Static and fatigue multi-axial traction/torsion loading of 3D reinforced composite materials
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Alaa KOBEISSI (FRANCE), Zoheir ABOURA (FRANCE), François RASSELET , Walid HARIZI (FRANCE), Kamel KHELILAbstract :
During the last decades, 3D composite materials have been widely used in different engineering applications due to their high mechanical performance and impact resistance. The introduction of tridimensional interlacing makes the study of this particular material behaviour more challenging [1]. In this study, the failure analysis of 3D carbon fibre composite subjected to out-of-plane multiaxial traction/torsion (σ11/τ13) loadings is investigated. A rectangular specimen is subjected to simultaneous traction/torsion static and fatigue cyclic loadings to examine the response of the material under this kind of complex stress state. Indeed, the traction/torsion on rectangular shape specimen induces a tri-axial stress state including normal stress σ11 and two shear stresses τ12 and τ13. The distribution of these stress states along the specimen has been analyzed through finite element analysis. This analysis reveals that the torsional twisting of the specimen induces normal tensile and compressive stresses along the edges of the specimen. These local stresses can lead to a localized loading and unloading cycles in the material, potentially resulting in a non-uniform distribution of damage. According to Lekhnitskii theory [2], an experimental methodology is established to monitor different multi-axial fatigue tests A multi-instrumented test protocole (including stereo digital image correlation (stereo-DIC), acoustic emission (AE), and in-situ microscopic observation,) has been implemented for the monitoring and the analysis of the damage mechanisms.
The first part of the study aimed to complement the damage threshold envelope (σ11/τ13) established by Tableau et al [3]. Based on the generated envelope, multi-axial stress levels for the fatigue tests were defined , specifically addressing the influences of shear stress (τ13). A specialized test protocol was implemented to monitor the evolution of stiffness variation in both tension and shear. The analysis of strain fields facilitated the localization and progression of failure. The nature of this damage was identified through microscopic observations.
The damage distribution has been correlated with the stress fields in the specimen. The analysis reveal that the initiation of damage aligns with the finite element calculations. Regarding the propagation of this damage during fatigue tests, a post-test tomographic analysis was conducted, the observation illustrates clearly the dispersion of damage throughout the specimen.
The identified mechanisms in these studies will serve as the foundation for a more extensive exploration involving an integrated experimental/numerical approach based on phenomenological thermodynamic models.
The first part of the study aimed to complement the damage threshold envelope (σ11/τ13) established by Tableau et al [3]. Based on the generated envelope, multi-axial stress levels for the fatigue tests were defined , specifically addressing the influences of shear stress (τ13). A specialized test protocol was implemented to monitor the evolution of stiffness variation in both tension and shear. The analysis of strain fields facilitated the localization and progression of failure. The nature of this damage was identified through microscopic observations.
The damage distribution has been correlated with the stress fields in the specimen. The analysis reveal that the initiation of damage aligns with the finite element calculations. Regarding the propagation of this damage during fatigue tests, a post-test tomographic analysis was conducted, the observation illustrates clearly the dispersion of damage throughout the specimen.
The identified mechanisms in these studies will serve as the foundation for a more extensive exploration involving an integrated experimental/numerical approach based on phenomenological thermodynamic models.