Bioinspired Design Owoseni T A Materials Science and

Bioinspired Design Owoseni T. A Materials Science and Engineering Stream African University of Science and Technology, Abuja, Nigeria. M. Sc. Thesis Presentation Advisor: Prof. Soboyejo W. O April 2012 Sponsor: AUST/ADB & NMI

Outline Background and Introduction Literature Survey Characterization of the Multi-Scale Structure of Kinixys erosa Shell Analytical and Computational Model of Shell Structure Concluding Remarks and Suggested Future Work Acknowledgements

Background and Motivation • Bioinspired design involves the use of concepts observed in natural biological materials in engineering design. The hope is that the leveraging of biological materials in the engineering domain can lead to many technological innovations and novel products

Background and Motivation Cont’d • Unlike the design of conventional engineering materials that often involve the use of multiple materials chemistries in the design of engineering components and systems, natural biological materials are made from relatively few chemical constituents. For example, bone, cartilage, skin, and the cornea in the eye is built from type I collagen.

Background and Motivation Cont’d • Usually hard biological materials exist as composite. These high-performance natural composites are made up of relatively weak components (brittle minerals and soft proteins) arranged in intricate ways to achieve specific combinations of stiffness, strength and toughness.

Background and Motivation Cont’d • Determining which features control the performance of these materials is the first step in Biomimetics. These ‘key features’ can then be implemented into artificial bioinspired synthetic materials, using innovative techniques such as layer-by-layer crystallization. assembly or icetemplated

Unresolved Issues • The microstructure and mechanical property of different species of turtle have been studied, but there have not been detailed studies of the effects of shell structure on their mechanical properties.

Unresolved Issues cont’d • Shell theory has been sparsely applied in the bioinspired design of materials and structures. These will be explored in this study using a combination of experiments and analytical/computational models.

Objectives of Research • The objective of this thesis is to develop a fundamental understanding of the deformation and stress responses of a Kinixys erosa tortoise shell structure as a potential source of inspiration for the design of a failure resistant shell/layered structure.

Scope of the Work • This work presents a combination of experimental, theoretical and computational studies of the structure and mechanical properties of kinixys erosa tortoise shell structures as potential sources of bioinspiration for the design of shell structures that are resistant to bending.

Literature Survey • Meyers et al (2008) studied several biological materials (e. g. nacre, ligaments, hoof, blood vessels, beak interior, chameleon, etc. ) using diverse approaches, like SEM, TEM, AFM, Nano-Indentation, and Molecular Simulations and Modelling, among others, identifying their unique features.

Literature Survey cont’d • Rhee et al (2009) studied the mutilscale structure of Terrapene carolina carapace (Tc) using a combination microscopic technique, characterization. EDX, and mechanical

Click to edit the outline text format Second Outline Level Third Outline Levelhierarchy and structure Figure 1: Mutilscale Fourth Outline Level of Terrapene carolina carapace Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Figure 2: Fourth Elemental Outline Level. Composition of Fifthcarolina Outline Level carapace Terrapene Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 3: Indentation Third Outlinetest Levelresults obtained from (a) nanoindentation and Fourth (b) Vickers hardness tests on the side Outline Level surface of the turtle shell carapace. Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 4: Stress/strain curves from the quasi-static compression Third Outline Level test results on the. Fourth turtle shell carapace coupon specimens under Outline Level various strain rates and specimen geometries. Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 5: Comparison of three-point bending test results obtained from Third Outline Level actual data and ABAQUS finite element simulations; (a) without Fourth Outline Level considering foam material effect, and (b) considering foam material effect. Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Literature Survey cont’d • Chenzhao et al (2012) carried out mechanical and structural characterization of both the shell and shell material of Trachemys scripta (Ts).

Click to edit the outline text format Second Outline Level Third Outline Level Figure 6: Microstructure of the turtle shell of Trachemys scripta. Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Figure 7: Load-displacement curve of Compression failure tests of Ts shell. Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level and strength of Ts shell materials. Table 1: The tensile modulus Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Table 2: The elastic modulus and ultimate strength of Ts strenghen rib. Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Literature Survey cont’d • Balani et al (2011) worked on freshwater snapping turtle, Chelydra serpentine (Cs). The microstructural-, compositional, nanomechanical characterization of Cs was carried out making samples from Cs carapace.

Click to edit the outline text format Second Outline Level Third Leveleliciting (a) a composite sandwich structure, (b) top Figure 8: Cross-sectional of Cs. Outline carapace three layers showing the top two waxy and Level the rigid 3 rd layer, (c) carbonaceous lamellae 4 th Fourth Outline and 5 th layers, and (d) inner structure eliciting ∼ 50%– 60% porous matrix (fractured and Fifth Outline Level polished cross-section without epoxy infiltration). Sixth Outline Level Seventh Outline Level. Click to edit Master text styles 24

Click to edit the outline text format Second Outline Level Third Outline Level Fig. 9: (a) X-ray diffraction pattern eliciting Fourth Outline Level diffused hydroxyapatite (HA) peak and (b) Raman spectrum showing presence amorphous top surface and calcium Fifth Outlineof Level phosphate in the bottom surface of the. Outline turtle’s carapace. Sixth Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Figure 10: Cross-sectional SEM image of (a) Turtle’s carapace, and elemental Fourth Outline Level mapping of (b) carbon, (c) phosphorous, and (d) calcium eliciting the presence Fifth Outline Level of carbon fibers in the calcium phosphate matrix. Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Figure 11: Load indentation-depth profile of the various layers, with the main image showing the structural rigid dense 3 rd layer and matrix, and the inset showing a zoomed Fourth Outline Level image of the dotted box for the top layer, waxy 2 nd layer, and the two carbonaceous Fifthof. Outline Level carapace. lamellae/fibrous 4 th and 5 th layers the turtle’s Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Fourth Outline Level Table 3: Construct of the layered structure in a turtle shell with consequent Fifthlayer. Outline Level mechanical properties of each Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Literature Survey cont’d Tan et al. (2011) studied the mechanical properties of moso culm functionally graded bamboo structures using a combinaton of nanoindentation, micro-tensile testing, and resistance curve experiments.

Click to edit the outline text format Second Outline Level of the functionally graded Figure 12: An. Third optical image Fourth Outline Level mesostructure of bamboo. Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Figure 13: The Young’s moduli Fourthdistribution Outline Level along the radial direction of the bamboo Fifth cross-section. Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

• Click to edit Master text styles Click to edit the outline text format Second Outline Level Click to edit Master text – Second level styles Third Outline Level – Third level • Fourth level – Second level Fourth Outline – Fifth level – Third level. Level • Fourth level Fifth Outline – Fifth level Level Sixth Outline Level Figure 14: (a) A representative stress–strain curve for the bamboo microtensile Seventh Outline Level. Click experiment. (b) Tensile strength of the outside, side and inside specimens. to edit Master text styles – Second level

Characterization of the Multi-Scale Structure of Kinixys erosa (Ke) Shell • Determining which features control the performance of biological materials is the first step in Biomimetics. Characterization is therefore necessary to decipher the key feature underlying the multi-functionality of hard biological materials using techniques like Microscopy, nanoindentation, mechanical testing, and X-ray diffraction.

Structure of a Tortoise Shell • A tortoise shell has two parts the upper portion-carapace and the bottom half-plastron both of which are actually made of many fused bones numbering up to 50. A bony bridge joins the carapace and the plastron along the side of the turtle.

Carapace Plastron Figure 15: Carapace and Plastron of kinixys erosa

Pleural Vertebral Marginal Cervical 1 1 2 3 4 3 2 5 6 4 3 7 8 5 12 4 9 11 10 Figure 16: Scutes on the Carapace Kinixys erosa

Bone Structure • Bone structure has two parts: cortical region and trabecular or cancellous type. The cortical region is dense and comprises the outer structure or cortex of the bone, while the interior consists of the trabecular tissue, made of thin plates or trabeculae loosely meshed and porous.

Microstructure of Kinixys erosa (Ke) carapace Click to edit the outline materials text format a a b Second Outline Level Third Outline Level Click to edit Master text Fourth Outline styles Level – Second level – Third level Fifth Outline • Fourth level Level – Fifth level Sixth Outline Level Seventh Outline Level. Click Figure 17: (a) Cross section of kinixys erosa bone structure (b) Schematic of kinixys to edit Master text styles erosa bone structure – Second level

Compositional Characterization of Kinixys erosa (Ke) Carapace Materials Diffused 9/17 -Amide nylon 6 olygomer Figure 18: X-ray Spectrum of kinixys erosa scute

Compositional Characterization of Kinixys erosa (Ke) Carapace Materials Diffused HA peaks Lower intensity HA peaks Figure 19: X-ray Spectrum of kinixys erosa bone structure

Micromechanical characterization of Kinixys erosa Bone Structure Figure 20: Stress-strain plot of compression test on kinixys erosa carapace bone structure

Micromechanical characterization of Kinixys erosa Bone Structure • Click to edit Master text styles – Second level – Third level • Fourth level – Fifth level Figure 21: Load/deformation plot three point flexural test on kinixys erosa carapace bone structure

Summary • The carapace is a sandwich composite structure having denser exterior lamellar bone layers (cortical bone) and an interior bony network of closed-cell fibrous foam layer (cancellous bone). • The bone structure was found to contain hydroxyapatite while The scute contains 9/17 -Amide nylon 6 olygomer. It was also found to be resistant to concentrated acid and base; however this requires further investigation.

Summary cont’d • Flexural strength of the bone structure was found to be as against its compressive strength which was, while the stiffness was -22. 4 KN/m. The Young’s modulus in bending (EB) was 6. 4 GPa with the flexural strain and maximum ultimate bending strain being 0. 35 and 0. 025 respectively.

Analytical and Computational Model of Shell Structure • Click to edit Master text styles – Second level – Third level • Fourth level – Fifth level

Analytical Model Based on Theory of Shell • Click to edit Master text styles – Second level – Third level • Fourth level – Fifth level

Analytical Model Based on Theory of Shell cont’d • Click to edit Master text styles – Second level – Third level • Fourth level – Fifth level

• Click to edit Master text styles – Second level – Third level • Fourth level – Fifth level Table 4: Analytical solutions based on theory of shell

Click to edit the outline text format Figure 22: Stress along the surface of the shell Second Outlinedistribution Level Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 23: Strain distribution along the surface of the shell Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 24: Tangential strain distribution along the surface of the shell Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 25: Radial strain distribution along the surface of the shell Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 26: Deformation distribution along the surface of the shell Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 27: Tangential deformation distribution along the surface of the shell Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Figure 28: Radial deformation distribution along the surface of the shell Third Outline Level Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Computational Finite Element Model • The finite element analyses of the shell structure were performed using a commercial code, ABAQUS, based on the material properties (EB = 6. 4 GPa and ) obtained from the bending tests presented in Chapter 3. A 2 -D model with element type CPS 4 R was established and the detailed simulation conditions are as presented in Table 5 below. The applied pressure load (Figure 29) is the same with that used in the analytical model.

Single layer shell Element type CPS 4 R Number of elements 715 Number of nodes 955 Number of degrees of freedom (DOF) 1, 910 Table 5: Finite element simulation conditions

Click to edit the outline text format Second Outline Level Third Outline Level Figure 29: Loaded 2 -D finite element model of the shell structure Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Figure 30: 2 -D finite element model showing stress distribution Fourth Outline Level along the surface of the shell Fifth Outline Level Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Click to edit the outline text format Second Outline Level Third Outline Level Fourth Outline model Level Figure 31: 3 -D finite element showing stress distribution Levelof the shell along. Fifth the. Outline surface Sixth Outline Level Seventh Outline Level. Click to edit Master text styles

Concluding Remarks • The carapace of Kinixys erosa (Ke) is a sandwich composite structure with a denser exterior lamellar bone layers (cortical bone) and an interior bony network of closed-cell fibrous foam layer (cancellous bone). • The scute of Kinixys erosa (Ke) was found to be resistant to concentrated acid and base.

Concluding Remarks cont’d • The analytical and computational models showed that the geometry of a shell structure has significant effects on its deformation and stress responses. • This work introduces the use of shell theory in studying the deformation and stress responses of tortoise shell.

Suggestions for future work • In addition to the optical microscopy and XRD, SEM and EDX study of Ke carapace materials will provide more insight into the microstructure and composition of Ke tortoise shell. • Nanoindentation technique should be used to measure the modulus of the individual layer of Ke tortoise shell carapace, which can then be used in:

• Object oriented finite element (OOF 2) analysis to estimate the effective modulus of the carapace. The modulus (EB) obtained from the bending test and the OOF 2 can then be compared. • Modeling of a multilayered-shell and layered structures to understand their deformation and stress responses.

Acknowledgements • AUST/ADB • NMI • A-MRS AUST Chapter • SHESTCO/NAEC • Prof. Soboyejo W. O. (AUST/Princeton) • Dr. Olukole S. G. (University of Ibadan) • Mr. Gadu A. I. (Nuclear Technology Center-SHESTCO) • Prof. Kana Z. (KWASU/SHESTCO) • Dr. Odusanya O. S. (SHESTCO) • Mr. Eniayehun (SHESTCO) • Other well wishers

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