PSI - Issue 80

R. Salem et al. / Procedia Structural Integrity 80 (2026) 256–268 Rania Salem / Structural Integrity Procedia 00 (2025) 000 – 000

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Nomenclature A hbr

Area of horizontal bonding regions Area of printed filament without bonding Area of vertical bonding regions

A nbr A vbr

A p A t

Area of porosity

Total area of the RVE

ABS AM

Acrylonitrile Butadiene Styrene

Additive Manufacturing ASTM American Society for Testing and Materials d h Horizontal length of the RVE d v Vertical length of the RVE E h Numerically homogenized Young modulus E hbr

Young’s modulus assigned to the horizontal inter -filaments bonding regions

E ref E vbr

Young’s modulus assigned to the non-bonded regions

Young’s modulus assigned to the vertical inter -filaments bonding regions

E p

Young’s modulus assigned to porosity region

FEA FFF HBR ISO

Finite Element Analysis Fused Filament Fabrication Horizontal Bonding Region

International Organization for Standardization

ME MT

Material Extrusion

Mori-Tanaka

NBR

Non-Bonded Region

r Radius of the printing filament Representative Volume Element VBR Vertical bonding regions ℎ volume fraction of horizontal bonding region volume fraction of non-bonded region porosity volume fraction volume fraction of vertical bonding region 1. Introduction RVE

Additive manufacturing (AM), particularly fused filament fabrication (FFF), builds thermoplastic parts layer-by layer, offering significant design freedom. FFF parts serve diverse applications, from consumer goods to flexible electronics, biomedical devices, and automotive/aerospace components (Brenken et al., 2018), while also contributing to sustainability through reduced waste and energy-efficient production (Alami et al., 2023). However, intrinsic defects, such as porosity, severely compromises mechanical performance and durability, limiting structural use (Aliheidari et al., 2018). Controlling porosity is therefore essential for mechanical integrity (Sahoo et al., 2024; Akhoundi and Behravesh, 2019). FFF's growth is impeded by a lack of standardized protocols, impacting repeatability and qualification for critical applications. Traditional standards (ASTM, ISO), designed for homogeneous materials, fail to accommodate FFF's anisotropy, porosity, adhesion issues, and raster orientation effects. Specifically, tensile standards neglect directional dependence and structural heterogeneities like voids (Sola et al., 2023), leading to unreliable comparisons and qualification, limiting end-use confidence. This standardization gap extends critically to tensile testing. Specimen geometry designed for homogeneous materials causes premature failure in FFF (e.g., dumbbell fillets), while rectangular specimens better reflect bulk behavior (Sola et al., 2023). Minor geometric variations cause significant