Fatigue and fracture behavior of a steel cord/rubber composite

Citation
S. Rao et al., Fatigue and fracture behavior of a steel cord/rubber composite, J THERM COM, 14(3), 2001, pp. 213-224
Citations number
5
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science & Engineering
Journal title
JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS
ISSN journal
0892-7057 → ACNP
Volume
14
Issue
3
Year of publication
2001
Pages
213 - 224
Database
ISI
SICI code
0892-7057(200105)14:3<213:FAFBOA>2.0.ZU;2-K
Abstract
The objective of this study was to investigate the fatigue and fracture beh avior of steel cord/rubber composites used in tire belts under constant cyc lic strain loading. The material was a specially made tire belt layer in th e form of rubber sheets reinforced with unidirectional cords consisting of two pairs of twisted steel wires. Failure mechanisms, damage development, a nd fatigue life were determined for single belt layers with different cord orientations. Tests were conducted at cord angles of 22 degrees, 72 degrees , and 90 degrees degrees with a cyclic strain amplitude of 8.3% at a freque ncy of 10 Hz. Five different stages of damage development were observed: mi crocrack initiation, microcrack multiplication, macrocrack formation, slow macrocrack propagation, and fast macrocrack propagation leading to final fa ilure. In the case of the 22 degrees cord specimens, where the in-plane she ar component was dominant, damage development consisted of microcrack initi ation at the cord/rubber interface, the formation of more microcracks and m acrocracks, and finally the formation of a major fatal macrocrack along the cord direction. In the case of 90 degrees cord specimens, dominated by tra nsverse tension, initial microcracks occurred within the cord, they propaga ted across the thickness of the specimen, and finally a major macrocrack pr opagated across the entire width of the specimen. The final crack propagate d in part along the cord/rubber interface and in part within the cord. In t he case of the 72 degrees cord specimens, where both in-plane shear and tra nsverse tension are critical, the initial microcracks occurred within the c ord and the final macrocrack along the interface. For the same cyclic strai n amplitude, the 90 degrees specimens had the shortest fatigue life, and th e 72 degrees specimens had the longest. Additional tests were conducted at different strain amplitudes. The normalized modulus decreases slowly and ne arly linearly with normalized fatigue lifetime up to a certain value of the latter, approximately 80% of the normalized logarithmic lifetime, and then it drops sharply. Cyclic strain amplitude also affects the failure mechani sms. High amplitudes produce localized damage, whereas low amplitudes produ ce dispersed damage. A residual life model was proposed based on stiffness degradation.