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Hypothesis: Characterizing the microstructure of an ice/surface interface and its effect on the icephobic behavior of surfaces remains a significant challenge. Introducing X-ray Computed Tomography (XCT) can provide unprecedented insights into the internal (porosity) and interfacial structures, i.e. wetting regime, between (super)hydrophobic surfaces and ice by visualizing these optically inaccessible regions. Experiments: Frozen droplets with controlled volume were deposited on top of metallic and polymeric substrates with different levels of wettability. Different modes of XCT (3D and 4D) were utilized to obtain information on the internal and interfacial structure of the ice/surface system. The results were supplemented by conventional surface analysis techniques, including optical profilometry and contact angle measurements. Findings: Using XCT on ice/surface systems, the 3D and 4D (imaging with temporal resolution) structural information can be visualized. From these datasets, qualitative and quantitative results were obtained, not only for characterizing the interface but also for analyzing the entire droplet/surface system, e.g., measurement of porosity size, shape, and location. These results highlight the potential of XCT in the characterization of both droplets and substrates and proves that the technique can aid to develop hydrophobic surfaces for use as icephobic materials.

Identification and analysis of interfacial failure mechanisms are key for any carbon fiber reinforced polymer (CFRP) as propagation of microcracks at the fiber/matrix interface is a common failure mechanism for these composites. In order to unveil these failure mechanisms, mechanical testing and modeling of interfacial interactions must be conducted in a safe, accurate and consistent manner. In this work, a low-cost, graphene-based surface treatment process was developed and analyzed to deposit graphene nanoparticles (GNPs) onto the surface of carbon fibers increasing surface roughness and interfacial properties. The compatibility between this high surface area GNP coating and the commercial sizings typically used in the carbon fiber industry is discussed and evaluated through mechanical testing, finite element analysis (FEA) modeling and surface characterization. The execution of this work is divided into three phases. The first phase is surface characterization of GNP self-assembly on the carbon fiber surface. Graphene agglomeration is widely accepted to result in depreciation of its benefits in practical applications, and shear mixing, ultrasonication and hydrogen passivation were utilized in this work to produce few-layer GNPs. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize GNPs deposited on the fiber surface. The second phase of this thesis pertains to single filament pullout testing used to quantify interfacial properties of single carbon filaments embedded in a fiberglass resin system with and without GNP surface treatment and polymeric commercial sizing. After completion of experimental testing, a linear, contact based cohesive zone model (CZM) with applicable traction separation law was developed using the Ansys FEA program to further understand interfacial failure mechanics in this test. The third phase applies composite four-point bend testing to study the performance of interfacial properties of composite beams made with 50,000 filament carbon fiber tows and the same fiberglass resin system used in single filament testing. Composite testing specimens were manufactured using a wet lay-up process, and load transfer efficiency was quantified using the modified rule of mixtures equation. Our results demonstrate that the GNP coating was successful in enhancing interfacial properties in single filaments and 50,000 filament carbon fiber tows embedded in a fiberglasss resin system. Furthermore, it was determined that the GNP coating increased interfacial properties in carbon fibers with and without a commercial sizing applied to the fiber surface, illustrating the compatibility between this GNP coating and other polymeric sizings typically used in the carbon fiber industry and opening the door for the next generation of high surface area nanoparticle surface treatment techniques in CFRPs.

Laser structuring is by far the most investigated metal surface-pretreatment method for creating adhesion in polymer–metal hybrids. Especially, cone-like protrusions show excellent wetting behaviour as well as high compound strength. However, the processing time is extremely high. Therefore, this paper assesses a process strategy for creating pin structures with scalable height by single pulse drilling with an Nd/YVO4 nanosecond laser system on EN AW-6082 aluminium alloy. The strength testing is carried out by butt-bonded hollow cylinder torsion. The samples are manufactured by heat-conduction thermal joining with polyamide 6. Ten different surface structures with two different ablation diameters are investigated and compared to cone-like protrusions in terms of processing time, wetting behaviour, shear strength and fracture behaviour. The experimental results show that pulse drilling pins structures with high aspect ratio reach-strength values close to cone-like protrusions but with 31 times higher processing rate.

Hybrid joints of metal- and fiber-reinforced-polymer offer great potential for lightweight applications. Thereby, a fast and reliable joining process is mandatory for mass-production applications. To this end, this study assesses inductive spot-joining in combination with prior thermal spray coating of the metal adherent. A nickel–aluminum 95/5 coating was applied to achieve high adhesion through mechanical interlocking and to act as susceptor for the inductive joining process. The joint strength was assessed with lap shear specimens consisting of EN AW-6082 aluminum alloy and glass fiber reinforced polyamide 6 or polypropylene, respectively. The joints were further investigated in terms of heating time and hygrothermal cyclic loading. The results showed that significant time savings for the joining process as well as strong adhesion were achieved due to the coating. Moreover, the high strengths were even preserved under hygrothermal cyclic loading.

Many animals exhibit strong mechanical interlocking in order to achieve efficient climbing against rough surfaces by using their claws in the pads. To maximally use the mechanical interlocking, an innovative robot which utilizes flexible pad with claws is designed. The mechanism for attachments of the claws against rough surfaces is further revealed according to the theoretical analysis. Moreover, the effects of the key parameters on the performances of the climbing robots are obtained. It indicates that decreasing the size of the tip of the claws while maintaining its stiffness unchanged can effectively improve the attachment ability. Furthermore, the structure of robot body and two foot trajectories are proposed and the new robot is presented. Using experimental tests, it demonstrates that this robot has high stability and adaptability while climbing on vertical rough surfaces up to a speed of 4.6 cm·s−1.

Due to a combination of different classes of materials, intrinsic hybrid composites are characterised by high strength and low weight. The mechanical properties of hybrid parts are mainly determined by the interface between the different materials. Consequently, this interface has to be considered in detail within the development of an intrinsic hybrid composite. The general approach of the considered composite is the combination of a mechanical form fit with adhesive bonding. This contribution focuses on the development, production and characterisation of the interface between aluminium and a fibre reinforced polymer as well as of the hybrid composite.

Kalkan, Ilker/0000-0002-5987-631X WOS:000567543000005 The present study pertains to the linear multiple regression analyses on a database of 185 hinged-beam experiments on FRP bars. The database was compiled from 51 tests conducted within the scope of the present study and 134 tests conducted by previous researchers. Bond strength and development length equations, taking different types of FRP bars and surface finishes into account, were developed and the estimates from the proposed equations were compared to the estimates from the respective equations of various international FRP-reinforced concrete codes. The proposed equations, addressing all kinds of FRP bars and surface finishes, were shown to be in much closer agreement with the experimental results compared to all previous equations according to different statistical evaluation criteria, i.e. the Coefficient of Determination, Root Mean Square Error and Mean Absolute Percentage Error. The code equations were established to yield to exteremely over-conservative and non-economical results in all types of FRP bars with different surface textures. Scientific Research Unit of Kirikkale UniversityKirikkale University [2018/014] The present paper is a summary of a portion of the Ph.D. dissertation conducted by Dr. Bogachan Basaran under the supervision of Assoc. Prof. Dr. Ilker Kalkan at the Department of Civil Engineering, Kirikkale University. The tests within the scope of the study were conducted at the Structural Mechanics Laboratory of the Vocational School of Technical Sciences of Amasya University. The financial support provided by the Scientific Research Unit of Kirikkale University through the project number 2018/014 is gratefully acknowledged. The authors also express gratitude to Prof. Dr. Sabahattin Aykac at the Department of Civil Engineering, Gazi University for his valuable comments and contribution throughout the course of study.

Stainless steel wires are the standard method for sternal closure because of their strength and rigidity, the simplicity of the process, and the short healing time that results from their application. Despite this, problems still exist with sternal stability due to micromotion between the two halves of the dissected and wired sternum. Recently, a novel glass-based adhesive was developed which, in cadaveric trials and in conjunction with wiring, was shown to restrict this micromotion. However, in order to avoid complications during resternotomy, the adhesive should adhere only to the bone and not the sternal wire. In this study, sternal wires were embedded in 8 mm discs manufactured from the novel glass-based adhesive and the constructs were then incubated at 37 °C for one, seven, and 30 days. The discs were manufactured in two different thicknesses: 2 and 3 mm. Wire pull-out tests were then performed on the constructs at three different strain rates (1, 0.1, and 0.01 mm/min). No statistically significant difference in pull-out force was found regardless of incubation time, loading rate, or construct thickness. The pull-out forces recorded were consistent with static friction between the wire and adhesive, rather than the adhesion between them. Scanning electron micrographs provided further proof of this. These results indicate that the novel adhesive may be suitable for sternal fixation without complicating a potential resternotomy.

We were successful in growing a dense Cu film on Al2O3 substrates at room temperature using an aerosol deposition (AD) method. The characteristics of Cu films were investigated through electrical resistivity and X-ray photoelectron spectroscopy (XPS). The resistivity of Cu films was low (9.2-12.5 μΩ cm), but it was five to seven times higher than that of bulk copper. The deterioration of the resistivity indicates that a Cu2O phase with CuO occurs due to a particle-to-particle collision. Moreover, the growth of Cu films was investigated by observing their microstructures. At the initial stage in the AD process, the impacted particles were flattened and deformed on a rough Al2O3 substrate. The continuous collision of impacted particles leads to the densification of deposited coating layers due to the plastic deformation of particles. The bonding between the Cu particles and the rough Al2O3 substrate was explained in terms of the adhesive properties on the surface roughness of Al2O3 substrates. It was revealed that the roughness of substrates was considerably associated with the mechanical interlocking between Cu particles and rough Al2O3 substrate.

Coatings of AISI H13 tool steel were made on low carbon steel by friction surfacing. Detailed microstructural studies and microhardness tests were carried out on the coatings. Studies revealed defect-free coatings and sound metallurgical bonding between the coating and the substrate. In addition, mechanical interlocking on a very fine scale was observed to occur between the coating and the substrate. Coatings exhibited martensitic microstructure with fine grain size and with no carbide particles. Coatings in as-deposited condition showed very high hardness (58 HRC) compared to the mechtrode material in annealed condition (20 HRC). Based on these findings, microstructural evolution during friction surfacing of H13 tool steel is discussed. The current work shows that friction surfaced tool steel coatings are suitable for use in as-deposited condition. Further improvements in coating microstructure and properties are possible with appropriate post-surfacing heat treatment. � 2010 Elsevier Ltd.

In this study, various structuring methods for creating adhesion by mechanical interlocking in the interface of metal/FRP (fiber-reinforced polymer) joints are investigated. A novel processing route using thermal spray coatings as additive structure is presented. Different coating systems are first assessed by axial loading tests with spray-coated plungers for the evaluation of the additive layer adhesion on the metallic base material. Additional microstructures, produced by different abrasive processes (corundum blasting, laser structuring, and fine milling) are compared with the additive structures. All surface structures are characterized by electron microscopy for two sheet materials: DC06 and AA6016-T4. The abrasive structures show a significant material dependence, while the selected coating system offers the adjustment to different base materials by an independent surface layer. The structured metal sheets were further joined to glass-fiber-reinforced polyamide 6 (PA6) by hot pressing to evaluate the interface properties in tensile shear tests. The results confirm a suitability of thermal spray coatings for providing a high bonding strength in metal/FRP joints for both investigated metallic substrate materials.