In particle reinforced and short-fiber reinforced composites, fracture of the reinforcement is a significant damage mode because the reinforcements lose load carrying capacity. The composite undergoing damage process contains intact and broken reinforcements in a matrix. To describe the load carrying capacity of the cracked reinforcement, the average stress of a cracked ellipsoidal inhomogeneity in infinite body which was proposed in the previous paper is introduced. An incremental constitutive relation of particle or short-fiber reinforced composites including the progressive damage of the reinforcements have been developed based on the Eshelby’s equivalent inclusion method and Mori and Tanaka's mean field concept. Influence of the cracking damage on the stress-strain response of the composites is demonstrated.

Analysis for Properties of Discontinuously-Reinforced Composites on the Basis of Micromechanics

In this paper, tensile tests are carried out on seven kinds of glass particle reinforced nylon 66 composites in which a particle volume fraction is varied in 0%, 10%, 20% and 30%, and glass particles treated or untreated with silan-coupling are used. The stress-strain response of the composites depends on both the particle volume fraction and the treatment of interface between the particles and matrix. Young's modulus and Poisson's ratio are characterized by only the particle volume fraction, while tensile strength is described as a function of the particle volume fraction and interface treatment. With increasing particle volume fraction, the tensile strength increases first and then becomes constant in the interface-treated composites, and decreases in the interface-untreated conventional composites. Numerical analysis is also carried out on stress-strain response and damage behavior of the seven kinds of composites. The stress-strain relations of the interface treated composites are explained only by influence of particle volume fraction while those of the conventional composites are characterized by considering the particle volume fraction and interfacial debonding between the particles and matrix.

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K. Mochizuki

Papers

Application Of Incremental Damage Theory ToGlass Particle Reinforced Nylon 66 Composites