MIAERAL EE ENNEERIINC C ELSEVIER Materials Science and Engineering C 11(2000)13-18 Bio-inspired study of structural materials B L. Zhou Institute of Metal Research, International Center for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110015, Accepted 20 September 1999 Abstract The terminology of materials study inspired by biological systems or phenomena is analyzed at first. It is pointed that the term bio-inspired may be better than the terms"bionic or"biomimetic', since the former is relatively easy to be accepted. The new trends of bio-inspired study of structural materials are analyzed in short. Some progress in bio-inspired design and processing of materials in this institute (IMRCAS)are summarized briefly in this talk, such as biomimetic design of worst bonding interface for composites dumbell-like whiskers simulating animal bone, fractal tree reinforcement by mimicry of branched roots in soil; etc The possibility of modification and recovery of materials by nonequilibrium bio-inspired treatment are further explored, including the inequilibrium process under transient heating, dissipative structure and self-organization process of open system, inspiration by living process, influence of high intensive electropulsing on the working life of materials, a possible way of fatigue recovery of materials and the healing effect of electropulsing in metals. Some tentative practice in biomaterial modification are also studied such as the reformed bamboo reinforced aluminium laminates, etc. a discussion on the methodology of bio-inspired study of materials consists briefly in th last part of the talk. C 2000 Elsevier Science S.A. All rights reserved Keywords: Bio-inspired; Bionic; Biomimetic, Structural materials 1. Introduction Some progress in bio-inspired design and processing of materials in this institute(IMRCAS)are summarized briefly Biomaterials are generally understood as the materials in this talk [1-6] and the possibility of modification and for human body repairment, while in a broad sense, it is recovery of materials by nonequilibrium bio-inspired treat- lefined as the materials of those for bio-improvement, by ments are further explored biomolecules and bio-inspired The man-made primary materials simulating living or- gans or biological tissues appeared more than thousands of 2. Bio-inspired design and processing of materials ears ago. while the term "bionic describing these was originally composed of"bio-""and electr-onic", and the 2. 1. Optimum bonding and worst bonding (4,57 term“ biomimetic is from“bio'and“ mimetic.Some times, there are some arguments between scientists be cause of different understanding of the term "mimetic The biomimetic design of interface bonding takes th Some take the meaning in a narrow sense, while the others ad vantage of fibers with enlarged ends simulating animal in a broad sense. Nevertheless, the term"bio-inspired bone or fractal-tree structure mimicking tree root to cause relatively easy to be accepted with less argument for its stress transfer from matrix to fiber mainly by compression flexibility across the interfaces between enlarged ends or branches nd the matrix condition, or, in other words, the stress transfer in this case is not sensitive to the bonding state of the interface even it Fax:+86-23891320 orst bond E- mail address: bizhou @imr accn (B L. Zhou mum bone 0928-4931/00/Ssee front matter o 2000 Elsevier Science S.A. All rights reserved PI:S0928-4931(00)00136-3
Materials Science and Engineering C 11 2000 13–18 Ž . www.elsevier.comrlocatermsec Bio-inspired study of structural materials B.L. Zhou) Institute of Metal Research, International Center for Materials Physics, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110015, People’s Republic of China Accepted 20 September 1999 Abstract The terminology of materials study inspired by biological systems or phenomena is analyzed at first. It is pointed that the term ‘‘bio-inspired’’ may be better than the terms ‘‘bionic’’ or ‘‘biomimetic’’, since the former is relatively easy to be accepted. The new trends of bio-inspired study of structural materials are analyzed in short. Some progress in bio-inspired design and processing of materials in this institute IMRCAS are summarized briefly in this talk, such as biomimetic design of worst bonding interface for composites; Ž . dumbell-like whiskers simulating animal bone; fractal tree reinforcement by mimicry of branched roots in soil; etc. The possibility of modification and recovery of materials by nonequilibrium bio-inspired treatment are further explored, including the nonequilibrium process under transient heating, dissipative structure and self-organization process of open system, inspiration by living process, influence of high intensive electropulsing on the working life of materials, a possible way of fatigue recovery of materials and the healing effect of electropulsing in metals. Some tentative practice in biomaterial modification are also studied such as the reformed bamboo reinforced aluminium laminates, etc. A discussion on the methodology of bio-inspired study of materials consists briefly in the last part of the talk. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Bio-inspired; Bionic; Biomimetic; Structural materials 1. Introduction Biomaterials are generally understood as the materials for human body repairment, while in a broad sense, it is defined as the materials of those for bio-improvement, by biomolecules and bio-inspired. The man-made primary materials simulating living organs or biological tissues appeared more than thousands of years ago, while the term ‘‘bionic’’ describing these was originally composed of ‘‘bio-’’and electr-‘‘onic’’, and the term ‘‘biomimetic’’ is from ‘‘bio’’ and ‘‘mimetic’’. Sometimes, there are some arguments between scientists because of different understanding of the term ‘‘mimetic’’. Some take the meaning in a narrow sense, while the others in a broad sense. Nevertheless, the term ‘‘bio-inspired’’ is relatively easy to be accepted with less argument for its flexibility. ) Fax: q86-23891320. E-mail address: bizhou@imr.ac.cn B.L. Zhou . Ž . Some progress in bio-inspired design and processing of materials in this institute IMRCAS are summarized briefly Ž . in this talk 1–6 and the possibility of modification and w x recovery of materials by nonequilibrium bio-inspired treatments are further explored. 2. Bio-inspired design and processing of materials 2.1. Optimum bonding and worst bonding 4,5 [ ] The biomimetic design of interface bonding takes the advantage of fibers with enlarged ends simulating animal bone or fractal-tree structure mimicking tree root to cause stress transfer from matrix to fiber mainly by compression across the interfaces between enlarged ends or branches and the matrix, without special requirement to the bonding condition, or, in other words, the stress transfer in this case is not sensitive to the bonding state of the interface even it is badly designed. Consequently, it is better to call it ‘‘worst bonding’’ in comparison with the so-called ‘‘optimum bonding’’. 0928-4931r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S0928- 4931 00 00136-3 Ž
B L Zhou/ Materials Science and Engineering C 11 (2000)13-18 Fig. 1. The morphology of dumbbell-like SiC whiskers [91 .2. The dumbbell-shaped Sic whiskers simulating animal The primary result of biomimetic SiC whiskers rein bone/2,7, 8/ forced PVC composite shows much larger elongation than hat of the matrix material A model of short fiber-reinforced composite is put forward from the viewpoint of biomimetic design Consid ering Poisson's contraction effect of the fiber, stress distri- 2. 3. The fractal tree reinforcement mimicking branched butions in plain and enlarged-end(dumbbell shaped) fiber reinforced composites are analyzed. When the interfacial nding is imperfect, the strength of composites with An approximate theory of the pullout of fibers with enlarged-end fibers is greater than that of the composites fractal-tree structure from a matrix has been proposed with plain fibers of the same properties and aspect ratio. [10, 1 1] with the aim of quantifying the effects of fractal-tre The theoretical model is verified by experiments structure of the fibers. This model is essentially suggested Sic whiskers commercially available are all plain fibers, from the simulation of branched roots of trees or grasses in while the dumbbell-shaped biomimetic whiskers shown in soil, as applied to the strengthening and toughening of Fig. I were manufactured by solid state reaction of Sio riverbanks or dam surfaces by planting trees and with C in this laboratory 9 In the experimental investigation of the pullout of syn The formation mechanism of biomimetic whiskers is as thetic fibers with fractal-tree structure, it was generally observed that the force and energy required for fiber Then SiO,(1<x<2) will be formed on he(1) pullout increases with the branching angle. The application SiO(g)+ 3CO(g)=SiC 2C02(g) of this theory to experiment is successful. The strength and plain fracture toughness of composites reinforced by this kind of whisker. The SiO, matter deposited and grew continously fiber are inferred to be greater than those of the composites and formed a series of small beads on the whiskers finally. reinforced by plain, unbranched fibers. Therefore, the study Fig. 2.(a)Morphology of vapor-grown carbon fibers and(b)structure of a branching point [12]
14 B.L. ZhourMaterials Science and Engineering C 11 2000 13–18 ( ) Fig. 1. The morphology of dumbbell-like SiC whiskers 9 . w x 2.2. The dumbbell-shaped SiC whiskers simulating animal bone 2,7,8 [ ] A model of short fiber-reinforced composite is put forward from the viewpoint of biomimetic design. Considering Poisson’s contraction effect of the fiber, stress distributions in plain and enlarged-end dumbbell shaped fiber Ž . reinforced composites are analyzed. When the interfacial bonding is imperfect, the strength of composites with enlarged-end fibers is greater than that of the composites with plain fibers of the same properties and aspect ratio. The theoretical model is verified by experiments. SiC whiskers commercially available are all plain fibers, while the dumbbell-shaped biomimetic whiskers shown in Fig. 1 were manufactured by solid state reaction of SiO2 with C in this laboratory 9 . w x The formation mechanism of biomimetic whiskers is as follows. SiO gŽ. Ž. Ž. Ž. q3CO g sSiCq2CO g 1 2 Then SiO 1 x Ž . -x-2 will be formed on the plain whisker. The SiO matter deposited and grew continously x and formed a series of small beads on the whiskers finally. The primary result of biomimetic SiC whiskers reinforced PVC composite shows much larger elongation than that of the matrix material. 2.3. The fractal tree reinforcement mimicking branched roots in soil 10,11 [ ] An approximate theory of the pullout of fibers with fractal-tree structure from a matrix has been proposed w x 10,11 with the aim of quantifying the effects of fractal-tree structure of the fibers. This model is essentially suggested from the simulation of branched roots of trees or grasses in soil, as applied to the strengthening and toughening of riverbanks or dam surfaces by planting trees and grasses. In the experimental investigation of the pullout of synthetic fibers with fractal-tree structure, it was generally observed that the force and energy required for fiber pullout increases with the branching angle. The application of this theory to experiment is successful. The strength and fracture toughness of composites reinforced by this kind of fiber are inferred to be greater than those of the composites reinforced by plain, unbranched fibers. Therefore, the study Fig. 2. a Morphology of vapor-grown carbon fibers and b structure of a branching point 12 . Ž. Ž. w x
B L Zhou/ Materials Science and Engineering C 11 (2000)13-18 aAa 4+gg℃Ho封 Fig. 3. Time process of temperature rise and thermal expansion. (1)Temperature rise, (2)thermal expansion [13, 14]. described [10, 11] may play an important role in guiding parameter, by definition 5=E(x-DsD),T=et, and U the design of fiber structure do/ak is the group velocity of second sound. p, B and The present work was carried out to synthesize are parameters. Knowing the moving velocity of soliton- using benzene as the carbon source, iron as the catalyst, nation of Fig 3 quantitaively sives the theoretical expla- fibers with a fractal-root structure through vapor gr and hydrogen as the carrying gas [12]. Fig. 2 illustrates the morphology of the branched vapor-grown fibers (a)and the structure of a branching point(b) 3.2. Dissipative structure and self-organization process of open system /15, 16/ 3. Possibility of modification and recovery of materials by nonequilibrium biomimetic treatment The theory of dissipative structure by the Prigogine 3.1. Nonequilibrium process under transient heating school [15, 16] can be applied to treat the nonequilibrium 6,13,147 problems in material processing, such Glandorf- development of high technol Prigogine criterion is taken to judge the heat transport and thermochemical process. As soon as the external condition heating rate tends to go higher and higher today. A series changes to a threshold value, the system will turn to an of transient processes will be consequently induced in ordered state of time, space and function from the original solids under extremely short laser pulse heating. Besides disordered state. This new structure under nonequilibrium the transport processes, some of the equilibrium properties condition is called the "dissipative structure".Its general will reveal their nonequilibrium characteristics. behavior is described in Fig. 4 Nonsynchronous change of temperature and thermal The system will lose its steadiness at Ae and transfer to expansion under transient heating was observed as shown an ordered state. It is called nonequilibrium phase transi in Fig. 3. The nonequilibrium localized phonon gas in a tion or self-organizing phenomenon hot spot' is studied using Boltzmann equation, leading to a soliton-like solution as follows [13] nP(s,T) y 5 exp(-iyr) 3.3. Inspiration by living process [17, 18/ (2) The coupled process of both nutrition and consume, where n(E, T) consists in the distribution function of fatigue and rest, as well as injury and healing, are all phonons at position x and time t. Let e be a Table I Fatigue life of four sample groups [20] Group no. Testing process Total life of (c) Frb FT250,000 cycles(cs)-rest-FT again 659, ⅣV(3) >5,044,600 2, 500, 000 CS-EPT-FT again 4. Above the special constraint value Ac, the system will t steady-state dissipative structure from the nonequilibrium steady Number of samples state in case of small perturbation: (a)AAe, new steady state [17, 18] Electropulsing treatment
B.L. ZhourMaterials Science and Engineering C 11 2000 13–18 ( ) 15 Fig. 3. Time process of temperature rise and thermal expansion. 1 Temperature rise, 2 thermal expansion 13,14 . Ž. Ž. w x described 10,11 may play an important role in guiding w x the design of fiber structure. The present work was carried out to synthesize carbon fibers with a fractal-root structure through vapor growth, using benzene as the carbon source, iron as the catalyst, and hydrogen as the carrying gas 12 . Fig. 2 illustrates the w x morphology of the branched vapor-grown fibers a and Ž . the structure of a branching point b . Ž . 3. Possibility of modification and recovery of materials by nonequilibrium biomimetic treatment 3.1. Nonequilibrium process under transient heating [ ] 6,13,14 Owing to the development of high technology, the heating rate tends to go higher and higher today. A series of transient processes will be consequently induced in solids under extremely short laser pulse heating. Besides the transport processes, some of the equilibrium properties will reveal their nonequilibrium characteristics. Nonsynchronous change of temperature and thermal expansion under transient heating was observed as shown in Fig. 3. The nonequilibrium localized phonon gas in a ‘‘hot spot’’ is studied using Boltzmann equation, leading to a soliton-like solution as follows 13 : w x y 1 2 1 2 2g g Ž1. n Ž. Ž . j ,t s sech y j exp yigt j1 ž / ž / ž / r b Ž . 2 Ž1. where n Ž . j ,t consists in the distribution function of j1 phonons at position x and time t. Let ´ be a small Fig. 4. Above the special constraint value l , the system will turn to a c new steady-state dissipative structure from the nonequilibrium steady state in case of small perturbation: aŽ. Ž. l-lc , steady state, b unsteady state, cŽ . l)l , new steady state 17,18 . w x c Ž . 2 parameter, by definition js´ xyÕs s t , ts´ t, and Õ s EvrEk is the group velocity of second sound. r, b and g are parameters. Knowing the moving velocity of solitonlike wave along the sample, it gives the theoretical explanation of Fig. 3 quantitatively. 3.2. DissipatiÕe structure and self-organization process of open system 15,16 [ ] The theory of dissipative structure by the Prigogine school 15,16 can be applied to treat the nonequilibrium w x problems in material processing, such as Glansdorf– Prigogine criterion is taken to judge the heat transport and thermochemical process. As soon as the external condition changes to a threshold value, the system will turn to an ordered state of time, space and function from the original disordered state. This new structure under nonequilibrium condition is called the ‘‘dissipative structure’’. Its general behavior is described in Fig. 4. The system will lose its steadiness at lc and transfer to an ordered state. It is called nonequilibrium phase transition or self-organizing phenomenon. 3.3. Inspiration by liÕing process 17,18 [ ] The coupled process of both nutrition and consume, fatigue and rest, as well as injury and healing, are all Table 1 Fatigue life of four sample groups 20 w x a Group no. Testing process Total life of fatigue cycles Ž . b I 3 FT 398,800 Ž . c II 3 EPT –FT 482,200 Ž . III 4 FT250,000 cycles cs –rest–FT again 659,900 Ž. Ž . IV 3 FT250,000 cs–EPT–FT again Ž . )5,044,600 2,500,000 cs–EPT–FT again a Number of samples. b Fatigue test. c Electropulsing treatment
B L Zhou/ Materials Science and Engineering C 11 (2000)13-18 4+4 Distance from outer surface (mm) matrix wound Fig. 7. Fibre volume fraction of bamboo(a) before and (O)after compression(compressive ratio is 0.49)[22] Coordinate Fig. 5. A schematic diagram of the growth process in the first-order phase transition theory [21] Electropulsing also improved the ductility of metal foils, which caused a significant increase of elongation of aluminum thin foils under stress in both cold-worked and self-organization processes of open system. One's life can annealed states only last for a week without eating and drinking, but several decades age can be obtained by regular living with 3.5. A possible way to recover the fatigue of materials input of energy and substance(food) in due time. It gives /17, 18, 20/ us a new way to simulate in the case of materials treat Electropulsing of high current density can be taken as a kind of transient input of energy, to cause reorganization 3. 4. Influence of high-intensity electropulsing on the work- of the microstructure of the material and to improve ing life of materials /19/ fatigue property [20]. Mild steel of 0. 13%C is taken testing material. The fatigue life of specimens are com- From the view point of structure evolution, the fatigue pared in Table 1. It can be seen from Table I that th process of material is the nucleation and growing process fatigue life of the fourth group is significantly raised of a new structure in an originally homogeneous structure The mechanism of this phenomenon is thought to be under the driving force of external load. The fatigue life of related to the decrease of number and width of persistent material corresponds to the growing time of the new phase slip band(PsB) by electropulsing [ 19] rom 0 to the critical value It means that the nucleation and growing of new phase 3.6. Healing effect of electropulsing in metals /217 ill make the free energy of system increase, that is, the existence of electropulsing prevents the nucleation and Now we consider a metallic material with an injur growing of new phase somewhere. The electric current takes the injured part far ActeD b《 e c&.dtmm (b) Fig. 6. Optical photographs of cross-sections of (a)normal bamboo and(b)reformed bamboo [22]
16 B.L. ZhourMaterials Science and Engineering C 11 2000 13–18 ( ) Fig. 5. A schematic diagram of the growth process in the first-order phase transition theory 21 . w x self-organization processes of open system. One’s life can only last for a week without eating and drinking, but several decades age can be obtained by regular living with input of energy and substance food in due time. It gives Ž . us a new way to simulate in the case of materials treatment. 3.4. Influence of high-intensity electropulsing on the working life of materials 19 [ ] From the view point of structure evolution, the fatigue process of material is the nucleation and growing process of a new structure in an originally homogeneous structure under the driving force of external load. The fatigue life of material corresponds to the growing time of the new phase from 0 to the critical value. It means that the nucleation and growing of new phase will make the free energy of system increase, that is, the existence of electropulsing prevents the nucleation and growing of new phase. Fig. 7. Fibre volume fraction of bamboo Ž. Ž. ^ before and v after compression compressive ratio is 0.49 22 . Ž . w x Electropulsing also improved the ductility of metal foils, which caused a significant increase of elongation of aluminum thin foils under stress in both cold-worked and annealed states. 3.5. A possible way to recoÕer the fatigue of materials [ ] 17,18,20 Electropulsing of high current density can be taken as a kind of transient input of energy, to cause reorganization of the microstructure of the material and to improve its fatigue property 20 . Mild steel of 0.13% C is taken as w x testing material. The fatigue life of specimens are compared in Table 1. It can be seen from Table 1 that the fatigue life of the fourth group is significantly raised. The mechanism of this phenomenon is thought to be related to the decrease of number and width of persistent slip band PSB by electropulsing 19 . Ž . w x 3.6. Healing effect of electropulsing in metals 21 [ ] Now we consider a metallic material with an injury somewhere. The electric current takes the injured part far Fig. 6. Optical photographs of cross-sections of a normal bamboo and b reformed bamboo 22 . Ž. Ž. w x
B L Zhou/ Materials Science and Engineering C 11 (2000)13-18 Phenomena Regularities simulation of biological regularities. The methodology is summarized in fig. 8 Inspiration Calculations Data evaluation The procedure may be repeated many times until satis- faction is attained It is necessary to point out that the bio-inspired design, processing and treatment of materials may be beneficial to the future studies of all kinds of materials. including Fig. 8. Procedure flow chart of biomimetic design of composite material metals, ceramics, polymers and composite materials 6. Concluding remarks from thermal equilibrium according to calculation. The wound therefore tries to adjust its distortion structures The biomimetic exploration of materials have been toward their equilibrium form. A lot of experiments show conducted since the late eighties in this institute, stressed that a pulse electric current can accelerate structural relax on composite materials at the first stage, and spread to ation anomalously other materials gradually. It started from the biomimetic Fig. 5 is a typical diagram of the growth process in the analyses, and step by step to the bio-inspired design, first-order phase transition theory [21] processing and treatment of materials. Some interesting of bio-inspired design and have bee obtained and offer the possibility to be applied in industry. 4. Some tentative practice in biomaterial modification while the bio-inspired treatment for material recovery and 22 healing are far from being complete and needs world wide cooperation between scientists from different disciplines 4.1. Reformed bamboo reinforced aluminium laminates A new technique has been developed which aims at References changing the form of bamboo from its natural circula ross-section into a plate for convenient use. Fig. 6 shows [1] B L. Zhou, C.X. ne bionic design of composite materials optical photographs of cross-sections of normal bamboo C- MRS Int. 90 Abstr. 1990. N21. Frontiers of materials (a) and reformed bamboo (b). The fibre volume fraction Research/Electro Optical Materials, Elsevier, 1991, p. 137, (invited) was also calculated, and is shown in Fig. 7 [2]B L. Zhou, Biomimetic Study of Composites Materials, JOM(1994) The fibre volume fraction, Ve, of normal ba 57-62.Feb creases gradiently along the radial direction after compres- 3] B.L. Zhou, The biomimetic design of worst bonding interface for sion(Fig. 7) [4]B L. Zhou, Some Progress in the Biomimetic Study of Composite Materials IUMRS-ICA-94, p. 117 4.2. Vibration damping characteristics of virAl lami []B L. Zhou, J Mater. Chem. Phys. 45(1996)114-119 nates/23/ [6 B L. Zhou, Improvement of mechanical properties of materials b biomimetic treatment, 3rd International Conference of Fracture ar Transflexural free vibration tests of the cantilever beam rength of Solids, Hong Kong, Key Eng. Mater. (1997)765 have been used for studying the vibration damping charac [7 X.B. Tian, X.P. Zhao, B L. Zhou, A bionic model of short fiber teristics of unidirectionally reinforced VIRALL (Vinylon- einforced composite materials: 1. Stress distribution of composite reinforced aluminum laminates) and the corresponding inforced by dumbbell fibers, Acta Metall. Sin. 30(4)(1994) monolithic aluminum alloy plate. The results show that the 180-186 former has higher vibration decay coefficient than the [8X P. Zhao, X.B. Tian, B L. Zhou, S.H. Li, A biomimetic model of short fiber reinforced materials: Il. Strength theory of latter. It is also found that the vibration damping properties imperfect-bonding interface, Acta Metall. Sin. 30(4)(1994)187. of ViRal laminates are influenced by the fiber orienta tion in It [9 X. Jia, H.M. Cheng, B L. Zhou, G.B. Zheng, Z.H. Shen, 94 Fall Symp. of Chin. Mater Res. Soc., Beijing, China, 1994, pp. 21-1353 [10] S.Y. Fu, B L. Zhou, C W. Lung, On the pull-out of fibers with 5. On the methodology of bio-inspired study of materi- fractal-tree structure and the inference of strength and fracture Ighness of composites, Smart Mater. Struct. 1(1992)180-1 als 4, 51 [11 S.Y. Fu, S.H. Li, G.H. He, B L. Zhou, C W. Lung, A study on branched structure fiber-reinforced composites, Scr. Metall. Mater. From the preceding descriptions of the bio-inspired 29(1993)1541-1546 design, processing and treatment of materials, it can be [12] H.M. Cheng, G B. Zhen, Z.M. Shen, R.H. Zhang, B L. Zhou cen that the philosophy is to make the bio-inspi biomimetic carbon fibers with fractal-root structure, The 22nd Biennial Conference on Carbon, The University lation alike in spirit, not only in appearance, i.e., the f California at San Diego, July 16-21, 1995, p. 306
B.L. ZhourMaterials Science and Engineering C 11 2000 13–18 ( ) 17 Fig. 8. Procedure flow chart of biomimetic design of composite materials w x 4,5 . from thermal equilibrium according to calculation. The wound therefore tries to adjust its distortion structures toward their equilibrium form. A lot of experiments show that a pulse electric current can accelerate structural relaxation anomalously. Fig. 5 is a typical diagram of the growth process in the first-order phase transition theory 21 . w x 4. Some tentative practice in biomaterial modification [ ] 22 4.1. Reformed bamboo reinforced aluminium laminates A new technique has been developed which aims at changing the form of bamboo from its natural circular cross-section into a plate for convenient use. Fig. 6 shows optical photographs of cross-sections of normal bamboo Ž. Ž. a and reformed bamboo b . The fibre volume fraction was also calculated, and is shown in Fig. 7. The fibre volume fraction, V , of normal bamboo de- f creases gradiently along the radial direction after compression Fig. 7 . Ž . 4.2. Vibration damping characteristics of VIRALL laminates 23 [ ] Transflexural free vibration tests of the cantilever beam have been used for studying the vibration damping characteristics of unidirectionally reinforced VIRALL Vinylon- Ž reinforced aluminum laminates and the corresponding . monolithic aluminum alloy plate. The results show that the former has higher vibration decay coefficient than the latter. It is also found that the vibration damping properties of VIRALL laminates are influenced by the fiber orientation in it. 5. On the methodology of bio-inspired study of materials 4,5 [ ] From the preceding descriptions of the bio-inspired design, processing and treatment of materials, it can be seen that the philosophy is to make the bio-inspired simulation alike in spirit, not only in appearance, i.e., the simulation of biological regularities. The methodology is summarized in Fig. 8. The procedure may be repeated many times until satisfaction is attained. It is necessary to point out that the bio-inspired design, processing and treatment of materials may be beneficial to the future studies of all kinds of materials, including metals, ceramics, polymers and composite materials. 6. Concluding remarks The biomimetic exploration of materials have been conducted since the late eighties in this institute, stressed on composite materials at the first stage, and spread to other materials gradually. It started from the biomimetic analyses, and step by step to the bio-inspired design, processing and treatment of materials. Some interesting results of bio-inspired design and processing have been obtained and offer the possibility to be applied in industry, while the bio-inspired treatment for material recovery and healing are far from being complete and needs world wide cooperation between scientists from different disciplines. References w x 1 B.L. Zhou, C.X. Shi, On the bionic design of composite materials, C-MRS Int. ’90 Abstr., 1990, N21. Frontiers of Materials ResearchrElectronic and Optical Materials, Elsevier, 1991, p. 137, Ž . invited . w x 2 B.L. Zhou, Biomimetic Study of Composites Materials, JOM 1994 Ž . 57–62, Feb. w x 3 B.L. Zhou, The biomimetic design of worst bonding interface for ceramic matrix composites, Compos. Eng. 5 10–11 1995 1261. Ž .Ž . w x 4 B.L. Zhou, Some Progress in the Biomimetic Study of Composite Materials IUMRS-ICA-94, p. 117. w x 5 B.L. Zhou, J. Mater. Chem. Phys. 45 1996 114–119. Ž . w x 6 B.L. Zhou, Improvement of mechanical properties of materials by biomimetic treatment,3rd International Conference of Fracture and Strength of Solids, Hong Kong, Key Eng. Mater. 1997 765, Ž . Ž . invited . w x 7 X.B. Tian, X.P. Zhao, B.L. Zhou, A bionic model of short fiber reinforced composite materials: 1. Stress distribution of composite reinforced by dumbbell fibers, Acta Metall. Sin. 30 4 1994 Ž. Ž . 180–186. w x 8 X.P. Zhao, X.B. Tian, B.L. Zhou, S.H. Li, A biomimetic model of short fiber reinforced composite materials: II. Strength theory of imperfect-bonding interface, Acta Metall. Sin. 30 4 1994 187– Ž.Ž . 193. w x 9 X. Jia, H.M. Cheng, B.L. Zhou, G.B. Zheng, Z.H. Shen, ’94 Fall Symp. of Chin. Mater. Res. Soc., Beijing, China, 1994, pp. 21–1353. w x 10 S.Y. Fu, B.L. Zhou, C.W. Lung, On the pull-out of fibers with fractal-tree structure and the inference of strength and fracture toughness of composites, Smart Mater. Struct. 1 1992 180–185. Ž . w x 11 S.Y. Fu, S.H. Li, G.H. He, B.L. Zhou, C.W. Lung, A study on branched structure fiber-reinforced composites, Scr. Metall. Mater. 29 1993 1541–1546. Ž . w x 12 H.M. Cheng, G.B. Zhen, Z.M. Shen, R.H. Zhang, B.L. Zhou, Preparation of vapor grown biomimetic carbon fibers with fractal-root structure, The 22nd Biennial Conference on Carbon, The University of California at San Diego, July 16–21, 1995, p. 306
B.L. Zhou/ Materials Science and Engineering C 11(2000)13-18 [13]. L. Zhou, G.H. He, Y.J. Gao, W L. Zhao, J.D. Guo, Int. J. [19] R.S. Qin, Y L. Xiao, B L. Zhou, 96 Symp. of Chin. Mater. Res. Thermophys.18(2)(1997)481 Soc., Beijing, China, 1996, K-Subsymp [14 D W. Tang, B L. Zhou, H. Cao, G.H. He, Appl. Phys. Lett. 59(24) [20] Y F. Shen, B L. Zhou, G H. He, G. Yao, H.C. Yan, Chin. J.Mater (1991)3113 Res.10(2)(1996)165 [15] R.B. Ouyang, Prog Phys. (China)(1987)313 [21]RS. Qin, S.X. Su, J D. Guo, G.H. He, B L. Zhou, A healing [16] K H Shen, X.F. Peng et al, Prigogine and the Theory of Dissipative Structure, Shanxi Publ. House of Sci and Tech [17] B L. Zhou, Nonequilibrium processes in materials processing, Chin. later.Res11(1997)576 static properties, J Mater. Sci. 29(1994)5990-5996 [18] B L. Zhou, Some nonequilibrium thermophysical problems in mate- [23] G.X. Sui, G H. He, L.Y. Bai, B L. Zhou, Vibration damping proper- rials processing, The 5th Asian Thermophysical Properties Confer- ties of VIRALL laminates, Acta Metall. Sin. 32(1)(1996)97, (in ence, August 30-Sept. 2, Seoul, Korea, 1998
18 B.L. ZhourMaterials Science and Engineering C 11 2000 13–18 ( ) w x 13 B.L. Zhou, G.H. He, Y.J. Gao, W.L. Zhao, J.D. Guo, Int. J. Thermophys. 18 2 1997 481. Ž .Ž . w x 14 D.W. Tang, B.L. Zhou, H. Cao, G.H. He, Appl. Phys. Lett. 59 24 Ž . Ž . 1991 3113. w x 15 R.B. Ouyang, Prog. Phys. China 7 1987 313. Ž .Ž . w x 16 K.H. Shen, X.F. Peng et al., Prigogine and the Theory of Dissipative Structure, Shanxi Publ. House of Sci. and Tech., Xi’an, 1982. w x 17 B.L. Zhou, Nonequilibrium processes in materials processing, Chin. J. Mater. Res. 11 1997 576. Ž . w x 18 B.L. Zhou, Some nonequilibrium thermophysical problems in materials processing, The 5th Asian Thermophysical Properties Conference, August 30–Sept. 2, Seoul, Korea, 1998. w x 19 R.S. Qin, Y.L. Xiao, B.L. Zhou., ’96 Symp. of Chin. Mater. Res. Soc., Beijing, China, 1996, K-Subsymp. w x 20 Y.F. Shen, B.L. Zhou, G.H. He, G. Yao, H.C. Yan, Chin. J. Mater. Res. 10 2 1996 165. Ž .Ž . w x 21 R.S. Qin, S.X. Su, J.D. Guo, G.H. He, B.L. Zhou, A healing model for metallic materials theoretical study, Biomimetics 4 1996 121. Ž . w x 22 S.H. Li, S.Y. Fu, B.L. Zhou, Reformed bamboo and reformed bamboorAl composite: Part I. Manufactural technique, structure and static properties, J. Mater. Sci. 29 1994 5990–5996. Ž . w x 23 G.X. Sui, G.H. He, L.Y. Bai, B.L. Zhou, Vibration damping properties of VIRALL laminates, Acta Metall. Sin. 32 1 1996 97, in Ž .Ž . Ž Chinese