Creep Resistance Of Composites Research Articles

Dual cantilever creep and recovery behavior of sisal/hemp fibre reinforced hybrid biocomposites: Effects of layering sequence, accelerated weathering and temperature

In this work, the influence of weathering on the creep behavior of the sisal (SSSS), hemp (HHHH), and their hybrid composites (HSSH, and HSHS) was investigated. Composites were exposed to accelerated weathering for 2222 h, which replicates conditions equivalent to 1 year of outdoor exposure. Bio-epoxy based composites were fabricated by the hot press technique. Creep study was performed in a dynamic mechanical analyzer under the dual cantilever creep mode at 30 °C and 50 °C testing temperature under a load of 5 N. The creep-recovery behavior of the weathered composite specimens was evaluated and compared with the unweathered specimens. The investigation revealed that creep strain decreased with the incorporation of the sisal and hemp fibres into the bio-epoxy matrix. The experimental creep response of the composites was also in good agreement with the analytical results from Burger’s model. Both the weathering and testing conditions at elevated temperature (50 °C) had a significant impact on the creep resistance of the composites. The creep resistance of the hybrid composites was found to be dependent on the layering sequence. HSHS configuration almost displayed similar creep properties before and after weathering. HSSH configuration was found to have lower creep resistance after weathering. Scanning electron microscopy was used out to examine the fibre-matrix interface of the composites.

Micromechanical response of two-dimensional transition metal carbonitride (MXene) reinforced epoxy composites

MXenes have attracted much attention as fillers in polymer composites due to their superior electrical and mechanical properties making them ideal for creating multifunctional composites. In this work, Ti3CN-epoxy composites were prepared via solvent processing and cured with amine-based hardener. The effects of Ti3CN content in the epoxy system on the thermal degradation behavior and micromechanical properties were investigated. The extent of intercalation of epoxy between MXene flakes was analyzed by transmission electron microscopy. Nanoindentation analysis of MXene-epoxy composites exhibited improved mechanical properties with increasing MXene content with highest increase to 12.8 GPa Young's modulus for 90 wt% Ti3CN. An increase in creep resistance of composites was observed at maximum loading of Ti3CN by 46% compared to neat epoxy.

Microstructural development and mechanical performance of mullite-alumina and hibonite-alumina ceramics with controlled addition of a glass phase

Robust mechanical properties of refractory ceramics are critical to their performance in industrial applications. To investigate the effects of glass on the sinterability and mechanical properties of refractory ceramics, a controlled amount of glassy phase (10wt%) was added to mullite (Al6Si2O13)-alumina (Al2O3) and hibonite (CaAl12O19)-alumina composites. Two liquid compositions within the Al2O3-SiO2-CaO system were chosen to produce a glass at 1600°C that exists in equilibrium with a mullite-alumina composite and a hibonite-alumina composite. We performed a comparative study of the mechanical properties (hardness, flexural strength, and creep resistance) of mullite-alumina and hibonite-alumina composites with and without glassy phases. The observed microstructures clearly affected the mechanical properties. The strong interface created between the three phases in each subsystem and the reduced amount of residual porosity in the composites with an added glassy phase may explain the increase in strength, hardness, and creep resistance of the composites. However, better mechanical properties and finer grain sizes of mullite make the mullite-alumina (-glass) system a better candidate for refractory applications that require improved mechanical properties.

Effects of Reinforcements on Creep Resistance of Hybrid-Reinforced Titanium Matrix Composites

Hybrid-reinforced titanium matrix composites (TMCs) were in-situ synthesized by common casting and hot-working technologies. High-temperature creep behavior of the matrix titanium alloy and composites was tested at 873, 923, and 973 K in the stress range from 20 to 300 MPa. Depending on the stress levels, creep behavior of the matrix alloy and composites was divided into two stress regions. Creep resistance of the composites was significantly enhanced by the reinforcements. Threshold stresses and stress transfer effects were introduced to explain the enhancement of creep resistance. In most cases, high volume fractions of reinforcements caused a deleterious effect on the creep resistance of composites. On the other hand, types and morphologies of reinforcements were the dominant factor contributing to the enhancement of creep resistance.

Processing and Creep Resistance of Nickel/Yttria Composites

In this study, pure nickel and yttria (Y2O3) were selected as a model system to investigate the feasibility of processing metal matrix composites (MMCs) through a powder metallurgy approach for the in-situ formation of a continuous three-dimensional reinforcement network or the in-situ formation of discrete reinforcements with certain degrees of interconnected clusters. Composites with a volume fraction of Y2O3 ranging from 20 to 50 % were prepared through hot pressing. The density, microstructure and creep resistance of these composites were evaluated as a function of the yttria volume fraction. It was found that a continuous Y2O3 network was formed in composites with 40 and 50 vol % Y2O3, while yttria was discrete with some degrees of interconnected clusters in composites with 20 and 30 vol % Y2O3. The creep rate was reduced by two to three orders of magnitude with the addition of 20 to 30 vol % Y2O3, and it continued to decrease with increasing the volume fraction of yttria to 50%. The analysis indicated that the load transfer to isolated yttria particles could not account for the improved creep resistance of composites with 20 and 30 vol % Y2O3, while the load transfer to a continuous yttria network in composites with 40 and 50 vol % Y2O3 could not be approximated by the model of the load transfer to continuous fibres. The discrepancies are believed to be related to the presence of interconnected yttria clusters, the low relative density of the yttria phase in the composite, and the low load-carrying capability through a three-dimensional network in comparison with the load-carrying capability through continuous fibres. It is suggested that the density of the yttria phase and hence the creep resistance of the composite can be further improved over what have been obtained in this study by densifying the composite at high temperatures and pressures.