Experimental and numerical investigations for compressive behavior of porous hydroxyapatite bone scaffold fabricated via freeze-gel casting method

Abstract

Artificial bone scaffolds with a porosity of ≥64% were manufactured using hydroxyapatite (HA). The Freeze-gel Casting method using tert-butyl alcohol (TBA) as a solvent was adopted to maintain proper mechanical strength. The manufactured HA scaffold had excellent internal connectivity owing to the continuous connection of the long columnar pores and arrangement of the constant pore walls. For the HA scaffold, compression tests at different strain rates under uniaxially compressed loads were performed, and the compressive behavior according to the strain rate was analyzed. A maximum yield stress of 2–3 MPa was observed, and the overall compressive behavior was divided into elastic, plateau, and densification sections, which were different from the brittleness behavior of ordinary ceramics and similar to that of polymer materials. The compressive behavior of the HA scaffold was successfully simulated by applying the Frank–Brockman–Zairi constitutive model used to simulate elasto-viscoplastic material behavior. Seven material parameters belonging to the constitutive equation were proposed for the HA scaffold by adopting a deterministic approach for material parameter identification. Models can be developed from methods for simulating the mechanical behavior of a porous ceramic scaffold to predict the long-term mechanical behavior of the scaffold inserted in vivo, which may help in bone defects recovery.

Keywords

• Hydroxyapatite
• Porous bone scaffold
• Elasto-viscoplastic constitutive model
• ABAQUS user-defined subroutine UMAT
• Material parameter identification
• Nonlinear material behavior