PSI - Issue 83

Manuel A.R.V. Esteves et al. / Procedia Structural Integrity 83 (2026) 146–153

151

40

40

30

10 Absorbed energy [kJ/m 2 ] 20

10 Absorbed energy [kJ/m 2 ] 20 30

0

0

a)

b)

Virgin PLA Recycled 220°C Recycled 237°C Recycled 255°C

Virgin PLA Recycled 220°C Recycled 237°C Recycled 255°C

Fig. 3. Charpy impact test results at (a) 24.1°C and (b) -30.9ºC.

Table 5. Summary of Charpy impact test results at 24.1°C and -30.9ºC, with CoV.

Temperature

Material

Absorbed energy ± deviation (kJ/m 2 )

CoV (%)

Pristine PLA

34.08±0.31 24.57±2.23 24.04±1.17 19.21±2.08 14.72±2.11 16.15±1.85 16.86±1.89 15.89±1.73

0.91 9.06 4.87

Recycled at 220°C Recycled at 237°C Recycled at 255°C Recycled at 220°C Recycled at 237°C Recycled at 255°C Pristine PLA

24.1ºC

10.80 14.36 11.45 11.23 10.87

-30.9ºC

At room temperature (24.1 °C), virgin PLA exhibited the highest impact energy absorption among all tested materials. For recycled PLA, the specimens printed at 220 °C showed the greatest absorbed energy, followed closely by those printed at 237 °C, whereas specimens printed at 255 °C displayed the lowest impact resistance. This trend indicates a progressive reduction in impact energy absorption with increasing extrusion temperature for recycled PLA. Despite not maximizing absorbed energy, the 237 °C printing condition resulted in the most consistent behavior, presenting the lowest average coefficient of variation (CoV=4.87%) among all recycled PLA configurations. Testing at -30.9 °C produced a markedly different response. Under these conditions, virgin PLA no longer exhibited the highest absorbed energy, nor did recycled PLA printed at 220 °C. Instead, recycled PLA printed at 237 °C demonstrated superior impact performance relative to the other configurations. Considering that its absorbed energy at 24.1 °C was already close to that of recycled PLA printed at 220 °C, this printing temperature can be regarded as the most favorable compromise for recycled PLA for both testing temperatures. A detailed comparison between materials and printing conditions reveals the following observations: • Virgin PLA showed highly repeatable results at 24.1 °C, with minimal scatter (CoV=0.91%). However, impact energy absorption decreased dramatically at -30.9 °C, with a reduction exceeding 130%, accompanied by a significant increase in result dispersion (CoV=14.36%). • Recycled PLA printed at 220 °C followed a similar trend, absorbing more energy at 24.1 °C than at -30.9 °C. Nevertheless, the reduction between temperatures was less pronounced (52.1%), and the variability remained relatively comparable between room and low temperatures (CoV=9.06% and 11.45%, respectively). • Recycled PLA printed at 237 °C exhibited improved impact performance and notably lower scatter at 24.1 °C compared with the other recycled configurations. Although absorbed energy still decreased at -30.9 °C (by 42.6%), this condition delivered the best overall balance between energy absorption and result consistency (CoV=11.23% at -30.9 °C). • Recycled PLA printed at 255 °C presented the smallest relative difference in absorbed energy between testing temperatures (20.9%), suggesting a convergence of brittle behaviour. The CoV values were similar at both temperatures (10.80% at 24.1 °C and 10.87% at -30.9 °C), indicating limited sensitivity to testing temperature but overall reduced impact resistance.