# Mechanical Behavior of Ti6 Al4V Scaffolds Filled with CaSiO\({}_{3}\) for Implant Applications
## 1 Introduction  
Titanium and its alloys have been widely used for biomedical and orthopedic applications, such as hip, knee, femur, vertebra, bone and skull, due to their excellent antibacterial/biocompatibility, strength-to-weight ratio and wear and corrosion resistance in comparison with stainless steel [1; 2; 3; 4; 5]. Implants have been made by computer numeric control (CNC) machining, or powder metallurgy, followed by different post-processing procedures. The metallic biomaterial scaffolds are applied for stent placement [6] or bone replacement [7]. Three dimensional (3D) printed porous scaffolds are suitable for seeding cells, delivering drugs, and are able to carry compression/tensile loading [2; 3]. Biological activities along the scaffold surface (cell growth) and structural design of the scaffolds for additive manufacturing (AM) are both very important, and extensive research has been conducted [8]. With the use of optimal scaffold material and the suitable design for AM, scaffolds with added functionalities, elastic modulus, and strength matching the human bone can be realized [9]. Triply periodic minimal surfaces (TPMS) are some of the designs that are expected to be optimal candidates for bone tissue engineering applications. Primary simulation of the TPMS are crucial for designing these scaffolds to figure out the stress distribution, deformation and failure mechanism of porous structure [10; 11]. Gradient structures, unit cell size, strut diameter, the volume fraction the of sample, plasticity and damage tolerance, as well as the minimizing of cost/time are considered during the computer-aided design (CAD) and simulation. In order to have optimized lightweight structures under loading and in vivo or in vitro conditions, printed scaffolds can be graded axially or radially [12]. Recently, research is focused upon polymeric printing using polyjet/inkjet deposition [13], which is faster with no post-processing, unlike metal printing. However, the low mechanical properties of polymer 3D printed materials make it non-applicable for in vivo conditions. Porous Ti6 Al4V structures have yield strength and compressive strength in the range of 90-220 MPa [14]. The computer-aided design (CAD) of porous scaffolds and finite element analysis (FEA) have recently attracted much attention in the tissue engineering field. Fluid permeability [15] and biocompatibility [16] of scaffolds depends directly on the pore geometry and topology [17] of structures. The curved shape, smoothness, good flowability, 3D manufacturability and biocompatibility of Ti6 Al4V powder particles makes Ti-based alloy promising for load bearing bone implants [18]. It is well known that the artificial bone scaffolds should have the following characteristics: (1) Biocompatibility with living tissues; (2) mechanical properties for trabecular bone and cortical bone (ranging from 0.7 to 15 MPa till \(>\)100 MPa [19]); and (3) porous fabricated structures for osteoporosis diseases. Periodic porous materials like TPMS are potential candidates for biomimetic scaffold architecture [19]. The main advantage of TPMS scaffolds is the open interconnected cell structure, deemed to facilitate cell migration, vitalization and vascularization, while retaining a high degree of structural stiffness [20]. Henceforth, mechanical properties, especially compressive strength, is considered as an important parameter for TPMS scaffolds. In this paper, we have performed compressive tests, where the experimental results are compared with the FEA for the selected promising TPMS structures. Ti6 Al4V is considered as excellent biomaterial because of higher fatigue strength, tensile strength and compressive strength [21; 22; 23; 24]. However, it is bioinert, where an improper integration takes place with the host bone, resulting in a weak interfacial bond. As a result, at the bone-implant interface, there can be an accumulation of the necrotic fibrous tissue [25].