COMPOSITES and NANOSTRUCTURES VOL 8 # 3 2016

 

CONTENTS

 

S.V.Dubinskiy, F.S.Sevastyanov, A.A.Safonov, S.G.Abaimov, N.V.Rozin, B.N.Fedulov

EVALUATION OF MECHANICAL PROPERTIES IN VACUUM INFUSED STRUCTURES WITH MICRO

AND MACRO VOIDS ……………………………………………………………………………………………151

The scatter in mechanical properties caused by uncertainties in raw materials and process induced defects appeared to be one of the most important issues on the way of cost- and weight effective composites production for primary large scale structures especially using liquid molding processes (RTM, vacuum infusion, e.t.c.).

In current paper the method to evaluate the effective mechanical properties of vacuum infused structure with micro/macro voidswas proposed. The method is based on Darcy law for resin flow in porous media, empirical relationship between flow rate and void formation and Chamis micromechanical theory. The proposed approach was verified experimentally and may be applied for 2-D and 3-D structures of any complex geometry (p. 151-159; fig. 5).

 

A.P.Guskov

THE DECOMPOSITION OF THE SOLUTION DURING THE FORMATION OF EUTECTIC COMPOSITES……. 160

Hunt and Jackson’s (HJ) theory formation of eutectic composites (EC) is currently the most popular. This theory explains the formation of the EC in the framework of equilibrium thermodynamics and it sets initially periodic alternation of eutectic phase solid solution, which is not explained. In contrast to the HD’s theory the present work shows that the solution can get into an unstable state during the phase transition. The boundary of such state is built here. This work show that the interaction of the interface instability, unstable solution a nd the kinetic of attachment of particles to the growing solid phase leads to the formation of the periodic structure of EC (p. 160-173; fig. 3).

 

A.S. Chainikova, D.V. Grashchenkov, M.L. Vaganova, S.Y. Modin

APPLICATION OF SPARK PLASMA SINTERING FOR SYNTHESIS OF COMPOSITE MATERIALS BASED ON ALUMINOSILICATE GLASS-CERAMICS REINFORCED

WITH SILICON NITRIDE…………………………………………………………………………………………… 174

Glass-ceramic composite materials based on Sr-anorthite glass-ceramics reinforced with α-Si₃N₄ and β- Si₃N₄ particles were synthesized using the sol-gel method and spark plasma sintering (SPS). It was shown that composites with density close to theoretical can be synthesized by

SPS at temperatures lower than by traditional sintering and hot pressing of these materials at 350 - 400 °C. An effect of prior co-milling of the component mixtures on the synthesis and structure of the composites was studied. It is found that co-milling has no influence on the sintering temperature, phase composition and mechanical properties of the materials, but it improves the distribution of the components in the materials, that contributes to an increase in their oxidation resistance, if SPS method is used. (p. 174-186; fig. 6).

 

G.P. Egorov, A.A. Volkov

THE CRITICAL STRESS MEASUREMENT IN THIN FILMS ………………………………………………187

Measurement of intrinsic stresses in thin films is a challenging issue due to to negative effects (cracking, delamination) that appear when critical values are attained. Experimental method based on the capacitance gauge device usage was employed to evaluate (measure) critical stresses. The device allows to indicate the failure point directly during the deposition process. Proposed experimental method involves two subsequent steps. It was demonstrated that selected parameters of the measuring steps enable to investigate stress generation kinetics with high sensitivity and relatively small stress error of about £~5%. The usage domain of proposed experimental method was obtained: substrate/ film thickness ratio should be greater than 150, the maximum deflection should be less than 4 mm. For the first time, critical stress and deformations values corresponding to the thin film delamination were obtained for thin films of Al, Ti, Cu and Ta sputtered on copper substrate and for Ta thin films sputtered on silica-based substrate. Proposed experimental method can be used for critical stress measurement in thin films produced not only by vacuum ion deposition, but with other thin film formation methods. Finally, recommendations for the measurement of intrinsic stresses in thin films can be derived based on the obtained results in various process flow stages (p. 187-203; fig. 13).

 

M.Golubev

EVALUATION OF EFFECTIVE ELASTIC CONSTANTS IN UNIDIRECTIONAL THREE-COMPONENT

COMPOSITE MATERIA………………………………………………………………………………………. 204

The problem of micromechanics is considered in application to unidirectional three-component composite material consisting of carbon fibers and two types of polymeric matrix – thermoset and thermoplastic. The first-order material model allowing for fiber and matrices volume fractions only and ignoring actual geometry of material microstructure is applied. As a result, elastic constants of the three-component composite material are determined as function of the component volume fractions and the problem of rational relationship between the fractions of thermoset and thermoplastic matrices is studied (p. 204-210; fig. 4).

 

Ó 11<1TT PAH «Композиты и Наноструктуры». 2016