Curing Adhesives Using Abaqus/Standard

Structural adhesives are widely used in aerospace, automotive, electronics, and life science applications due to their corrosion resistance, lightweight design, and clean bonding characteristics. However, the curing process, where a liquid adhesive transforms into a solid, introduces complex thermal and chemical effects. These effects can generate residual stresses that compromise the strength and durability of bonded assemblies if not properly accounted for. 

In this blog, we explore how Abaqus/Standard can be used to simulate adhesive curing, helping engineers optimize processing conditions and improve long-term bond performance.

Understanding Adhesive Curing and Its Simulation Challenges 

During curing, polymer chains undergo cross-linking reactions that drive the transformation from a viscous liquid to a rubbery solid, and eventually to a glassy solid. This chemical process is accompanied by thermal expansion and shrinkage, which can introduce residual stresses in the bonded joint. 

Accurate simulation is crucial to anticipate and mitigate these stresses, particularly in applications where mechanical performance and dimensional stability are critical. 

To model the adhesive curing process effectively, simulation must account for: 

• The thermal and chemical reactions driving polymerization 

• The viscoelastic behavior of the adhesive as it cures 

• The interaction between heat generation, mechanical deformation, and curing kinetics 

Abaqus Techniques for Simulating Adhesive Curing 

Abaqus/Standard provides several advanced features that enable detailed modeling of adhesive curing: 

• Thermorheologically simple (TRS) material model Captures the time-, temperature-, and cure-dependent viscoelastic response of the adhesive. Data is typically obtained from DMA (Dynamic Mechanical Analysis) testing. 

• Tangent thermal expansion Allows simulation of temperature-dependent expansion and shrinkage during heating and cooling. Crucial for capturing dimensional changes throughout cure and post-cure. 

• Fully coupled temperature-displacement analysis Solves thermal and mechanical fields simultaneously, allowing prediction of deformation and stress induced by curing and exothermic heat generation. 

Time-temperature-cure dependency based on DMA test results

Simulation Example: modeling the Watts test 

The Watts test is a widely used method to validate cure simulation approaches. In this test, a disc-shaped adhesive specimen is sandwiched between two glass plates, with a thin diaphragm on top. As the adhesive cures and shrinks, the upper diaphragm deflects, providing measurable data on internal stress buildup. 

The simulation replicates this process using three main steps: 

• Curing step 

• The system is heated to activate polymerization. 

• The exothermic reaction is modeled to simulate temperature rise and heat accumulation. 

• Cooling step 

• After curing, the model is cooled to room temperature. 

• Thermal contraction and viscoelastic relaxation are simulated. 

• Relaxation step 

• The simulation captures stress relaxation as the adhesive approaches its final state. 

Schematic overview of adhesive curing setup

Annotated diagram of the Watts test experimental setup

Material Properties and Boundary Conditions 

• Curing kinetics: Modeled using the Kamal equation, which relates temperature and degree of cure to reaction rate. 

• Viscoelasticity: Defined using DMA data and implemented via the TRS model for time-temperature-cure dependence. 

• Initial temperature: Set to 22 °C, with thermal loads applied to simulate heating/cooling. 

• Boundary conditions: Symmetry conditions are used. Proper mechanical interactions between layers ensure realistic deformation behavior. 

Results and Validation 

Simulation outputs include: 

• Conversion history 

• Degree of cure over time, confirming reaction progression 

• Temperature and cure profile 

• Shows thermal response and peak exothermic effects during curing 

• Deflection of the diaphragm 

• Final deformation matches experimental measurements and validates accuracy 

The simulation successfully captures key phenomena like cross-linking, heat generation, shrinkage, and relaxation. The final deflection of the diaphragm is consistent with test results from the Abaqus Example Problems Manual and 3M-sourced data, supporting the reliability of this modeling approach. 

Conclusion: Enabling Reliable Adhesive Bonding Through Simulation 

Modeling the curing process of adhesives with Abaqus/Standard gives engineers the insight needed to optimize process conditions, reduce physical prototyping, and avoid premature bond failures. By combining advanced material models, curing kinetics, and thermal-mechanical coupling, simulation becomes a powerful tool for predicting performance and designing robust adhesive joints in demanding applications. 

Interested in Simulating Adhesive Curing in Your Products?

Fill in our contact form or email us at sales@4realsim.com to discover how 4RealSim can help you integrate curing analysis with Abaqus and optimize your simulation process.