The Criterion of Particle-Induced Cracking of Filled Polymers

Abstract

Failure of high density polyethylene, low density polyethylene, and polypropylene filled with grinded rubber particles was studied. In tension, particles debond from the matrix and initiate appearance of pores. Small particles lead to formation of elliptical pores. In contrast, large particles initiate appearance of diamond cracks leading to fast failure of filled polymer. In the intermediate case elliptical pore gradually transforms into diamond crack. The diamond crack appears when the elongation of an elliptical pore reaches the critical crack tip opening of the unfilled polymer. The size D of filler particles should be lower thanG Ic is the fracture toughness,  d -the draw stress and  d -the natural draw ratio of the matrix in the neck.Ductile or brittle behavior of filled polymer depends on whether the polymer yields uniformly or with necking. If the neck does not appear, filler particles usually do not initiate brittle fracture. In contrast, filled polymers, yielding with necking, often are brittle.