PSI - Issue 56

Dan Micota et al. / Procedia Structural Integrity 56 (2024) 144–152 Dan Micota / Structural Integrity Procedia 00 (2019) 000 – 000

149

6

Graphic results of the Digimat MX calibration for both materials with the increased 3.2mm specimen thickness are presented in Fig. 4. The main targets of the curve fitting calibration were the 0° orientation longitudinal curves as these contribute the most to the overall strength of the specimens/materials.

(a)

(b)

Fig. 4. Digimat calibration curves for PPA-GF33 (a) and PPS-GF40 (b) fitted at 0°,45° and 90° orientations.

In order to build a micromechanical virtual model for each of the tested specimen type the fiber orientation tensor (FOT) data had to be obtained Isaincu et al.(2022). Injection molding simulations have been ran, using Autodesk Moldflow software Li et al.(2017), for the 3.2mm wall thickness plates with both materials. From these simulations the mesh and FOT files have been exported for the mapping process done in Digimat MAP module ( Digimat 2022.4 MAP User's Guide Digimat MAP User's Guide , 1992). In this process the specific orientation specimen geometries (already meshed in ANSYS Mechanical) are overlayed onto the mesh of the full injected plate and elements that are detected to share the same approximate space/volume get attributed the specific differentiated value of FOT (fiber orientation tensor). This mapping process is transforming the specimen models into micromechanical structures that are composed of many areas of different oriented fibers, which also follow a stratified structure of good and poor oriented fibers throughout the specimens wall thickness. Fact that can be observed in Fig. 5 where the 0° angled 2mm thick specimen (a) presents shell-core-shell structure model, Bernasconi et al. (2007), with highly oriented fibers in the flow direction for the shell layers and poorly oriented fibers in the core layer. While the same angled specimen of the higher thickness has a skin-shell-core-shell-skin structure, in which the good orientation shell layers occupy less material/thickness percentage than the less in flow-oriented skin and core layers. Thus, explaining the reduction of in flow strength of the higher wall thickness specimens and the anisotropy difference, as the poorly oriented layers behave almost the same regardless of the loading angle.