Numerical Simulation of Mechanical Properties of Nano Particle Modified Polyamide 6 via RVE Modeling

Abstract

In this paper the mechanical behavior of a Polyamide 6 (PA 6)/Montmorillonit (MMT)-nanocomposite is examined by a selected structure modification within a numerical parameter study. Experimental data of tensile tests of three different volume fractions at ambient temperature are used as reference. These were compared to homogenized stress-strain curves calculated with 3D representative volume elements (RVE) under periodic boundary conditions. Thereby the curve areas are considered until the tensile yield strength is reached. Besides the influence of filler orientation, exfoliation and its volume fraction, especially the adhesive interface behavior between filler and matrix, and local, partially crystalline interphases around the MMT-plates were taken into account. The interface behavior was described using a cohesive zone model whereby the implemented values where derived from a Molecular Dynamics (MD) simulation. The local, partially crystalline interphases around the MMT plates were modeled with a thickness of 30 - 40 nm. These areas were assumed to be transversely isotropic both in the elastic and in the plastic regime, whereby the transverse plane is defined by the lateral particle surface. A good approximation of the experimental curves was achieved only after the introduction of those interphases. In the elastic regime an excellent agreement is found between experimental and numerical values. In the plastic regime especially the largest MMT volume fraction investigated, matches perfectly with the experimental reference, whereby lower filler contents slightly underestimate the mechanical values.