Modeling and Characterization of Fatigue Strength of Laminated Composites with Knitted Fabric Reinforcement

• Published in: Journal of composite materials Vol. 36; no. 15; pp. 1781 - 1801
• Main Authors: Huang, Zheng-Ming, Ramakrishna, S., Thwe, Aye Aye
• Format: Journal Article
• Language: English
• Published: Thousand Oaks, CA SAGE Publications 01-08-2002; Technomic; Sage Publications Ltd
• Subjects: Applied sciences; Composites; Exact sciences and technology; Forms of application and semi-finished materials; Fracture mechanics (crack, fatigue, damage...); Fracture mechanics, fatigue and cracks; Fundamental areas of phenomenology (including applications); Physics; Polymer industry, paints, wood; Solid mechanics; Structural and continuum mechanics; Technology of polymers; fatigue strength; S–N curve; life prediction; laminated composites; knitted fabric composites; experimental correlation; bridging model; micromechanics; Fatigue life; Stratified material; Epoxy resin; Experimental study; Fatigue fracture; Modeling; Composite material; Crack bridging; Fatigue strength; Woven material; Microstructure; Structural analysis; Carbon fiber
• ISSN: 0021-9983; 1530-793X
• DOI: 10.1177/0021998302036015168

Results from both theoretical and experimental investigations on laminated epoxy composites reinforced with plain weft-knitted carbon fiber fabrics of different arrangements subjected to fatigue loads are presented in this paper. The stacking sequences used are [0/0/0/0], [0/45/−45/0], [90/90/90/90], [0/90/90/0], and [90/45/−45/90] where 0 refers to the fabric wale direction and 90 to the course direction. Tensile fatigue with stress control was applied to the laminates as well as to the monolithic matrix material, with a stress ratio of R = 0.1 and a cycling frequency of 5 Hz. The theoretical prediction for the laminate fatigue strength was made using a general methodology, which is a combination of the classical lamination theory and the bridging micromechanics model. The stresses sustained by each lamina layer in the laminate were determined according to the classical lamination theory, whereas the internal fatigue stresses generated in the fiber and matrix materials of the lamina were obtained by virtue of the bridging model. The internal stresses were detected against the constituent fatigue strengths at the similar loading conditions as applied to the laminate. Thus, the laminate fatigue strength was predicted only using the constituent fatigue data and the laminate geometric parameters, which were measured/determined independently. Reasonably good agreement has been found between the predicted and experimental S–N curves of all the five laminates.