Bending fracture of textile reinforced cement laminates monitored by acoustic emission: Influence of aspect ratio

Textile reinforced cement based composites (TRC) are a new class of sustainable construction materials with superior tensile strength and ductility. These materials have the potential for becoming load bearing structural members, therefore a wide array of structural and non-structural applications are possible. However, their heterogeneous, laminated, fibrous nature complicates the understanding of their fracture behavior. During bending, the developed stresses lead to the activation of damage mechanisms like matrix cracking, fiber pull-out delamination and in succession or in overlap. In this study, the flexural behavior of TRC laminates is monitored by acoustic emission (AE). AE sensors record the elastic waves radiated from the damage sources and enable the characterization of the fracture behavior in any stage. The aim is to examine if AE is sensitive enough to provide feedback on the applied stress field in such heterogeneous systems. Therefore, the three-point bending span is varied to modify the stress field and specifically the proportion of shear to normal stress. AE waveform parameters like duration and frequency reveal information about the mode of fracture for the different spans, while the stress field is derived by a finite element model (FEM). The results show that AE is suitable to characterize the stress field even from the early loading stages, monitor the corresponding damage mechanisms and provide valuable feedback to the material modeling.