Analyzing the behavior of the fiber-reinforced polymer PVDF with a numerical framework
Tom Lenders defended his PhD thesis at the Department of Mechanical Engineering on February 4th.
To ensure a safe and reliable application of carbon fiber-reinforced PVDF, it鈥檚 important to gain more knowledge about the behavior of the material in different conditions by performing experiments. Tests with this carbon fiber-reinforced composite revealed brittle failure, particularly when the carbon fiber-reinforced PVDF is under tension. Microscopy analysis showed an uneven distribution of carbon fibers and poor adhesion between carbon fibers and the PVDF matrix. This contributed to the brittle failure of the material. To also capture the behavior of the composite at microscale, numerical tools are needed. In his PhD research Tom Lenders provides a framework to describe and predict the rate- and temperature-dependent behavior of carbon fiber-reinforced PVDF.
A 3D numerical model
The rate- and temperature-dependence of the composite鈥檚 mechanical response is dominated by the intrinsic behavior of the PVDF matrix. Because of that, part of this PhD research focuses on describing and predicting the response of pure PVDF with a detailed material model. This model is validated with experimental data. With this information, Tom Lenders developed a 3D numerical model to describe the behavior of carbon-fiber reinforced PVDF. The geometry of this model is defined from microscopic scans of the composite. An efficient algorithm is used to apply deformations to the 3D model, mimicking the deformations applied during the experiments. The developed model can accurately describe the macroscale behavior of the composite, while at the same time providing valuable insights into the microscale deformations.
Efficient and accurate analysis
Creating a detailed model like this is challenging, as the simulations are prone to instabilities due to the complexity of the material鈥檚 behavior. To address this problem, an innovative solver was enhanced to handle time-dependent calculations and capture intricate failure processes. This solver proved to be highly effective in analyzing the composite鈥檚 damage behavior. The poor adhesion between the carbon fibers and the PVDF matrix was also included in the model with a fiber/matrix cohesive zone interface.
The developed numerical framework makes it possible to analyze the mechanical behavior of the composite material efficiently and accurately. For example, the results of this model underscore the importance of improving the fiber/matrix bond to increase the composite鈥檚 strength and reliability. These insights can be used to enhance the design process of fiber-reinforced polymers and speed up the transition from conventional engineering materials towards fiber-reinforced composites.
Title of PhD thesis: . Promotor: Dr. Joris Remmers and Prof. Marc Geers. Co-promotor: Prof. Leon Govaert.