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Determining orthotropic elastic properties like Young’s modulus E1 and E2 for composites is done efficiently and accurately with the Resonalyser equipment. At IMCE in Genk, we provide measurement systems as well as a service that measures the orthotropic elastic properties and internal friction of orthotropic materials like carbon fiber reinforced composites. With the impulse excitation technique as a basic measurement procedure, we use and provide the Resonalyser to analyse and measure the engineering constants: Young’s moduli E1 and E2, Poisson’s ratio ν12 and the in-plane shear modulus G12 for composites and various other types of orthotropic materials.

Publications

Wetting/drying cyclic effects on mechanical and physicochemical properties of quasi-isotopic flax/epoxy composites.
Authors:

Sodoke, F. K., Toubal, L., & Laperrière, L. (2019). Polymer Degradation and Stability.

Abstract:

The aim of this work is to investigate the effects of wet/dry aging cycles on flax/epoxy composite properties for long-term structural applications. The mechanical performance of flax/epoxy exposed to wet/dry cycles during 104 days was evaluated. The physicochemical changes induced by wet/dry cycles were also studied. Unaged and cyclic aged samples were characterized by tensile test, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The tensile test results showed good aging performance of this composite. FTIR chemical investigation revealed the disappearance of the characteristic peaks of the cyanoethylation treatment at the fiber/matrix interface during cyclic aging. TGA data showed an improvement in thermal properties of the composite after the hydrolysis of cyanoethyl group, as well as the increase of the crystallinity index, as measured from XRD during cyclic wet/dry aging. This explains the limitation of mechanical degradation of this composite despite the severe wetting-drying cycles aging conditions. The results also show the positive effects of the cyanoethylation fiber treatment on the long-term durability of flax/epoxy composite.

Effect of the exposition temperature on the behaviour of partially pyrolysed hybrid basalt fibre composites.
Authors:

Chlup, Z., Černý, M., Strachota, A., Hadraba, H., Kácha, P., & Halasová, M. (2018). Composites Part B: Engineering 147, 122-127.

Abstract:

Composites utilising long fibres as reinforcement are the most effective from the point of view of the toughening effect. A brittle matrix reinforced by brittle fibres was investigated in this work. Polysiloxane resin was used as matrix precursor in the studied composite, while continuous basalt fibres served as reinforcement. An optimised pyrolysis process conducted at 650 °C under nitrogen atmosphere turned the polymeric precursor into the so-called hybrid matrix consisting of nano-domains of pyrolytic SiOC glass and of non-transformed polysiloxane polymer. The pyrolysis temperature of 650 °C was found to be optimal, resulting in the fracture toughness attacking the level of 20 MPa m1/2 and the strength reaching the value of 1 GPa. The main aim of this paper is to investigate microstructural changes occurring during long-term (1000 h = 41.7 days) exposition to an oxidative air atmosphere at temperatures from 250 °C to 600 °C and to describe the effect on the mechanical properties of the studied hybrid-matrix composite. The increasing exposition temperature leads to a significant embrittlement of the composite, while the elastic properties (modulus) remain unchanged. Chemical or microstructural changes in the basalt fibres were not detected after the long-term exposition to the tested high temperatures. Nevertheless, fibre embrittlement can be estimated from the tests. Both matrix and fibre-matrix interface were found to suffer from the applied exposition. Distinct changes in chemical composition as well as in microstructure were observed for the matrix. Hence, the observed embrittlement of the composite can be ascribed partly to the changes in the hybrid matrix and the fibre-matrix interface, and partially to fibre embrittlement.

Low-temperature consolidation of high-strength TiB2 ceramic composites via grain-boundary engineering using Ni-W alloy.
Authors:

Chlup, Z., Bača, Ľ., Hadraba, H., Kuběna, I., Roupcová, P., & Kováčová, Z. (2018). Materials Science and Engineering: A 738, 194-202.

Abstract:

The concept of the consolidation of titanium diboride at relatively low temperature via formation of the solid solution was used in this research. A specially designed Ni-W alloy prepared by mechanical alloying method was used as the solid solution formation additive. The low amount of Ni-W alloy and TiB2 powder were mixed together and consequently consolidated in the temperature interval from 1300 °C to 1400 °C. The development of the microstructure and resulting mechanical behaviour of these composites were analysed in detail. The grain size of TiB2 below 3 micrometres was obtained for all processing temperatures. The highest processing temperature of 1400 °C resulted in the flexural strength on the level of 875 MPa and the elastic modulus being nearly 500 GPa. The fracture toughness was about 5 MPa m0.5. Formation of the solid solution was confirmed by XRD and TEM analysis. Due to the targeted change in chemical composition on grain boundaries and TiB2 lattice distortions by addition of transition metals with higher ionic radii a hypothesis about the preferential formation of solid solution layer on the surface of TiB2 grains taking into account their orientation was formulated.

Effect of oxidation and residual stress on mechanical properties of SiC seal coated C/SiC composite.
Authors:
Patel, M., Kiran, M. P. S., Kumari, S., Singh, V., Singh, S., & Prasad, V. B. (2018). Ceramics International 44(2), 1633-1640
Abstract:
The effect of oxidation and thermal residual stress on mechanical properties of SiC seal coated C/SiC composite at ambient temperature and high temperature were studied. The oxidation of SiC seal coated C/SiC composite at 1300 and 1500 °C resulted in carbon fibres burn area near through thickness micro cracks in the SiC seal coating. With the increase in exposure time, the formation of SiO2 layer in SiC matrix near carbon fibres burns area was found. Residual mechanical properties of SiC seal coated C/SiC composite after exposure in air show significant degradation. First time, a continuous measurement of Young’s modulus with temperature of C/SiC composite was carried out using an impulse excitation technique. The effect of relaxation of thermal residual stress on mechanical properties was observed with the help of continuous measurement of Young’s modulus as a function of temperature in an inert atmosphere.
Microstructures and Mechanical Properties of Al3Ti/Al Composites Produced In Situ by High Shearing Technology.
Authors:
Zeng, Y., Himmler, D., Randelzhofer, P., & Körner, C. (2018). Advanced Engineering Materials 1800259.
Abstract:
Due to its low density, high strength, and stiffness the intermetallic phase Al3Ti is a good candidate as reinforcement for Al alloys. In this work, in situ Al3Ti particle reinforced Al composites are fabricated from Ti particles and Al melt via melt stirring with a high shearing mixer. Microstructure and mechanical properties are investigated. The results indicate that, owing to the high shearing effect and intensive macroscopic flow of the melt, reinforced particles are distributed homogeneously on the microscopic and macroscopic scale. Furthermore, Al3Ti particles are proved to be effective nuclei for heterogeneous nucleation of α‐Al, thus the grain size of the Al matrix is significantly decreased. As a result of the fine grains and the uniform distribution of Al3Ti particles, E‐modulus, yield, and tensile strength of the composites are enhanced.
An experimental investigation of the mechanical behavior and damage of thick laminated carbon/epoxy composite.
Authors:
Djabali, A., Toubal, L., Zitoune, R., & Rechak, S. (2018). Composite Structures 184, 178-190.
Abstract:
In this study, mechanical behavior and damage of thick laminated carbon/epoxy composite are investigated through static and fatigue three-point bending tests. In order to supply a maximum of information about the mechanical behavior of these materials, which have been little studied in the literature, and to provide an accurate description of the different mechanisms involved during their damage process, three non-destructive evaluation and monitoring techniques were used in this study. The acoustic emission for damage assessment, identification, and their threshold detection, the infrared thermography for fatigue damage evaluation and fatigue limit estimation and the digital image correlation for strain and displacement fields measurements.
Microstructure and mechanical properties study of slip-cast copper–alumina composites.
Authors:
Stratigaki, M., Pabst, W., Nečina, V., Hajíček, M., & Gotsis, A. D. (2019). SN Applied Sciences 1(1), 40.
Abstract:
Alumina matrix composites reinforced with metallic copper were produced and their microstructure and mechanical properties were studied. The composites were fabricated by aqueous slip casting technique, and sintered at 1500 °C in a hydrogen atmosphere. The samples showed low porosity and a core-skin structure with copper-free skin and a uniform spatial distribution of copper particles in the core. The addition of metallic Cu particles at low amounts in the Al2O3 matrix resulted in a small reduction in the stiffness and the hardness but augmented impact resistance. The mechanical properties of the composites were in good agreement with porosity-corrected predictions of the simple rule of mixtures, indicating that this fabrication method produces composites for which the enhanced toughness is not accompanied by a large reduction of their other mechanical properties.
Hygrothermal aging effects on mechanical and fatigue behaviors of a short-natural-fiber-reinforced composite.
Authors:
Mejri, M., Toubal, L., Cuillière, J. C., & François, V. (2018).International Journal of Fatigue , 108, 96-108.
Abstract:
A new natural fiber composite made of high density polyethylene (HDPE) and 40% wt of short birch fibers (SBF) was developed to replace polyamide (better known under its industrial name “Nylon”) in spur gear manufacturing. The effect of hygrothermal aging on quasi-static and fatigue bending behaviors of this new composite has been studied in this work. Once hygrothermal aging is completed, flexural quasi-static tests have been performed on aged specimens and results compared with those obtained from unaged specimens. It has been observed that hygrothermal aging has no significant effect on flexural mechanical properties of this composite. After characterization, bending fatigue tests have been conducted on aged specimens and results have been compared with those of unaged specimens. These fatigue tests show that hygrothermal aging decreases the high cycles fatigue strength (HCFS) of this composite. The cause of this fatigue durability decrease has been investigated using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and a scanning electron microscope (SEM). These tests show that the chemical composition and thermal behavior of this composite are not affected by hygrothermal aging. On the contrary, these tests show that damage mechanisms of this composite (HDPE/40% wt of SBF) are directly affected by this type of aging.
Insight into cytotoxicity of Mg nanocomposites using MTT assay technique.
Authors:
Ong, T. H. D., Yu, N., Meenashisundaram, G. K., Schaller, B., & Gupta, M. (2017).Materials Science and Engineering: C , 78, 647-652.
Abstract:
In the present study, Young’s modulus measurements and indirect cytotoxicity test were performed on Mg (0.97, 1.98, 2.5) vol% TiO2, Mg (0.58, 0.97, 1.98) vol% TiC, and Mg (0.58, 0.97, 1.98) vol% TiN, synthesized using the Disintegrated Melt Deposition technique to determine the cytotoxicity of low volume nano-particulate reinforcement on magnesium. The results of the indirect MTT assay on Day 3 and Day 5 indicate that 2.5 vol% TiO2, TiC and TiN has little effect on the cytotoxicity when added as low volume fraction reinforcement to magnesium. While (0.97, 1.98) vol% TiO2 negatively affected the cytotoxicity when added to Mg. The Young’s modulus of the materials was found to remain close to that of cortical bone which would suggest that the stress shielding effect would be reduced as the increase in Young’s modulus was mitigated by the low volume addition of reinforcements.
Modelling of carbon nanotube dispersion and strengthening mechanisms in Al matrix composites prepared by high energy ball milling-powder metallurgy method.
Authors:
Liu, Z. Y., Xiao, B. L., Wang, W. G., & Ma, Z. Y. (2017). Composites Part A: Applied Science and Manufacturing , 94, 189-198.
Abstract:
Carbon nanotube (CNT) reinforced Al-5Mg composites were prepared by combining ball milling, hot-pressing and subsequent hot extrusion. CNT distribution during milling and strengthening mechanism of the composites were investigated. A model based on the ratio of minimum necessary time for uniformly dispersing CNT to flattening time of composite powders was proposed to analyze the effect of milling rotation rate on CNT distribution, and it indicated that both low and high milling rotation rates are not beneficial to CNT distribution, due to small deformation ratio and severe cold-welding, respectively. Under a milling rotation rate of 400 rpm, CNTs could be uniformly dispersed after 8 h of milling and aligned along the extruding direction after extrusion. Elastic moduli and strengths of the composites were significantly increased. Load transfer, grain refinement, and mismatch dislocation mechanisms were determined to contribute to the strength increase of CNT/Al-5Mg composites.
Mechanical properties of hybrid composites prepared by ice-templating of alumina.
Authors:
Roleček, J., Salamon, D., & Chlup, Z. (2017).Journal of the European Ceramic Society.
Abstract:
Ceramic-polymer hybrid composites are often designed for its high strength and low density. Ice-templating (freeze casting) is a promising method for preparation of such composites. However, the most of the reported mechanical properties were gained from a small volume of material. In this work 70 cm3 of the lamellar composite with lamella length, up to 70 mm was prepared by ice-templating followed by polymer infiltration. The volume of ceramic (alumina) in starting suspensions was varied from 25 to 45 vol.% and the same manufacturing process was applied. The fracture toughness and flexural strength were determined on prepared beams from plates by loading in bending. The fractographic analysis conducted on the fracture surfaces and obtained mechanical properties demonstrated that an optimal strength/density ratio lies between 51 and 55% of alumina volume fraction. The density ranking from 2.6 to 2.8 cm−3 of these composites results in values of Weibull strength above 110 MPa.
Wear behaviour of CrB2+ 5 wt.% MoSi2 composite against cemented tungsten carbide (WC-Co) under dry reciprocative sliding condition.
Authors:
Bhatt, B., Murthy, T. C., Nagaraj, A., Singh, K., Sonber, J. K., Sairam, K., … & Kain, V. (2017). Journal of the Australian Ceramic Society, 1-15.
Abstract:
In the present work, reciprocative sliding wear behaviour of CrB2 + 5 wt.% MoSi2 composite was studied against WC-Co ball using different normal loads (5, 10 and 20 N) and frequencies (10, 15 Hz) under dry condition. Coefficient of friction (COF) and wear rate were measured at all test conditions. Wear mechanism was analysed by micro-structural characterization. It was found that COF is decreased from 0.68 to 0.32 with increasing load (5 to 20 N) and reciprocating frequency (10 to 15 Hz). The wear rate measured was minimum at 10 N load and 15 Hz frequency combination and was found to be 1.06 × 10–6 mm³/N m. The wear mechanisms identified during reciprocative sliding wear of CrB2 + 5 wt.% MoSi2 composite were abrasion, micro-fracture and surface tribo-oxidative reactions with delamination from tribo-zone. While abrasion with mild oxidative wear is the dominant wear mechanism at lower load (5 N) and frequency (10 Hz) combination, intensive tribo-oxidative wear was observed at higher loads (>10 N) and frequency (15 Hz).
Mechanical Properties of Supports and Half‐Cells for Solid Oxide Electrolysis Influenced by Alumina‐Zirconia Composites.
Authors:
Charlas, B., Ni, D. W., Frandsen, H. L., Brodersen, K., & Chen, M. (2017).Fuel Cells, 17(2), 132-143.
Abstract:
Zirconia/alumina composites were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with 0–30 mol% alumina particulates or platelets. Flexure strength and fracture toughness of both particulate and platelet composites increased with increasing alumina content. For a given alumina content, strength of particulate composites was greater than that of platelet composites; whereas, difference in fracture toughness between the two composite systems was negligible. No difference in elastic modulus and density was observed for a given alumina content between particulate and platelet composites. Thermal cycling up to 10 cycles between 200 and 1000 °C did not show any strength degradation of the 30 mol% platelet composites, indicative of negligible influence of coefficient-of-thermal-expansion mismatch between YSZ and alumina grains.
Scratch Testing of Hot-Pressed Monolithic Chromium Diboride (CrB2) and CrB2+ MoSi2 Composite.
Authors:
Bhatt, B., Murthy, T. C., Singh, K., Sashanka, A., Vishwanadh, B., Sonber, J. K., … & Kain, V. (2017)Journal of Materials Engineering and Performance, 26(10), 5043-5055.
Abstract:
The tribological performance of hot-pressed monolithic CrB2 and a newly developed CrB2 + 20 vol.% MoSi2 composite was investigated by using scratch test. The test was carried out under progressive loading ranging from 0.9 to 30 N over a scratch distance of 3 mm. In situ values of coefficient of friction (COF), depth of penetration and acoustic emission were recorded. The wear volume and fracture toughness were also calculated. COF of both materials is increased with increasing the scratch length and progressive load. COF of the composite was observed to be slightly higher compared to the monolithic CrB2. The wear volume of the composite is 60% higher compared to monolithic CrB2. Fracture toughness values of ~2.48 and ~2.81 MPa m1/2 were calculated for monolithic CrB2 and CrB2 + 20 vol.% MoSi2 composite, respectively. Microstructural characterization indicates that the abrasive wear is the dominant wear mechanism in both the materials.
Composites matching the properties of human cortical bones: The design of porous titanium-zirconia (Ti-ZrO 2) nanocomposites using polymethyl methacrylate powders.
Authors:
Gain, A. K., Zhang, L., & Quadir, M. Z. (2016). Materials Science and Engineering: A, 662, 258-267.
Abstract:
Bone-like low elastic modulus micro-porous titanium (Ti) and titanium-zirconia (Ti-ZrO2) nanocomposites were fabricated by a pressureless sintering process with biocompatible polymethyl methacrylate (PMMA) powders as the pore-forming agents. A microstructural analysis revealed that the method can successfully make randomly distributed pores in the sintered monolithic and nanocomposite, and the pore-forming agents can be removed by a heat treatment process. The material properties, i.e., the relative density, pore morphology, microhardness and elastic modulus, can be dramatically altered with the pore-forming agent. Moreover, the porous Ti-based nanocomposites produced in this way (50 vol% PMMA) have interconnected pores, higher biocompatibility, better mechanical properties and well controlled the Ti grain size, when compared with the monolithic porous Ti bodies through the second phase strengthening mechanism. The elastic moduli of the highly porous monolithic Ti and Ti-ZrO2 nanocomposites can be controlled to be about 20.0 and 22.4 GPa, respectively, which are almost the same as human cortical bones (7–25 GPa).
Nanostructured HfC–SiC composites prepared by high-energy ball-milling and reactive spark plasma sintering.
Authors:
Feng, L., Lee, S. H., Wang, H. L., & Lee, H. S. (2016). Journal of the European Ceramic Society, 36(1), 235-238.
Abstract:
The combined effects of high-energy ball milling (HEBM) and reactive spark plasma sintering (R-SPS) of HfSi2 and C powder mixture on the densification and microstructure of nanostructured HfC-SiC composites were investigated. HEBM significantly promoted the densification and improved the microstructure of the HfC-SiC composites. In contrast, the reactions between HfSi2 and C did not directly promote the densification of the HfC-SiC composites. While the reaction was mostly completed at 1300 °C, the onset temperature of significant densification was 1610 °C. Fine and homogeneously distributed HfC and SiC particles formed by HEBM and R-SPS were the key factors for promoting the densification of the HfC-SiC composites. The fine particles had high surface energy, which provided enough driving force for densification. In addition, the homogeneously distributed SiC particles effectively suppressed the growth of HfC matrix grains during densification.
Fuzzy logic response to Young's modulus characterization of a flax–epoxy natural fiber composite.
Authors:
Sodoke, K. F., Laperrière, L., Toubal, L., & Khakestar, R. S. (2016). Materials & Design, 89, 273-285.
Abstract:
Most design approaches use the experimental elastic modulus as input variable to describe the material properties. In most cases the uncertainty and the variability of the modulus are neglected. In the worst case this can lead to bad estimations of the material performance and more iterations to the final solution. The purpose of this work is to reconcile the Young’s modulus of three configurations ([0]10, [0]20 and [± 45]10) of flax–epoxy composites obtained by different techniques including acoustic impulse, tensile and bending tests, according to ISO and ASTM standards. Results obtained with these techniques all show different levels of variability in Young’s modulus values. A fuzzy logic model is used to obtain a simplified view of linguistic variables representing the modulus of elasticity and to reconcile different modules by including the uncertainty inherent to the different measuring techniques. Results have shown a strong potential for fuzzy logic to reconcile the disparity of Young modulus of natural fiber composites.
Magnesium Powder Injection Molding (MIM) of Orthopedic Implants for Biomedical Applications.
Authors:
Wolff, M., Schaper, J. G., Suckert, M. R., Dahms, M., Ebel, T., Willumeit-Römer, R., & Klassen, T. (2016). JOM, 68(4), 1191-1197.
Abstract:
Metal injection molding (MIM) has a high potential for the economic near-net-shape mass production of small-sized and complex-shaped parts. The motivation for launching Mg into the MIM processing chain for manufacturing biodegradable medical implants is related to its compatibility with human bone and its degradation in a non-toxic matter. It has been recognized that the load-bearing capacity of MIM Mg parts is superior to that of biodegradable polymeric components. However, the choice of appropriate polymeric binder components and alloying elements enabling defect-free injection molding and sintering is a major challenge for the use of MIM Mg parts. This study considered the full processing chain for MIM of Mg–Ca alloys to achieve ultimate tensile strength of up to 141 MPa with tensile yield strength of 73 MPa, elongation at fracture Af of 7% and a Young’s modulus of 38 GPa. To achieve these mechanical properties, a thermal debinding study was performed to determine optimal furnace and atmosphere conditions, sintering temperature, heating rates, sintering time and pressure.
Mechanical and Thermal Properties of Yb2SiO5: A Promising Material for T/EBCs Applications.
Authors:
Lu, M. H., Xiang, H. M., Feng, Z. H., Wang, X. Y., & Zhou, Y. C. (2016). Journal of the American Ceramic Society, 99(4), 1404-1411.
Abstract:
Yb2SiO5 is a promising material for thermal/environmental barrier coatings (T/EBCs), and its mechanical and thermal properties, which are essential to the coating design and applications, are investigated in this work. Yb2SiO5 has relatively high fracture toughness, bending and compressive strength, but low Young’s modulus. It is also tolerant to damage, which is underpinned by grain delamination and cleavage along {100}, {001}, and {040} planes. The average linear coefficient of thermal expansion (CTE) is 6.3 × 10−6 K−1 (473–1673 K) and the anisotropic CTEs are: αa = (2.98 ± 0.16) × 10−6 K−1,αb = (6.51 ± 0.19) × 10−6 K−1, and αc = (9.08 ± 0.16) × 10−6 K−1. The thermal conductivities are 2.3 and 1.5 W (m·K)−1 at 300 and 1200 K, respectively. The unique combination of these properties warrants Yb2SiO5 promising for T/EBCs applications.
Low‐Temperature Sintering of HfC/SiC Nanocomposites Using HfSi2‐C Additives.
Authors:
Feng, L., Lee, S. H., & Yin, J. (2016). Journal of the American Ceramic Society.
Abstract:
HfC/SiC nanocomposites were fabricated via the reactive spark plasma sintering (R‐SPS) of a nano‐HfC powder and HfSi2‐C sintering additives. The densification temperature decreased to 1750°C as the additive content increased. XRD analysis indicated the formation of pure HfC–(19.3–33.8 vol%) SiC within the sintered composites without residual silicide or oxide phases or secondary nonoxide phases. Ultrafine and homogeneously distributed HfC (470 nm) and SiC (300 nm) grains were obtained in the dense composites using nano‐HfC powder through the high‐energy ball‐milling of the raw powders and R‐SPS. Grain growth was further suppressed by the low‐temperature sintering using R‐SPS. No amorphous phase was identified at the grain boundary. The maximum Vickers hardness, Young’s modulus, and fracture toughness values of the HfC/SiC nanocomposites were 22 GPa, 292 GPa, and 2.44 MPa·m1/2, respectively.
Hygrothermal effects on fatigue behavior of quasi-isotropic flax/epoxy composites using principal component analysis.
Authors:
Sodoke, F. K., Toubal, L., & Laperrière, L. (2016). Journal of Materials Science, 51(24), 10793-10805.
Abstract:
This work studies the long-term hygrothermal (HT) aging effect on the fatigue behavior of a flax/epoxy bio-composite arranged in [02/902/±45]S lay-ups. The effect of aging on static tensile mechanical properties was first investigated. Tension–tension fatigue tests were also performed for both unaged and aged samples. The distribution of fatigue life for both unaged and aged sample was determined. The evolution of fatigue properties was also investigated. Fatigue tests were coupled with acoustic emission (AE) for a better understanding of how these composites react to fatigue loading in wet environmental conditions. Static tests show that water absorption affects negatively the elastic properties of this material. S–N curves show a good performance in fatigue strength of unaged samples. This performance dropped significantly with HT aging. The analysis of stress–strain hysteresis loops allowed to determine the minimal strain such as the desirable fatigue properties to explain fatigue damage evolution for single stress component. Hwang–Han’s model based on minimal strain was also used to predict the fatigue damage of the tested flax/epoxy composites. Principal component analysis enabled to separate the fatigue damage evolution of unaged and aged samples. AE results confirmed that the damage evolution of both samples is not the same. AE analyses were permitted to identify the growing fiber/matrix debonding and pull-out mechanism in the unaged samples. Correlation between AE and scanning electron microscope observations enabled the identification of several damage mechanisms and their evolution during the fatigue tests.
Theoretical prediction, preparation, and mechanical properties of YbB 6, a candidate interphase material for future UHTC f/UHTC composites.
Authors:
Zhou, Y., Wang, X., Xiang, H., Feng, Z., & Wang, G. (2016). Journal of the European Ceramic Society.
Abstract:
High melting point, low shear deformation resistance and high volume expansion upon oxidation are the basic requirements for interphase materials of future ultrahigh-temperature ceramic fiber reinforced ultrahigh-temperature ceramic matrix (UHTCf/UHTC) composites. YbB6 is one of the materials that possesses a combination of these properties. In this work, using a combination of first-principles calculations based on density functional theory and experimental investigations, low shear deformation resistance of YbB6 (theoretically predicted 81 GPa, experimentally determined 80 GPa) is confirmed. In addition, YbB6 has low Pugh’s ratio G/B, low brittleness index M = Hv/KIC, but high damage tolerant index , which endow that cracks are arrested or deflected when propagated from the matrix if it was used as an interphase material for UHTCf/UHTC composites. Details on the preparation, structural features and mechanical properties (hardness, strength, fracture toughness) of YbB6 are also given.
Preparation of mullite-zirconia composites from waste foundry sand and alumina.
Authors:
Xiang, R., Li, Y., Li, S., Li, Y., & Sang, S. (2015). Journal of the Ceramic Society of Japan, 123(1441), 892-896.
Abstract:
Waste foundry sand (WFS) collected from lost foam casting (LFC) is adopted to prepare low cost mullite-zirconia composites with the addition of alumina by reaction sintering. The mixture samples of WFS and alumina as well as samples containing only WFS are sintered from 1200 to 1600°C. Thermal shock behaviors are evaluated by cool water quenching test with temperature differentials (δT) between 2001000°C and 14 repeated cycles for δT = 1000°C. The degree of damage with thermal shock severity is measured through dynamic elastic modulus E using the impulse excitation method. The result shows that mullitezirconia composites can be successfully manufactured at 1500 and 1600°C, but the thermal shock (TS) resistance for composites sintered at 1600°C is not satisfied. The critical temperature gradient (δTc) is below 200°C, and after three TS cycles with δT = 1000°C, the E/E0 reduced to a nearly constant.
Synthesis of an Al/Al 2 O 3 composite by severe plastic deformation.
Authors:
Kunčická, L., Lowe, T. C., Davis, C. F., Kocich, R., & Pohludka, M. (2015). Materials Science and Engineering: A, 646, 234-241.
Abstract:
In this work, four different volume fractions of Al2O3 (10, 20, 30 and 40 vol.%) were mixed with the fine Al powder and the powder blends were milled for 5 h. Scanning electron microscopy analysis, particle size analysis and bulk density measurements were used to investigate the morphological changes and achieving the steady state conditions. The results showed that increasing the Al2O3 content can provide the steady state particle size in 5 h milling process. It was found that increasing the volume fraction of Al2O3 leads to increasing the uniformity of Al2O3. Standard deviations of microhardness measurements confirmed this result. The XRD pattern and XRF investigations depicted that increasing the Al2O3 content causes an increase in the crystal defects, micro-strain and Fe contamination during 5 h milling process of nanocrystalline composite powders while the grain size is decreased. To investigate the effect of milling time, Al–30 vol.% Al2O3 (which achieved steady state during 5 h milling process) was milled for 1–4 h. The results depicted that the milling time lower than 5 h, do not achieve to steady state conditions.Research highlights► In the low time milling the effect of Al2O3 amount is investigated ► Al2O3 particles are distributed uniformly in the Al matrix ► In the low time milling it is possible to produce nanostructured composite powder ► Median size and bulk density measurements demonstrate reaching the steady state.
Effect of carbon nanotube orientation on mechanical properties and thermal expansion coefficient of carbon nanotube-reinforced aluminum matrix composites.
Authors:
Liu, Z. Y., Xiao, B. L., Wang, W. G., & Ma, Z. Y. (2014). Acta Metallurgica Sinica (English Letters), 27(5), 901-908.
Abstract:
Carbon nanotube-reinforced 2009Al (CNT/2009Al) composites with randomly oriented CNTs and aligned CNTs were fabricated by friction stir processing (FSP) and FSP-rolling, respectively. The CNT/2009Al composites with aligned CNTs showed much better tensile properties at room temperature and elevated temperature compared with those with the randomly oriented CNTs, which is mainly attributed to larger equivalent aspect ratio of the CNTs and avoidance of preferential fracture problems. However, much finer grain size was not beneficial to obtaining high strength above 473 K. The aligned CNTs resulted in tensile anisotropy, with the best tensile properties being achieved along the direction of CNT aligning. As the off-axis angle increased, the tensile properties were reduced due to the weakening of the load transfer ability. Furthermore, aligned CNTs resulted in much lower coefficient of thermal expansion compared with randomly oriented CNTs.
High‐Temperature Creep Behavior of Dense SiOC‐Based Ceramic Nanocomposites: Microstructural and Phase Composition Effects.
Authors:
Papendorf, B., Ionescu, E., Kleebe, H. J., Linck, C., Guillon, O., Nonnenmacher, K., & Riedel, R. (2013). Journal of the American Ceramic Society, 96(1), 272-280.
Abstract:
In this work, dense monolithic polymer‐derived ceramic nanocomposites (SiOC, SiZrOC, and SiHfOC) were synthesized via hot‐pressing techniques and were evaluated with respect to their compression creep behavior at temperatures beyond 1000°C. The creep rates, stress exponents as well as activation energies were determined. The high‐temperature creep in all materials has been shown to rely on viscous flow. In the quaternary materials (i.e., SiZrOC and SiHfOC), higher creep rates and activation energies were determined as compared to those of monolithic SiOC. The increase in the creep rates upon modification of SiOC with Zr/Hf relies on the significant decrease in the volume fraction of segregated carbon; whereas the increase of the activation energies corresponds to an increase of the size of the silica nanodomains upon Zr/Hf modification. Within this context, a model is proposed, which correlates the phase composition as well as network architecture of the investigated samples with their creep behavior and agrees well with the experimentally determined data.
Elastic behaviour of zirconium titanate-zirconia bulk composite materials at room and high temperature.
Authors:
López-López, E., Erauw, J. P., Moreno, R., Cambier, F., & Baudín, C. (2013). Journal of the European Ceramic Society, 33(15), 3195-3200.
Abstract:
Zirconium titanate (ZrTiO4) is a well known compound in the field of electroceramics, however, its potential for structural applications has never been analysed. Moreover, it is compatible with zirconia, thus, zirconium titanate–zirconia composites might have potential for structural applications in oxidizing atmospheres. Nevertheless, there are currently no data about elastic properties of zirconium titanate materials in the literature. In view of the importance of these properties for the structural integrity of components subjected to high temperature and mechanical strains, an attempt was done in this work to determine the elastic properties of ZrTiO4, both at room and high temperature. Young’s modulus (161 ± 4 GPa), shear modulus (61 ± 1 GPa) and Poisson’s ratio (0.32 ± 0.01) values at room temperature have been estimated for a fully dense single phase ZrTiO4 material from experimental data of sintered single phase ZrTiO4 materials with different porosities (6–19%). Values for room temperature Young’s modulus are in agreement with those obtained by nanoindentation. Young’s modulus up to 1400 °C shows an unusual dependence on temperature with no significant variation up to 500 °C an extremely low decrease from 500 to 1000 °C (≈0.02–0.03% every 100 °C) followed by a larger decrease that can be attributed to grain boundary sliding up to 1400 °C.
Developing high-performance aluminum matrix composites with directionally aligned carbon nanotubes by combining friction stir processing and subsequent rolling.
Authors:
Liu, Z. Y., Xiao, B. L., Wang, W. G., & Ma, Z. Y. (2013). Carbon, 62, 35-42.
Abstract:
A route combining friction stir processing and subsequent rolling processing was established to fabricate 1.5–4.5 vol.% carbon nanotube (CNT)-reinforced 2009Al composites. Microstructural observations indicated that CNTs were individually dispersed and directionally aligned in the aluminum matrix of the CNT/2009Al composites. The tube structure of the CNTs was retained and the CNT–Al interface was bonded without pores. As a result, great increases in yield strength, ultimate tensile strength, and Young’s modulus were achieved when a higher concentration of CNTs was incorporated. Moreover, the composites exhibited good ductility. In particular, 3 vol.% CNT/2009Al composite exhibited an ultimate tensile strength of 600 MPa and elongation of 10%, much higher strength–ductility than the corresponding values for CNT/Al composites fabricated by other processes.
On the influence of silica type on the structural integrity of dense La 9.33 Si 2 Ge 4 O 26 electrolytes for SOFCs.
Authors:
Alves, C., Marcelo, T., Oliveira, F. A. C., Alves, L. C., Mascarenhas, J., & Trindade, B. (2013). Journal of the European Ceramic Society, 33(12), 2251-2258.
Abstract:
Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball mill with different rotation speeds (150–350 rpm) and increasing milling times up to 35 h in order to obtain the La9.33Si2Ge4O26 apatite phase at room temperature. The results showed that the higher the rotation speed the lower the time required for the formation of the apatite phase. No reaction between the starting powders was observed at 150 rpm. Thermal analysis of the unreacted powders milled at 150 rpm showed formation of the apatite phase around 800 ◦C, with enthalpies ranging from 43.5 and 48.6 kJ mol−1. An activation energy Ea of 65 kJ mol−1 was obtained applying the Kissinger equation. The mean Avrami exponent n calculated was 1.5, indicating that the apatite phase transformation occurs by a diffusion controlled process.
Microstructure and mechanical properties of milled fibre/SiC multilayer composites prepared by tape casting and pressureless sintering.
Authors:
Yang, W. S., Biamino, S., Padovano, E., Pavese, M., Chen, X., Fino, P., & Badini, C. (2013). Materials Science and Engineering: A, 588, 103-110.
Abstract:
In the present work, milled carbon fibre with high mechanical properties was used to reinforce silicon carbide, and C-sf/SiC multilayer composites were prepared by tape casting and pressureless sintering. The milled C fibres were firstly dispersed in solvents with the aid of dispersant (Triton X-100) and then mixed with SiC slurry to make green C-sf/SiC tapes to limit fibre breakage. The average length of C fibres slightly decreased with the increase of mixing time in the present duration, indicating that mixing the SiC slurry with the fibre-predispersed solution is an effective method for adding fibres with limited breakage. Fibres were homogeneously distributed in the tapes and tended to align fairly well along the tape casting direction. The relative density of the composite containing milled C fibres decreased with the fibre amount. The C-sf/SiC multilayer composites demonstrated significant anisotropic shrinkage behaviour in different directions, while the addition of short C fibres hindered the shrinkage in the plane containing the fibres during sintering. Elastic modulus and bending strength decreased with increased porosity, which implies that bending properties are affected more significantly by residual porosity rather than fibres’ properties.
Comparative assessment of Young’s modulus measurements of metal–ceramic composites using mechanical and non-destructive tests and micro-CT based computational modeling.
Authors:
Węglewski, W., Bochenek, K., Basista, M., Schubert, T., Jehring, U., Litniewski, J., & Mackiewicz, S. (2013). Computational Materials Science, 77, 19-30.
Abstract:
It is commonly known that the available non-destructive and mechanical methods of the Young modulus measurement yield different results. This paper presents comparison of the results of experimental determination and numerical modeling of the Young modulus of Cr–Al2O3–Re composites (MMC) processed by a powder metallurgical method (SPS). In the computational model a finite element analysis is combined with images of the real material microstructure obtained from micro-computed tomography (micro-CT). Experimental measurements were carried out by four testing methods: three-point bending, resonance frequency damping analysis (RFDA), ultrasonic pulse-echo technique, and scanning acoustic microscopy. The paper also addresses the issue which of the four experimental methods at hand gives results closest to the theoretical predictions of the micro-CT based FEM model.
Elastic properties and damping behavior of alumina–zirconia composites at room temperature.
Authors:
Pabst, W., Gregorová, E., Malangré, D., & Hostaša, J. (2012). Ceramics International, 38(7), 5931-5939.
Abstract:
This work focuses on the elastic properties and damping behaviour of alumina–alumina/zirconia laminates and their constituent layers as a function of temperature. The laminates were made by warm pressing and sintering tape-casted layers of alumina and alumina/zirconia (60/40 vol.%). The laminate stacking sequence and thickness of the constituent layers were tailored so as to have compressive residual stresses on the laminate surface, improving thus the laminate wear resistance. The temperature dependence of the elastic properties and damping behaviour of the laminates was determined using the impulse excitation technique (IET). Furthermore, the measured elastic properties were validated with the help of a finite element model (FE-model).
Microstructure and mechanical properties of short carbon fibre/SiC multilayer composites prepared by tape casting.
Authors:
Yang, W. S., Biamino, S., Padovano, E., Fuso, L., Pavese, M., Marchisio, S., … & Badini, C. (2012). Composites Science and Technology, 72(6), 675-680.
Abstract:
Silicon carbide multilayer composites containing short carbon fibres (Csf/SiC) were prepared by tape casting and pressureless sintering. The C fibres were dispersed in solvents with dispersant (Triton X-100) firstly and then mixed with the SiC slurry to make green Csf/SiC tapes. Fibres were homogeneously distributed in the tape and tended to align fairly well along the tape casting direction. The addition of short C fibre hindered the shrinkage in the plane containing the fibres as well as the grain growth of SiC during sintering. The weight loss occurring during oxidation tests of Csf/SiC multilayer composites increased with fibre amount and material porosity. Elastic modulus of Csf/SiC multilayer composites decreased linearly with fibre amount. Bending strength presented clear relationship with the relative density, that is with the total porosity.
Innovative metal-graphite composites as thermally conducting materials.
Authors:
Hutsch, T., Schubert, T., Schmidt, J., Weißgärber, T., & Kieback, B. (2010). Proceedings of the powder metallurgy world congress and exhibition. PM2010 (pp. 361-368).
Abstract:
Metal matrix composites (MMC’s) made by powder metallurgy offer the possibility to tailor the thermal properties of the metal by adding carbon based reinforcements, e.g. natural graphite flakes. The microstructure, thermal conductivity (TC), coefficient of thermal expansion (CTE) and the damping behaviour of the composites based on Cu-C, Al-C, Fe-C and W-C will be displayed and discussed. The produced composites exhibit TC in the range of 300 W/ mK to 550 W/ mK combined with a reduced CTE in the range of 3 ppm/ K to 10 ppm/ K and a high mechanical damping. The tungsten- graphite composites represent a TC of 400 W/ mK and a low CTE of 3 to 5 ppm/ K. Anisotropy of the properties of metalgraphite composites due to intrinsic anisotropic properties of the graphite flake must be considered and is displayed for the CTE.
Constrained sintering of a glass ceramic composite: I. Asymmetric laminate.
Authors:
Ollagnier, J. B., Guillon, O., & Rödel, J. (2010). Journal of the American Ceramic Society, 93(1), 74-81.
Abstract:
A self-constrained low-temperature-cofired ceramic (LTCC) system, composed of a low-fire La2O3–B2O3–CaO–Al2O3-based glass (LBG)+alumina (LBGA) and high-fire BaO–B2O3–SiO2-based glass (BBSG)+alumina (BBSGA), has been developed. As the densification temperature range required for the LBGA is lower than that for the BBSGA, both systems densify and constrain alternatively during cofiring of a multilayer LBGA/BBSGA laminate. This results in the linear shrinkage of multilayer LBGA/BBSGA laminate taking place only in the Z direction with little shrinkage in the X–Y directions, exhibiting promising characteristics of self-constrained densification.
Effects of SiO2 formed on SiC filler particulates on the thermal and mechanical properties of a SiC/Si-CN composite.
Authors:
Lee, S. H. (2010). Journal of the Ceramic Society of Japan, 118(1384), 1163-1165.
Abstract:
SiO2 surface layer of SiC filler particles decreased thermal stability and creep resistance of particulate-reinforced Si–C–N-based ceramic composites made by precursor-impregnation and pyrolysis (PIP) method due to the decomposition of SiO2 at and above 1350°C. The oxide layer could be removed by a pre-treatment of SiC particle compact at 1750°C in Ar before precursor impregnation. The composites fabricated with pre-treated SiC compact show clear improvements in thermal stability and creep resistance.

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