PSI - Issue 56

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

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Another phenomenon that can be observed between the thicknesses for both materials is that the 2mm thick specimens have a wider spread of the stress-strain curves in the orientations range, while the ones for 3.2mm wall thickness are more closely grouped. This is an indication of the anisotropy of the 2 types of specimen thicknesses, high anisotropy in the orientations range for 2mm thickness and low anisotropy for increased wall thickness (3.2mm). Regardless of specimen orientation the material response to loading being similar to an extent, for the higher wall thickness specimens.

Table 1. Mean values ( μ ), standard deviation ( σ ), and coefficient of variation (CV) for the Young’s modulus, tensile strength and strain at break of the increased wall thickness (3.2mm) specimens for PPA-GF33 and PPS-GF40, also the percentual difference (PD) from the lower wall thickness (2mm) specimens.

Young’s modulus

Tensile strength

Strain at break

θ (°)

μ (MPa)

σ (MPa)

CV (%)

PD (%)

μ (MPa)

σ (MPa)

CV (%)

PD (%)

μ (MPa)

σ (MPa) ±0.07 ±0.12 ±0.05 ±0.16 ±0.04 ±0.12 ±0.05 ±0.06 ±0.08 ±0.09 ±0.05 ±0.05

CV (%)

PD (%)

Mat. PPA GF33

0

8996 8797 8113 6980 6665 6363

±210 ±101 ±198 ±407 ±228 ±209 ±733 ±389 ±333 ±170 ±591 ±243

2.3 1.2 2.4 5.8 3.4 3.3 6.3 3.5 3.3 1.9 6.6 2.6

-23.1 -12.8 +2.8 +7.2 +18.6 +13.3 -26.6 -20.6

147 145 136 125 116 111 134 130 121 106 101

±2 ±1 ±2 ±3 ±2 ±2 ±5 ±4 ±3 ±4 ±3 ±3

1.7% -21.3 0.8% -11.2 1.6% +3.4 2.8% +13.4 1.9% +16.9 1.9% +16.0 3.7% -31.1 3.0% -26.4 2.2% -17.5 3.8% -12.6 2.9% -6.6 3.1% -0.2

2.83 3.21 3.45 3.74 3.33 3.57 1.45 1.49 1.59 1.45 1.37 1.28

2.6 3.7 1.6 4.4 1.1 3.4 3.3 3.9 5.1 6.4 3.8 4.2

+28.9 +18.6 -17.6 -27.1 -39.2 -29.0 -10.4 -28.1 -33.3 -33.8 -28.5 -6.8

15 30 45 60 90 15 30 45 60 90 0

PPS GF40

11693 11247 10074

-4.3 +4.7

9051 8887 9191

+18.0 +24.5

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5. Material modeling and calibration With the resulted experimental data, 2 two material models have been developed and calibrated, for the PPA and PPS, similar to (Micota, Isaincu, & Marsavina, 2021), using specialized software Digimat, MX module (Digimat 2022.4 MX User’s Guide Digimat MX User’s Guid e, 1992). This enabled the reverse engineering approach for homogenizing the matrix polymer properties with the elastic properties of the filler (GF), resulting in elasto-plastic material cards based on the Tsai-Hill fracture criterion ( Tsai-Hill Criterion , n.d.). The reverse engineering approach of the Digimat MX ( Digimat 2022.4 MX User's Guide Digimat MX Users Guide , 1992) module is done by varying the material parameters presented in Table 2, each in a physical accurate range of values, until the best possible (optimized) fitting is done simultaneously on the 0°, 45° and 90° stress-strain curves (engineering values in this case), Micota, Isaincu & Marsavina, (2021). The specimen geometry, elaboration technology and filler type have also been accounted for.

Table 2. Material parameters for the Tsai-Hill model used in Digimat MX calibrations.

Material

Matrix Young’s modulus [MPa]

Poisson’s ratio

Yield stress

Hardening modulus

Hardening exponent

Linear hardening modulus [MPa]

Plastic strain multiplier [-]

Fiber aspect ratio [-]

[-]

[MPa]

[MPa]

[-]

PPA-GF33 PPS-GF40

3000 3450

0.37 0.41

22.5 32.5

60

250 150

10 10

3.9

22 25

45.05

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