Influence of Crack Width in Alternating Tension–Compression Regimes on Crack-Bridging Behaviour and Degradation of PVA Microfibres Embedded in Cement-Based Matrix

Abstract

The use of high-performance polymeric microfibres in enhancing the ductility of cementitious composites is widespread. A vivid example is the application of strain-hardening cement-based composites (SHCCs) in the construction industry. However, there are a few challenges which need to be addressed with respect to material design. For instance, the ductility of SHCC diminishes under alternating tension–compression loading, where the fibres lose their crack-bridging capacity due to specific damage mechanisms. The damage development and its influence on crack-bridging capacity have been studied in previous works by the authors. The paper at hand focuses on the influence of crack width on the crack-bridging capacity of polymeric microfibres in conjunction with the number of cycles in an alternating tension–compression regime with different cyclic compressive force levels. It shows that bridging capacity can be markedly influenced by crack width: an increase in crack width leads to more severe damage to the fibres and thus to lower crack-bridging capacity. Then, after analysing the specimens by means of electron microscopy, a hypothesis is presented to address the effect of crack width on damage development. Finally, a simple approach is proposed for estimating the influence of different parameters on fibre degradation.

Increasing the Fatigue Resistance of Strain-Hardening Cement-Based Composites (SHCC) by Experimental-Virtual Multi-Scale Material Design

“…Since the study suggests that crack width has a significant influence on the buckling and defibrillation of the fibre and, therefore, on fibre failure, Ranjbarian and Mechtcherine [ 26 ] investigated the influence of the initial crack width on the fibre degradation with the same test setup as before. The authors recognised a clear dependence of fibre degradation on crack width.…”

“…Due to this fibre degradation, fibres tend to rupture already in the cyclic stage when the initial crack width is large. Since the PVA fibres possess poor mechanical properties in the transverse direction, a “fibrillar” fracture type can be observed [ 26 ]; see Figure 18 .…”

“…Due to the significant influence of the initial crack width on mechanical behaviour and fibre deterioration, the damage quantification approach derived in [ 23 ] mentioned above had to be extended to include another variable, i.e., crack width (ω). Detailed information about the algorithm can be found elsewhere [ 26 ].…”

“… Influence of crack width on the force at rupture of PVA fibres subjected to 2000 loading cycles depending on lower reversal point [ 26 ] (Copyright permission are granted by the corresponding journal): ( a ) small crack width (40 µm); ( b ) large crack width (100 µm). …”

“…For a better understanding of the phenomena observed, micromechanical tests must be performed. The article at hand is intended to summarize the micromechanical experimental investigations by Ranjbarian and Mechtcherine [ 22 , 23 , 24 , 25 ] and Ranjbarian et al [ 26 , 27 , 28 ]. Based on the experimental data, a numerical simulation tool was developed to enable the validation of experimental assumptions and observations and, finally, facilitate prediction of the performance of SHCC and optimisation of the composite material.…”