Behaviour of cementitious matrix composites under displacement controlled cyclic loading

• Type: Article in International Conference Proceedings Book
• Date: 1993

Authors

António Magalhães (Author) Other; António Torres Marques (Author) FEUP; Fernando de Oliveira (Author) FEUP; P. Soukatchoff (Author) Other; Paulo Tavares de Castro (Author) FEUP

Conference proceedings International

Title: ICCM-9

9th International Conference on Composite Materials - ICCM

Madrid, Spain

Other information

Resumo (PT): Under cyclic leading ruptures rnay occur at a stress lower than the maxirnurn perrnissible for static loading This phenornenon - fatigue - leads to rupture after a nurnber of cycles if the stress amplitude is higher than the fatigue lirnit. The nurnber of cycles until final rupture is composed of two phases: initiation of a defect and its propagation until final rupture. Fatigue rupture is a function of a large nurnber of factors, such as surface quality, ternperature, type and rate of loading, for exarnple. They justify a large scatter and the need for a statistical characterization of the fatigue lirnit. Some materials, such as concrete, do not display a fatigue limit, and their fatigue strength is conventionally defined at a given number of cycles such as l06. For cementitious matrix composites, in the presence of sand and other aggregates, behaviour is markedly non-linear, and progressive growth of fissures substitutes catastrophic rupture. The slow growth is reinforced by the presence of fibers, which anchor the fissures, namely through the creation of fibre-bridges subjecting- fibres to a pull-out process whereby fibres bresk or are extracted from the matrix. Analysis of cyclic behaviour may be carried out quantifying the accurnulated irreversible damage. After developing a machine for displacement controlled cyclic testing, the authors studied the behaviour of cementitious matrix composites under this type of loading, particularly stress range and modulus as a function of number of cycles.

Abstract (EN): Under cyclic leading ruptures rnay occur at a stress lower than the maxirnurn perrnissible for static loading This phenornenon - fatigue - leads to rupture after a nurnber of cycles if the stress amplitude is higher than the fatigue lirnit. The nurnber of cycles until final rupture is composed of two phases: initiation of a defect and its propagation until final rupture. Fatigue rupture is a function of a large nurnber of factors, such as surface quality, ternperature, type and rate of loading, for exarnple. They justify a large scatter and the need for a statistical characterization of the fatigue lirnit. Some materials, such as concrete, do not display a fatigue limit, and their fatigue strength is conventionally defined at a given number of cycles such as l06. For cementitious matrix composites, in the presence of sand and other aggregates, behaviour is markedly non-linear, and progressive growth of fissures substitutes catastrophic rupture. The slow growth is reinforced by the presence of fibers, which anchor the fissures, namely through the creation of fibre-bridges subjecting- fibres to a pull-out process whereby fibres bresk or are extracted from the matrix. Analysis of cyclic behaviour may be carried out quantifying the accurnulated irreversible damage. After developing a machine for displacement controlled cyclic testing, the authors studied the behaviour of cementitious matrix composites under this type of loading, particularly stress range and modulus as a function of number of cycles.

Language: Portuguese

Type (Professor's evaluation): Scientific