Experimental study on the fatigue performance of CFRP beams with structured surface load introduction under cyclic loading

CFRP is widely used in lightweight structures subjected to cyclic loading. However, the fatigue performance at the structural level, particularly with mechanical joints, remains insufficiently understood. This study investigates the fatigue behavior of quasi-isotropic CFRP square tubes under cyclic 3-point bending, with a focus on a load introduction concept using bolted connections with structured surface plates. The specimens are tested under fully reversed loading at 1 Hz. Quasi-static baseline tests reveale linear behavior up to failure and high reproducibility between specimens. Cyclic tests show a clear increase in fatigue life with decreasing load amplitude. Hysteresis analysis reveals asymmetric behavior and narrowing around the zero-crossing prior to failure, especially in high-cycle specimens. The specimen with the highest cycle count exhibited a distinct fiber fracture on the tensile side, suggesting a change in failure mode compared to quasi-static loading. The results highlight the relevance of the hysteresis loop shape as a potential indicator for fatigue damage and structural monitoring. The findings underscore that fatigue failure may occur in locations different from those under static loading, suggesting that conventional design approaches based on static safety factors may be insufficient for the design of CFRP structures.

Subjects

3-point bending

CFRP

Cyclic loading

Fatigue testing

Load introduction

DDC Class

624.17: Structural Analysis and Design

620.11: Engineering Materials

530.41: Mechanics of Solids

Lizenz

https://creativecommons.org/licenses/by-sa/4.0/

Publication version

publishedVersion

Name

ICCM24_Final_Paper_156.pdf

Type

Main Article

Size

2.65 MB

Format

Adobe PDF

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Experimental study on the fatigue performance of CFRP beams with structured surface load introduction under cyclic loading