PSI - Issue 28

D. Rigon et al. / Procedia Structural Integrity 28 (2020) 1655–1663 Rigon et al. / Structural Integrity Procedia 00 (2019) 000–000

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tensile strength of the FDM_vPPis in agreement with the reference scatter of the IM material, the average value of the Young’ modulus of the FDM_vPP is 1.06 GPa against the one relevant of IM_vPP that turns out to be 1.63 GPa. Table 4. Percentage difference between the average tensile strength of virgin materials produced by IM (taken as reference) and the virgin and recycled ones produced by IM and FDM. Process ABS PP PP-GF30 virgin recycled virgin recycled virgin recycled IM 37.8 [MPa]* 11% 34.8 [MPa]* -40% 64.8[MPa]*° -51% + FDM_0° -33% n.a. -5% n.a. n.a. n.a. FDM_45° -73% n.a. -8% n.a. n.a. n.a. FDM_90° -76% n.a. -6% n.a. n.a. n.a. FDM_0/90° -39% # n.a. -9% n.a. n.a. n.a. FDM_±45° -47% -11% -21% n.a. -40% + n.a. * average value of IM virgin materials from Tables 1, 2 and 3. # calculated by using the average value of relevant data ° the average value includes PP-GF30 characterized by different fiber length. + missing data concerning fiber length. Regarding the short fiber reinforced polypropylene, the tensile properties taken from the literature are synthesized in Table 3 and Fig. 5. Fig. 5 shows that σ UTS of the IM_vPP-GF30 varies from 52.2 to 87.9 MPa. This variability depends on several factors related to the length and orientation of the glass fiber as well as the strength of the fiber matrix interface. Such variability can be extended the recycled IM material as well as the FDM one. According to the data reported in Fig. 5, IM_rPP-GF30 and FDM_rPP-GF30 have 39% and 25% lower tensile strength than the minimum σ UTS obtained for IM_vPP-GF30, respectively. The percentage differences between the tensile strength of IM virgin materials and the other material processed are reported in table 4. It is worth underling that the percentage differences of IM_0°_vPP-GF30, FDM_±45°_vPP GF30 and IM_0°_rPP-GF30 were calculated without considering the material with the same fiber length. 4. Fatigue strength Fig. 6 reports the fatigue test results relevant to IM_vABS and FDM_vABS (Fig. 6a), IM_vPP and IM_rPP (Fig. 6b), and IM_rPP-GF30 and IM_rPP-GF30 (Fig. 6c). Fig. 6a shows that fatigue strength of FDM_vABS specimens for load ratio R = 0 is lower than IM_vABS. Table 5. Percentage difference of the fatigue strength evaluated at 10 4 cycles for the ABS and 2∙10 6 cycles for PP and PP-GF30. The average fatigue strength of IM materials is taken as reference. Process ABS PP PP-GF30 virgin recycled virgin recycled virgin recycled IM 26.2 [MPa]* n.a. 24.4 [MPa]° -32% 63.3 [MPa] # -38% + FDM_0° -51% n.a. n.a. n.a. n.a. n.a. FDM_45° -81% n.a. n.a. n.a. n.a. n.a. FDM_90° -84% n.a. n.a. n.a. n.a. n.a. FDM_0/90° -56% n.a. n.a. n.a. n.a. n.a. FDM_±45° -58% n.a. n.a. n.a. n.a. n.a.

* average fatigue strength of IM ABS data evaluated at 10 4 cycles for R=0. ° average fatigue strength of IM PP data evaluated at 2∙10 6 cycles for R=-1. # average fatigue strength of IM PP-GF30 data from (Meneghetti (2014)) evaluated at 2∙10 6 cycles for R=-1. + missing data concerning fiber length.