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Experimental investigation and numerical simulation of residual stresses in pultruded high performance composites.
The objective of this thesis is to investigate the formation of residual stresses in high performance thermoplastic composites and their influence on the material performance. The experimental approach and results will be validated through material testing and a thermomechanical FEM model.
Thermoplastic pultrusion is one of the most promising manufacturing techniques for high quality, high performance composites at a competitive cost. In this joint research project with the Swiss industry, a novel pultrusion concept has been developed at CMASLab, which is currently able to manufacture rods up to Ø10mm.
As the current process consists of melting polymer fibres mixed with reinforcing fibres in a circular die to impregnate the material and then cool the composite rod from outside until solidification, large residual stresses are expected to occur in the material for larger rod diameters up to Ø100mm. These residual stresses could lead to cracks or other defects in the material. To overcome those challenges, those stresses need to be experimentally studied and compared with results from numerical simulations.
Thermoplastic pultrusion is one of the most promising manufacturing techniques for high quality, high performance composites at a competitive cost. In this joint research project with the Swiss industry, a novel pultrusion concept has been developed at CMASLab, which is currently able to manufacture rods up to Ø10mm. As the current process consists of melting polymer fibres mixed with reinforcing fibres in a circular die to impregnate the material and then cool the composite rod from outside until solidification, large residual stresses are expected to occur in the material for larger rod diameters up to Ø100mm. These residual stresses could lead to cracks or other defects in the material. To overcome those challenges, those stresses need to be experimentally studied and compared with results from numerical simulations.
To accurately quantify the residual stresses occurring in the material, suitable characterization methods need to be investigated. One possibility would consist of measuring the strains using a micro digital image correlation (µ-DIC) system while a defect such as a hole is introduced in the material. Once the strains are determined, a suitable method to obtain the corresponding mechanical stresses would be necessary to compare to the values resulting from an existing thermomechanical FEM simulation
Tasks:
-Literature review of residual stress characterization methods, adaptation to new conditions or development of own methods
-Manufacturing of thermoplastic composite rods suitable for experimental investigation and determination of their residual stresses
-Adaptation of existing thermo-mechanical FEM model to new conditions and comparison with experimental results
The content as well as starting dates can be discussed to suit a Masters, Semester or Bachelor thesis as well as the personal interests of the student.
Image credit: https://de.wikipedia.org/wiki/Delamination#/media/File:Delamination-CFRP.jpg
Supervisor Prof. Dr. P. Ermanni
Tutor Max Volk
To accurately quantify the residual stresses occurring in the material, suitable characterization methods need to be investigated. One possibility would consist of measuring the strains using a micro digital image correlation (µ-DIC) system while a defect such as a hole is introduced in the material. Once the strains are determined, a suitable method to obtain the corresponding mechanical stresses would be necessary to compare to the values resulting from an existing thermomechanical FEM simulation
Tasks:
-Literature review of residual stress characterization methods, adaptation to new conditions or development of own methods
-Manufacturing of thermoplastic composite rods suitable for experimental investigation and determination of their residual stresses
-Adaptation of existing thermo-mechanical FEM model to new conditions and comparison with experimental results
The content as well as starting dates can be discussed to suit a Masters, Semester or Bachelor thesis as well as the personal interests of the student.