Micromechanical finite-element modeling and experimental characterization of the compressive mechanical properties of polycaprolactone–hydroxyapatite composite scaffolds prepared by selective laser sintering for bone tissue engineering

Abstract

Bioresorbable scaffolds with mechanical properties suitable for bone tissue engineering were fabricated from polycaprolactone (PCL) and hydroxyapatite (HA) by selective laser sintering (SLS) and modeled by finite element analysis (FEA). Both solid gage parts and scaffolds having 1-D, 2-D and 3-D orthogonal, periodic porous architectures were made with 0, 10, 20 and 30% HA by volume. PCL:HA scaffolds manufactured by SLS had nearly full density (99%) in the designed solid regions and had excellent geometric and dimensional control. Through optimization of the SLS process, the compressive moduli for our solid gage parts and scaffolds are the highest reported in the literature for additive manufacturing. The compressive moduli of solid gage parts were 299.3, 311.2, 415.5 and 498.3 MPa for PCL:HA loading at 100:0, 90:10, 80:20 and 70:30 respectively. The compressive effective stiffness tended to increase as the loading of HA was increased and the designed porosity was lowered. In the case of the most 3-D porous scaffold, the compressive modulus more than doubled from 14.9 MPa to 36.2 MPa when changing the material from 100:0 to 70:30 PCL:HA. A micromechanical finite element analysis (FEA) model was developed to investigate the reinforcement effect of HA loading on the compressive modulus of the bulk material. Using a first-principles based approach, the random distribution of HA particles in a solidified PCL matrix was modeled for any loading of HA to predict the bulk mechanical properties of the composites. The bulk mechanical properties were also used for FEA of the scaffold geometries. Results of the FEA were found to be in good agreement with experimental mechanical testing. The development of patient and site-specific composite tissue engineering constructs with tailored properties can be seen as a direct extension of this work on computational design, a priori modeling of mechanical properties and direct digital manufacturing.

Predicting the Elastic Properties of Selective Laser Sintered PCL/β-TCP Bone Scaffold Materials Using Computational Modelling

“…This approach was used by Eshragi et al to determine the bulk mechanical properties of a PCL/hydroxyapatite SLS scaffold 14 .…”

“…Idealised microstructures were used in FE modelling of idealised sintered PCL/Hydroxyapatite scaffold geometries to predict the effect of varying percentages of HA on scaffold stiffness by Eshraghi et al 14 . The lack of realistic geometries and microstructures in their study may account for some of the discrepancies between computational and experimental results.…”

An nMgO containing scaffold: Antibacterial activity, degradation properties and cell responses

“…The specimens (cylinder, 12.7 mm in diameter by 25.4 mm) were compressed to 50% strain at a rate of 1 mm/min [24,25] . The compressive strength and compressive modulus of the scaffolds were determined from the obtained compressive stressstrain curves.…”

Modelling of additive manufacturing processes: a review and classification

“…Modelling of the topology/dimensional accuracy takes places in [28] (analytical-numerical approach), in [29][30][31][32][33][34] (numerical) and in [35] (empirical). Mechanical properties and microstructure modelling has been carried out in [30,[36][37][38][39][40][41] using numerical approaches, whereas in [42] an empirical one has been followed. According to [43], the microstructure, physical and mechanical properties of the parts' being manufactured with the use of SLS, are fundamentally affected by laser power, laser scan speed and laser scan spacing.…”