Hygrothermal Degradation in Fiber Reinforced Composites | Abaqus Parallel Simulation with Python Scripts and Fortran Subroutines

Introduction | Parallel Finite Element Analysis with Abaqus

When we face a problem that requires two simultaneous finite element analysis, Abaqus is one of the best and most accurate software available in this field. For this purpose, it is necessary to use coding in different environments of the Abaqus software, i.e. python scripting in the noGUI environment and Fortran coding in the subroutine environment. In the present Abaqus tutorial for parallel finite element analysis, we have presented the software skills that a person needs when he wants to perform a parallel finite element analysis such as a micro-macro scale analysis. The Abaqus tutorial for parallel finite element analysis covers all you need to write a python scripting code for noGUI environment and also Fortran code for the UMAT subroutine environment of Abaqus to execute a parallel finite element analysis via the Abaqus software.

In this tutorial, we investigate the hygrothermal degradation of elastic properties in fiber-reinforced composites using parallel finite element analysis. In the present Abaqus tutorial for parallel finite element analysis we have presented two algorithms of the ABAQUS python scripting micro modeling (APSMM) and the ABAQUS parallel finite element analysis (APFEA), which are very worthy for analyzing complex problems.

Hygrothermal Degradation in Fiber Reinforced Composites

Aerospace, marine, automotive, and civil engineering industries widely use fiber-reinforced composites (FRCs) because of their high strength-to-weight ratio and adaptability. These composites often operate in environments with varying moisture and temperature, such as marine and aerospace applications. Over time, exposure to such conditions can lead to significant changes in their mechanical properties. Therefore, hygrothermal analysis is essential to ensure the performance and longevity of these materials. From aircraft components to wind turbine blades and automotive structures, understanding how composites degrade under these conditions is key to enhancing durability and preventing premature failure.

Hygrothermal degradation refers to the deterioration of a material’s elastic properties when exposed to combined moisture and temperature variations over time. FRCs, particularly those with polymeric matrices, are susceptible to this degradation, which can significantly alter their mechanical behavior. Moisture absorption leads to swelling and softening of the matrix, reducing stiffness and strength, while temperature changes can affect the glass transition temperature of the polymer, causing further mechanical property loss.

Importance of Analyzing Hygrothermal Degradation

Analyzing hygrothermal degradation is crucial to predict how FRCs will perform under real-world conditions. Industries often use these composites in environments where long-term exposure to humidity and temperature can cause premature failure. For example, in marine environments, the continuous exposure to water and varying temperatures can significantly weaken the structure, while in aerospace, failure of composite parts due to environmental degradation can lead to catastrophic consequences. Therefore, accurately predicting the extent of degradation helps in designing materials with higher durability and ensuring safety.

Predicting Hygrothermal Degradation: Numerical vs. Experimental Methods

You can predict hygrothermal degradation using two primary approaches: experimental testing and numerical analysis.

Experimental Methods

This approach involves physically testing composite samples under controlled environmental conditions. While experimental methods provide accurate and real-time data, they are time-consuming, expensive, and often impractical for complex or large structures.

Numerical Methods

Numerical simulations, such as Finite Element Analysis (FEA), offer a cost-effective and efficient alternative to experimental testing. These methods use mathematical models to predict how materials will behave under different environmental conditions, reducing the need for extensive physical testing. They also allow for the simulation of various scenarios that might not be easily replicated in a laboratory.

Concluding Remarks

Numerical methods have gained popularity due to their ability to model complex geometries and environmental conditions. However, they still require validation against experimental data to ensure accuracy.

Using ABAQUS for the Simulation of Hygrothermal Degradation

Engineers widely use ABAQUS, a leading software tool, to conduct finite element analysis (FEA) and simulate the mechanical behavior of materials under various conditions. In the context of hygrothermal degradation, ABAQUS allows for detailed modeling of the composite’s response to moisture and temperature changes. The software can simulate both transient and steady-state conditions, making it an ideal choice for studying time-dependent hygrothermal degradation effects.

Parallel ABAQUS Modeling and Scripting

In the study of hygrothermal degradation, a parallel ABAQUS model was utilized, which leverages ABAQUS’s capability to perform large-scale simulations across multiple processors. This improves computational efficiency, especially when dealing with time-dependent, transient simulations that require extensive iterations.

Additionally, the modeling process employed an ABAQUS Python Scripting Micro Modeling (APSMM) algorithm, which allows for the automatic calculation of degraded elastic constants under various conditions. By integrating APSMM with a custom UMAT subroutine written in FORTRAN, the model accounts for position and time-dependent variations in moisture and temperature. This hybrid approach provides a comprehensive framework for predicting the material’s behavior under a wide range of environmental conditions.

ABAQUS Scripting and Subroutines

We developed custom subroutines to enhance the functionality of ABAQUS in this context. The APSMM algorithm, written in Python, facilitates the modeling of fiber-reinforced composites at the microscale. This algorithm reads input data such as temperature, time, and moisture content, then calculates the corresponding degradation in elastic properties. The UMAT subroutine further extends the model by accounting for the effects of moisture concentration and temperature gradients within the composite.

These subroutines make it possible to simulate complex hygrothermal conditions that may vary both spatially and temporally. So, they give a detailed insight into how different parts of the composite degrade over time.

Key Results that Can be Extracted from the ABAQUS Model

The ABAQUS simulation provided insights into how the elastic properties of the fiber-reinforced composites degrade under specific hygrothermal conditions. Key results that can be extracted include:

• Degradation of Young’s Modulus: As moisture content increases, Young’s modulus decreases, especially at higher temperatures. This is critical for predicting the lifespan of structural components.
• Shear Modulus Variation: The shear modulus is similarly affected by moisture absorption, with a sharp decline observed under elevated temperatures and humidity.
• Time-Dependent Moisture Absorption: The model accurately predicts the time it takes for the material to reach moisture saturation. This allows for a better understanding of the long-term durability of the composite.

Who Benefits from These Models?

The numerical models developed for predicting hygrothermal degradation of fiber-reinforced composites are beneficial to several stakeholders:

• Engineers and Designers: These models help in designing more durable composite materials that can withstand harsh environmental conditions.
• Aerospace and Marine Industries: These sectors heavily rely on FRCs for critical structural components. They can benefit from the predictive power of these models to enhance safety and performance.
• Researchers: The detailed numerical models provide a framework for further research into the degradation of other composite materials. So, they can be adapted to study different environmental effects.
• Manufacturers: By using numerical predictions, manufacturers can optimize their material selection and processing methods to produce composites with enhanced resistance to hygrothermal conditions.

Conclusion: The Value of ABAQUS Modeling for Fiber-Reinforced Composites

ABAQUS provides a robust platform for analyzing the hygrothermal degradation of fiber-reinforced composites. By using both Python scripting and parallel processing, the model offers an efficient and accurate way to predict material behavior under various environmental conditions. This enables engineers, researchers, and manufacturers to design better composites. In other words, they can predict their long-term performance, ultimately leading to safer and more durable structures.