This book provides readers with an elementary understanding of the material behavior of structural silicones in façades. Based on extensive experimental investigations on a transparent structural silicone adhesive (TSSA), the material behavior, failure, and microscopic effects such as stress whitening, cavitation failure, and the Mullins effect are analyzed. In turn, novel hyperelastic material models are developed to account for nonlinear material behavior under arbitrary deformations. The development of a volumetric hyperelastic model makes it possible for the first time to approximate the structural behavior of TSSA under constrained tensile load and cavitation. The material models discussed here were implemented in a finite element code for validation, and their quality was confirmed by three-dimensional numerical simulations, in which an additional stretch-based failure criterion was evaluated for failure prediction. The numerical studies are in good agreement with the experimental results.
Author(s): Michael Drass
Publisher: Springer Vieweg
Year: 2020
Language: English
Pages: 311
Acknowledgement
Abstract
Zusammenfassung
Résumé
Contents
Glossaries
Abbreviations
Symbols
1 Introduction
1.1 Motivation and Problem Statement
1.2 Objectives and Limitations
1.3 Concept and Structure
1.4 Author’s Publications Prior to this Thesis
2 Theoretical Principles on Mechanics
2.1 Aspects on Continuum Mechanics
2.1.1 Continua, Material Bodies and Motion of Continuous Bodies
2.1.2 Deformations and Strain Measures
2.1.3 Stress Measures
2.1.4 Balance Principles in Continuum Mechanics
2.2 Failure Criteria and Limit State Analyses
2.2.1 Basics of Failure Criteria
2.2.2 Visualization Methods
2.2.3 Convexity Constraints
2.3 Micromechanics and Homogenization
2.3.1 Concept of Representative Volume Elements
2.3.2 Micromechanical Homogenization
2.3.3 Approximate Solutions and Bounds in Micromechanics
3 Elastomers and their Mechanical Behaviour
3.1 Classification of Polymers
3.1.1 General Polymer Structures and Properties
3.1.2 Mechanical Behaviour and Emergent Effects of Rubbers
3.2 Hyperelastic Material Modelling
3.2.1 Incompressible Hyperelasticity
3.2.2 Compressible Hyperelasticity
3.2.3 Remarks on Volumetric-Isochoric Split
3.2.4 Isochoric Hyperelastic Constitutive Models
3.2.5 Volumetric Hyperelastic Constitutive Models
3.3 Hyperelasticity for Porous Continua
3.4 Concept of Pseudo-Elasticity
4 Experiments on Transparent Structural Silicone Adhesive
4.1 Transparent Structural Silicone Adhesive - TSSA
4.2 Homogeneous Experimental Tests
4.2.1 Uniaxial Tension
4.2.2 Cyclic Uniaxial Tension
4.2.3 Uniaxial Compression
4.2.4 Biaxial Tension
4.2.5 Shear-Pancake
4.3 Inhomogeneous Experimental Tests
4.3.1 Pancake Tension Tension
4.3.2 Cyclic Pancake Tension Test
4.4 Micro-Structure Analyses
4.4.1 Studies on Porosity
4.4.2 Stress Whitening Effect
4.5 Conclusions
5 Development of Constitutive Models for Poro-Hyperelastic Materials
5.1 Isochoric Helmholtz Free Energy Function
5.1.1 Classification of Isochoric Hyperelastic Material Model
5.1.2 New Isochoric Hyperelastic Material Model
5.1.3 Proof of Polyconvexity
5.1.4 Proof of Convexity vs. Drucker’s Stability Postulate
5.1.5 Reconciling Phenomenological and Molecular-Statistical Theory
5.2 Novel Volumetric Helmholtz Free Energy Function
5.2.1 Single and Multi-Voided Representative Volume Elements
5.2.2 Homogenization Concepts at Finite Strains
5.2.3 RVE vs. EHM - Numerical Homogenization
5.2.4 Bounds in Micro-Mechanics
5.2.5 Remarks on Volumetric Helmholtz Free Energy Functions
5.3 Pseudo-Elastic Cavitation Model
5.3.1 General Concept
5.3.2 Isoperimetric Inequality
5.3.3 Equivalent Void Growth Measure
5.3.4 Constitutive Modelling and Algorithmic Settings
5.3.5 Parameter Studies of Isoperimetric Extension of Volumetric Helmholtz Free Energy Function
5.4 Extension of Pseudo-Elastic Cavitation Model for Cyclic Loading
5.4.1 Motivation
5.4.2 General Concept
5.4.3 Isochoric Mullins Damage under Cyclic Loading
5.4.4 Volumetric Damage and Healing under Cyclic Loading
5.4.5 Parameter Studies on Cyclic Pseudo-Elastic Cavitation Model
5.5 Numerical Validation of Constitutive Models
5.5.1 Approximation of Different Hyperelastic Materials
5.5.2 Simulation of ETAG H-shaped Test Sample
5.5.3 Simulation of Dumbbell-Shaped Tensile Test
5.5.4 Simulation of Bulge-Test
5.5.5 Simulation of Pancake Tension Tests
5.5.6 Simulation of Cyclic Uniaxial and Constrained Tensile Test
5.6 Conclusions
6 Development of Failure Criteria for Poro-Hyperelastic Materials
6.1 Isochoric Failure Criteria
6.2 Classical Cavitation Criteria
6.2.1 Gent & Lindley Criterion
6.2.2 Hou & Abeyaratne Criterion
6.2.3 Lopez-Pamies et al. Criterion
6.3 Generalized Cavitation Criterion
6.3.1 Extended Podgórski Criterion Accounting for Cavitation
6.3.2 Parameter Studies on Extended Podgórski Criterion
6.3.3 Virtual Data For Cavitation Failure at Finite Porosity
6.3.4 Approximation of Cavitation Failure in Stress Space
6.3.5 Approximation of Cavitation Failure in Stretch Space
6.4 Coupled Distortional-Dilatational Failure Criterion
6.4.1 Concept of Coupled Distortional-Dilatational Failure Criterion
6.4.2 Coupled Failure Surface in Section Planes
6.4.3 Novel Failure Criterion for DOWSIL™ TSSA
6.5 Numerical Validation of Failure Criteria
6.5.1 Limit State Analysis - Uniaxial Tensile Test
6.5.2 Limit State Analysis - Bulge Test
6.5.3 Limit State Analysis - Pancake Tension Test
6.6 Conclusions
7 Design Methods for Structural Silicone Adhesives
7.1 Normative Concepts on Structural Sealant Glazing Systems
7.1.1 ETAG 002 Concept
7.1.2 DIBt Concept
7.2 Logical Experimental Testing Program
7.3 Material Parameter Identification
7.4 Modelling of Silicone Adhesive Joints
7.4.1 Classification of Adhesive Joints
7.4.2 Classification of Material Models
7.5 Safety Concept and Limit State Analyses
7.6 Conclusions
8 Conclusion and Outlook
8.1 Conclusions
8.2 Future Research
Bibliography
Own Publications
Standards
Bibliography
Appendix A Triaxiality in 3D Stress Space
A.1 Numerical Examples of Modified Triaxiality
A.2 Numerical Examples
Appendix B Pancake Tension Test under Temperature
Appendix C Porosity of TSSA
Appendix D Engineering Approach Determining Experimental Testing Speed
Appendix E Molecular-Statistical Approaches
E.1 Gaussian Statistics
E.2 Non-Gaussian Statistics (Langevin Approach)
E.3 Relaxed Langevin Approach
E.4 Tube Statistics
Appendix F User-Defined Material Models in ANSYS FE-Code
