# Size Effect on the Acoustic Emission Behavior of Textile-Reinforced Cement Composites  
[PERSON]  
1 Department Mechanics of Materials & Constructions (MeMC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium; [PERSON] (N.O.); [PERSON] (E.T.) Laboratoire de Tribologie et de Dynamique des Systemes (LTDS), Universite de Lyon, Ecole Nationale d'Ingenieurs de Saint-Eteure (ENISE), 58 Rue Jean Parot, 4200 Saint-Etienne, France;  
[EMAIL_ADDRESS] (A.H.); [EMAIL_ADDRESS] (A.S.L.)  
[PERSON]  
1 Department Mechanics of Materials & Constructions (MeMC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium; [PERSON] (N.O.); [PERSON] (E.T.) Laboratoire de Tribologie et de Dynamique des Systemes (LTDS), Universite de Lyon, Ecole Nationale d'Ingenieurs de Saint-Eteure (ENISE), 58 Rue Jean Parot, 4200 Saint-Etienne, France;
While the effectiveness of the technique has been demonstrated at a laboratory scale, and AE is extremely useful in material-oriented studies, the full potential has not been realized at a larger service scale. The reasons for this include larger propagation distances and thus higher attenuation, more possible sources of external noise and more severe signal distortion due reflections, scattering and dispersion. Therefore, away from the laboratory, the AE is mainly limited to crack detection and localization [11; 12; 13; 14], while the sensitivity to the fracture mode and stress field are in their infancy.  
The aforementioned issue of the large propagation distance has been demonstrated in bulk [15] as well as plate structures [16; 17; 18; 19]. Studies occupying different propagation distances in thin plates have shown that due to plate wave dispersion, the elastic signals continuously undergo a waveform shape change. This is mainly because different frequency components propagate with different velocities, something that is also demonstrated herein for the specific material of interest (cementitious composite for construction). In addition, the main focus comes from an issue not sufficiently investigated in the literature. This is the lateral dimension of the plate. Practically speaking, this is the difference in the acquired AE, when varying the width of the plate without altering the nominal propagation distance between the damage source and sensor and the fracture mechanism (see Figure 2). As the width of the plate is small, the geometry is closer to a beam, and the wave propagation is essentially one-dimensional, leading to strong waveguide behavior (Figure 2a). For larger widths though, the propagation opens in a circular wavefront, the energy is spread to larger area, and the wave travels a longer distance until it is possibly reflected by the edges (see Figure 2c), while Figure 2b shows an intermediate situation.  
The influence of the width on wave propagation has been studied in straight metal plates [20; 21] and only recently in structural composites [22]. In general, it was found that the recorded waveforms in beams showed higher frequency contents and amplitudes than in the plates. The reason was attributed to edge reflections, which are dominant for small specimens and distort the frequency content but weaken in large dimensions. An equivalent interpretation from another point of view was given through the essentially one-dimensional propagation in the beam, which resembled the propagation in a waveguide, avoiding the spreading of the wavefront. This is the first time that the effect of the plate width is studied in curved composite elements. The specific material is TRC, a cementitious matrix reinforced by chopped, randomly oriented glass fibers. Details on the material and experimental procedure follow in the next section.  
Figure 1: Average frequency–rise time plot from bending tests on TRC beams, taken from [7].