Numerical investigation of fracture behaviour of polyurethane adhesives under the influence of moisture

TL;DR

This paper develops a finite-strain viscoelastic and phase-field coupled model to study how moisture affects the fracture behavior of polyurethane adhesives, validated by experiments on aged samples.

Contribution

It introduces a novel coupled finite-strain viscoelastic and phase-field model specifically for moisture-influenced fracture analysis of polyurethane adhesives.

Findings

Moisture degrades tear strength of polyurethane adhesives.

The phase-field model accurately predicts fracture behavior under different humid conditions.

Experimental data helps calibrate the numerical model.

Abstract

Polyurethane adhesives are extensively used in manufacturing of the lightweight components. These adhesives are hygroscopic in nature causing the material to degrade their mechanical properties due to ageing under environmental conditions. Polyurethane adhesive shows non-linear rate-dependent behaviour due to viscoelastic properties and assumes nearly incompressible deformation. Finite-strain viscoelastic model is formulated based on the continuum rheological model by combining spring and Maxwell elements in parallel. Nearly incompressible property is considered by decomposing the mechanical free energy into volumetric and isochoric parts. This work focuses on the investigation of the influence of moisture on the fracture behaviour. Phase-field damage model proved to be an efficient method to investigate the fracture behaviour. Therefore, the finite-strain viscoelastic material model is coupled with the phase-field model to investigate fracture behaviour. Material is assumed to be isotropic, therefore the total mechanical energy is considered for bulk degradation. Experiments are conducted on the samples aged for different humid conditions to understand tear strength. These test results are used to identify the phase-field damage material parameters from numerical investigation.