Wyniki wyszukiwania - BazTech

1

Effect of particle shape and imperfect filler-matrix interface on effective thermal conductivity of epoxy-aluminum composite

Pietrak K., Kubiś M., Langowski M., Kropielnicki M., Wultański P.

Composites Theory and Practice

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2017

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R. 17, nr 4

183--188

EN

The predictions of major effective medium models and 2-dimensional numerical models implemented in Ansys Fluent were tested against the results of experimental measurements of macroscopic thermal conductivity for a polymer filled with aluminum powder. The examined composite may be regarded as a representative of materials used for heat management purposes, for example for the manufacture of electronic device housings. The study demonstrates the effect of particle shape and imperfect filler-matrix interface on the theoretical value of thermal conductivity of the considered material. It also creates the opportunity to discuss the versatility and accuracy of various methods devised to predict the effective thermal conductivity of heterogeneous materials. It was found that the effective medium approximation proposed by Duan et al., which considers the effect of the particle aspect ratio, outrivaled other predictive schemes in accuracy and cost-effectiveness. Effective medium approximations that assume spherically-shaped reinforcement as well as finite volume models implemented in Ansys Fluent, greatly underestimated the parameter in question.

PL

Przewidywania popularnych, analitycznych modeli predykcyjnych efektywnej przewodności cieplnej kompozytów cząsteczkowych zostały porównane z danymi eksperymentalnymi uzyskanymi dla kompozytów polimerowych napełnionych proszkiem aluminiowym oraz z wynikami obliczeń numerycznych wykonanych metodą objętości skończonych w programie Ansys Fluent. Testowany materiał reprezentuje grupę materiałów stosowanych w technice cieplnej, np. do wytwarzania obudów urządzeń elektronicznych. Wyniki badania pokazują efekt kształtu wtrąceń oraz niedoskonałego kontaktu termicznego na granicy zbrojenie-osnowa na teoretyczną wartość efektywnej przewodności cieplnej rozważanego materiału. Są też podstawą do dyskusji na temat wad i zalet stosowania analitycznych metod przewidywania przewodności cieplnej materiałów kompozytowych (tzw. effective medium models). Najlepszą zgodność z eksperymentem otrzymano za pomocą jednego z modeli analitycznych (Duan i in.), który uwzględnia wydłużony kształt cząsteczek napełniacza. Przewidywania modeli analitycznych zakładających sferyczny kształt cząsteczek okazały się silnie zaniżone, podobnie jak przewidywania dwuwymiarowych modeli numerycznych zaimplementowanych w środowisku Ansys Fluent.

2

A review of models for effective thermal conductivity of composite materials

Pietrak K., Wiśniewski T.

Journal of Power Technologies

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2015

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Vol. 95, nr 1

14--24

EN

The solutions of Maxwell and Rayleigh were the first of many attempts to determine the effective thermal conductivity of heterogeneous material. Early models assumed that no thermal resistance exists between the phases in heterogeneous material. Later studies on solid-liquid and solid-solid boundaries revealed that a temperature drop occurs when heat flows through a boundary between two phases and, as a consequence, the interfacial thermal resistance should be included in the heat transfer model. This paper is a review of the most popular expressions for predicting the effective thermal conductivity of composite materials using the properties and volume fractions of constituent phases. Subject to review were empirical, analytical and numerical models, among others.

3

Methods for experimental determination of solid-solid interfacial thermal resistance with application to composite materials

Pietrak K., Wiśniewski T. S.

Journal of Power Technologies

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2014

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Vol. 94, nr 4

270--285

EN

Interfacial thermal resistance (ITR) exists between filler and matrix in any composite material and has a significant influence on its effective thermal conductivity. To predict the effective thermal conductivity of composite material, the conductivities of each component as well as the ITR must be known. Theoretical models, like the acoustic mismatch model (AMM), allow for accurate ITR determination only for an idealized case of perfect contact (no interfacial gaps and good bonding). The interfacial bonding in typical composites for thermal conduction, like diamond-reinforced metal matrix composites (MMCs) is usually highly imperfect and the ITR, in composites of the same type, depends highly on the individual manufacturing conditions. Therefore, a great need exists for reliable experimental ITR measurement techniques. In this paper, the main difficulties regarding experimental ITR measurements are discussed. A review of measurement techniques is presented, with the main focus put on the principle of each technique and its appropriateness for the purpose of composite materials. The strengths and weaknesses of each technique are discussed.