K.H. Lo

Bio: K.H. Lo is an academic researcher from Royal Dutch Shell. The author has contributed to research in topics: Transverse isotropy & Composite number. The author has an hindex of 1, co-authored 1 publications receiving 1859 citations.

Solutions for effective shear properties in three phase sphere and cylinder models

Abstract: S olutions are presented for the effective shear modulus of two types of composite material models. The first type is that of a macroscopically isotropic composite medium containing spherical inclusions. The corresponding model employed is that involving three phases: the spherical inclusion, a spherical annulus of matrix material and an outer region of equivalent homogeneous material of unlimited extent. The corresponding two-dimensional, polar model is used to represent a transversely isotropic, fiber reinforced medium. In the latter case only the transverse effective shear modulus is obtained. The relative volumes of the inclusion phase to the matrix annulus phase in the three phase models are taken to be the given volume fractions of the inclusion phases in the composite materials at large. The results are found to differ from those of the well-known Kerner and Hermans formulae for the same models. The latter works are now understood to violate a continuity condition at the matrix to equivalent homogeneous medium interface. The present results are compared extensively with results from other related models. Conditions of linear elasticity are assumed.

A Mechanism-based General Theory for Friction of PTFE/PEEK Composite: Effects of PTFE Morphology and Composite Microstructure

Abstract: A combined experimental and analytical investigation is conducted to develop a mechanism-based general friction theory for PTFE/PEEK composite. The PTFE/PEEK composites with PTFE and PEEK volume contents ranged from 0% to 100% were fabricated; their microstructure features were examined and recorded; and their friction coefficients were determined by sliding friction experiments. From the observed microstructure features of PTFE/PEEK composite with different PTFE and PEEK volume contents and the well-recognized unique “band” morphology and sliding deformation mechanisms of the semi-crystalline PTFE, associated “apparent” sliding friction behavior is ascribed to the PTFE material in accordance with its volume content in the composite. A mechanism-based general friction theory is developed for PTFE/PEEK composite based on the associated “apparent” friction coefficient of the PTFE phase in composite. The general friction theory is validated through the excellent agreement obtained between the analytical predictions of composite friction coefficients and the comprehensive experimental results obtained from the sliding friction tests conducted in-house with a pin-on-disk tribometer, and also from those (obtained with different types of tribo-testers) reported in the literature.

Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites

Abstract: There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate–polymer nanocomposites containing fillers with small aspect ratios are also an important class of polymer composites. However, they have been apparently overlooked. Thus, in this paper, detailed discussions on the effects of particle size, particle/matrix interface adhesion and particle loading on the stiffness, strength and toughness of such particulate–polymer composites are reviewed. To develop high performance particulate composites, it is necessary to have some basic understanding of the stiffening, strengthening and toughening mechanisms of these composites. A critical evaluation of published experimental results in comparison with theoretical models is given.

Analysis of Composite Materials—A Survey

Abstract: The purpose of the present survey is to review the analysis of composite materials from the applied mechanics and engineering science point of view. The subjects under consideration will be analysis of the following properties of various kinds of composite materials: elasticity, thermal expansion, moisture swelling, viscoelasticity, conductivity (which includes, by mathematical analogy, dielectrics, magnetics, and diffusion) static strength, and fatigue failure.

Elastic Solids with Many Cracks and Related Problems

Abstract: Publisher Summary This chapter discusses some basic problems in mechanics of elastic solids containing multiple cracks. A number of mathematical aspects that frequently constitute fields of their own (like various numerical techniques) are discussed very briefly in the chapter. The focus is on physically important effects produced by crack interactions and to present results in the simplest form possible. The problems considered in this chapter can be divided into two groups: (1) The impact of interactions on individual cracks, particularly on the stress intensity factors (SIFs), and (2) the effective elastic properties of solids with many cracks. Problems of the first group are, generally, relevant for the fracture-related considerations; solutions are sensitive to the positions of individual cracks. Problems of the second group deal with the volume average quantities; they are relatively insensitive to the information on individual cracks. The chapter discusses, in this connection, whether correlations exist between these two groups of quantities; in particular, whether microcracking can be reliably monitored by measuring changes in the effective elastic moduli.