Numerical and experimental analysis of the mechanical response of thin-ply cross-ply composites

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dc.contributor.authorHagvall, Robin
dc.contributor.authorJohansson, Simon
dc.contributor.departmentChalmers tekniska högskola / Institutionen för industri- och materialvetenskapsv
dc.contributor.departmentChalmers University of Technology / Department of Industrial and Materials Scienceen
dc.date.accessioned2019-07-05T11:52:48Z
dc.date.available2019-07-05T11:52:48Z
dc.date.issued2019
dc.description.abstractOne of the major strivings of today is to reduce the emission of green house gases. Within the transport vehicle industry this can be achieved by reducing their structural weight, which lowers the fuel consumption. That strive motivates the use of fibre reinforced polymers, which offers an increased weight to stiffness ratio compared to metallic materials. Moreover, it has been shown that further advantages can be achieved if the thickness of certain plies in a composite is reduced. More specifically, if the thickness of a transversely loaded ply embedded in a multidirectional laminate is reduced, the onset of transverse cracks can be substantially delayed. This is called the in-situ effect. The aim of this project is to, with one experimental study and one numerical study, investigate this in-situ effect for thinner plies for which it has not yet been fully established. The thickness range considered is between 20 μm and 240 μm. For the experimental study test specimens are manufactured and subjected to a tensile load while the edges are inspected for cracks. The numerical analysis is conducted within the framework of Abaqus, where a cohesive zone model is developed in combination with extended FEM. The outcome of the experiments show a small delay in the onset of transverse cracks when the thickness of the 90°-ply is reduced. For some cases it is also seen that the crack density decreases when the thickness is reduced. Finally, the stiffness of the adjacent plies does not seem to have a large impact on the in-situ effect. However, difficulties related to manufacturing complicates the interpretation of those results and their validity can be questioned. The numerical study shows an in-situ effect in a model in which no in-situ properties are used. For the thinner case, the result aligns well with analytical models. It is shown that an extremely fine mesh is necessary in order to resolve the crack zone correctly, and the dependency of input variables such as the critical energy release rate and interface strength is demonstrated. It is also shown that for one of the studied material a transition from stable to unstable crack growth occurs at the thickness 80 μm, where a crack grows stably for thinner plies and unstably for a thicker plies. Taking into account the manufacturing complications, the results still, on the whole, indicate that the in-situ effect exist for the thin-ply composites studied in this project. This further motivates the development and research connected to thin-ply composites.
dc.identifier.urihttps://hdl.handle.net/20.500.12380/256831
dc.language.isoeng
dc.setspec.uppsokTechnology
dc.subjectMaterialvetenskap
dc.subjectProduktion
dc.subjectMaskinteknik
dc.subjectMaterialteknik
dc.subjectMaterials Science
dc.subjectProduction
dc.subjectMechanical Engineering
dc.subjectMaterials Engineering
dc.titleNumerical and experimental analysis of the mechanical response of thin-ply cross-ply composites
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster Thesisen
dc.type.uppsokH
local.programmeApplied mechanics (MPAME), MSc
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