PSI - Issue 83

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

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Table 4. Printing parameters used for specimens’ fabrication.

Parameter

Value/description

Extrusion nozzle diameter (mm)

0.4 0.4 50

Layer height (mm) Infill density (%)

Infill pattern

Rectilinear

Printing speed – first layer outline (mm/s) Printing speed – first layer infill (mm/s)

50

105 200 300 250 200 X-Y

Printing speed – outer wall of intermediate layers (mm/s) Printing speed – inner wall of intermediate layers (mm/s) Printing speed – infill of intermediate layers (mm/s)

Printing speed – last layer (mm/s)

Printing direction

2.4. Testing procedure Impact tests were performed using a compact, portable Charpy testing machine equipped with a manually operated pendulum system (Fig. 2), specifically designed for the characterization of polymeric materials. The equipment was manufactured by Hounsfield (UK) and features an analogue scale calibrated in imperial units (lb·ft). Following testing, all recorded values were converted to the International System of Units using the conversion tables supplied by the manufacturer with the device.

a)

b)

Fig. 2. Charpy impact equipment: visual scale for toughness measurement (a) and overall view of the equipment (b).

The testing system allows the use of interchangeable pendulum impactors to accommodate materials with different impact resistance levels. At the time of experimentation, a set of seven impactors was available, with nominal masses of 2, 1, 0.5, 0.25, 0.125, 0.0625, and 0.03125 lb. Considering the expected toughness of the PLA specimens, the 0.125 lb pendulum was selected as the most appropriate compromise between measurement sensitivity and energy resolution for the materials under investigation. 3. Fracture testing results Charpy impact tests were conducted at two testing temperatures, 24.1 °C and -30.9 °C, using the 0.125 lb pendulum for all specimens. The absorbed energy results are comparatively illustrated in Fig. 3 for both temperatures, while the corresponding numerical values are reported in Table 5. These data allow direct assessment of the combined influence of material condition (virgin or recycled PLA), printing temperature, and testing temperature on impact energy absorption.