Investigating the fracture behavior of 3D printed orthotropic porous materials under mixed-mode I/II loading

Porous materials possess holes, voids, and free space within their structures. Typically, these pores exhibit a random shape, size, and orientation distribution. The complexities in the structure affect the overall properties of these materials. This work investigates the fracture behavior of orthotropic porous materials using theoretical and experimental approaches. Two novel mixed-mode criteria are developed based on the overall mechanical properties of porous materials derived from uniform deterioration across directions (UDAD) and a combination of generalized elastic moduli with a reinforced isotropic solid model (GE-RIS) methodology. Several experimental tests were conducted on single-edge notch tensile (SENT) specimens of Polylactic Acid (PLA) reinforced with short fibers. The intricate nature of the geometries necessitated the use of the fused deposition modeling (FDM) technique for manufacturing. These specimens were designed to have a random distribution of pores in shape, size, location, and orientation, with porosity varying from 0 to 0.4. With the determination of the fracture load for each case, the critical stress intensity factors (SIF) were calculated using the finite element method. The results indicate that the stress intensity factor depends on porosity, and increasing porosity reduces the failure load but raises the critical SIF of these materials. Additionally, the effect of porosity on the material's fracture toughness is included in the developed mixed-mode I/II criteria. These criteria can serve as upper and lower bounds for estimating the fracture of porous materials. Finally, the proposed criteria were validated with experimental results. • The fracture behavior of orthotropic porous materials with varying pore densities is investigated theoretically and experimentally using the FDM technique. • Novel method developed for creating 3D printed porous material with controlled pore density. • Two novel mixed-mode criteria are developed based on the overall mechanical properties of porous materials derived from Uniform Deterioration Across Directions (UDAD) and a combination of Generalized Elastic moduli with Reinforced Isotropic Solid model (GE-RIS) methodologies. • New modified single-edge notch tensile (SENT) Specimens have been fabricated and tested using the Fused Deposition Modeling technique. • The experimental result shows that the fracture load and toughness depend on the materials' porosity, which is considered in the new criteria