Evaluation of micro peel testing to gain rational data for interfacial characterization
Zubair, Junaid (2024)
Zubair, Junaid
2024
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2024-08-26
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202408218231
https://urn.fi/URN:NBN:fi:tuni-202408218231
Tiivistelmä
This thesis focuses on identifying and investigating interfacial properties between single pulp fibre and polylactide acid (PLA) matrix using the micro peel testing data and finite element analysis (FEA). The analysis uses experimental micro peel test force and displacement data as a reference for developing a detailed FEA. Cohesive zone model (CZM) is used to model the pulp fibre-PLA matrix interaction, which is an effective approach based on the traction-separation law. The FEA closely replicates the experimental conditions, including detailed geometry, material specifications, and boundary conditions.
The primary objective of this thesis is to iteratively determine the critical quadratic traction value for the damage onset and the critical fracture energy for the damage propagation. Through iterations of these CZM parameters, force and displacement graphs are achieved which are then compared to experimental data. It was observed that higher critical fracture energies increase the average force required for debonding. Additionally, higher critical traction values increase strength of the pulp fibre-PLA interface hence delaying onset of the damage, which results in a force displacement curve with large fluctuations per debonding. A significant focus of this study is the shape of force and displacement graph, which closely follows the profile of the groove. This groove is replicated accurately from the actual test data. Extensive analyses have identified that the critical fracture energy of 55 J/m² and the critical quadratic traction value of 70 MPa provide a reasonable correlation with experimental results.
To further increase the accuracy of the analysis, plastic material properties are added into the material model of PLA. The results showed that the plastic model resulted in permanent deformation, which in turn delayed debonding. Moreover, varying mode I and mode II damage parameters significantly influenced the force and displacement graph, indicating the mixed mode nature of the fracture process.
These iterative adjustments explain the sensitivity of the interfacial properties, highlighting their important role in the debonding process. The findings suggest that optimizing CZM parameters is crucial for accurately predicting the behaviour of composites under loading. Furthermore, these results show the importance of using CZM in FEA for accurately predicting interfacial behaviour of the fibre-matrix interface. The iterative approach to adjust the critical quadratic traction values and the critical fracture energy may result in enhancing predictive accuracy of the model.
The primary objective of this thesis is to iteratively determine the critical quadratic traction value for the damage onset and the critical fracture energy for the damage propagation. Through iterations of these CZM parameters, force and displacement graphs are achieved which are then compared to experimental data. It was observed that higher critical fracture energies increase the average force required for debonding. Additionally, higher critical traction values increase strength of the pulp fibre-PLA interface hence delaying onset of the damage, which results in a force displacement curve with large fluctuations per debonding. A significant focus of this study is the shape of force and displacement graph, which closely follows the profile of the groove. This groove is replicated accurately from the actual test data. Extensive analyses have identified that the critical fracture energy of 55 J/m² and the critical quadratic traction value of 70 MPa provide a reasonable correlation with experimental results.
To further increase the accuracy of the analysis, plastic material properties are added into the material model of PLA. The results showed that the plastic model resulted in permanent deformation, which in turn delayed debonding. Moreover, varying mode I and mode II damage parameters significantly influenced the force and displacement graph, indicating the mixed mode nature of the fracture process.
These iterative adjustments explain the sensitivity of the interfacial properties, highlighting their important role in the debonding process. The findings suggest that optimizing CZM parameters is crucial for accurately predicting the behaviour of composites under loading. Furthermore, these results show the importance of using CZM in FEA for accurately predicting interfacial behaviour of the fibre-matrix interface. The iterative approach to adjust the critical quadratic traction values and the critical fracture energy may result in enhancing predictive accuracy of the model.