Pullout modelling of viscoelastic synthetic fibres for cementitious composites

Abstract

The problem of the pullout of a viscoelastic synthetic fibre embedded in a cementitiuos matrix and subjected to an external time-dependent axial load is considered in the present work. A 1D phenomenological model able to simulate the contribution of viscoelastic relaxation as well as the hardening behavior due to abrasion phenomena during slippage is developed. The cement matrix compliance is neglected with respect to the fibre elongation. The interfacial shear stress between the fibre and the surrounding matrix is assumed to depend on the slippage distance through a second degree polynomial law, thus involving three constitutive parameters. Two distinct phases are recognized: An earlier debonding stage followed by the effective fibre pullout process. Two different creep functions have been assumed for modelling the viscous response of polymeric fibres: A function based on the fraction-exponential Rabotnov operator and a classical exponential model. Identification of the governing constitutive parameters allows obtaining the relation between the external strain and the axial displacement, which has been compared with experimental results provided by pullout tests both on plain and treated fibres, finding a good agreement. It is shown that the proposed approach can predict the whole pullout process of discrete synthetic macrofibres.

Analytical Approach for Modelling the Pull-Out Mechanism of Recycled Synthetic Fibres in Fibre-Reinforced Concrete (FRC)

“…Analysing the experimental results, the three kinds of fibres here compared exhibit different response against pull-out. Untreated PP fibres (UT-PP) attain the peak strain (namely the imposed axial load N) at the transition between debonding and pull-out stages, whereas S-PP fibres reach the maximum value during the pull-out stage, in compliance with the observations by Di Maida et al for fibres immersed in basic-catalysed silica bath for long time [15,21]. In the latter case, the hardening attitude appears even more pronounced due to the particular coating technique.…”

“…The present work shows the results of an experimental characterisation of the pull-out behaviour of partially recycled plastic fibres embedded in a cement-based matrix. A simple one-dimensional analytical model for the pull-out process is also proposed, further simplifying the formulation discussed by Sorzia et al [21] and Radi et al [22]. The model involves two different stages, namely debonding and pull-out, and is applied to describe the behaviour of the aforementioned partially recycled plastic fibres.…”

“…Only Di Maida et al datasets about S-PP fibres exhibit a pronounced non-linear behaviour [15]. Sorzia et al show that constitutive parameters are substantially related to the bonding properties between the fibre and the matrix and regardless of the embedded length of the fibre [21]. Besides, setting correctly τ 0 , a, b, the model is able to describe the pull-out test also for different kind of fibres, e.g.…”