1. 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 21/08/13

2. 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 2 21/08/13

3. 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 3 Background and Motivation 21/08/13

4. 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. 4 21/08/13

5. 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. 5 Background and Motivation Cont’d 21/08/13

6. Determining which features control the performance of these materials is the first step in Biomimetics. These ‘key features’ can then be implemented into artificial bio- inspired synthetic materials, using innovative techniques such as layer-by-layer assembly or icetemplated crystallization. 6 Background and Motivation Cont’d 21/08/13

7. 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. 7 Unresolved Issues 21/08/13

8. 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. 8 21/08/13

9. 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. 9 21/08/13

10. 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. 10 21/08/13

11. 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. 11 21/08/13

12. Literature Survey cont’d Rhee et al (2009) studied the mutilscale structure of Terrapene carolina carapace (Tc) using a combination microscopic technique, EDX, and mechanical characterization. 12 21/08/13

13. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 1: Mutilscale hierarchy and structure of Terrapene carolina carapace 13 21/08/13

14. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 2: Elemental Composition of Terrapene carolina carapace 14 21/08/13

15. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 3: Indentation test results obtained from (a) nano- indentation and (b) Vickers hardness tests on the side surface of the turtle shell carapace. 15 21/08/13

16. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 4: Stress/strain curves from the quasi-static compression test results on the turtle shell carapace coupon specimens under various strain rates and specimen geometries. 16 21/08/13

17. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 5: Comparison of three-point bending test results obtained from actual data and ABAQUS finite element simulations; (a) without considering foam material effect, and (b) considering foam material effect. 17 21/08/13

18. 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). 18 21/08/13

19. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 6: Microstructure of the turtle shell of Trachemys scripta. 19 21/08/13

20. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 7: Load-displacement curve of Compression failure tests of Ts shell. 20 21/08/13

21. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Table 1: The tensile modulus and strength of Ts shell materials. 21 21/08/13

22. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Table 2: The elastic modulus and ultimate strength of Ts strenghen rib. 22 21/08/13

23. 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. 23 21/08/13

24. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 8: Cross-sectional of Cs carapace eliciting (a) a composite sandwich structure, (b) top three layers showing the top two waxy and the rigid 3rd layer, (c) carbonaceous lamellae 4th and 5th layers, and (d) inner structure eliciting ∼ 50%–60% porous matrix (fractured and polished cross-section without epoxy infiltration). 24 21/08/13

25. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Fig. 9: (a) X-ray diffraction pattern eliciting diffused hydroxyapatite (HA) peak and (b) Raman spectrum showing presence of amorphous top surface and calcium- phosphate in the bottom surface of the turtle’s carapace. 25 21/08/13

26. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 10: Cross-sectional SEM image of (a) Turtle’s carapace, and elemental mapping of (b) carbon, (c) phosphorous, and (d) calcium eliciting the presence of carbon fibers in the calcium phosphate matrix. 26 21/08/13

27. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 11: Load indentation-depth profile of the various layers, with the main image showing the structural rigid dense 3rd layer and matrix, and the inset showing a zoomed image of the dotted box for the top layer, waxy 2nd layer, and the two carbonaceous lamellae/fibrous 4th and 5th layers of the turtle’s carapace. 27 21/08/13

28. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Table 3: Construct of the layered structure in a turtle shell with consequent mechanical properties of each layer. 28 21/08/13

29. 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. 29 21/08/13

30. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 21/08/13 30 Figure 12: An optical image of the functionally graded mesostructure of bamboo.

31. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles Figure 13: The Young’s moduli distribution along the radial direction of the bamboo cross-section. 31 21/08/13

32. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles – Second level – Third level Fourth level – Fifth level 21/08/13 32 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 Figure 14: (a) A representative stress–strain curve for the bamboo microtensile experiment. (b) Tensile strength of the outside, side and inside specimens.

33. 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. 33 21/08/13

34. 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. 34 21/08/13

35. 35 Carapace Plastron Figure15: Carapace and Plastron of kinixys erosa 21/08/13

36. 36 1 2 3 4 5 1 23 4 1 2 3 4 5 67 8 9 10 11 12 Vertebral Cervical Pleural Marginal Figure 16: Scutes on the Carapace Kinixys erosa 21/08/13

37. 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. 37 21/08/13

38. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles – Second level – Third level Fourth level – Fifth level Microstructure of Kinixys erosa (Ke) carapace materials 38 Click to edit Master text styles – Second level – Third level Fourth level – Fifth level Figure 17: (a) Cross section of kinixys erosa bone structure (b) Schematic of kinixys erosa bone structure ab 21/08/13 a

39. Compositional Characterization of Kinixys erosa (Ke) Carapace Materials 39 Figure 18: X-ray Spectrum of kinixys erosa scute 21/08/13 Diffused 9/17-Amide nylon 6 olygomer

40. Compositional Characterization of Kinixys erosa (Ke) Carapace Materials 40 Figure 19: X-ray Spectrum of kinixys erosa bone structure 21/08/13 Diffused HA peaks Lower intensity HA peaks

41. Micromechanical characterization of Kinixys erosa Bone Structure 41 Figure 20: Stress-strain plot of compression test on kinixys erosa carapace bone structure 21/08/13

42. Micromechanical characterization of Kinixys erosa Bone Structure 42 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 21/08/13

43. 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. 43 21/08/13

44. 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. 44 21/08/13

45. Analytical and Computational Model of Shell Structure 45 Click to edit Master text styles – Second level – Third level Fourth level – Fifth level 21/08/13

46. Analytical Model Based on Theory of Shell 46 Click to edit Master text styles – Second level – Third level Fourth level – Fifth level 21/08/13

47. Analytical Model Based on Theory of Shell cont’d 47 Click to edit Master text styles – Second level – Third level Fourth level – Fifth level 21/08/13

48. Click to edit Master text styles – Second level – Third level Fourth level – Fifth level 48 Table 4: Analytical solutions based on theory of shell 21/08/13

49. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 49 Figure 22: Stress distribution along the surface of the shell 21/08/13

50. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 50 Figure 23: Strain distribution along the surface of the shell 21/08/13

51. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 51 Figure 24: Tangential strain distribution along the surface of the shell 21/08/13

52. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 52 Figure 25: Radial strain distribution along the surface of the shell 21/08/13

53. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 53 Figure 26: Deformation distribution along the surface of the shell 21/08/13

54. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 54 Figure 27: Tangential deformation distribution along the surface of the shell 21/08/13

55. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 55 Figure 28: Radial deformation distribution along the surface of the shell 21/08/13

56. 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 CPS4R 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. 21/08/13 56

57. Single layer shell Element typeCPS4R Number of elements715 Number of nodes955 Number of degrees of freedom (DOF) 1,910 21/08/13 57 Table 5: Finite element simulation conditions

58. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 21/08/13 58 Figure 29: Loaded 2-D finite element model of the shell structure

59. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 21/08/13 59 Figure 30: 2-D finite element model showing stress distribution along the surface of the shell

60. Click to edit the outline text format  Second Outline Level Third Outline Level  Fourth Outline Level Fifth Outline Level Sixth Outline Level Seventh Outline LevelClick to edit Master text styles 21/08/1360 Figure 31: 3-D finite element model showing stress distribution along the surface of the shell

61. 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. 61 21/08/13

62. 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. 21/08/1362

63. 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: 21/08/1363

64. Object oriented finite element (OOF2) analysis to estimate the effective modulus of the carapace. The modulus (EB) obtained from the bending test and the OOF2 can then be compared. Modeling of a multilayered-shell and layered structures to understand their deformation and stress responses. 21/08/1364

65. 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 65 21/08/13

66. 66 21/08/13 Thank you