STR-954: FLEXURAL BEHAVIOR OF SANDWICH PANELS MADE OF FRP COMPOSITES: SYNTHETIC AND NATURAL FIBERS

Sandwich panels made of fiber-reinforced polymer (FRP) skins and light-weight core materials have the potential to be effectively used in several structural applications such as cladding, decking, and roofing panels. The FRP skins resist the tensile and compressive stresses resulting from the flexure induced by transverse loadings and the core resists shear stresses, serves as insulation, and separates the FRP skins at a desired distance to provide required moment of inertial. In this study, two types of fiber materials, namely synthetic (glass) and natural (flax) fibers, as well as two types of core materials, namely polypropylene honeycomb (thickness: 6.4, 12.7, and 25.4 mm; density 80 kg/m3) and cork (thickness: 11 and 22 mm; density 200 kg/m3) core materials were used to make sandwich panels. A total of 105 small-scale sandwich beam specimens (50 mm wide × 200 and 350 mm long) were prepared and tested under four-point bending. The load-deflection behavior, strength, stiffness, and failure mode of the specimens were evaluated. Also, an analytical model was adopted to compute the flexural stiffness, shear rigidity, and core shear modulus of the sandwich panels. The analytical results showed a good agreement with the test results. Overall, the natural fiber and core materials showed a promising structural performance compared to their synthetic counterparts

Method for Analytical Representation of the Maximum Inaccuracies of Indirectly Measurable Variable

Let us have an indirectly measurable variable which is a function of directly measurable variables. In this survey we present the introduced by us method for analytical representation of its maximum absolute and relative inaccuracy as functions, respectively, of the maximum absolute and of the relative inaccuracies of the directly measurable variables. Our new approach consists of assuming for fixed variables the statistical mean values of the absolute values of the coefficients of influence, respectively, of the absolute and relative inaccuracies of the directly measurable variables in order to determine the analytical form of the maximum absolute and relative inaccuracies of an indirectly measurable variable. Moreover, we give a method for determining the numerical values of the maximum absolute and relative inaccuracies. We define a sample plane of the ideal perfectly accurate experiment and using it we give a universal numerical characteristic – a dimensionless scale for determining the quality (accuracy) of the experiment

Model of Close Packing for Determination of the Major Characteristics of the Liquid Dispersions Components

We introduce a close packing model of the particles from the disperse phase of a liquid dispersion. With this model, we find the sediment volumes, the emergent, and the bound dispersion medium. We formulate a new approach for determining the equivalent radii of the particles from the sediment and the emergent (different from the Stokes method). We also describe an easy manner to apply algebraic method for determining the average volumetric mass densities of the ultimate sediment and emergent, as well as the free dispersion medium (without using any pycnometers or densitometers). The masses of the different components and the density of the dispersion phase in the investigated liquid dispersion are also determined by means of the established densities. We introduce for the first time a dimensionless scale for numeric characterization and therefore an index for predicting the sedimentation stability of liquid dispersions in case of straight and/or reverse sedimentation. We also find the quantity of the pure substance (without pouring out or drying) in the dispersion phase of the liquid dispersions