The present paper deals with the study of microstructure and wear characteristics of TiB2 reinforced aluminium metal matrix composites (MMCs). Matrix alloys with 5, 10 and 15% of TiB2 were made using stir casting technique. Effect of sliding velocity on the wear behaviour and tribo-chemistry of the worn surfaces of both matrix and composites sliding against a EN24 steel disc has been investigated under dry conditions. A pin-on-disc wear testing machine was used to find the wear rate, in which EN24 steel disc was used as the counter face, loads of 10-60N in steps of 10N and speeds of 100, 200, 300, 400 and 500 rpm were employed. The results showed that the wear rate was increased with an increase in load and sliding speed for both the materials. However, a lower wear rate was obtained for MMCs when compared to the matrix alloys. The wear transition from slight to severe was presented at the critical applied loads. The transition loads for the MMCs were much higher than that of the matrix alloy. The transition loads were increased with increase in TiB2 and the same was decreased with the increase of sliding speeds. The SEM and EDS analyses were undertaken to demonstrate the effect of TiB2 particles on the wear mechanism for each conditions.
This article is concerned with a study on the energy absorption behavior of polyurethane (PU) foams such as flexible high resilience (HR), flexible viscoelastic (VE) and semi-rigid (SR) foams as a function of the overall foam density. Foam samples were prepared in the form of cubes by mixing appropriate polyol and isocyanate compounds produced by Huntsman International India Pvt. Ltd. in varying proportions leading to a range of densities for each type of foam. The cubical samples were tested under compressive load in a standard UTM. Based on the measured load—displacement behaviors, variations of peak load and energy-absorption attributes with respect to density are plotted for each type of foam and the possible existence of an optimum foam density is shown.
Density is an important parameter that influences the properties and performances of rigid polyurethane foam. In this study, a systematic engineering approach is presented for determining the effect of density on mechanical properties of rigid/crushable PU foam for design applications. To this end, several mechanical performance parameters, that is, mean load and strength, secant modulus, energy absorption efficiency and densification strain are at first identified for the PU foam. Foam samples of different densities are obtained by varying the amount of liquid polyol–isocyanate of a desired mixing ratio in a constant-volume cubical mould and letting the blow and gelation reactions progress to completion. By conducting compression tests on cubic specimens of foam obtained, it is shown that various mechanical parameters of interest increase monotonically with respect to density. An SEM-based study on the effect of density on foam microstructure has also been carried out.
This paper deals with preparation and characterization of cellulose nano fibers (CNF) extracted from the bamboo pulp using TEMPO (2,2,6,6,-Tetramethyl-1-piperidinyloxy) oxidization method. The CNF was used as a binder to prepare biocomposites (particleboards) from bamboo particles.The specimens were fabricated using an industrial oven and further hot pressing. Morphological analysis of bamboo pulp and CNF was carried out using scanning electron microscope (SEM), confirming fiber formation in nanoscale. Dynamic Mechanical Analysis (DMA) of the pure CNF film shows storage modulus of 121.58 GPa. Composite specimens prepared were subjected to tensile and flexural tests to characterize the mechanical properties. The tensile strength was found to be 0.19 MPa for oven-dried (OD) samples and 0.661 MPa for hot-pressed (HP) samples. The modulus of elasticity (MOE) for OD samples was 121.8 and 1065.5 MPa for HP samples, respectively. Modulus of rupture (MOR) was found to be 0.77 and 3.25 MPa, for OD and HP samples, respectively. The present study results show that the CNF extracted from the bamboo pulp can be used as a sole binder in making biocomposites.
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