Title: Cyclic Damage to PVA Microfibre Embedded in Cementitious Matrix in Alternating Tension-Compression Regime

Author(s): Ranjbarian, M.; Mechtcherine, V.

Publication: Symposium Paper

Volume: 343

Issue:

Appears on pages(s): 321-329

Keywords: SHCC, cement-based composites, PVA microfibre, fibre pull-out test, fatigue, cyclic tension-compression loading regime, cyclic damage

DOI:

Date: 10/1/2020

Abstract:
The structures subject to dynamic loading demand more ductile materials to prevent catastrophic failure. The results of investigations on strain-hardening cement-based composites (SHCCs) distinguished this group of materials – due to their highly ductile behaviour – as a suitable alternative for structures with high resistance against seismic, impact and cyclic loadings. While mechanical properties of SHCC are determined mostly by bridging behaviour of dispersed fibres crossing cracks and properties of fibre-matrix interface, the dependency of these mechanisms on the loading regime is pronounced. Specifically, under cyclic loading, the number of cycles to failure decreases dramatically when SHCC is subject to alternating tension-compression regime. Degradation of fibres compressed between the crack faces and deterioration of their bridging capacity are responsible for such early failure and necessitate further investigations at the micro level. The article at hand presents the influence of loading history in cyclic tension-compression regime on the bridging capacity of the single PVA microfibre embedded in cementitious matrix. A novel double-sided single fibre pull-out setup is used for the experimental investigations. First the test setup, material composition and testing procedure are explained. Next, the results of double-sided pull-out specimens, tested under monotonic and cyclic tension-compression regimes, are discussed. It is shown that the deterioration of fibre bridging capacity can be assessed by applying cyclic loading in post-cracking stage, followed by pulling the fibre out of the matrix. Possibility of a change in pull-out behaviour of PVA microfibre from “fibre rupture” to “fibre pullout”, also a change of behaviour in post debonding regime from “hardening” to “softening” are also observed. Eventually, the results of microscopic analysis are presented and discussed, which show the specific phenomena responsible for changes in pull-out behaviour.