Analysis of bone as a composite material

Bone is considered to be a composite material consisting of a high elastic modulus mineral ‘fibres’ embedded in a low elastic modulus organic matrix permeated with pores filled with liquids.Properties and distribution of phases are established or estimated from the experimental data. Theories of composite materials are applied to bone with various contents of phases, and the discussion summarizes possible modes of deformation under load. Elastic behaviour is attributed to the joint properties of collagen and hydroxyapatite. Plastic deformation may occur in the amorphous portions of both mineral and organic phases. Visco-elastic characteristics are credited to the flow of liquids and viscous deformation of gels and sols.     

Characterization of a peek composite segmental bone replacement implant

A composite material of polyetheretherketone and short, chopped E-glass fibers was used to produce a segmental bone replacement implant. Problems with current metallic implants include stress-shielding of the surrounding bone and subsequent loosening of the implant. A better match between the bulk material properties of the implant and the bone it replaces can decrease the occurrence of these problems. Composite materials were chosen because their properties can be tailored to match the requirements. Material selection was accomplished with the aid of modeling software, which predicted the composite properties based on its composition and fiber directional parameters. Prototype parts were completed through a series of in-house molding and machining processes. Sections complete with an embedded metallic porous surface were tested to measure the strength of the attachment of the surface. The molded parts were characterized both destructively and nondestructively. The results of tensile tests performed on molded parts were comparable to those using commercially supplied samples. The fiber orientation was measured to verify the random positioning of fibers throughout the part, as assumed in the initial material selection. Ultrasonic C-scanned images confirmed that the molded parts had a very low density of air pockets or voids.     

Characterization of silane coated hollow sphere alumina-reinforced ultra high molecular weight polyethylene composite as a possible bone substitute material

Silane coated hollow sphere alumina ceramic particles were moulded with ultra high molecular weight polyethylene (UHMWPE) to form a series of composites with alumina weight percent in the range from 15 to 50. The composites were prepared in a cylindrical mould using powder-processing technique. The composites were characterized for mechanical properties using destructive and non-destructive ultrasonic testing methods. The physical properties of the composite were determined and compared with those of cortical bone.     

Preparation and characterization of a novel bone graft composite containing bone ash and egg shell powder

Egg shells which were hitherto discarded as wastes were collected, purified and powdered into a particle size in the range of 5–50 μm. A composite bone graft material in cylindrical form was prepared using egg shell powder (ESP), bone ash (BA) and gelatin. These bone grafts were characterized for their FT–IR, TGA, XRD, SEM and mechanical properties. The mechanical studies indicate that the composite having a stoichiometric ratio of BA (3 g) and ESP (7 g) has shown better mechanical properties. X-ray diffraction (XRD) data indicated the crystallographic nature of BA is akin to hydroxyapatite (HA) and both BA and ESP did not lose their crystalline nature when bone grafts were prepared. This revealed that ESP may be used as a component in bone graft utilizing the solid waste from the poultry industry.     

注射式骨修复多孔复合材料的性能研究

骨缺损在临床上是一种常见现象,通过制备纳米羟基磷灰石/聚酰胺66复合材料粉末,并以纳米羟基磷灰石/聚酰胺66和海藻酸钠的混合粉末作为主要固体成分,以聚乙烯醇水溶液为主要液相,通过混合搅拌制备了注射式骨修复多孔复合材料.通过X射线衍射(XRD)、红外(IR)、扫描电镜(SEM)和透射电镜(TEM)对材料的性能进行表征,表征结果表明制备的注射式骨修复材料中含有与天然骨中相似的无机成分,具有好的生物相容性和生物活性.材料的固化时间与材料的固液比、比表面积和温度等因素有关.通过调整材料的固相、液相比例,可以获得不同固化时间和不同孔隙率的骨修复材料.     

Analysis of the inorganic component of autogenous tooth bone graft material

This study was performed to identify the calcium phosphate minerals, chemical element and Ca/P ratio and to examine the surface structure of autogenous tooth bone grafting material (AutoBT) which recently developed and applied clinically as a bone graft materials. The analytical results showed that AutoBT is composed of low-crystalline hydroxyapatite (HA) and possibly other calcium phosphate minerals, which is similar to the minerals of human bone tissues. And the dental crown portion was composed of high-crystalline calcium phosphate minerals (mainly HA) with higher Ca/P ratio while the root portion was mainly composed of low-crystalline calcium phosphates with relatively low Ca/P ratio.     

复合骨修复材料——聚氨基酸/硫酸钙的生物相容性研究

采用原位熔融缩聚法合成聚氨基酸/硫酸钙(poly(amino acids)/calcium sulfate,PAA/CS)复合材料.分别将PAA/CS圆片和其浸提液与L929细胞共培养后观察细胞形态变化,采用CCK-8试剂盒检测细胞增殖活性,流式细胞仪测定细胞周期.将致密圆柱状PAA/CS材料植入兔胫骨近端干骺端,进行...     

Porous phosphate-gelatine composite as bone graft with drug delivery function

The design and synthesis of porous phosphate-gelatine composite implant which mimicks the structure of natural bone and has drug delivery function is proposed. Gelatine reproducing the proteinaceous part of bone was cross-linked in order to modulate its solubility in the physiologic fluids. The kinetic of gelatine release from ceramic matrix was also evaluated as model of the release of any therapeutic compound which can be loaded into gelatine.     

Plain concrete as a composite material

The purpose of this paper is to study the consequences of the composite nature of concrete. A plausible energy balance equation is postulated and the Green-Rivlin invariance principle is applied to it to derive the linear and angular momentum balance laws. General constitutive equations are discussed with the aid of thermodynamic potentials and Coleman's method. The distribution of the applied stresses between mortar and aggregate is also studied in detail, showing for instance that substantial tensile lateral stresses may appear in mortar under uniaxial compressive loading. These results are used to derive a criterion for the onset of inelasticity in concrete.     

Development of a new synthetic bone graft

A process for the replication of bovine cancellous bone in synthetic bioceramic materials for use as artificial bone graft substitutes is described. The process detailed here may be easily implemented to allow production of large numbers of blocks of material, even on a laboratory scale. The graft material has a pore morphology and interconnectivity identical with that of the original cancellous bone used as a starting material. Strength of the material is adequate, and at lower porosity levels it meets the FDA requirements for coralline materials for spinal applications. The synthetic graft is also shown to have excellent fluid-retention characteristics, making it a potential carrier for morphogenic agents such as solutions of bone morphogenic protein. © 1998 Kluwer Academic Publishers/p>     

High-strain fatigue studies of a composite material

The reinforcement of metallic matrices with stronger, stiffer ceramic fibres is one approach which is currently being pursued in an effort to develop materials which will withstand the demanding conditions imposed by present-day engineering requirements. The gains in tensile strength which might be obtained by suitable combination of fibres and metal have been widely speculated upon [1] and, recently, experimental verification of some of these predictions has been obtained [2]. As yet, however, little attention has been directed towards assessing the limitations of such composite systems, isolating their causes and attempting to overcome them.     

Immobilization of a bone and cartilage stimulating peptide to a synthetic bone graft

A synthetic peptide fragment of human collagen type I (BCSP™-1) was linked to the surface of a commercially available ceramic in an effort to improve the properties of the bone graft substitute to accelerate local healing. BCSP™-1 was covalently immobilized on the surface of the ceramic via the linkers 3-aminopropyl-triethoxysilane (APTES) and suberic acid bis-N-hydroxysuccinimide ester (DSS). The chosen chemistry was non-cytotoxic. A rat calvaria cell assay using alkaline phosphatase (ALP) as an osteoblast differentiation marker, showed that modifying the surface of the ceramic was enough to enhance ALP activity, although the total cell population on the surface decreased. A significant increase in ALP activity/cell was noted with serum albumin bound to the surface, however, the BCSP™-1 bound surface exhibited an even greater ALP activity that showed a surface concentration dependent trend. An optimal BCSP™-1 surface density in the range of 0.87–2.24 nmol/cm² elicited the maximum ALP activity/cell at day 6 of culture. The peptide bound ceramic generated an ALP activity/cell that was roughly 3-fold higher than the non-modified ceramic and 2-fold higher than the APTES-grafted ceramic.     

Development and testing of a self-deformed composite material

A multifunctional – hybrid – composite material that incorporates carbon and glass fibres embedded into an epoxy matrix was developed. This material can be made to undergo a shape change without inserting activators. This is accomplished by selective heating of the embedded carbon fibres through the application of an electric current (Joule effect). The resulting shape change was determined and the stresses generated during heating were measured via a 3-point bending device. The possibility of using the reinforcing fibres of a multi-directional composite as activators for inducing specific deformation modes is discussed.     

Development of a pultruded composite material highway guardrail

Fiber-reinforced polymer (FRP) composite materials are being used to develop products for use as highway appurtenances, such as, sign supports, luminaire supports and guardrails (crash barriers). These structures, that are located alongside highways and roads, are subjected to vehicular impacts and must be designed to be ‘crashworthy’ to ensure the safety of the driving public. This paper reviews an ongoing 10-year research and development program funded by the United States federal highway administration (FHWA) and the United States department of transportation (DOT) to produce a crashworthy composite material highway guardrail system. An overview of the research and development leading to a patented pultruded composite material guardrail is provided.     

Vibrational analysis of a double-layer composite material structure

As new manufacturing techniques for glass reinforced polymers are developed and existing ones improved, new structural engineering design methods will become available for the construction industry to exploit. The most promising area currently is the pultruded double-layer skeletal fibre/matrix structural system. Considerable research effort has been directed towards design techniques and structural imperfections associated with those systems under static loading. This paper discusses the analysis of a particular type of double-layer skeletal structure, under dynamic loading and manufactured by the pultrusion method. Analytical and experimental techniques have been used in the analysis, and a discussion of these techniques is presented. It is concluded that, provided great care is taken in modelling the analytical system, good agreement between the two methods of analysis is obtained; it is necessary that mechanical properties of the material of the prototype are accurately determined.     

On the hygrothermomechanical behavior of a composite material

We establish the system of equations for the hygrothermomechanical behaviour of a composite material, using the homogenization method. The macroscopic coefficients are deduced and it is proved that the macroscopic system of equations is a coupled one, the temperature and moisture equations containing new terms. Finally the convergence theorem for the homogenization process is proved.     

Mechanical behaviour of concrete as a composite material

Several theories of composite materials have been used to predict the mechanical properties of concrete. In many cases there is no basis to judge the relative superiority of one model over that of the other. It is, however, essential that the model and the related assumptions are axiomatically acceptable, and have physical relevance to the problem under consideration. In this paper the suitability of a new model of multiphase materials to concrete is examined. It is shown that the model predicts the effective Young's modulus and shrinkage of concrete quite accurately. As far as prediction of creep behaviour is concerned, the model qualitatively compares well with many other models proposed earlier. However, further studies are essential into more refined formulation of the problem of creep phenomenon.

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Résumé On s'est appuyé sur plusieurs théories des matériaux composites pour prédire les propriétés mécaniques du béton. Dans beaucoup de cas, aucune base ne permet de juger de la supériorité relative d'un modèle sur un autre. Il importe pourtant que le modèle et les hypothèses qui lui sont associées soient axiomatiquement acceptables et qu'ils présentent une pertinence physique par rapport au problème étudié. On examine ici l'aptitude d'un nouveau modèle de matériaux polyphases à l'étude du béton. On montre que ce modèle permet de prédire le module de Young effectif et le retrait du béton très exactement pour ce qui regarde le comportement en fluage, qualitativement le modèle soutient la comparaison avec beaucoup d'autres modèles antérieurs. Mais une formulation plus affinée du problème du fluage exigera de nouvelles études.