For this purpose, the analysis is carried out using the finite element method (the final analysis of the limited elements). The aim of this study is to study the features of the proposed new hip implant with finite element analysis. Based on the digital geometry of the anatomy of the femur, a 3D model of the femur was developed. Stress and strain, obtained with the help of the computer program ANSYS as a result of loads on the head of the thigh, were investigated by the finite element analysis method. Based on the Pawel classification, 3 groups of femoral neck fracture models were created, corresponding to the fracture angles closer to 30, 50 and 70 degrees (type 1, type 2 and type 3). In each group, the corresponding implants are analyzed in 2 types: without a slit and with a slit. For the spongiform bone, the UTS (Ultimate Tensile Stres) is defined as 20 MPA, and for the cortical bone, 150 MPA. In all analyzes, the force loaded in the vertical direction onto the head of the computer model of the femur was calculated to be 4000 N. Given that the slits on the surface of the implant can cross waves, homogeneously distribute the force and pressure throughout the entire implant, on the basis of this, a decrease in pressure on the surface of the bone tissue was observed. It is believed that this process can increase the stability of the implant and minimize the level of damage to the bone tissue.
Open Access
Polyhedral oligomeric silsesquioxane-based hybrid networks obtained via thiol-epoxy click chemistry
(Springer, 2017) Bekin Acar, S.; Ozcelik, M.; Uyar, Tamer; Tasdelen, M. A.
A series of hybrid networks based on polyhedral oligomeric silsesquioxane (POSS) were prepared by thiol-epoxy click reaction using commercially available octakis-glycidyl-POSS (G-POSS), trimethylolpropane triglycidyl ether, and trimethylolpropane tris(3-mercaptopropionate) as monomers. The click reaction was simply catalyzed by lithium hydroxide which proceeded readily at ambient conditions in very good yields. The incorporation of G-POSS into the network was clearly determined by transmission electron microscopy, FTIR, and 1H-NMR spectroscopy techniques performed with a model study using 1-butane thiol and G-POSS molecules. The homogeneous distribution of G-POSS up to 5 wt% in the hybrid network was apparently confirmed by morphological investigations. By increasing G-POSS content higher than 5 wt%, the heterogeneous dispersion of G-POSS was determined from the tensile strength measurements. The significant decrease in tensile strength was possible due to the agglomeration of G-POSS. On the other hand, thermal properties of hybrid networks were compared together by thermogravimetric analyses, where all samples exhibited one-step degradation in the range of 220–500 °C. The thermal decomposition of hybrid network led to complete degradation of the organic part and favored the formation of stable carbonaceous and inorganic residues as char. Thus, the char yields of hybrid networks were increased to 6.2, 7.8, 10.1, 12.7, and 15.1% by G-POSS loadings from 0 to 15 wt%. This improvement was also a proof of the incorporation of G-POSS into the hybrid networks that resulted in high heat-resistant POSS-based hybrid networks compared to a sample without G-POSS.