PSI - Issue 56

Cristina Vălean et al. / Procedia Structural Integrity 56 (2024) 97– 104 Author name / Structural Integrity Procedia 00 (2023) 000 – 000

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The high values of the elastic properties (flexural modulus) and strength (flexural strength and stress at break) of the PLA+CF samples are replaced by low values of the strain properties (Figure 5c). In this case, the PLA samples show the highest strain at strength, followed in order by the PLA+GF, PLA+BP and finally PLA+CF samples. The biggest difference is obtained between PLA and PLA+CF samples (53.7%), and the smallest between PLA+GF and PLA+BP (5.5%). As for the size of the values, strain at break largely follows the same order as strain at strength, the PLA samples showing the highest value, respectively PLA+CF the lowest.

Fig. 5. The variation of flexural modulus (a), strength (b), strain (c) and energy (d) properties with the type of sample

Due to the extension of the stress-strain curve (see Figure 4a), and also the area under this curve, the unreinforced PLA samples show the highest fracture energy (2.76 MJ/m 3 , Figure 5d). The lowest energy values are identified for the PLA+BP samples, where decreases of up to 77% are recorded compared to the PLA samples. Between the two types, there are PLA+GF and PLA+CF samples with fracture energy values of 1.34 and 0.79 MJ/m 3 , respectively. Energy at strength shows a pattern similar to fracture energy, obtaining differences of 70% between the extreme values. The biggest differences between fracture energy and energy at strength are found for PLA samples (39.8%), and the smallest in the case of PLA+CF samples (6.5%). This aspect is given by the ductile behavior (PLA), respectively quasi-brittle (PLA+CF) of the matrix of the investigated samples.