Computing the bond strength of 3D printed polylactic acid scaffolds in mode I and II using experimental tests, finite element method and cohesive zone modeling

Abstract

The advent of the Three-Dimensional (3D) printing technique, as an Additive Manufacturing (AM) technology, made the manufacture of complex porous scaffolds plausible in the tissue engineering field. In Fused Deposition Modeling (FDM) based 3D printing, layer upon layer deposition of filaments produces voids and gaps, leading to a crack generation and loose bonding.Cohesive Zone Model (CZM), a fracture mechanics concept, is a promising theory to study the layers bond behavior. In this paper, a combination of experimental and computational investigations was proposed to obtain bond parameters and evaluate the effect of porosity and microstructure on these parameters. First, we considered two different designs for scaffolds beside a non-porous Bulk design. Then, we performed Double Cantilever Beam (DCB) and Singe Lap Shear (SLS) tests on the 3D printed samples for Modes I and II, respectively. Afterward, we developed the numerical simulations of these tests using the Finite Element Method (FEM) to obtain CZM bond parameters. Results demonstrate that the initial stiffness and cohesive strength were pretty similar for all designs in Mode I. However, the cohesive energy for the Bulk sample was approximately four times of porous samples. Furthermore, for Mode II, the initial stiffness and cohesive energy of the Bulk model were five and four times of porous designs while their cohesive strengths were almost the same. Also, using cohesive parameters was significantly enhanced the accuracy of FEM predictions in comparison with fully bonded assumption. It can be concluded that for the numerical analysis of 3D printed parts mechanical behavior, it is necessary to obtain and suppose the cohesive parameters. The present work illustrates the effectiveness of CZM and FEM combination to obtain the layer adhesive parameters of the 3D printed scaffold.

Multilayer 3D bioprinting and complex mechanical properties of alginate-gelatin mesostructures

“…This observation can be explained by the fact that layers are only partially bonded in printed samples in contrast to molded ones. For instance, a study investigating polylactic acid (PLA) constructs proved that the bonding between layers is not perfect in printed samples 4 . Our findings thus further highlight the importance of assessing the mechanical properties of printed not molded materials when designing biofabricated tissue-mimicking models.…”

“…3D printing is a promising technology to produce complex structures layer by layer 1 – 4 . It becomes feasible to fabricate complicated geometries that are impossible to obtain through conventional manufacturing methods 5 – 8 .…”

Mechanical and microstructural characterization of titanium gr.5 parts produced by different manufacturing routes

“…While various additive manufacturing processes are currently accessible, one of the main issues is to control input parameters such as powder size, energy input, and feeding methods, as well as to be able to predict the final product quality. For processing titanium and related alloys, direct energy deposition (DED) and powder bed fusion (PBF) can be considered standard AM processes [ 14 ], while novel 3D printing techniques are continually being developed [ 15 ]. There are several methods for creating 3D-printed metal designs but understanding the resulting material properties is critical for proper implementation.…”

Predicting the hyperelastic properties of alginate-gelatin hydrogels and 3D bioprinted mesostructures

“…The mechanical properties of the matrix material and the printing pattern are two influential parameters for tuning the properties of the final construct 8 – 12 . Different materials have previously been used in the biofabrication field, such as thermoplastics 13 , 14 , ceramics 15 , and hydrogels 16 – 18 . However, only hydrogels can be used for cell printing in soft and hard tissue engineering applications.…”