Determination of the interfacial properties of carbon fiber reinforced polymers using nanoindentation

The mechanical properties of the interphase play a key role in determining the overall performance of carbon fiber reinforced polymer (CFRP) composite materials. For this reason, it is important to develop a method to easily and precisely investigate the mechanical performance of the interphase of CFRP materials. In this work, the surface topography of the CFRP material was examined using scanning probe microscopy (SPM), which revealed the polished flat sample can meet the requirements of the nanoindentation testing. The local mechanical performance of the interphase of the CFRP was determined using nanoindentation based on the continuous stiffness measurement (CSM) method. The results show that the size of the interphase between the carbon fiber and the matrix is about 1.5 μm, and the corresponding modulus and hardness values were estimated to be 5–11 and 0.4–3.3 GPa, respectively, considering the fiber-bias effects. Mapping of the local mechanical properties of a selected area revealed that nanoindentation reproduced excellently the surface topography and characterized precisely the properties of the interphase between the carbon fibers and the matrix.

Mechanical Behavior of Spin-Coated Sb2S3 light Absorption Thin Films

To measure the mechanical properties of Sb2S3, a two-component compound semiconductor used in the light absorption layer of a solar cell, Sb2S3 thin films were formed on FTO glass using the spin coating method. The spin-coated Sb2S3 thin films were heat-treated at 200 ^oC in an Ar atmosphere for up to 1 hour to form a thin film with continuous crystalline structures. A nanoindentation system was used to measure the mechanical properties of the spin-coated Sb2S3 thin films, and the phenomena appearing during indentation were analyzed. We used the continuous stiffness measurement (CSM) technique, and Young's modulus and hardness measured with the indentation depth of 250 nm were about 53.1 GPa and 1.43 GPa, respectively. The results were analyzed and compared with literature values, which varied from 40 GPa for the nanowire forms of Sb2S3 to 117 GPa, based upon simulation results. Since there are few studies on the mechanical properties of spin-coated Sb2S3 thin films, the results of this study are worthwhile. Besides, we observed that the Sb2S3 thin film had a little brittleness in the indentation test at higher load, and the microstructure was pushed around the indenter depending on the degree of bonding to the FTO glass substrate. This is a matter to be considered when making flexible devices in the future.

Microstructure Characteristics, Tribology and Nano-Hardness of HVOF Sprayed NiCrRe Coating

The high-velocity oxy-fuel technique (HVOF) was used to produce dense NiCrRe coating on boiler steel substrate with a minimal amount of oxide impurities and low porosity. Microstructure analysis, tribology and nano-hardness measurement have been realized with the aim to characterize the systems. The microstructure was studied using scanning electron microscopy and Energy-dispersive X-ray spectroscopy. Tribological characteristics have been studied under the dry sliding condition at applied loads of 5, 10 and 20 N using the ball-on-flat technique with SiC ball at room temperature. Nano-hardness was investigated in continuous stiffness measurement (CSM) mode, the indentation depth limit was 1500 nm. Microstructure analyses proved that the HVOF sprayed layer, with a thickness approximately 870 µm, contains a relatively low volume fraction of porosity with a chemical composition based on Nickel, Chromium, with white areas of Rhenium. The wear rate of the coating is significantly lower than the wear rate of 16Mo3 steel. The average values of indentation modulus and hardness were EIT = 237.6 GPa and HIT = 6.3 GPa, respectively.

Microstructure Characteristics, Tribology and Nano-Hardness of Plasma Sprayed NiCrRe Coating

This paper presents the results of the investigation of NiCrRe coating deposited by plasma spray process at the atmospheric pressure on boiler steel substrate. These coatings were characterized by means of a scanning electron microscopy, and Energy-dispersive X-ray spectroscopy. The wear resistance of plasma sprayed NiCrRe coatings has been investigated under dry sliding conditions at applied load of 10 N in air. The continuous stiffness measurement (CSM) method was used for the investigation of nanohardness using Agilent G200 Nano-indenter in order to determine the mechanical properties of the coatings. Microstructural observations pointed out that the NiCr layer with white isles of rhenium possessed porosity, oxidized, un-melted and semi-melted particles, and inclusions. According to the results the thickness of the layer is 450 µm, the indentation modulus 158 ± 24.4 GPa, hardness 3.74 ± 0.76 GPa and the coefficient of friction is 0.45.

Nanomechanical Characterization for Cold Spray: From Feedstock to Consolidated Material Properties

Cold gas-dynamic spray is a solid-state materials consolidation technology that has experienced successful adoption within the coatings, remanufacturing and repair sectors of the advanced manufacturing community. As of late, cold spray has also emerged as a high deposition rate metal additive manufacturing method for structural and nonstructural applications. As cold spray enjoys wider recognition and adoption, the demand for versatile, high-throughput and significant methods of particulate feedstock as well consolidated materials characterization has also become more notable. In order to address the interest for such an instrument, nanoindentation is presented herein as a viable means of achieving the desired mechanical characterization abilities. In this work, conventionally static nanoindentation testing using both Berkovich and spherical indenter tips, as well as nanoindentation using the continuous stiffness measurement mode of testing, will be applied to a range of powder-based feedstocks and cold sprayed materials.

Nanoindentation Properties of 18CrNiMo7-6 Steel after Carburizing and Quenching Determined by Continuous Stiffness Measurement Method

In this work, the nanomechanical properties involving the indentation size effect (ISE) and yield strength of a surface-modified layer of 18CrNiMo7-6 steel after case hardening were investigated via nanoindentation experiments. The experimental results showed that the hardness increased with an increase in strain rate; the contact stiffness versus indentation depth curves take the form of upper convexity due to residual compressive stress relaxation. On the basis of the Ruiz-Moreno model, a modified model considering the cutoff parameter as a function of indentation depth was proposed. This model was able to better describe the ISE of the surface-modified layer. With the Hough transform error angle of 0.1° as the critical value (h0.1° is the corresponding depth), when h > h0.1°, the yield strength calculated by the Ma model started to disperse at the depth of h0.1°. These results provide useful insight into the local mechanical properties of 18CrNiMo7-6 steel after carburizing and quenching treatment.