Tag Archives: porosity

1050–1056 V. Křepčík, J. Lev and F. Kumhála
Development and testing of apparatus for wooden chips voids measurement
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Development and testing of apparatus for wooden chips voids measurement

V. Křepčík¹*, J. Lev² and F. Kumhála¹

¹ Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Agricultural Machines, Kamýcká 129, CZ165 00 Praha 6 – Suchdol, Czech Republic
² Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Physics, Kamýcká 129, CZ165 00 Praha 6 - Suchdol, Czech Republic
*Correspondence: krepcik@tf.czu.cz

Abstract:

The interparticle porosity of wooden chips (commonly called voids) is a very important factor which significantly affects properties of wooden chips, i.e. bulk density, combustion speed or dielectric properties. Dielectric properties can be used for the measurement of its moisture content and it is the moisture content which is one of the most important factors that affect wooden chips calorific value. This paper is focusing on the development of measuring apparatus for wooden chips voids measurement. The principle of measuring apparatus is based on a gas displacement method. Measuring apparatus is composed from two chambers; both with the same volume. One from chambers is comparative one and second is experimental one. The pressure operating range was from 1,000 to 1,500 Pa. Results showed nontrivial behaviour of wooden material with the change of moisture content which was probably caused by different structures of tested materials.

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1116–1122 P. Valášek
Study on impact strength of sisal fibers reinforced epoxy composites using experimental methods
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Study on impact strength of sisal fibers reinforced epoxy composites using experimental methods

P. Valášek

Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ 165 21 Prague; e-mail: valasekp@tf.czu.cz

Abstract:

 Among the advantages of composite materials is their ability to exploit the properties of partial phases that creates the composite. Common materials used as matrix materials include polymeric composites. The properties of these matrices can be optimized by using synthetic or also natural fibers. Natural fibers are inexpensive, ranks among renewable resources and when respecting their biological nature, they can replace synthetic fibers in many applications. This paper describes the impact strength of epoxy resins filled with unordered short sisal fibers with a length of 2–6 mm. From the experimental results it is evident that the presence of fibers of sisal examined as epoxy resins, increases the impact strength, up to 143%. SEM (scanning electron microscopy) was used to assess the failure of mechanism of these composites.

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