On the behavior of compression loaded multidirectional carbon fiber laminates after first ply failure

Abstract: Carbon fiber composites are interesting due to their high specific stiffness properties as well as thickness and strength tailorability. Furthermore, they outperform conventional metal material in terms of specific energy absorption. This makes the material an appealing candidate in components subjected to a crash load case. The adoption of the material however has mainly reached industries where a very high performance is required. Further penetration of the material is possibly halted by following reasons: high material and production costs, challenging interface design or the complex failure behavior. In order to enable a broader carbon fiber composite penetration, this work focuses on the acquisition, virtual representation and identification of failure evolution on compression loaded laminates to improve the knowledge on the material’s failure behavior.

The first part of the work focuses on the strain evaluation of compression tests. A promising strain measurement technique - digital image correlation (DIC) - is used to gain a deeper insight on the strain progression after initial failure. The switch from conventional strain measurement technique to DIC sparked investigations such as optimal strain measurement surfaces and data reduction. Results show that side view measurement data in combination with long extensometer report the most consistent results. A novel bending criterion based on DIC data has been presented so that the established validity check based on conventional strain measurement techniques remains in place.

The second section describes the generation of a detailed finite element simulation using a state of the art physically based failure model focusing on fiber kinking. This model is used to compare the stress strain envelope obtained in the first part. Outcome of the simulations show a good stiffness and strength agreement. Additionally, this model gives useful insights on the failure mode propagation for the investigated layups.

The third component of this thesis shows failure evolution in compression loaded laminates using ex-situ computerized tomography (CT) scans. It is the first time that failure evolution in multi directional laminates on such detailed level has been captured. Obtained results show a distinct propagation of failure modes inside the coupon. Furthermore, the progress is shown to be repeatable. Gathered failure propagations are set side by side with the virtual counter part which shows a satisfying agreement.

These three fields contribute to the understanding of failure evolution in carbon fiber composites. First, by acquiring the stress strain envelope accurately in the compression load case. Secondly, by comparing this behavior with finite element simulations and finally presenting a methodology to physically capture the failure propagation in a compression loaded coupon

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2022

Klassifikation und Themen

• Schlagwort: Laminat ; Mechanisches Versagen ; Spannungs-Dehnungs-Beziehung ; Faserverstärkter Kunststoff ; Festigkeit ; Stoßbeanspruchung ; Faserverbundwerkstoff ; Kohlenstofffaserverstärkter Kohlenstoffwerkstoff ; Bruchmechanik ; Finite-Elemente-Methode ; Materialcharakterisierung ; Bruchverhalten

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2023
• Urheber: D'haen, Jonas
• Beteiligte Personen und Organisationen: Hiermaier, Stefan ; Eberl, Christoph ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Weitere Informationen

• DOI: 10.6094/UNIFR/237373
• URN: urn:nbn:de:bsz:25-freidok-2373734
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 14.08.2025, 11:00 MESZ