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Title
Japanese: 
English:A Continuum Model of Interface to Investigate Stress Transfer on Fiber-Matrix Composite 
Author
Japanese: BudimanBentang Arief, 高橋航圭, 因幡和晃, 岸本喜久雄.  
English: Bentang Arief Budiman, Kosuke Takahashi, Kazuaki Inaba, KIKUO KISHIMOTO.  
Language English 
Journal/Book name
Japanese: 
English: 
Volume, Number, Page        
Published date 2015 
Publisher
Japanese: 
English: 
Conference name
Japanese: 
English:International Conference on Advances in Composite Materials and Structures 
Conference site
Japanese: 
English:Istanbul 
Abstract Interface of fiber/matrix composite has important role for overall composite performance as load bearing structure because it has to effectively transfer stress from matrix to fiber and vice versa. Failure initiation in composite is also mainly caused by cracks at the interface. Single fiber fragmentation test (SFFT) is popular method in assessing the bonding quality because it represents actual stress transfer in real composite. Several models to describe the stress transfer on SFFT have been proposed. The resemblance of those SFFT models are in assuming perfect bonding condition which describes the interface as rigid surface. However, recent studies show that the interface is a thin layer having different mechanical properties from fiber or matrix. The layer is formed on manufacturing process of composite which strongly depends on characteristics of fiber surface. Several micro cracks at the interface might also appear due to poor manufacturing process of composite. Those studies indicate that imperfect bonding should occur regardless of how strong the bonding condition is, and there should be always a relative displacement at the interface. Therefore, the stress transfer may not be estimated accurately because the imperfect bonding can reduce bonding quality and create an ineffective stress transfer. This study aims to investigate the effectiveness of stress transfer on SFFT. Theoretical analyses of stress transfer were developed by considering the interface having imperfect bonding. A continuum damage model of the interface was proposed by following bilinear traction-separation law. The equation of stress transfer at the interface was derived theoretically. Numerical analyses using finite element method were also conducted by developing axis-symmetric model representing SFFT. Comparison between theoretical and numerical analyses was clearly demonstrated and showed good agreement. The results were also compared with conventional model that the interface is traditionally assumed as rigid surface. It was found that the presumption of SFFT cannot be used when accurate evaluation is required because imperfect bonding causes significant effect to evaluation results. An experimental verification was also conducted in order to clarify the influence of imperfect bonding at the interface using single carbon fiber-epoxy specimen since we have proposed the evaluation of bonding quality based on stress contour in matrix. The method can possibly estimate interfacial properties defined by continuum damage model which was difficult problem in recent years.

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