abstract: Polymer and polymer matrix composites (PMCs) materials are being used extensively in different civil and mechanical engineering applications. The behavior of the epoxy resin polymers under different types of loading conditions has to be understood before the mechanical behavior of Polymer Matrix Composites (PMCs) can be accurately predicted. In many structural applications, PMC structures are subjected to large flexural loadings, examples include repair of structures against earthquake and engine fan cases. Therefore it is important to characterize and model the flexural mechanical behavior of epoxy resin materials. In this thesis, a comprehensive research effort was undertaken combining experiments and theoretical modeling to investigate the mechanical behavior of epoxy resins subject to different loading conditions. Epoxy resin E 863 was tested at different strain rates. Samples with dog-bone geometry were used in the tension tests. Small sized cubic, prismatic, and cylindrical samples were used in compression tests. Flexural tests were conducted on samples with different sizes and loading conditions. Strains were measured using the digital image correlation (DIC) technique, extensometers, strain gauges, and actuators. Effects of triaxiality state of stress were studied. Cubic, prismatic, and cylindrical compression samples undergo stress drop at yield, but it was found that only cubic samples experience strain hardening before failure. Characteristic points of tensile and compressive stress strain relation and load deflection curve in flexure were measured and their variations with strain rate studied. Two different stress strain models were used to investigate the effect of out-of-plane loading on the uniaxial stress strain response of the epoxy resin material. The first model is a strain softening with plastic flow for tension and compression. The influence of softening localization on material behavior was investigated using the DIC system. It was found that compression plastic flow has negligible influence on flexural behavior in epoxy resins, which are stronger in pre-peak and post-peak softening in compression than in tension. The second model was a piecewise-linear stress strain curve simplified in the post-peak response. Beams and plates with different boundary conditions were tested and analytically studied. The flexural over-strength factor for epoxy resin polymeric materials were also evaluated. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011

abstract: Raman scattering from Ge-Si core-shell nanowires is investigated theoretically and experimentally. A theoretical model that makes it possible to extract quantitative strain information from the measured Raman spectra is presented for the first time. Geometrical and elastic simplifications are introduced to keep the model analytical, which facilitates comparison with experimental results. In particular, the nanowires are assumed to be cylindrical, and their elastic constants isotropic. The simple analytical model is subsequently validated by performing numerical calculations using realistic nanowire geometries and cubic, anisotropic elastic constants. The comparison confirms that the analytic model is an excellent approximation that greatly facilitates quantitative Raman work, with expected errors in the strain determination that do not exceed 10%. Experimental Raman spectra of a variety of core-shell nanowires are presented, and the strain in the nanowires is assessed using the models described above. It is found that all structures present a significant degree of strain relaxation relative to ideal, fully strained Ge-Si core-shell structures. The analytical models are modified to quantify this strain relaxation. / Dissertation/Thesis / Ph.D. Physics 2011

The primary goal of the American football helmet has been protection of players against skull fractures and other traumatic brain injuries (TBI) [Cantu 2003, Benson 2009]. TBI can result from short, high magnitude linear impact events typical of when the head impacts a hard surface [Gilcrhist 2003, Doorly 2007]. The modern helmet, which has evolved and become well designed to mitigate TBI injuries, does not offer sufficient protection against injury such as concussion, and the incident rate remains high in sport [Broglio 2009, Rowson 2012]. Researchers speculate rotation of the head leads to shear strain on the brain tissue, which may be the underlying mechanism of injury leading to concussive type injuries [Gennarelli 1971, Ommaya 1974, Gennarelli 1982, Prange 2002, Gilcrhist 2003, Aare 2003, Zhang 2004, Takhounts 2008, Greenwald 2008, Meaney 2011]. This has led researchers to investigate new liner materials and technologies to improve helmet performance and include concussive injury risk protection by attempting to address rotational acceleration of the brain [Mills 2003, Benson 2009, Caserta 2011, Caccese 2013]. To improve current football helmet designs, technology must be shown to reduce the motion of the brain, resulting in lower magnitudes of dynamic response thus reducing maximum principal strain and the corresponding risk of injury [Margulies 1992, Zhang 2004, Mills 2003, Kleiven 2007, Yoganandan 2008 Caserta 2011, McAllister 2012, Caccese 2013, Post 2013, Fowler 2015, Post 2015a/b]. Recent research has studied the use of decoupling liner systems in addition to the existing liner technology, to address resultant rotational acceleration. However, none of this previous work has evaluated the results in terms of the relationship between brain motion, tissue strain, and injury risk reduction. This thesis hypothesises the use of decoupling strategies to reduce the dominant coordinate component of acceleration in order to decrease maximum principal strain values. The dominant component of acceleration, defined as the coordinate component with the highest contribution to the resultant acceleration for each impact, is a targetable design parameter for helmet innovation. The objective of this thesis was to demonstrate the effect liner strategies to reduce the dominant component of rotational acceleration to decrease maximum principal strain in American football helmets.

Graphene is a single atomic sheet of graphite that exhibits a diverse range of unique properties. The electrons in intrinsic graphene behave like relativistic Dirac fermions; graphene has a record high Young's modulus but extremely low bending rigidity; and suspended graphene exhibits very high thermal conductivity. These properties are made more intriguing because with a thickness of only a single atomic layer, graphene is both especially affected by its environment and readily manipulated. In this dissertation the interaction between graphene and its environment as well as the exciting new physics realized by manipulating graphene's lattice are investigated. Lattice manipulations in the form of strain cause alterations in graphene's electrical dispersion mathematically analogous to the vector potential associated with a magnetic field. We complete the standard description of the strain-induced vector potential by explicitly including the lattice deformations and find new, leading order terms. Additionally, a strain engineered device with large, localized, plasmonically enhanced pseudomagnetic fields is proposed to couple light to pseudomagnetic fields. Accurate strain engineering requires a complete understanding of the interactions between a two dimensional material and its environment, particularly the adhesion and friction between graphene and its supporting substrate. We measure the load dependent sliding friction between mono-, bi-, and trilayer graphene and the commonly used silicon dioxide substrate by analyzing Raman spectra of circular, graphene sealed microchambers under variable external pressure. We find that the sliding friction for trilayer graphene behaves normally, scaling with the applied load, whereas the friction for monolayer and bilayer graphene is anomalous, scaling with the inverse of the strain in the graphene. Both strain and graphene's environment are expected to affect the quadratically dispersed out of plane acoustic phonon. Although this phonon is believed to provide the majority of graphene's very high thermal conductivity, its contributions have never been isolated. By measuring strain and pressure dependent thermal conductivity, we gain insight into the mechanism of graphene's thermal transport.

Gamma titanium aluminide alloys are emerging as a lightweight replacement to nickel superalloys, with current application in turbine stages of aero-engines, as well as in high performance automobiles and potentially the nuclear industry. The lack of toughness of its two constitutive intermetallic phases, γ-TiAl and α2-Ti3Al, prevents a conventional damage tolerant approach to fatigue lifing. To gain confidence in the use of γ-TiAl alloys and extend the temperature-stress envelope of applicability, the present work aims to achieve an understanding of the development of plasticity and flaw formation during cyclic loading. The general plasticity of a γ-TiAl alloy, Ti-45Al-2Nb-2Mn(at.%)-0.8vol.%TiB2, in compression was investigated by mapping the development of localised strain at the specimen surface. Methods were developed to produce speckle patterns for high resolution digital image correlation that were stable at test temperatures of 700 °C in air, in order to study the extent of plasticity generated by differing deformation mechanisms at application-relevant temperatures, with nano-scale resolution. At the colony scale (i.e. single stacks of co-planar α2-Ti3Al and γ-TiAl lamellae, where each stack is formed from a single high temperature disordered α-TiAl grain), macroscopic deformation bands were observed to develop at only a few percent strain. Within such bands, which propagated across many colonies of differing lamellar orientations, considerable lattice curvature and localised slip and twin operation occurred. This correlated with colony boundary failure in such bands. Twinning of the γ-TiAl phase parallel to the lamellar interfaces, longitudinal twinning, has rarely been studied, despite generalised twinning in equiaxed γ-TiAl grains being known to cause boundary decohesion. Here, the occurrence of longitudinal twinning in both microcompression and polycrystalline testpieces was investigated up to 700 °C by electron backscatter diffraction. The strength of constraint by surrounding lamellar domains was found to be the determining factor in the increased prominence of twinning at 700 °C, and hence determined whether twinning shear-induced flaws formed at colony boundaries. Using the high temperature digital image correlation strain mapping and electron backscatter diffraction techniques developed, along with transmission electron microscopy, the onset of plasticity at temperatures up to 700 °C was studied in both micro-scale and macro-scale test specimens for different lamellar thicknesses. Testpieces were loaded below the macroscopic yield stress in both monotonic and high cycle fatigue regimes, to 107 cycles, at a tensile stress ratio of R = 0.1. Longitudinal plasticity occurred in most colonies with soft mode lamellar orientations, and was located just 30 - 50 nm from lamellar interfaces. Lamellar refinement caused an increased number of slip bands to develop. In most cases, plastic strains decreased to zero by the colony boundary and strain transfer across such boundaries in high cycle fatigue was rare. At room temperature, the maximum applied stress was found to influence the number of slip bands more than the number of loading cycles.

abstract: Pb-free solder joints are commonly used as interconnects in semiconductor packaging. One of the major defects affecting the mechanical performance of solder joints are reflow pores that form during processing. These pores exhibit significant variability in size and distribution, and understanding the effects of pore geometry on failure is an important reliability concern. In this thesis, the pore microstructures of solder joint samples and the localized plastic deformation around individual pores was characterized in 3D using lab scale X-ray Microtomography. To observe the deformation of a solder joint in 3D, a solder joint was imaged with Microtomography after reflow and then deformed in shear in several loading steps with additional tomography data taken between each. The 3D tomography datasets were then segmented using the 3D Livewire technique into regions corresponding to solder and pores, and used to generate 3D models of the joint at each strain value using Mimics software. The extent of deformation of individual pores in the joint as a function of strain was quantified using sphericity measurements, and correlated with the observed cracking in the joint. In addition, the error inherent in the data acquisition and 3D modeling process was also quantified. The progression of damage observed with X-ray Microtomography was then used to validate the deformation and failure predicted by a Finite Element (FE) simulation. The FE model was based on the as-reflowed tomography data, and incorporated a ductile damage failure model to simulate fracture. Using the measured sphericity change and cracking information obtained from the tomography data, the FE model is shown to correctly capture the broad plastic deformation and strain localization seen in the actual joint, as well as the crack propagation. Lastly, Digital Image Correlation was investigated as a method of obtaining improved local strain measurements in 3D. This technique measures the displacement of the inherent microstructural features of the joint, and can give localized strain measurements that can be directly comparable to that predicted by modeling. The technique is demonstrated in 2D on Pb-Sn solder, and example 3D data is presented for future analysis. / Dissertation/Thesis / M.S. Materials Science and Engineering 2012

[pt] É apresentado um modelo não-linear para estruturas unidimensionais em equilíbrio, onde não são feitas restrições de caráter geométrico. Este modelo é capaz de descrever movimentos que envolvam flexão, torção, cilhamento e extensão. As configurações de referência e deformada têm sua geometria descrita através da posição espacial de uma curva e da orientação de uma base ortonormal associada a cada ponto dessa curva. O uso dos ângulos de Euler na descrição das rotações, o que pode implicar em instabilidades numéricas, é evitado através do uso de uma nova parametrização para o problema. O problema de equilíbrio que envolve o comportamento não-linear de uma estrutura unidimensional é formulado de diferentes maneiras. São apresentados dois métodos numéricos para a solução desse problema. Um deles é baseado numa decomposição via lagrangeano aumentado e outro é um método de Newton não convencional. São discutidos detalhes acerca da implementação computacional desses métodos. A validade das formulações é atestada através de alguns exemplos numéricos. Em particular. São analisadas algumas aplicações relacionadas com operações de cabos umbilicais em prospecção petrolífera, que envolvem carregamentos estáticos complicados como aqueles ocasionados por flutuadores e pela atração gravitacional. / [en] It is presented a model of the static geometrically non-linear behavior of an elastic rod which considers flexion, torsion, shear and tension. The geometry of the body, in the reference and deformed configurations, is described given the position of the centerline and the geometry of a rigid frame attached to each point of the line. A particular parametrization that avoids the difficulties associated with the use of Euler angles is employed simplifying the numerical treatment. The equilibrium problem for a nonlinear rod is formulated in several different ways and two numerical methods for solution of these problems are presented. One is based on augmented Lagrangian splitting and the second is a non-standard Newton’s method. Details pertaining to the implementation of that method are discussed. A number of numerical simulations have been documented to demonstrate the robustness of the formulations. In particular, some applications in connection with Off shore pipe lines operations, which involves complicated static loading conditions that includes floaters and gravitational forces, are analysed.

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2841号 ; 請求記号: 新制/工/1418 ; 整理番号: 25526 / The consolidation of peat is complex due to the resultant large strain associated with the highly compressible nature of natural peat deposits and to the rapid changes in soil properties during the consolidation process. In addition, the consolidation process is further complicated by the occurrence of secondary compression which significantly contributes to the overall settlement of peaty soil. Therefore, it is necessary to take these properties into account in order to obtain better predictions from peat consolidation analyses. In the present study, the consolidation behavior of peaty clay found in Sri Lanka is extensively studied using a model based on the elasto-viscoplastic theory. The model can describe the prominent creep behavior of peaty soil as a continuous process. In addition, the model can accommodate the effect of structural degradation on the consolidation process. The analysis takes into account all the main features involved in the peat consolidation process, namely, finite strain, variable permeability, and the effect of secondary compression. Also, it considers the variable compressibility for stage-constructed embankments which exert high levels of pressure on the peaty subsoil. The constitutive equations used in the model and the procedure adapted to account for the above-mentioned features of the analysis are described. The constitutive model is based on Perzyna’s type viscoplastic theory and the Cambridge elasto-plastic theory combined with empirical evidence. In the finite element formulations, which are based on the finite deformation theory, an updated Lagrangian method is adopted. A description of the material parameters used in the model and the procedures applied to evaluate them, with standard laboratory and field tests, are explained. In addition, a performance of the model incorporating the original and the modified Cam-clay theory is evaluated by simulating triaxial test results. A comparison shows that with the present definition of the parameters, the original model yields more representative results than the model based on the modified Cam-clay theory. Initially, the capability of the constitutive model to capture the consolidation behavior is verified using the consolidation model test data on peaty clay found in Sri Lanka. It is confirmed that the constitutive model is able to predict the observed creep characteristics and the effect of sample thickness on settlement predictions for the material under consideration. The performance of the model in predicting the consolidation behavior under field conditions is studied using field data on instrumented earth fill constructed on peaty clay. One-dimensional compression is assumed for the peaty clay due to the large plane area of the fill. Separate analyses are carried out by the model considering the infinitesimal strain theory, the finite strain theory, and the finite strain theory together with the effect of structural degradation in order to explore how these features describe the observed field behavior. Analyses reveal that it is necessary to consider finite deformation together with the effect of structural degradation in order to successfully simulate the resultant large strain and the stagnated pore water pressure observed in the field. The construction of road embankments over peat deposits is quite problematic, and thus, it is often done after first improving the properties of the peaty soil through the utilization of appropriate ground-improvement techniques. Understanding the field response of peaty clay during this improvement process is naturally of great importance. A constitutive model is applied to predict the field performance of embankments constructed on peaty clay using different ground-improvement techniques. The back analysis of embankments constructed with the preloading method indicates that the model can be successfully applied to predict both the deformation and the stability of structures constructed on peaty clays. The stability of the embankment during and after construction is verified by investigating the stress-strain characteristics of the subsoil. The model applications used to predict the consolidation behavior of embankments constructed by the preloading method, combined with other ground-improvement techniques, are then discussed. Embankments constructed with prefabricated vertical drains (PVDs) and sand compaction piles (SCPs) are considered, and finite element analyses are carried out in all cases by converting the actual three-dimensional conditions that exist around the drains into simplified two-dimensional plane strain conditions. The field behavior when PVDs are installed in the peaty clay is simulated using the equivalent vertical permeability for the PVD-improved subsoil. In the case of SCPs, a conversion scheme is used to transform the axisymmetric nature of sand columns into equivalent plane strain conditions. A comparison of the predicted results with the field observations shows a reasonable agreement. An analysis of the PVD-improved foundation indicates that the installation of PVDs not only accelerates the rate of consolidation, but influences the deformation pattern of the subsoil due to embankment loading. The analysis also shows that the use of PVDs can significantly increase embankment stability. The model prediction for the SCP-improved foundation reveals that the stiffness and the area replacement ratio used in the conversion scheme play vital roles in predicting the behavior of SCP-improved soft grounds. The observed improvements in the bearing capacity of the subsoil and in the stability of the embankment, brought about by the installation of SCPs, can be simulated by the model. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13370号 / 工博第2841号 / 新制||工||1418(附属図書館) / 25526 / UT51-2007-Q771 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 田村 武, 准教授 木元 小百合 / 学位規則第4条第1項該当

A large number of bone fractures are treated with stabilisation devices that utilise metal wires or screws, which traverse the bone and are connected to an external frame or internal plate. Clinically, fixation devices are required to be able to: sustain loads; minimise patient discomfort and possible implant loosening; and promote healing. In the recent years locking plates have become increasingly popular for osteoporotic or complex fractures, which can be difficult to manage. It, however, remains unclear as to how these devices need to be configured for optimum clinical performance. This thesis investigates the mechanics of locking plates, factors that influence their performance and provides guidance to optimise the placement of screws. Finite element simulation and analytical models were developed and validated using lab-based experimental models. The local behaviour around the screw-bone interface is considered and the implications of different modelling assumptions assessed. A novel method of simulating the effect of radial interference due to pilot-hole size is proposed. Different screw types are evaluated: osteoporotic bone is found to be particularly susceptible to the screw tightening preload used in compression screws; far-cortical locking screws are found to slightly reduce device stiffness but substantially increase strain levels around screw holes. Finite element simulations show that many of the local effects, such as preloads and contact modelling, can profoundly influence the prediction of strains around screws but do not generally influence the global load-displacement behaviour; the screw-plate connection and bone/plate material and geometric properties are found to have an influence on global stiffness predictions. The key determinants of load-displacement behaviour evaluated through models are the loading and restraint conditions, which explain the huge range of stiffness predictions in the literature (three orders of magnitude). An analytical model based on 7 bone-plate construct parameters is developed. Despite its simplicity, the model is found to be able to predict the axial stiffness for experimental tests conducted and for 16 other cases from five previous studies with an average error of 20%. The manner of load application, not considered in the literature, is shown to dramatically alter predictions of plate stress, strains within the bone and conclusions regarding screw placement. Even with the inclusion of muscles forces, the choice of restraint condition dominates the mechanical behaviour. Using the models, the influence of screw position is systematically evaluated in varying bone qualities under axial loading and torsion and guidance for optimising fixation is developed.

Introdução. Rupturas agudas do tendão de Aquiles afetam as propriedades mecânicas tendíneas. Estudos vêm preconizando o uso de mobilização precoce (tratamento acelerado) para evitar grandes prejuízos tendíneos. Entretanto, estudos que avaliem as propriedades mecânicas do tendão de Aquiles de humanos após ruptura total, submetidos à mobilização precoce, não foram encontrados na literatura específica da área. Objetivo: comparar as propriedades mecânicas e morfológicas do tendão de Aquiles entre pacientes submetidos a tratamento conservador e pacientes submetidos a tratamento acelerado (mobilização precoce) após a sutura do tendão de Aquiles. Materiais e Métodos: A amostra foi dividida intencionalmente em três grupos: controle (CTR; n=9), grupo conservador (CON; n=9; Pós-Cirúrgico: 28,3±3,6 meses) e grupo acelerado (ACE; n=9; Pós-Cirúrgico: 29,8±4,8 meses). Um dinamômetro isocinético foi utilizado para avaliação do torque dos grupos musculares flexores plantares e flexores dorsais do tornozelo. Foram obtidos os valores de área de secção transversa (AST) e comprimento do tendão (CT) de Aquiles. Para a avaliação da relação stress-strain os sujeitos realizaram duas contrações voluntárias máximas em rampa para flexão plantar no ângulo de 0º com duração de 10 segundos cada. Durante as duas contrações voluntárias máximas o deslocamento da JMT do músculo gastrocnêmio medial com o tendão de Aquiles foi verificado por meio de ultrassonografia utilizando uma sonda com arranjo linear. Simultaneamente a este procedimento, foi adquirido o sinal eletromiográfico do músculo tibial anterior, utilizado para a correção da força do tendão de Aquiles. As imagens necessárias para o cálculo do strain, bem como os sinais EMG e de torque foram sincronizados. Os valores máximos de stress, strain, força, deformação, módulo de Young, CT e AST foram comparados. Resultados: Não foram encontradas diferenças significativas nas propriedades mecânicas e morfológicas entre membros do grupo CTR. Não houve diferença significativa entre os membros saudáveis dos grupos CON e ACE e os do grupo CTR. Dessa forma, os membros saudáveis dos grupos CON e ACE foram utilizados como controle do membro lesão em ambos os grupos. Tanto no grupo CON, quanto no grupo ACE, o stress, a força e o módulo de Young apresentaram menores valores no membro lesionado, enquanto que o strain obtido em 10MPa e a AST foram maiores neste membro comparado ao contralateral saudável. Não houve diferença significativa no CT entre os membros, independente do grupo. Não foram encontradas diferenças significativas nas propriedades mecânicas, bem como na morfologia do tendão de Aquiles na comparação entre os membros lesionados dos grupos CON e ACE. Discussão: Esta maior complacência tendínea encontrada nos tendões lesados, independente do grupo, pode estar associada tanto as adaptações decorrentes da lesão que não recuperaram a níveis de normalidade, bem como a mudança nos hábitos de vida após a lesão. Além disso, o protocolo acelerado de reabilitação não foi capaz de reduzir as perdas advindas da ruptura tendínea. Tal resultado pode estar associado à especificidade do protocolo utilizado, que foi desenhado para ganho de flexibilidade no tornozelo e não para força muscular. Conclusão: Em um período mínimo de 21 meses de pós-operatório o tendão de Aquiles ainda apresenta efeitos deletérios da ruptura total nas propriedades estruturais e mecânicas do tendão. O protocolo de reabilitação utilizado não foi eficaz para a redução de tais efeitos. / Introduction. Acute Achilles tendon rupture affects the mechanical properties of the tendon. Despite the tendinous adaptations generated by decreased use, few studies have used early weight bearing (accelerated treatment) to avoid the large losses in the musculoskeletal tissues. In addition, studies that evaluated the mechanical properties of human Achilles tendon after acute rupture, subjected to early weight bearing were not found. Purpose: to compare the mechanical and morphological properties of the Achilles tendon between patients undergoing conservative and accelerated treatment, after Achilles tendon suture. Materials and Methods: subjects were intentionally allocated into three groups: control (CTR; n=9), conservative treatment (CON; n=9; Postsurgical time: 28.3±3.6 months) and accelerated treatment (ACC; n=9; Postsurgical time: 29.8±4.8 months). An isokinetic dynamometer was used to evaluate the torque production of ankle dorsi- and plantar-flexor muscles. The values of Achilles tendon cross sectional area (CSA) and length were obtained. To evaluate the stress-strain relation, patients were asked to produce two isometric maximal voluntary contractions during a ramp protocol (angle: neutral position; duration: 10 seconds) of the plantar flexor muscles. During the maximal contractions the displacement of the myotendinous junction of the gastrocnemius medialis muscle was evaluated by ultrasound with a linear array probe. Simultaneously, the electromyography (EMG) signal of the tibialis anterior was recorded, and used to correct the Achilles tendon force. The ultrasound images, EMG signals and torque were synchronized. The maximal values of stress, strain, force, displacement, Young’s modulus, tendon length and CSA were compared. Results: there were no significant differences in the morphological and mechanical properties between limbs in the CTR group. Moreover, there were no significant differences in the morphological and mechanical properties between healthy limbs amongst groups. Thus, the healthy limbs of the CON and ACC groups were used as control of the injured limb. In CON and ACC groups the stress, force and Young’s modulus had lower values in the injured limb compared to the contralateral healthy limb, while the strain obtained at 10MPa and the CSA were higher in the injured limb. There were no significant differences in the tendon length between groups and limbs. Moreover, there were no significant differences in the morphological and mechanical properties between injured limbs (CON and ACC). Discussion: The highest tendinous compliance found on the injured tendons, independent of the group might be associated to both the adaptations due to injury that did not return to normal healthy levels and to possible changes in the daily life activities after injury. In addition, the accelerated treatment was unable to reduce the losses due to tendon rupture. These results might be associated to the specificity of the rehabilitation protocol used that was designed for the gain of flexibility and not for strength gains. Conclusion: Twenty-one months post-surgery were unable to recover the deleterious effects of acute Achilles tendon rupture on the structural and mechanical tendon properties. The accelerated rehabilitation protocol was ineffective to reduce these deleterious effects.