Glass-ceramic Matrix Composites Research Articles

Polymer-derived Biosilicate-C composite foams: Phase development and photothermal effect

Glass-ceramic matrix composites for bone-tissue regeneration were produced in the form of highly porous foams utilizing the ‘polymer-derived ceramics’ (PDCs) approach. More precisely, two different commercial silicone polymers (a poly-methyl-siloxane, MK, and a polymethyl-phenyl-silsesquioxane, H44), reacting with suitable Na2O, CaO, and P2O5 yielding fillers were considered. The reaction was designed to yield products resembling Biosilicate® glass-ceramic i.e. Na2CaSi2O6 embedded in a silico-phosphate glass matrix. Subsequently, the samples were heat treated either in the air or in the N2 atmosphere, implying improvements in the mechanical properties and providing extra functionality. The pyrolysis in an inert atmosphere led to composites comprising a carbon phase, which promoted the absorption of infrared radiation. Such functionality makes the obtained composites promising in the perspective of disinfection of bone-tissue implants and photothermal therapy.

Enabling pseudo-ductility in geopolymer based glass-ceramics matrix composites by slurry dilution

Carbon fibre reinforced composites with matrix consisting of porous glass-ceramics obtained by high temperature heat-treatment of geopolymer based material are studied. The matrix is obtained from a slurry. Several composites have been manufactured by in-laboratory stratification of pre-impregnated plies with slurries diluted at various rates. Slurry dilution changes the porosity and leads to pseudo-ductile behaviour of the composite. Dilution implies a drop of non-linearity stress threshold together with a slower decrease of the strength. An optimal dilution rate is evidenced, which exhibits high strength but lower non-linearity stress threshold, and then, a significant failure strain. The optimized prepreg material is compared with a reference composite processed by an industrial prepreg process. The origin of the pseudo-ductility is related to decohesion at the interface between tows and inter-tow matrix. RTM also provides a pseudo-ductile composite but with very low non-linearity stress threshold, in relation to poorly impregnated tows.

Wear response of glass fiber and ceramic tile-reinforced hybrid epoxy matrix composites

This study presents the tribological behavior of epoxy matrix composites containing two different fillers. The composites contain fillers with different particle sizes (< 90 µm and in the range of 150–300 µm) and different wall tile to glass fiber waste ratios (55:5, 50:10 and 40:20). The total amount of filler was fixed to 60 wt% in all of the composites to reveal the effect of variations in filler content on properties. The physico-mechanical properties, such as bulk density, porosity, impact resistance, shore hardness, flexural strength and wear characteristics of developed materials were determined. Tribological tests were carried out by ball-on-disk configuration and rotational sliding at room temperature against 6-Co/WC ball with a diameter of 3 mm. 3N of constant test load was applied and the wear distance was kept as 400 m. The results showed that the steady-state coefficient of frictions was changed in the range 0.38–0.47 and the wear rate was obtained between 1.74 × 10−5 and 1.09 × 10−4 mm3/Nm. When the coarser particle size filler was used, it resulted in worsening of the wear resistance. It can generally be concluded that the properties were improved with the increasing amount of wall tile addition, and also better properties were obtained in both types of filled composites compared to the epoxy matrix.

Effect of boron doping on fracture behavior of carbon fiber reinforced lithium aluminosilicate glass ceramics matrix composites

Boron doped carbon fibers reinforced lithium aluminosilicate matrix composites (Cf/LAS) were prepared by slurry infiltration combining with hot pressing procedure. The doping of boron significantly enhances the fracture toughness and fracture work of the Cf/LAS composites, which could reach the highest fracture toughness of 25.0±0.4MPam1/2 and the work of fracture of 24.5±2.8kJ/m2, respectively. The work of fracture of boron doped Cf/LAS composites is 2.2 times of that of the boron free Cf/LAS composites. The fracture mode of Cf/LAS composites changed from ductile fracture to brittleness fracture with increasing the boron content from 0 to 4wt%. The connection of the fracture behavior and the interfacial microstructure was examined to establish a direct relationship among interfacial microstructure, interfacial chemistry and fracture behavior of the studied composites.

Preparation of silicon nitride–barium aluminum silicate composites by freeze gelation

An effective approach to prepare silicon nitride–barium aluminum silicate (Si3N4/BAS) composites by freeze gelation was described. Utilizing the gelation of particulate silica sol by freezing to solidify ceramic slurry, in the forming and drying process, the cracking and warpage of green body were avoided, and the shrinkage rate was 0.6%. The added barium oxide and alumina absorbed silica in sol to prepare Si3N4/BAS glass ceramic matrix composites, and the flexural strength, work of fracture and density of Si3N4/BAS composites were 342MPa, 181J/m2 and 3.0g/cm3, respectively.

The effect of microstructural features on the mechanical properties of LZSA glass-ceramic matrix composites

This work reports on the characterization of ZrSiO4 particulate-reinforced Li2O-ZrO2-SiO2-Al2O3 (LZSA) glass-ceramic matrix composites. The typical physical/mechanical and chemical properties of the glass batches and the composites were measured. A composition with 60 wt.% ZrSiO4 was preliminarily selected because it demonstrated the highest values of bending strength (190 MPa) and deep abrasion resistance (51 mm³). To this same composition was given a 7 wt.% bentonite addition in order to obtain plasticity behavior suitable for extrusion. The sintered samples (1150 ºC for 10 min) presented a thermal linear shrinkage of 14% and bending strength values of 220 MPa.

Synthesis and properties of SiC/Si3N4 co-reinforced La-containing glass ceramic matrix composites

In-situ grown β-Si3N4 and α-SiC co-reinforced La-containing glass ceramic matrix composites using ZrO2 as addition were obtained by a two-step sintering process. These composites were pressureless sintered under a nitrogen atmosphere at different sintering conditions for comparison of phase transformation and mechanical properties. Densities of the samples were measured and analyses of resultant products were carried out using X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that additions of La-containing glass can effectively promote α-Si3N4 to β-Si3N4 phase transformation. However, β-Si3N4 grain growth was hindered by the existent α-SiC. The La-containing glass-ceramic matrix composites exhibit high mechanical properties.

Damage Accumulation in Cyclically-Loaded Glass-Ceramic Matrix Composites Monitored by Acoustic Emission

Barium osumilite (BMAS) ceramic matrix composites reinforced with SiC-Tyranno fibers are tested in a cyclic loading protocol. Broadband acoustic emission (AE) sensors are used for monitoring the occurrence of different possible damage mechanisms. Improved use of AE indices is proposed by excluding low-severity signals based on waveform parameters, rather than only threshold criteria. The application of such improvements enhances the accuracy of the indices as accumulated damage descriptors. RA-value, duration, and signal energy follow the extension cycles indicating moments of maximum or minimum strain, while the frequency content of the AE signals proves very sensitive to the pull-out mechanism.

Large-scale interfacial damage and residual stresses in a glass–ceramic matrix composite

The current work is concerned with the micro-mechanics of fracture of a SiC-fiber-reinforced barium osumilite (BMAS) ceramic matrix composite tested under both monotonic and cyclic tension. The double-edge notch (DEN) specimen configuration was employed in order to confine material damage within a predefined gage length. The imposition of successive loops of unloading to complete load relaxation and subsequent reloading were found to result in an increase by 20% in material strength as compared to pure tension; the finding is attributed to energy dissipation from large-scale interfacial debonding phenomena that dominated the post-elastic mechanical behavior of the composite. Cyclic loading also helped establish the axial residual stress state of the fibers in the composite, of tensile nature, via a well-defined common intersection point of unloading–reloading cycles. An approach consisting of the application of a translation vector in the stress–strain plane was successfully used to derive the residual stress-free properties of the composite and reconcile the scatter noted in elastic properties of specimens with respect to theoretical expectations.

Fiber-Matrix Compatibility in LZSA Glass-Ceramic Matrix Composites

Continuous fiber reinforced glass-ceramic (GC) matrix composites are potential candidates for thermomechanical applications at moderate temperatures (up to 1000°C) due to the combination of interesting properties such as high specific strength and toughness. Crack deflection into fiber-matrix interface, as well as subsequent fiber pullout and bridging are the respective toughening mechanisms. In this paper, the compatibility between LZSA glass-ceramic matrix and commercially available oxide alumina fibers (NextelTM610) is qualitatively examined. Toughening mechanisms such as crack deflection and fiber pullout are investigated by analyzing the path of Vickers-induced matrix cracks formed in the vicinity of the fibers and by investigating the crack surface of bending samples, respectively. GC matrix samples sintered and crystallized at different heat-treatment conditions have shown strong interfacial bonds between matrix and fibers, which leads to a brittle fracture without significant fiber pullout in all cases. This behavior indicates the requirement of using fiber coatings in this CMC system, to produce weak interfaces that enable toughening mechanisms to take place.

Influence of brick pattern interface structure on mechanical properties of continuous carbon fiber reinforced lithium aluminosilicate glass–ceramics matrix composites

Continuous carbon fiber reinforced lithium aluminosilicate glass–ceramic matrix composites have been fabricated by sol–gel process and hot pressing technique. The results show that the Cf/β-eucryptite composites hot pressed at 1300 °C and Cf/β-spodumene composites hot pressed at 1400 °C form weak interface with brick pattern characteristics, leading to high mechanical performance. The maximum flexural strength and fracture toughness reach 571 ± 32 MPa and 9.8 ± 0.6 MPa m1/2 for Cf/β-eucryptite composites and 640 ± 72 MPa and 19.9 ± 1.8 MPa m1/2 for Cf/β-spodumene composites. On increasing the hot pressing temperature, the active chemical diffusion consumes brick pattern interface layer, which leads to the formation of strong bonding between carbon fiber and the matrix. As a result, the composites exhibit brittle fracture behavior and the mechanical properties decrease significantly.

Ablation Properties of C Fibers and SiC Fibers Reinforced Glass Ceramic Matrix Composites Upon Oxyacetylene Torch Exposure

The ablation properties of two laminated composites, having both a glass ceramic matrix and different kinds of fibers (C or SiC) with the same architecture, are evaluated and compared. Ablation tests are performed using an oxyacetylene torch on samples having two different thicknesses. Mass loss and ablation depth are measured after flame exposure. The results obtained show that the decomposition of SiC fibers during thermal exposure has a significant impact on ablation behavior. Oxidation of SiC produces a liquid SiO2 film at the top of the material during ablation. This leads to an improved ablation resistance compared to the glass ceramic matrix/C composite, especially in case of successive flame exposures where the SiO2 film consumes a substantial fraction of the heat flow during its liquefaction upon re-heating.

Thermal shock fracture in cross-ply fibre-reinforced ceramic–matrix composites

The onset of matrix cracking due to thermal shock in a range of simple and multi-layer cross-ply laminates comprising a calcium aluminosilicate (CAS) matrix reinforced with Nicalon® fibres is investigated analytically. A comprehensive stress analysis under conditions of thermal shock, ignoring transient effects, is performed and fracture criteria based on either a recently derived model for the thermal shock resistance of unidirectional Nicalon®/glass ceramic–matrix composites or fracture mechanics considerations are formulated. The effect of material thickness on the apparent thermal shock resistance is also modelled. Comparison with experimental results reveals that the accuracy of the predictions is satisfactory and the reasons for some discrepancies are discussed. In addition, a theoretical argument based on thermal shock theory is formulated to explain the observed cracking patterns.

Microstructure compatibility and its effect on the mechanical properties of the α-SiC/β-Si3N4 co-reinforced barium aluminosilicate glass ceramic matrix composites

Monolithic α-SiC particles and in situ β-Si3N4-reinforced barium aluminosilicate (BAS) glass ceramic matrix composites with good mechanical properties were obtained by spark plasma sintering. However, attempts at the synthesis of ternary phase composites in order to maximize the reinforcing effects by co-adding α-SiC and β-Si3N4 were only partly successful. β-Si3N4 grain growth was remarkably hindered by the coexistent α-SiC, thus the resultant composite suffered a loss of reinforcement efficiency.

Hot-pressed phosphate glass–ceramic matrix composites containing calcium phosphate particles for nuclear waste encapsulation

Sodium aluminium phosphate (NaAlP) glass–ceramic composites were produced as potential wasteforms for the immobilization of special categories of halide-containing radioactive waste. Sintering conditions for encapsulating a simulated waste (a calcinated mixture of calcium phosphate host and various oxides) in the cold-pressed NaAlP glass–ceramic were first determined and the results were compared with similar samples prepared by hot pressing. In both cases, the conditions aimed to provide a very high-density material, via as low production temperatures as possible, in conjunction with a high waste loading (75 wt.% simulated waste to 25 wt.% glass). It was found that by hot pressing and using a NaAlP glass–ceramic containing 2 mol% B2O3, significantly lower temperatures could be employed compared to the cold pressing and sintering route. The lowest temperature at which a sufficiently dense hot-pressed product was achieved (86% theoretical density), that exhibited mechanical properties similar to those of borosilicate glass (e.g. Young’s modulus 67 ± 2 GPa), was 550 °C. This processing temperature is considerably lower than values reported in the literature for similar systems. As such, hot pressing can be considered as a convenient technique for the fabrication of this type of composite for waste encapsulation.

Extruded ZrSiO 4 particulate-reinforced LZSA glass–ceramics matrix composite

This work reports on the characterization of ZrSiO 4 particulate-reinforced Li 2O–ZrO 2–SiO 2–Al 2O 3 (LZSA) glass–ceramic matrix composite added with bentonite as binder and formed by extrusion. The glass batches and composites were characterized on the point of view of their typical physical/mechanical and chemical properties. Composition with 60 wt.% ZrSiO 4 was preliminary selected, since it showed the best results in terms of bending strength (190 MPa) and deep abrasion resistance (51 mm 3). The same composition as before but added with 7 wt.% bentonite was selected for further studies since it exhibited the highest plasticity index, which resulted in good billets after extrusion. In this last case, the extruded samples, after sintering at 1150 °C for 10 min, showed a thermal linear shrinkage of 14% and deep abrasion resistance and bending strength of 51 mm 3 and 220 MPa, respectively.

Fabrication and mechanical properties of carbon short fiber reinforced barium aluminosilicate glass–ceramic matrix composites

Dense BaSi 2Al 2O 8 (BAS) and Ba 0.75Sr 0.25Si 2Al 2O 8 (BSAS) glass–ceramic matrix composites reinforced with carbon short fibers (C sf) were fabricated by hot pressing technique. The microstructure, mechanical properties and fracture behavior of the composites were investigated by X-ray diffraction, scanning and transmission electron microscopies, and three-point bend tests. The carbon fibers had a good chemical compatibility with the glass–ceramic matrices and can effectively reinforce the BAS (or BSAS) glass–ceramic because of associated toughening mechanisms such as crack deflection, fiber bridging and pullout effects. Doping of BAS with 25 mol% SrSi 2Al 2O 8 (SAS) can accelerate the hexacelsian to celsian transformation and result in the formation of pure monoclinic celsian in C sf/BSAS composites, which can avoid the undesirable reversible hexacelsian to orthorhombic transformation at ∼300 °C and reduce the thermal expansion mismatch between the fiber and matrix.

Sintered feldspar glass–ceramics and glass–ceramic matrix composites

Sintering with simultaneous crystallization of fine glass powders allowed the preparation of dense glass–ceramics based on unusual feldspar crystals (constituted by microcline and orthoclase, KAlSi 3O 8), at a very low temperature (750 °C) and with limited processing times. Al 2O 3 platelets, added to the glass powders, caused a remarkable improvement of bending strength (exceeding 100 MPa), microhardness (approaching 9 GPa) and fracture toughness (approaching 2 MPa m 0.5), even for limited concentrations (which varied from 5 to 15 vol%). Due to the simple and low cost manufacturing technique, the glass–ceramic matrix composites obtained could find applications in the construction industry.

Fracture Behavior of Ceramic Matrix Composites during Monotonic and Cyclic Loadings

The fracture behavior of ceramic matrix composites (CMCs) was investigated using the infrared (IR) thermography nondestructive evaluation (NDE) technique during monotonic and cyclic loadings. The CMCs used for this investigation are continuous Nicalon (silicon carbide fiber) fiber reinforced calsium aluminosilicate (CAS) glass-ceramics matrix composites. During monotonic tension and cyclic fatigue loadings, IR camera was used for in-situ monitoring of temperature evolution, and the temperature changes during testing were measured. Microstructural characterizations using scanning electron microscopy (SEM) were performed to investigate fracture modes and failure mechanisms of Nicalon/CAS samples. In this investigation, the NDE technique and SEM characterization were employed to facilitate a better understanding of damage evolution and progress of Nicalon/CAS composites during monotonic and cyclic loadings.

Synthesis of 30 wt%BAS/Si 3N 4 composite by spark plasma sintering

30 wt%BAS/Si 3N 4 composite was fabricated via spark plasma sintering (SPS) process. The as-sintered specimens were subsequently heat-treated at 1800 °C to further optimize the microstructure and mechanical properties. The results show that SPS could effectively promote the reaction synthesis of BAS glass and α- to β-Si 3N 4 phase transformation, resulting in a dense 30 wt%BAS/Si 3N 4 composite with fine elongated β-Si 3N 4 grains dispersed in the continuous BAS glass matrix. Post heat-treatment could realize the complete crystallization of BAS and microstructural optimization. The obtained composite exhibits excellent mechanical properties compared to unreinforced BAS glass–ceramic. The flexural strength and fracture toughness could reach 944 MPa and 8.9 MPa m 1/2, respectively, which reach the level of conventional Si 3N 4 composites sintered by traditional sintering process. SPS followed by heat-treatment provides a feasible way to control microstructure, thus optimizes the mechanical performance of glass–ceramics matrix composites.