PSI - Issue 64

Rosario Lombardi et al. / Procedia Structural Integrity 64 (2024) 1919–1926 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2. Mechanical characterization

3.2.1. Tensile Tests Figure 6 represents the average maximum stress observed in the tensile tests. Furthermore, the values (purged of any initial elongation of the yarn) of the strain at the time of the maximum stress are reported.

Figure 6 - Tensile test results

Various aspects can be observed from Figure 6. As a matter of principle, the yarns obtained present greater stiffness as the deposited PLA increases and, during the tensile tests, it was possible to observe a fragile behavior of the yarn, with clear breakage at a specific point of the sample. The maximum breaking force values are always greater for the impregnated yarn compared to the non-impregnated yarn. Specifically, as the concentration of PLA increases there is an increase equal to: 134%, 161% and 185% for Jute (320 g/m 2 ); 123%, 144% and 162% for Flax (125 g/m 2 ). The addition of PLA, therefore, allows an increase in the resistance of the fabrics. This increase in resistance can be linked to a beneficial effect resulting from the impregnation, which allows a greater distribution of tensions to the various fibers of the yarn. Furthermore, these values increase as the deposited PLA increases. This trend is more visible for Jute (320 g/m 2 ) and Flax (125 g/m 2 ). 4. Conclusions The experimental tests carried out in the present study lead to the main observations listed hereafter: • it was possible to observe that the fabric stiffens significantly following impregnation, even for lower PLA concentrations, which is a positive aspect relevant for a possible use of the fabric as a reinforcement in TRM technology; • the use of PLA as a possible polymer to be used for the coating of natural fabrics has proven to be practically feasible and relatively easy; • another positive aspect is that the yarns are able to reach a tensile strength as the concentration of PLA used increases: this demonstrates a beneficial effect of the PLA impregnation on the mechanical behavior of the fibers; • the PLA impregnation resulted in an increase in the cross-sectional area of the section, which means an increase in the lateral surface area of the yarn, which is likely to lead to a better behavior when the fabric is immersed in the mortar; • as regards water absorption, no significant variations were observed on samples with different PLA concentration. This aspect needs to be further investigated with the aim to better understand the behavior of impregnated fibers and fabrics in a durability perspective. In conclusion, the use of PLA as a polymer for the coating treatment of plant tissues has proven to be an applicable solution. The results obtained are certainly interesting and encouraging for future use in NTRM systems. The aspects that are considered necessary to investigate in the future are essentially two: the durability of the fabric, in order to understand the effect of the impregnation studied on the resistance of the yarn; the adhesion with the mortar, in order to verify whether the presence of PLA on the surface of the yarn has a negative effect in this sense.