Feasibility study of scapula bone as a next-generation material for biomedical applications

ABSTRACT

This study investigates the influence of material thickness on the mechanical properties, specifically flexural and tensile properties, of scapula bone specimens from Deccani breed sheep in India. A three-point bending test and a tensile test were conducted on samples with varying thicknesses (1, 2 and 5 mm), and the flexural strength, flexural modulus, ultimate load, tensile deformation and von Mises stress were measured. Thicker specimens exhibited higher flexural properties than thinner counterparts. Statistical analysis using one-way ANOVA confirmed that material thickness significantly impacted the flexural and tensile properties of the samples. Additionally, a simulation analysis was performed using ANSYS Workbench to validate the experimental results and provide insights into the tensile and flexural behaviour of the specimens. The findings suggest that thicker samples are better equipped to handle bending stresses and tensile loads and are more suitable for applications requiring resistance to bending loads, stiffness, load-bearing capacity and tensile strength.

KEYWORDS:

• Scapula bone
• ANSYS
• ANOVA
• tensile/flexural strength

1. Introduction

Currently, the world is focusing on sustainable development goals (SDGs) out of which this study focuses on SDG 12, i.e. responsible consumption and production. As Sheep have many body parts (namely horn, scapula bone and hoof) once taken out from the slaughterhouse will be thrown on earth as waste material. Bone is a living organ that is both intricate and dynamic. The bones in all the vertebrates meet a diverse set of functional demands, not all of which are mechanical. The most proximal bone of the sheep’s forelimb is the scapula. The scapula is located on the lateral wall of the thorax's cranial portion. It is a predominant bone for the relative motion of the forelimb. To adapt to the form of the thoracic wall, it is slightly curved and sloped laterally. It has a triangle outline, with a longer vertebral border and a narrower neck. The scapular spine is less tuberous. There are many studies to replace the scapula bone in sheep with various novel materials such as polylacrocaptone tricalcium phosphate (Spalthoff et al. 2019), polylactic acid and thermoplastic polyurethane (Kurt et al. 2022) and polyether ether ketone(PEEK) (Katsifis et al. 2023) as osseo-integration either directly with scaffold via 3D printing or plasma immersion ion implantation (PIII) imparts osteo-adhesion on 3D printed PEEK (Kruse et al. 2022). In India, the sheep is considered to be a workshop animal killed in the slaughterhouse and its parts such as the scapula, hoof and horn are thrown as waste materials on earth. This has created a lot of biowaste in the environment which is unutilized. However, it has lot many potential features such as the material once cleansed for biomedical applications has biocompatibility, biodegradability, eco-environmental and economically viable solutions and can replace many of the prerequisites of today’s biomedical world. As the tuber scapula is attached to the glenoid cavity's rim, the inferior or glenoid extremity is longer. The subscapular fossa has a large rim. Scapula bone is one of the most critical and unutilized parts in animals to date, which is left over from the slaughterhouse. Some of the parts such as the scapula, horn and hoop are the left-over parts in a typical big sheep horn animal (Mysore et al. 2021). Sheep and goats are common animals liced from the slaughterhouse and to date there is no proper utilization of these in society. As per census 2017 in India, the big sheep horn of Deccani has more than 4 million population in three states (Mysore et al. 2021; Lin and Kang 2021). Today, hardly there are any works identified by authors on scapula bone usage in real-time applications. The objective is to determine the variations in the mechanical properties of tthe scapula and the mechanical anisotropy along both longitudinal and transverse directions (Luo et al. 2019). The work by Albert (Beckers et al. 1998) focused on the microvascular mandibular construction in dental implants using the iliac crest and scapula bone. The density of the bone and thickness of the cortical seem to be matching with the iliac crest and scapula. Another study focused on the biometrical analysis of the scapula of the Indian civet, leopard cat and fishing cat (Pathak et al. 2021). The literature says swimming and climbing species disclose wider scapula bone (Charles and Bechtol 1980). Biometric study reveals the nomenclatures of each individual part of the scapula with the comparison of leopard cat, fishing cat and Indian civet (Galvez-Lopez 2020). Three cases of scapula bone have been studied ipsilateral upper limb and lower limb (Stacy and Yousefzadeh 2000).

The objective of the current work includes a comparative biometrical analysis of the scapula of animals with different compositions and structures of bone tissue (fishing cat, leopard cat and small Indian civet). This article provides a review and practical guide to understanding and analysing the mechanical properties of scapula bone defined by stress–strain curve performed under a uniaxial tensile testing machine until failure. Tensile, flexural, impact and bio-chemical tests and the like have been accomplished to understand material properties at different cross-section areas of the scapula. The solution data are further analysed using statistical and simulation tools. A thorough understanding of bone strength and the data on mechanical behaviour under various physical loads is arrived.

The study of the mechanical properties of biological materials is crucial for understanding their structural and functional role in living organisms (Currey 2006; Fratzl and Weinkamer 2007). Bones, in particular, play an essential part in providing support, protection and mobility to the body. The scapula bone, commonly referred to as the shoulder blade, is a flat, triangular bone that connects the humerus (upper arm bone) to the clavicle (collarbone) (Bar-On et al. 2018). The entire bone structure is non-uniform. It plays a vital role in the movement and stability of the shoulder joint, making it an essential subject for investigation. This research article aims to explore the mechanical properties of scapula bones from different animal species, to gain insights into their adaptability, resilience and evolutionary implications.

Scapula bones are unique in their shape and function, often exhibiting species-specific morphologies that reflect the animals’ locomotive habits, biomechanical needs and environmental pressures (Bar-On et al. 2018; Blob and Biewener 2001). The mechanical properties of the scapula can influence an animal's overall skeletal system, affecting its ability to withstand loads, resist fractures and adapt to various activities (Reilly and Currey 2000). Previous studies have focused on the mechanical properties of long bones, such as the femur and tibia (Currey 2006; Reilly and Currey 2000), while scapula bones have received comparatively less attention. By investigating the mechanical properties of scapula bones, this study will contribute to the broader understanding of bone biomechanics, biomaterials and comparative anatomy.

In this research article, we will examine the mechanical properties of scapula bones from various animal species, including mammals, birds and reptiles. We will employ a combination of experimental techniques, such as tensile testing, compression testing and three-point bending tests, to measure the strength, stiffness and toughness of the bone samples (Turner and Burr 1993). Additionally, we will investigate the microstructure of the scapula bone, analysing its mineral composition, collagen orientation and trabecular structure using scanning electron microscopy (SEM) and X-ray diffraction (XRD) (Fratzl et al. 2004).

Through a comprehensive understanding of the mechanical properties of scapula bones in animals, we aim to provide valuable insights into the structure–function relationship, the evolutionary adaptation of bones to different biomechanical needs and potential applications in the fields of orthopaedics, prosthetics and bio-inspired material designs (Bar-On et al. 2018; Fratzl and Weinkamer 2007). The findings of this study will not only advance our knowledge of bone biomechanics but also contribute to the development of innovative solutions for human health and well-being. Table 1 illustrates the various kinds of animals having scapula bone with composition for a comparative study analysis.

Table 1. Composition of scapula bone available on earth with various animals.

Animal Species	Hydroxyapatite	Collagen	Water	Lipids	Calcium	Phosphorus	Magnesium	Sodium	Potassium	Trace elements	References
Chicken	53–58	28–33	8–11	4–7	22–27	8–11	0.1–0.2	0.1–0.2	0.1–0.2	0.1–0.3	Fratzl et al. (2004), Alexander and Pond (1992), Martiniaková et al. (2006)
Kangaroo	64–69	22–27	6–11	1–5	27–32	12–17	0.3–0.7	0.1–0.3	0.1–0.3	0.1–0.3	Reilly and Currey (2000), Fratzl et al. (2004)
Alligator	61–66	19–23	4–7	2–5	25–30	11–14	0.2–0.5	0.1–0.3	0.1–0.3	0.1–0.3	Fratzl and Weinkamer (2007), Boskey and Posner (1984)
Turkey	58–63	27–32	12–17	8–13	20–25	5–10	0.5–0.9	0.1–0.3	0.1–0.3	0.1–0.3	Fratzl et al. (2004), Alexander and Pond (1992), Martiniaková et al. (2006)
Deer	66–71	23–28	7–12	3–8	26–31	11–16	0.6–1.0	0.1–0.3	0.1–0.3	0.1–0.3	Reilly and Currey (2000), Boskey and Posner (1984), Currey (2006)
Rat	56–61	28–33	9–14	3–7	22–27	9–14	0.1–0.5	0.1–0.3	0.1–0.3	0.1–0.3	Turner and Burr (1993), Fratzl and Weinkamer (2007), Alexander and Pond (1992)
Ostrich	50–55	30–35	10–15	4–8	21–26	7–12	0.1–0.3	0.1–0.2	0.1–0.2	0.1–0.3	Fratzl et al. (2004), Alexander and Pond (1992), Martiniaková et al. (2006)
Dolphin	65–70	20–25	4–9	1–6	29–34	14–19	0.9–1.3	0.1–0.3	0.1–0.3	0.1–0.3	Turner and Burr (1993), Boskey and Posner (1984), Fratzl et al. (2004)
Elephant	63–68	19–24	3–8	0–5	30–35	15–20	1.0–1.4	0.1–0.3	0.1–0.3	0.1–0.3	Reilly and Currey (2000), Fratzl et al. (2004), Currey (2006)
Human	60–65	20–25	5–10	1–6	25–30	10–15	0.2–0.6	0.1–0.3	0.1–0.3	0.1–0.3	Fratzl et al. (2004), Currey (2006), Price et al. (2005)
Cow	65–70	18–22	6–9	1–4	26–31	12–15	0.3–0.6	0.2–0.4	0.2–0.4	0.1–0.3	Turner and Burr (1993), Fratzl and Weinkamer (2007)
Horse	63–68	22–27	7–12	3–8	23–28	8–13	0.2–0.4	0.1–0.2	0.1–0.2	0.1–0.3	Fratzl et al. (2004), Fratzl and Weinkamer (2007)
Pig	62–67	23–28	8–13	4–9	22–27	7–12	0.1–0.3	0.1–0.2	0.1–0.2	0.1–0.3	Alexander and Pond (1992), Currey (2006)
Sheep	62–67	21–25	5–8	5–10	21–26	6–11	0.2–0.6	0.1–0.3	0.1–0.3	0.1–0.3	Reilly and Currey (2000), Alexander and Pond (1992), Boskey and Posner (1984)
Dog	58–63	22–27	7–12	3–6	23–28	9–12	0.1–0.3	0.1–0.3	0.1–0.3	0.1–0.3	Turner and Burr (1993), Fratzl and Weinkamer (2007), Currey (2006)

2. Materials and methods

2.1. Materials

The focus of the study was on leftover parts from the slaughterhouse resulting in three of the main constituents in sheep. They are horn, scapula bone and hoof. However horn-related work has already been published (Mysore et al. 2021), whereas scapula bone and hoof are in the process of investigation for the feasibility study out of which scapula bone has been considered in this current work, as shown in Figure 2, the Scapula bones of 1-year-old Deccani breed sheep (Karnataka sheep; Ovis Canadensis) were taken within 24 h of slaughter from a local butcher (Used for food purposes; Hubballi Taluq, Dharwad District, Karnataka, India). Before the specimens were extracted, the scapula bones were kept cool in a controlled atmosphere. The slicing strategy for obtaining the maximum number of coupons is depicted in Figures 1 and 2.

Figure 1. Scapula bone location for sheep and goats.

Figure 2. Scapula bone of Deccani sheep.

2.2. Methodology

In the form of methodology, a road map for the complete research project is framed. The details are depicted in Figure 3 with the process map. The project began with the extraction of a characteristic breed, ‘Deccani’, from a slaughterhouse. Each bone was chopped under certain ideal settings to get the most coupons from it. The specimens were removed following the ASTM standard and filed to produce the exact form and size shown in Figure 4.

Figure 3. Thick-thin-medium portion on scapula bone.

Figure 4. Experimental process methodology.

Table 2 illustrates the mechanical and physical properties of scapula bone from various literature sources. These values are extracted as quoted in the predecessor work. The variation in terms of values might be because of many reasons to name a few the geographical indication and every species will have variation in its material properties as it evolved over some time based on the gene, climatic and local adoptive conditions.

Table 2. Mechanical and physical properties of scapula bone in various available sources.

Animal species	Young's modulus (MPa)	Yield strength (MPa)	Ultimate strength (MPa)	Poisson's ratio	Compressive yield (MPa)	Density (g/cm³)	Reference
Horse	6000–8000	80–120	100–150	0.3–0.4	100–150	1.7–2.0	Reilly and Burstein (1975), Skedros et al. (2003b)
Cow	6000–8000	80–120	100–150	0.3–0.4	100–150	1.7–2.0	Reilly and Burstein (1975), Skedros et al. (2003b)
Sheep	4000–6000	60–90	80–120	0.3–0.4	70–100	1.6–1.9	Reilly and Burstein (1975), Skedros et al. (2003b)
Dog	5000–7000	70–110	90–130	0.3–0.4	90–130	1.6–1.9	Reilly and Burstein (1975), Skedros et al. (2003b)
Chicken	2000–4000	40–60	60–80	0.3–0.4	40–70	1.4–1.7	Yeni and Fyhrie (2001), Shaw and Stock (2009)
Alligator	3000–5000	50–80	70–110	0.3–0.4	60–90	1.5–1.8	Currey (2006)
Emu	2500–4500	45–70	65–85	0.3–0.4	45–75	1.4–1.7	Yeni and Brown (1998)
Dolphin	5000–7000	70–110	90–130	0.3–0.4	90–130	1.6–1.9	Bar-On et al. (2018)
Beaver	4500–6500	60–100	80–120	0.3–0.4	80–110	1.6–1.9	Skedros et al. (2003a)
Red Kangaroo	4000–6000	60–90	80–120	0.3–0.4	70–100	1.6–1.9	Blob and Biewener (2001)

3. Experimental tests

The current work is based on a thorough examination of the tensile and flexural properties of the scapula bone. All specimens are removed from the bone and scraped with 120-grit sandpaper. Five samples were created for each condition of specimen thickness, as shown in Figure 5. The thin specimen is 1 mm thick, while the medium and thick specimens are 2 mm and 5 mm thick, respectively. The ASTM standard requires the flat specimens for result extraction and it is mandatory to have coupons of flat and longitudinal for the testing. The samples were tested in a dry (ambient) environment.

a.	Tensile test:

Figure 5. Coupons for tensile test.

Tensile tests were performed on a total of 15 samples. Five of them, in particular, are in thin, medium and thick condition. Tensile testing was carried out using Micro-universal testing equipment outfitted with 10KN load cells. The miniature specimens were created in accordance with ASTM D-3039 (Carlson and Judex 2007). To prevent sliding, the two ends of each sample were covered with a 100-grit sandpaper. On one end of the gripper, a uni-axial load is scoped. The gauge length was set at 25 mm, and the crosshead speed was set at 2 mm/min.

b.	Flexural test:

Flexural strength testing determines the bending strength of a specific specimen. The coupons were sliced into rectangular prisms in accordance with ASTM D790–07 (ASTM International 2007; Yeni and Brown 1998). The coupon test for a 10-tonne capacity was performed using a Micro Universal Testing Machine (UTM) manufactured by Tinius Olsen in India (Bar-On et al. 2018). To create three sets of samples, fifteen coupons were etched, five for each thickness condition.

4. Results and discussion

4.1. Tensile strength test

Tensile strength tests were performed on three examples, and the results are shown in Figure 8.

The tensile yield strength measured for the thin section of scapula bone is 81.3 MPa, which is more than that of High-Density Polyethylene, ABS, Polypropylene and comparable Poly-methyl-methacrylate (PMMA) and higher than that of other fibre-reinforced polymer composites (Yeni and Fyhrie 2001). The thin section is in a pristine form comprising calcium and hydroxyapatite which is strong in terms of tensile behaviour but in the case of the medium and thick sections in between bone there will be a soft tissue which does not provide a sufficient amount of strength during tensile strength test. Figure 6.

Figure 6. Stress–strain curve for all samples.

Figure 7 illustrates the mechanical properties with thin and thick conditions. The yield strength of a thin specimen is 24.55% higher than that of a medium specimen and 87.72% higher than that of a thick specimen. Young's modulus for thin is 23.84% and 83.11% greater than for the other two situations. Failure strain is 36.18% higher in the medium condition and 63% higher in the thin and thick situations, respectively. Medium-condition specimens absorb 23.57% more energy and bend plastically without shattering than thick- and thick-condition specimens, respectively. Finally, distortion in the medium condition specimen is more than in other peers. However, we find that the yield strength of thin condition is 27.43% higher than the yield strength of dry longitudinal condition of large sheep horn (Mysore et al. 2021). Toughness for medium-conditioned specimens is 81% more than toughness for moist longitudinal conditions (Mysore et al. 2021) (Table 3).

Figure 7. Mechanical properties yield strength and ultimate strength.

Table 3. Material properties of scapula bone with varied thickness.

	Thin (1 mm)	Medium (2 mm)	Thick (5 mm)
Young’s modulus (MPa)	109.9	83.70	18.56
Yield strength (MPa)	81.3	61.34	9.98
Ultimate strength (MPa)	84.7	61.68	11.2
Failure strain (%)	1.9375	3.04	1.125
Toughness (M J/m^3)	106.62625	139.7925	11.4925

The data presented in the table show the mechanical properties of materials with varying thicknesses (1, 2 and 5 mm). The properties include Young's Modulus, Yield Strength, Ultimate Strength, Failure Strain and Toughness. A statistical analysis of these properties can provide insights into the behaviour and performance of these materials under different conditions.

Upon examining the mean values, there is a significant decrease in Young's Modulus, Yield Strength and Ultimate Strength as the material thickness increases. This trend may be attributed to the potential changes in material microstructure, porosity or overall structural integrity as the thickness increases. The thinner samples (1 and 2 mm) appear to have higher stiffness and strength compared to the thick (5 mm) sample, making them potentially better suited for applications requiring high load-bearing capacity and resistance to deformation.

The Failure Strain, which represents the material's ability to deform before failure, shows an interesting trend. The medium-thickness sample (2 mm) exhibits the highest failure strain among the three samples, suggesting that it may possess a better balance between stiffness and ductility compared to the thin (1 mm) and thick (5 mm) samples. This property could be advantageous for applications where energy absorption and resistance to fracture are crucial, such as in impact or dynamic loading situations.

The toughness values also show a noticeable trend, with the medium-thickness sample (2 mm) exhibiting the highest toughness, followed by the thin (1 mm) and thick (5 mm) samples. The higher toughness value for the medium-thickness sample indicates its potential ability to absorb more energy before failure, making it more suitable for applications where impact resistance and energy absorption are critical factors.

However, the coefficients of variation for these properties are relatively high, ranging from 33.25% to 52.97%. This suggests that there may be significant variability in the material properties across the samples, which could be attributed to factors such as inconsistencies in material processing, variations in microstructure or differences in the testing methodologies. It is essential to consider these variations when interpreting the results and making conclusions about the overall material behaviour.

However, from theabove table, it is quite clear that substantial results are achieved for thin- and medium-condition specimens. To confirm the importance of thickness on mechanical characteristics, a one-way ANOVA analysis was performed on the findings shown in Table 4 using the Statistics Kingdom two-way ANOVA calculator. The influence of specimen thickness on yield stress, Young's modulus, ultimate strength and failure strain was investigated independently using one-way ANOVA. In Table 4, DF denotes the degree of freedom; SS denotes the sum of squares and MS is the mean square. Furthermore, the F-value and P-value are critical parameters to determine if thickness has a substantial effect on mechanical characteristics; we accept or reject the Null hypothesis depending on the values of F and P.

Table 4. One-way ANOVA results on the tensile properties of Deccani sheep scapula bone.

One-Way ANOVA	Yield strength	Young’s modulus	Ultimate strength	Failure strain
DF	2	2	2	2
SS	13321.99397	20304.24101	15108.16085	10.135982
MS	6660.996987	10152.12051	7554.080427	5.067991
F-Statistic Value	485.578066	384.595103	1199.537814	69.262907
P-value	$3.30636\times {10}^{-12}$	$1.31385\times {10}^{-11}$	$1.52101\times {10}^{-14}$	$2.56697\times {10}^{-7}$

If the F-value tabulated in Tables 4 and 6 is greater than the F-value determined using the F-table, the null hypothesis is rejected. Secondly, the P-value is used to decide the validity of the null hypothesis. If the P-value is less than the level of significance, i.e. P < 0.05, it can be said that thickness has a significant effect on mechanical property. For instance, here we will study the effect of thickness on yield strength, after executing one-way ANOVA since p-value <0.05, hence null hypothesis is rejected. The difference between the averages of some groups is big enough to be statistically significant.

From Table 3, it is concluded that significance of significance of thickness does exist on the mechanical properties of the scapula bone of Deccani breed sheep.

In conclusion, the provided data and statistical analysis suggest that material thickness has a substantial impact on the mechanical properties, with thinner samples generally exhibiting higher stiffness and strength, and medium-thickness samples demonstrating improved ductility and toughness. Further investigation, including more samples and additional property measurements, is required to obtain a comprehensive understanding of the relationship between material thickness and mechanical performance, as well as to identify the underlying factors responsible for these trends.

4.2. Flexural strength test

For all three thickness circumstances, a three-point bend test was performed on a scapula bone specimen. Figures 8 and 9 indicate the variation of flexural characteristics with regard to scapula bone thickness. Flexural characteristics for thick specimens are determined to be the highest when compared to other peers. Flexural strength for thick specimens is 36.97%, 10% higher than for thin and medium conditioned specimens, but 29.76% lower than for huge sheep horns [our study]. Whereas the flexural modulus of a thick conditioned specimen is 74.85%, 63.71% higher than that of a thin or medium specimen and 55% higher than that of a huge sheep horn of the same breed [our work]. As a result, thick-conditioned specimens may withstand bending loads better than their contemporaries. However, the thin section is in a pristine form comprising calcium and hydroxyapatite which is strong in terms of tensile behaviour but weak in flexural strength test resulting in early failure compared to medium and thick sections. This provides additional bending strength to the member which will behave in ductile failure rather than mere brittle failure for thin sections (Table 5). $\mathrm{The}\mathrm{flexural}\mathrm{Strength}\mathrm{calculation}\sigma ={\displaystyle \frac{3\mathrm{PL}}{2b{d}^2}(3)}$Upon examining the data, it can be observed that the Flexural Strength, which represents the material's ability to resist failure under bending loads, increases as the material thickness increases. The thick sample (5 mm) has the highest Flexural Strength, followed by the medium (2 mm) and thin (1 mm) samples. This trend suggests that thicker samples are better equipped to handle bending stresses and may be more suitable for applications where bending loads are expected.

Figure 8. Flexural modulus for thin, medium and thick condition specimen by three-point bend test.

Figure 9. Maximum flexural strength for thin, medium and thick condition specimens by three-point bend test.

Table 5. Flexural properties of Deccani sheep scapula bone.

	Thin (1 mm)	Medium (2 mm)	Thick (5 mm)
Flexural strength (M Pa)	75	107.06	118.8
Flexural modulus (M Pa)	1420.45	2080.66	5650.684
Ultimate load (KN)	0.0095	0.0571	0.384

The Flexural Modulus, which indicates the material's stiffness under bending conditions, also increases with material thickness. The thick sample (5 mm) exhibits a considerably higher Flexural Modulus compared to the medium (2 mm) and thin (1 mm) samples. This finding implies that the thick sample is much stiffer and less prone to deformation under bending loads, making it a suitable candidate for applications requiring high stiffness and resistance to bending deformation.

The Ultimate Load, which represents the maximum load a material can withstand before failure, shows a significant increase as the material thickness increases. The thick sample (5 mm) demonstrates a substantially higher Ultimate Load compared to the medium (2 mm) and thin (1 mm) samples. This result is consistent with the trends observed for Flexural Strength and Flexural Modulus, further reinforcing the notion that thicker samples are better equipped to handle higher bending loads before failing.

Calculation: The steps to calculate Bending Strength are as mentioned below.

Formula $\sigma ={\displaystyle \frac{3\mathrm{PL}}{2b{d}^2}}$where P = Ultimate load (N); L = Gauge length (mm); b = Width of Specimen(mm); d = Depth or thickness of Specimen (mm).

Specimen dimension $40\mathrm{mm}\times 5\mathrm{mm}\times 1\mathrm{mm}$where Total length = 40 mm; Gauge length(L) = 25 mm; Width of specimen (b) =  5 mm; Thickness of specimen (d) =  1 mm.

Sample calculation $\sigma ={\displaystyle \frac{3\mathrm{PL}}{2b{d}^2}={\displaystyle \frac{3\times 0.01\times 1000\times 25}{2\times 5\times 1^2}=75\mathrm{MPa}}}$

Flexural modulus $E_{\mathrm{flexural}}={\displaystyle \frac{P{L}^3}{48I\delta }}$Figure 8 shows flexural modulus for thin, medium and thick condition specimens by three-point bend test and Figure 9 illustrates the maximum flexural strength for thin, medium and thick condition specimens by the three-point bend test.

The one-way ANOVA test results for flexural characteristics of deccani sheep scapula bone are shown in Table 6. When all of the F-values are compared to the critical values from the table, it is obvious that thickness has a substantial influence on the flexural modulus and flexural strength of the Scapula bone.

Table 6. One-way ANOVA results on the flexural properties of scapula bone of Deccani breed sheep.

One-way ANOVA	Flexural modulus	Flexural strength
DF	2	2
SS	52351612.13	4345.087413
MS	26175806.07	2172.543707
F-statistic value	1287.445973	120.874334
P-value	$9.99201\times {10}^{-15}$	$1.11857\times {10}^{-8}$

The data presented in the table suggest that material thickness has a considerable impact on the flexural properties of the samples. Thicker samples generally exhibit higher Flexural Strength, Flexural Modulus and Ultimate Load, making them more suitable for applications where resistance to bending loads, stiffness and load-bearing capacity is a critical factor. However, it is essential to consider the specific requirements of an application and weigh the benefits of higher flexural properties against other factors, such as weight, manufacturing complexity and cost, before making any final material selection decisions.

5. Simulation

The work is incomplete and costlier if we do not follow the simulation analysis. It is a simulation that can make a lot of difference in terms of optimal design and experimental reduction. The entire analysis involves ANSYS Workbench as a tool for realizing the comparative study of experimental and simulation results.

5.1. Tensile strength

a.	Thickness 1 mm

The typical model was developed with a dimension of $25\times 2.5\times 250\mathrm{mm}$ as per ASTM 3039M and using a design modeller the micro-gripping regions split for load and boundary condition application. The element type used in this model is SOLID186 with second-order elements for 20 nodes. The entire model meshed with 1896 nodes and 264 elements keeping in mind the stress concentration regions at the microgripper region. The details are depicted in Figure 10 for the 1 mm thickness tensile strength model.

b.	Thickness 2 mm

Figure 10. Tensile strength model for 1 mm thickness.

The entire assembly is subjected to a load of 250N at one end and constrained at the other end with all the degrees of freedom. The results, shown in Figure 11, discuss total deformation as 0.118 mm and 53.62 MPa. In comparison to 1 mm thickness 0.231 mm and 85.88 MPa show high stress for lower thickness values.

c.	Thickness 5 mm

Figure 11. Tensile strength model for 2 mm thickness.

The results shown in Figure 12 depict total deformation as 0.052 mm and 31.08 MPa. In comparison to 1 mm thickness 0.231 mm and 85.88 MPa show high stress for lower thickness values.

Figure 12. Tensile strength model for 5 mm thickness.

5.2. Flexural strength

a.	Thickness 1 mm

The typical model developed with a dimension of $25\times 4\times 250\mathrm{mm}$ as per ASTM D7264M and using design modeller the simply supported rollers considered at the base and on top of it a roller will enforce a load as per description as micro-gripping regions split for load and boundary condition application. The element type used in this model is SOLID186 with second-order elements for 20 nodes. The entire model is meshed with 1712 nodes and 200 elements keeping in mind the stress concentration regions at the microgripper region. The details are depicted in Figure 13 for the 1 mm thickness flexural strength model. Figure 14 discusses the 2 mm thick model, 2700 nodes and 400 elements and finally 5 mm thick model as illustrated in Figure 15 with 5400 nodes and 950 elements.

Figure 13. Flexural strength model for 1 mm thickness.

Figure 14. Flexural strength model for 2 mm thickness.

Figure 15. Flexural strength model for 5 mm thickness.

Table 7 shows the details about the comparative study between the flexural strength and tensile strength for the thickness of scapula bone from 1 mm to 5 mm specimen.

Table 7. Comparative data with tensile and flexural strength.

Sl. No.	Description	Tensile		Flexural
		Total deformation in mm	Von mises stress in MPa	Total deformation in mm	Von mises stress in MPa
1	1 mm	0.23	85.88	0.415	33.06
2	2 mm	0.12	53.62	0.33	47.83
3	5 mm	0.05	31.08	0.22	57.02

6. Conclusion

This study demonstrates a clear relationship between the thickness of scapula bone specimens from Deccani breed sheep and their mechanical properties, specifically flexural and tensile properties. The results from both the experimental and simulation analyses indicate that as the material thickness increases, the flexural strength, flexural modulus, ultimate load, tensile deformation and von Mises stress all exhibit a corresponding increase. Statistical analysis using one-way ANOVA further confirmed the significant impact of material thickness on these properties.

• Thin samples have the highest Young's modulus (109.9 MPa), followed by medium samples (83.70 MPa) and the lowest value for thick samples (18.56 MPa). This indicates that thin samples are the stiffest, while thick samples are the most compliant.

• Both yield strength and ultimate strength show a similar trend, with the highest values in thin samples (81.3 and 84.7 MPa), followed by medium samples (61.34 and 61.68 MPa) and the lowest in thick samples (9.98 and 11.2 MPa). This implies that thin samples can withstand higher stresses before undergoing plastic deformation or failure.

• Medium samples have the highest failure strain (3.04%), followed by thin samples (1.9375%), and the lowest in thick samples (1.125%). This result indicates that medium samples can undergo more deformation before failure compared to thin and thick samples.

• Medium samples exhibit the highest toughness (139.7925 MJ/m^3), followed by thin samples (106.62625 MJ/m^3) and the lowest in thick samples (11.4925 MJ/m^3). This suggests that medium samples can absorb more energy before failure, making them more resistant to fractures.

• Thick samples have the highest flexural strength (118.8 MPa), followed by medium samples (107.06 MPa) and the lowest in thin samples (75 MPa). This implies that thick samples can withstand higher bending stresses before failure.

• Thick samples demonstrate the highest flexural modulus (5650.684 MPa), followed by medium samples (2080.66 MPa) and the lowest in thin samples (1420.45 MPa). This indicates that thick samples are the stiffest under bending loads.

• Thick samples have the highest ultimate load (0.384 kN), followed by medium samples (0.0571 kN) and the lowest in thin samples (0.0095 kN). This result suggests that thick samples can support more weight before failure.

In summary, the mechanical properties of scapula bones vary with thickness. Thin samples generally have higher tensile properties, while thick samples exhibit superior flexural properties. Medium samples exhibit the highest failure strain and toughness, indicating their ability to withstand more deformation and energy absorption before failure. These comparisons are essential when designing implants or prosthetics to ensure appropriate mechanical properties and functionality.

Thicker specimens, therefore, show greater resistance to bending loads, higher stiffness, enhanced load-bearing capacity and improved tensile strength. It depends on the application whether a brittle fracture is the design criteria or ductile fracture is the design criteria for the end applications. According to these aspects, a suitable thickness material may be considered for use. This information is valuable for material selection and design in various applications where these properties are critical factors. However, it is essential to consider the specific requirements of each application and evaluate the benefits of increased mechanical properties against other factors such as weight, manufacturing complexity and cost.

Future research could focus on optimizing the material thickness for specific applications, investigating the influence of other factors such as material composition and exploring alternative materials that exhibit similar or improved mechanical properties. Overall, this study contributes essential knowledge to the field of material science and engineering, helping to inform material selection and design processes in applications where flexural and tensile properties are vital considerations.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Manipal Academy of Higher Education. The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through a Small Group Research Project under grant number (R.G.P 1/182/44).