Applied Engineering Letters

111-119

Authors: V. Lazić, D. Arsić, M. Mutavdžić, R. R. Nikolić, B. Hadzima

This paper presents an analysis and the test results of certain physical properties of the rock materials excavated from quarries in Serbia. The four rock aggregates, considered in this analysis, are used for building the driveway constructions' layers on roads, streets, airports and base layers on railways. To that purpose, both the general and specific technical properties (petrographic, physical, mechanical and technological) of those rocks must be known to users. The four rocks, whose physical properties are analyzed, are the most important types of the building stones: limestone, dolomite marble, calcite-dolomite marble and andesite. Their physical properties tested included volumetric mass, specific mass (density), porosity and water absorption. The service life, reparation jobs and maintenance procedures of the construction machinery parts, which come into direct contact with building materials like rocks and stones, strongly depend on those stones' properties. The four tested rock materials belong into a group of the massive rocks with various porosities and tendency to absorb water.

126-134

Authors: H. U. Zaman, R. A. Khan

Unidirectional composites of polypropylene (PP), reinforced with abaca fiber was fabricated by compression molding with and without the presence of stearic acid (SA) as a coupling agent. Raw abaca fiber was utilized and four levels of filler loading (10, 20, 30 and 40 wt%) were used during composite manufacturing. Mechanical tests (tensile, bending and impact properties) of the resultant composites were conducted. Based on fiber loading, 30% fiber-reinforced composites had the optimum set of mechanical properties. Optimized abaca fiber was chemically treated with SA to increase its compatibility with the polymer matrix. SA treated abaca fiber-reinforced composites yielded better mechanical properties compared to the raw composites. In order to know more about the fibermatrix adhesion, scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between abaca and PP matrix upon treatment with SA. Water uptake and simulating weathering test of the composites were also investigated.

142-151

Authors: F. Synák, J. Synák

The article focuses on determining the impact of using different types of gasoline on selected vehicle properties. To perform the measurements, there were six types of gasoline chosen from different gas stations and they differed in price, octane rating, and in an amount of additives and biocomponents. The immediate effect of petrol on engine performance and torque, exhaust gas composition and fuel purchase costs was examined. The results have shown a relatively low impact of gasoline on a vehicle’s dynamic properties. The most visible change was measured when comparing the most expensive fuel to the cheapest one. There was an increase in the engine torque from 156 Nm to 160 Nm measured. Such a difference is lower than the deviation of measuring. The differences measured in the composition of the exhaust gases are low. However, there is a significant impact in choice of gasoline on the costs of fuel purchase.