A novel compression-tension fatigue test for textile cord-elastomer composites

Fatigue damage in textile cord–elastomer composites is particularly sensitive to compression-tension cycling. However, existing testing methods offer limited control over these loading conditions. To overcome these limitations, this study proposes the Extension-Compression-Uniaxial (ECU) test. This new setup enables strictly uniaxial loading, independent control of tensile and compressive strain amplitudes, and direct load transfer to the textile cords. At the same time, the specimen preserves an architecture that is representative of industrial reinforced rubber products. An experimental campaign was conducted on textile cords with different filament materials, cord architectures, and elastomer matrices under pure tension, pure compression, and combined compression–tension fatigue loading. Combined loading causes significantly greater degradation of cord breaking strength than either loading mode applied independently. Pure compression fatigue leads to extensive elastomer cracking but limited loss of cord strength, whereas pure tension fatigue causes comparatively moderate degradation. Within the explored range, the stiffness of the elastomer is of secondary importance. Instead, temperature and number of cycles effectively accelerate fatigue damage. Post-mortem X-ray tomography and scanning electron microscopy uncover the multiscale damage mechanisms that drive mechanical degradation. Elastomer cracking occurs under compressive loading, while filament damage governs the loss of strength. The identified modes of filament failure include flexion fatigue, crushing, tensile fatigue, and kink band defects due to compression. Notably, the latter are particularly dominant in aramid cords.