# Numerical Simulations: Using Material Models for Adhesively-Bonded Structures

Engineers now use simulations of adhesively bonded joints as a common design tool. Robust numerical simulation of adhesively bonded structures requires detailed Material Models based on solid experimental data. These models should take into account the temperature dependence of the adhesive material.

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Huntsman offers Material Models that provide key experimental data for the entire ARALDITE® adhesive line. This aims to assist engineers in developing a robust simulation of adhesive joints.

Reliable assessment of joint deformation and strength under thermo-mechanical loading is a significant challenge in designing adhesively bonded structures.

Evaluations must consider the combined effect of design parameters such as joint configuration and bond line thickness and the adhesive material’s varying properties over time and under different operating conditions.

Reliability analysis of adhesively bonded assemblies often requires using complex numerical computational methods such as finite element analysis (FEA).

## Tensile Properties

Tensile tests determine how much force is required to break an adhesive specimen and how far the specimen stretches or elongates up to the breaking point. Tensile testing determines the material’s strength, modulus, and elongation across various temperatures.

## Poisson’s Ratio

Poisson's ratio describes the correlation between how far a material is stretched and how thin it becomes during the stretching process. Poisson’s ratio is a commonly used structural design tool that allows engineers to predict the dimensional changes of a given material under load.

## Fracture Toughness

The possibility of crack growth leading to joint failure, either within or at the adhesive-adherend interface, is an essential factor when designing adhesively bonded structures.

Fracture toughness testing involves simulating a minor flaw in a standardized material specimen (via a pre-crack) and measuring the load required to propagate the crack.

## Lap Shear Strength

Lap shear strength is a measurement of how much shear force can be applied to a lap joint before failure occurs. It is an important feature of any adhesive because it serves as an indicator of bond strength and durability in use.

## Peel Strength

Peel strength measures the amount of force required to separate two flexible adherends after bonding. A T-peel test determines an adhesive’s peel strength by measuring the peeling force of a T-shaped bonded assembly made up of two flexible adherends.

## Thermal Expansion

Linear Thermal Expansion is used to calculate the rate at which a material expands as a function of temperature. This test can be used for design purposes and to determine whether or not thermal stress will cause failure.

## Glass Transition Temperature

The glass transition temperature is the temperature at which the adhesive undergoes a reversible change as it is heated, characterized by a shift from a rigid glassy state to a flexible elastomeric state. The glass transition temperature (Tg) shows the temperature range at which an adhesive can be used.

## Volumetric Shrinkage

Volumetric shrinkage refers to the shrinkage of polymeric adhesives during the hardening step and is typically stated as a percentage. The amount of shrinkage varies depending on the temperature reached during the adhesive curing process.

## Shore Hardness

Shore hardness assesses the relative hardness of softer materials like adhesives. A durometer evaluates the penetration of a hardened indenter into the adhesive under a given force.

## Cured Density

Density is the degree of compactness of an adhesive, measured in mass per unit of volume. It is often employed to track variations in the physical structure or composition of adhesives.

This information has been sourced, reviewed and adapted from materials provided by Huntsman Advanced Materials.

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