Rheological Behavior and Dynamic Mechanical Properties for Interpretation of Layer Adhesion in FDM 3D Printing

Abstract

Commercial filaments of poly(lactic acid) (PLA) composites with particulate filler, carbon fiber, and copper powder with different contents were fabricated by FDM 3D printing in XZ-direction at bed temperatures of 45 °C and 60 °C. The effects of additives and bed temperatures on layer adhesion, fracture behavior, and mechanical performance of the PLA composites 3D printing were evaluated. Rheological properties informed viscous nature of all filaments and interface bonding in the PLA composites, which improved printability and dimensional stability of the 3D printing. Crystallinity of the PLA composites 3D printing increased with increasing bed temperature resulting in an improvement of storage modulus, tensile, and flexural properties. On the contrary, the ductility of the 3D printing was raised when printed at low bed temperature. Dynamic mechanical properties, the degree of entanglement, the adhesion factor, the effectiveness coefficient, the reinforcing efficiency factor, and the Cole–Cole analysis were used to understand the layer adhesion, and the interfacial interaction of the composites as compared to the compression molded sheets. SEM images revealed good adhesion between the additives and the PLA matrix. However, the additives induced faster solidification and showed larger voids in the 3D printing, which indicated lower layer adhesion as compared to neat PLA. It can be noted that the combination of the additives and the optimized 3D printing conditions would be obtain superior mechanical performance even layer adhesion has been restricted.

Rheology, crystallization, and process conditions: The effect on interlayer properties in three-dimensional printing

“…The variation in the degree of crystallinity of PLA prints is illustrated in Figure4(b). The values are in good agreement with that reported in literature for PLA printed under similar conditions39,[52][53][54] . Although the values are relatively low compared to most semicrystalline polymers, a distinct increasing trend is observed where the crystal fraction in the prints increases with print temperature.…”

Study of the interlayer bonding strength for combined 3D printing and milling of polyetheretherketone

“…The storage modulus represents the amount of energy stored in the material due to elastic reversible deformation. The increased interlayer bonding strength results in an increase in the overall stiffness of the specimen and a consequent increase in the storage modulus 34 . However, when the temperature is too high, the PEEK molecular chains begin to degrade, 10 and the overall mechanical strength of the specimen decreases faster than the increase in interlayer bonding strength, so the storage modulus also decreases slowly.…”

“…As shown in Figure 8b, the storage modulus shows a gradual slowing decline trend in the interval from 0.1 to 0.3 mm of the layer thickness, while there is a small increase in the interval from 0.3 to 0.4 mm. This is because an increase in layer thickness causes a drop in contact pressure on the material's bonding surface, which weakens inter‐molecular diffusion on the bonding surface 34 . The interlayer bonding strength decreases, and the storage modulus decreases accordingly.…”

A Comparative Analysis of Chemical, Plasma and In Situ Modification of Graphene Nanoplateletes for Improved Performance of Fused Filament Fabricated Thermoplastic Polyurethane Composites Parts

“…Rheological properties can confirm the molecular entanglement and molecular relaxation of the polymer composites and guideline of the final construction of FDM parts [ 40 , 41 ]. Figure 3 a,b demonstrate the relationship between shear stress and shear viscosity on the steady shear rate of the different TPU/GnPs composites.…”

“…Over the entire range of shear rates investigated, all the non-Newtonian fluids followed a power-law relationship. At higher shear rates, the shear stress and shear viscosity of all the composites are revealed comparable regardless of the incorporation of fillers [ 41 ]. Figure 3 c shows log–log plots of shear viscosity versus shear rate and the power-law index ( n ) for all TPU/GnPs composites at 190 °C.…”