PSI - Issue 66

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Mohammad Jameel Ziedan et al. / Procedia Structural Integrity 66 (2024) 229–246 Author name / Structural Integrity Procedia 00 (2024) 000–000

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model using ABAQUS software with a hyperelastic material model, considering temperature dependence for accurate predictions of forces, thickness reduction, and temperature distribution. (Franzen et al., 2009) explored the use of SPIF for shaping commercial PVC sheets at room temperature. CATIA V5 software was employed for toolpath generation, geometry analysis, and evaluation of deviations between the formed parts and the original CAD models. Three failure modes were identified; cracking due to stretching, wrinkling from twisting, and cracking from redundant straining. Surface finish quality was significantly influenced by the tool diameter. Experiments with various polymers (polyethylene terephthalate (PET), polyamide (PA), PVC and PC revealed that PET exhibits exceptional formability, while PC maintains transparency after forming. A theoretical framework based on membrane analysis was developed to explain the mechanics of deformation and the influence of process parameters. The process involves common equipment such as a blank holding fixture, heat gun, CNC machine, and software for toolpath planning. Three software tools are used; SolidWorks for generating CAD models of the desired shapes, Slic3r for generating G-code toolpaths from the CAD models, and Universal G-code sender for controlling the CNC machine and executing the toolpaths. 1.6. Biocompatible Polymers SPIF is used for many applications, including those requiring biocompatible materials like Polylactic Acid (PLA), Polylacticglycolicacid (PLGA), Polyethylene glycol (PEG), Polycaprolactone (PCL), Polyethylene (PE), Polypropylene (PP), Polylacticaprolactone (PLCL), ultrahigh molecular weight polyethylene (UHMWPE), and poly methyl methacrylate (PMMA). These biocompatible polymers offer properties such as biocompatibility, mechanical strength, processability, and controllable degradation, making them suitable for SPIF applications in medical and healthcare industries (Centeno et al., 2017; Clavijo-Chaparro et al., 2018a; Hernández-Ávila et al., 2019; Raheem & Al-Mukhtar, 2020; Raheem & Al ‐ Mukhtar, 2021). The implants using a polymer known for its biocompatibility, light weight, and bone-like mechanical properties have been manufactured (Raheem & Al-Mukhtar, 2020; Raheem & Al ‐ Mukhtar, 2021). The SPIF method resulted in lower accuracy, the TPIF variant with a negative die achieved better geometric precision (Table 5). These results are the most important in the context of the bilayer approach. This method offers potential for creating parts with combined properties, such as strength and elasticity, which could be valuable for biocompatible applications like medical devices, see Fig. 4. (Bagudanch et al., 2019) explored the use of (ISF) to manufacture cranial implants from biocompatible polymers and the formability of (PCL) have been inveiagted. But were found it exhibited significant springback, leading to geometric inaccuracies. Work with (UHMWPE) shows promising results. By using (TPIF), the suitable geometric accuracy has achieved and demonstrated the possible of ISF for creating low-cost, customized cranial implants with properties similar to bone; see Table 3. The impact tests on the samples for various alloys and thicknesses, anchored to supports made of (PMMA) have been conducted (Bagudanch et al., 2019). It was found that the prostheses effectively absorbed impact energy without fracturing, with energy absorption exceeding 70% in most cases. Table 5. Comparison of nonabsorbable polymers for cranial implants (Bagudanch et al., 2018). Polymer Advantages Disadvantages PMMA - Biocompatible and biostable - No resorption - Low cost - Elastic modulus similar to the skull bone (between 3.0 and 3.4 GPa) - Large amount of heat is required to mold the part, which could damage surrounding tissues - Fracture due to impact trauma - Tissue ingrowth is not possible - Migration

PEEK

- Strong, inert and biocompatible - Density, mechanical strength and elastic modulus (3.24 GPa), comparable to cortical bone

- Lack of osteointegration - High cost

- Risk of infection

PE

- Bone ingrowth for porous PE enhancing biocompatibility - Elastic modulus between 0.3 and 1.0 GPa - Easy to shape