Transverse Compression Research Articles

Stress invariant-based failure criteria for predicting matrix failure of transversely isotropic composites: Theoretical assessment and rationalized improvement

Stress invariant-based failure criteria, which are acknowledged for their simple expression but elegant description, still remain irrational considerations in its original formulation with regard to matrix failure in FRP composite materials. This study firstly re-examines the debatable hypothesis of infinite strength under equi-biaxial transverse compression. Afterwards, further attention is paid to the intrinsic relationship of transverse strengths when employing the assumption of transverse isotropy. During the formulation of the improved failure criteria from invariant theory, one notable feature is that deductions of strength coefficients, rather than direct use of measured strengths, are preferred to satisfy the mathematical and physical logic underlying the predefined assumptions and conditions. The analytical expressions for transverse shear strength and biaxial tensile strengths are deduced with Mohr’s fracture hypothesis, while biaxial compressive strength is estimated according to the theory of ductile/brittle transition. The predictions are validated based on computational micromechanics. The proposed criteria can be totally defined in terms of conventionally uniaxial strengths, thereby eliminating the need of biaxial strength parameters that are difficult to be measured experimentally. Combined practically and virtually experimental evaluations show that more reasonable and more accurate predictions under various stress conditions can be achieved by the developed stress invariant-based criteria, especially for the combined transverse normal stress case.

A novel modeling method for the mechanical behavior of 3D woven fabrics considering yarn distortion

Three-dimensional woven fabrics feature complex meso-architectures, such as yarn torsion and cross-section variation. This paper aims to developing a novel numerical modeling method to simulate the mechanical behaviors of reinforcements considering realistic yarn geometries. The initial as-woven unit cell is first simulated by the digital element analysis. A reconstruction algorithm is then used to generate mesoscale high-fidelity solid geometric models from digital chains. Fiber directional orientation within torsional yarns of the high-fidelity model is described by a digital-chain tracing method and analyzed in detail. Furthermore, based on the high-fidelity model, a hyper-elastic constitutive model is employed for the numerical analysis of the mechanical properties of reinforcements. The finite element analysis (FEA) of transverse compression, tensile deformation and in-plane shearing deformation combined with in-situ Micro-CT experiments are carried out to verify the method. The proposed method agrees well with experimental tests. Defining fiber orientations of torsional yarns using the digital-chain tracing method leads to more accurate simulation results. The developed numerical method can be extended for the composites design and structure optimization due to its high-fidelity simulation capabilities.

Mechanical Properties of the Component “Column Web in Compression” in Steel Beam‐to‐column Joints

AbstractThe component method is widely used nowadays for the analytical prediction of the mechanical properties (rotational elastic stiffness, design resistance and ductility/deformation capacity) of steel and composite beam‐to‐column joints. Eurocode 3 Part 1‐8 (EN 1993‐1‐8) provides expressions for the evaluation of the properties of many different joint components. However, a quick examination of EN 1993‐1‐8 highlights a glaring disproportion between the quantity of information related to rotational stiffness and plastic resistance, and that related to ductility and deformation capacity. For the latter, only few recommendations are provided, sometimes in line, and sometimes even not with the component approach itself. Present paper concerns one of these components, the “column web in transverse compression” (CWC), for which no information is basically available in terms of ductility. An original procedure for the prediction of the plastic deformation capacity is presented. It relies on a preliminary evaluation of the four main component properties: elastic stiffness, plastic resistance, post‐plastic stiffness and ultimate resistance. Through this study, more accurate analytical formulae than those provided by EN 1993‐1‐8 for the evaluation of the plastic resistance are also suggested. All the developments are validated through extensive comparisons with available experimental tests.

Characterization of unstiffened column webs in transverse compression in steel beam-to-column joints

The component method is widely used nowadays for the analytical prediction of the mechanical properties (rotational elastic stiffness, design resistance and ductility/deformation capacity) of steel and composite beam-to-column joints. The Part 1-8 of Eurocode 3 (EN 1993-1-8) provides expressions for the evaluation of the properties of many different joint components. However, a quick examination of EN 1993-1-8 highlights a glaring disproportion between the quantity of information related to rotational stiffness and plastic resistance, and that related to ductility and deformation capacity. For the latter, only few recommendations are provided, sometimes in line, and sometimes even not with the component approach itself. Present paper concerns one of these components, the “column web in transverse compression” (CWC), for which no information is basically available in terms of ductility. An original procedure for the prediction of the plastic deformation capacity is presented. It relies on a preliminary evaluation of the four main component properties: elastic stiffness, plastic resistance, post-plastic stiffness and ultimate resistance. Through this study, more accurate analytical formulae than those provided by EN 1993-1-8 for the evaluation of the plastic resistance are also suggested. All the developments are validated through extensive comparisons with already available experimental tests performed in various countries.

Development of High Refractive Index Polydimethylsiloxane Waveguides Doped with Benzophenone via Solvent-Free Fabrication for Biomedical Pressure Sensing

We present the fabrication and characterization of elastomeric optical waveguides, to be used for the manufacture of a conformable, water-resistant, and cost-effective pressure sensor that is amenable to the development of smart wearable health monitoring devices. To achieve this goal, high-sensitivity polydimethylsiloxane waveguides with a rectangular cross-section were fabricated. A new up-doping procedure, to tailor the refractive index of the ensuing waveguides, was experimentally developed using benzophenone additives. With this method we demonstrated a high refractive index change (up to +0.05) as a linear function of the benzophenone doping concentration. Propagation losses of about 0.37 dB/cm in the visible range and a high sensitivity to transverse compression of 0.10%/dB optical power loss were measured. It was also shown that one can further control the refractive index of the waveguide core and cladding regions through proper selection of the polydimethylsiloxane base to curing agent mixing ratio.

Analysis of multiple impact tests’ damage to three-dimensional four-directional braided composites

Abstract This article was designed with a plurality of impact tests of three-dimensional four-directional braided composites, and the impact response of specimen impacted by a circular punch was studied. Ultrasonic C-scanning was used to detect the internal damage area to study the damage propagation process under multiple impact loads. The finite-element software ABAQUS was used to model the meso-structure of three-dimensional four-directional braided composites. Based on material characteristics, the three-dimensional Hashin damage criterion was used for the fiber bundle, and the maximum stress criterion was used for the matrix to judge the material damage. Combined with test and simulation results, the failure mode and damage evolution process of the specimen under multiple impact loads were studied. The results showed that the impact resistance of the three-dimensional woven composite material is affected by the braided angle. The larger the braided angle of the specimen, the better the impact resistance. The damaged area of the large braided angle material expanded to the periphery, and the damaged area of the small braided angle material was primarily developed in the longitudinal direction. The failure modes of the specimen during the impact process were primarily a longitudinal tensile failure of fiber bundles, transverse tensile failure and transverse compression failure of fiber bundles and matrix.

Time-dependent p-delta analysis of Timoshenko viscoelastic beams and Mindlin viscoelastic plates with different shapes

This research introduces a closed-form solution for the time-dependent p-delta analysis of a viscoelastic plate based on the linear static analysis of an elastic plate for the first time, by defining an exponential time function having three unknown coefficients. The new point of the proposed method is that the time response of a Mindlin viscoelastic plate subjected to transversal load and in-plane compression simultaneously is explicitly formulated in the time domain with low computational cost. By finding the minimum eigenvalue in the Laplace-Carson domain, and satisfying the equilibrium equation at two asymptotic times, the three unknown coefficients of the time function are determined. The stress-strain relations are written for linear viscoelasticity with constant bulk modulus according to the Boltzmann integral law. The simple hp cloud meshfree method is utilized for discretizing the equations in the space domain. Numerical results are compared with other available references to demonstrate the accuracy of the proposed formulation. The effect of geometrical, material, and loading parameters on the coefficients of the time function is investigated.

Transfocal Osteotomy to Treat Shear (Oblique) Non-union of Tibia.

Aseptic non-unions of tibial shaft fractures often need surgical treatment which carry significant socio-economic implications. The causes for non-union include patient co-morbidities, high energy trauma, open fractures and fracture geometry. Oblique fractures are subject to shear forces and, if not adequately neutralised, will fail to unite. Experiments have shown that callus formation is poor in oblique fractures due to local shear stresses. We report a technique of minimally invasive transfocal transverse osteotomy and compression in a hexapod circular fixator, Taylor Spatial Frame (TSF) for 12 patients treated with a shear non-union of tibia between 2010 and 2019. There are four female and eight male patients. The average age is 49 years (range from 26 to 72 years). The fracture pattern was oblique (30–45°) in all cases. Healing of the non-union occurred in 12 cases with one case needed additional treatment with bone marrow aspirate and demineralized bone matrix. The technique of creating a minimally invasive transfocal transverse osteotomy through the oblique non-union of tibia and the use of a hexapod circular fixator to compress the osteotomy is described and adds to the range of treatments available for aseptic non-union of tibia.How to cite this articleLahoti O, Abhishetty N, Al-Mukhtar M. Transfocal Osteotomy to Treat Shear (Oblique) Non-union of Tibia. Strategies Trauma Limb Reconstr 2022;17(2):117–122.

Static Behavior of Circular Section CFRP Concrete-Filled Steel Tubes Under Compressive–Torsional Load

In order to study the compressive torsional behavior of concrete-filled CFRP steel tubes (CF-CFRP-STs), the static test of eight circular section CF-CFRP-ST compression torsional specimens was carried out. The characteristics of the torque–angle (T–θ) curve and shear stress shear–strain (τ–γ) curve, failure mode, cooperative work between steel tubes and CFRP, and cross-section assumption were studied. The T–θ curve, τ–γ curve, and failure mode of the specimen are simulated by ABAQUS. Based on the above research, the stress distribution of each component material is analyzed. The effects of transverse CFRP layers, material strength, steel ratio, and axial compression ratio on the static performance of members are discussed. Based on the performance analysis, the bearing capacity equation of CF-CFRP-ST compression-torsional members is proposed.

An experimental and numerical investigation on buckling strength assessment of perforated plates under combined in-plane loads

Openings and cut-outs are widely used in ship structures for inspection, maintenance, service purposes, and lightning of the structure, reducing the buckling strength of the plates. This paper presents linear and elastic buckling analyses of the perforated plates, located in the double bottom floor of a container ship, under mutual interaction of both geometric discontinuities (opening and cut-outs) and subjected to combined in-plane loads (longitudinal compression, transverse compression, biaxial compression, and in-plane edge shear loading). A series of experimental and numerical analyses are undertaken on perforated plates under the determination of the influence of different stiffening methods, their relation to the load condition and different values of the plate slenderness ratio. The most effective stiffening method is obtained and alternative geometries that optimize the weight of the structure are proposed by means of topology optimization. The results shown are useful for understanding this structural failure and provide design and recommendation guidelines, improving the quality of the hull inspections and the ability to evaluate the structural defects.

A Novel Mathematical Method to Diagnose the Transverse Growth Deficit of the Nasomaxillary Complex.

The diagnosis of transverse growth deficit of the maxilla in daily clinical practice is carried out mainly through the experience of a well-trained clinician, which implies a lack of objective criteria applicable in a protocolized manner. The objective of this study was to establish a mathematical method to diagnose maxillary compression in relation to the dimensions of the skull and mandible. Methods: Records of 97 cases with an overall mean age of 9.8 ± 2.6 years were analyzed by three experienced orthodontists. The group of transverse compression was comprised of 62 cases and the control group of 35 cases. The main measurements of the widths were made on a frontal teleradiography of the skull (cranial, zygomatic, orbital, maxillary, bigonial and biantegonial width) and a lateral teleradiography of the skull (facial axis, mandibular plane, SNA, SNB, ANB and Wits). It was established that from the cranial width it is possible to predict the group to which each subject studied belongs—the compression group or the control group. A mathematical formula was obtained in the form of logistic regression that allows for the diagnosis of the presence of maxillary compression based on the cranial, maxillary and orbital widths with a sensitivity of 88.7% and a specificity of 77.1%.

Improving Transverse Compressive Modulus of Carbon Fibers during Wet Spinning of Polyacrylonitrile

The performance of carbon fibers depends on the properties of the precursor polyacrylonitrile (PAN) fibers. Stretching of PAN fibers results in improved tensile properties, while potentially reducing its compressive properties. To determine optimization trade-offs, the effect of coagulation conditions and the stretching process on the compressive modulus in the transverse direction (ET) was investigated. A method for accurately determining ET from polymer fibers with non-circular cross-sectional shapes is presented. X-ray diffraction was used to measure the crystallite size, crystallinity, and crystallite orientation of the fibers. ET was found to increase with decreasing crystallite orientation along the drawing direction, which decreases the tensile modulus in the longitudinal direction (EL) proportionally to crystallite orientation. Stretching resulted in greater crystallite orientation along the drawing direction for fibers formed under the same coagulation conditions. Increasing the solvent concentration in the coagulation bath resulted in a higher average orientation, but reduced the impact of stretching on the orientation. The relationship between ET and EL observed in the precursor PAN fiber is retained after carbonization, with a 20% increase in ET achieved for a 2% decrease in EL. This indicates that controlled stretching of PAN fiber allows for highly efficient trading off of EL for ET in carbon fiber.

ДОСЛІДЖЕННЯ ДЕФОРМУВАННЯ БАГАТОШАРОВОЇ ТРАНСВЕРСАЛЬНО-ІЗОТРОПНОЇ ПЛИТИ НА ЖОРСТКІЙ ОСНОВІ ЗА БЕЗЗГИНОВОЮ УТОЧНЕНОЮ КОНТИНУАЛЬНОЮ МОДЕЛЛЮ

The high-precision estimation of the stress-strain state (SSS) of multilayered plates on a rigid foundation under the action of stationary transverse loading is an urgent task. As its includes the calculations of strength and deformability of various homogeneous and multilayer coatings. This is the calculation of road surface on relatively rigid bridge structures, or on a non-deformable underlying layer or calculation protective multilayer coatings of flat structural elements of greater rigidity than coatings, etc. The combining of materials with isotropic and transversal-isotropic physical characteristics into a multilayer package allows creating of the multifunctional designs. The SSS of such structures due to their structural heterogeneity and the relatively low transverse stiffness of the individual layers is significantly associated with the effect of transverse shear deformations and transverse compression deformations. Therefore, the problem of refined modelling of SSS of plates, which takes into account these types of deformations, is an urgent one. Based on the decomposition the SSS of plate into the flexural and unflexural components, it is proposed to optimize the design diagram of deformation a rectangular multilayer plate on a rigid foundation. The essence of optimization is to consider such a design diagram of the plate, in which the SSS of plate would be fully described by only one component, namely the unflexural component of SSS. To do this, instead of the actual design of the multilayer plate, which is deformed without separation from the foundation, it is suggested to consider the design diagram of the plate, which is formed by supplementing it with a symmetric one about the contact surface of the foundation. In this case, the plate will be symmetrically loaded with respect to the middle surface of the plate, and the thickness of the plate will double. The SSS of plate will be unflexural, which greatly simplifies its modeling. For unflexural SSS, a twodimensional and high-degree iterative approximation but three-dimensional by the nature reflection of SSS, model of deformation of multilayer rectangular plates on a rigid foundation with isotropic and transverse-isotropic layers is constructed in an elastic formulation. This model takes full account deformations of transverse shear and of transverse compression at transverse loading of a plate. Calculations of homogeneous and two-layer transverse-isotropic plates on a rigid foundation under the action evenly distributed and localized transverse loads on the surface of a plate are performed by the finite difference method.

Numerical simulation of transverse compression and densification of wood

Densification is commonly adopted to increase the mechanical performance of wood, but research on the micromechanical behaviour of the material during transverse compression is limited. Robust numerical models will enable better predictions of the performance of wood during compression and optimise the manufacturing process of densified wood minimising experimentation. The densification stress–strain response of wood after chemical treatment is reported via numerical simulations. A 3D finite element model of wood microstructure is studied under transverse compression using ABAQUS/Explicit software. A lower cellulose, hemicellulose and lignin content in the chemically treated wood is considered in the material parameters of the cell wall, and an ideal elastoplastic material model is used to represent the nonlinear stress–strain response. Parametric studies regarding the cell wall thickness, yield stress and chemical treatment are also considered. The numerical predictions agree well with microscopy studies of densified wood, and the nominal stress–strain curve obtained is similar to experimental findings under transverse compression as found in the literature. The cell wall thickness and yield stress are found to significantly affect the compressive stress–strain response of wood.

Combined Internal Iliac Artery Ligation, Transverse B-Lynch Suture and Intrauterine Balloon to Control Bleeding from Placenta Accreta during Caesarean Delivery

Introduction and aim: Placenta praevia and accreta are associated with high morbidity and mortality. Bleeding is the sole etiology of both morbidity and mortality. Thus, anti-bleeding measures are mandatory and research continues to search for ideal prophylactic measure. This work was designed to assess the efficacy of bilateral internal iliac artery ligation followed by Transverse B-Lynch compression suturing and intrauterine balloon tamponade as a conservative methods to control placental site bleeding due to placenta praevia accreta.
 Methodology: The study included 24 pregnant females with placenta praevia accreta who were scheduled for elective cesarean section. All participants were subject to history taking, clinical evaluation and laboratory investigations. Ultrasound examination was carried out for assessment of: Estimated fetal weight, confirmation of gestational age, confirm diagnosis of placenta previa accreta and level of the placental edge in lower uterine segment. Deliveries were scheduled to take place between 36-37 weeks of gestation. The primary outcome was the amount of intra-operative blood loss.
 Results: Blood loss ranged between 249.29 and 560.43 ml, and there was statistically significant decrease of hematocrit percent and platelets after surgery when compared to corresponding values before surgery. All females need blood transfusion. However, none of them need further surgical intervention or intensive care unit admission.
 Conclusion: Prophylactic bilateral internal iliac artery ligations before extraction of placenta accreta followed by transverse B Lynch suture and intrauterine balloon tamponade seemed to be an effective and safe technique to reduce intrapartum and postpartum complications, and to avoid emergent peripartum hysterectomy.

A real micro-structural model to simulate the transversal compression behaviors of unidirectional composites based on the μ-CT detection

In this paper, the microstructural model of the unidirectional (UD) composite was firstly built based on a series of computed tomography (CT) images captured with the micro-CT (μ-CT) technique. During the modeling process, a fast and simple algorithm based on the image processing technique was developed to find out the centroids of fibers in CT images. The validity of the microstructural model was then verified by comparing it with some other ideal models and experimental results. The verification results indicated the fiber accumulated array is responsible for the compression modulus, strength, and failure model of UD composite. Besides, the resin bubble has the most significant effect on the transversal compression behavior of UD composite. The idea of creating the real microstructural model for UD composite can also be used for other types of composites to improve the precision of the related numerical models.

Platen parallelism significance and control in single fiber transverse compression tests

Transverse compression tests are the established way to identify the transverse mechanical properties of single fibers. However, to the authors knowledge, the influence of an angle between the two compression platens has never been studied or quantified. In this paper, the importance of platen parallelism is studied for the first time through: numerical simulation and experimental investigation. A sensitivity analysis complements these studies by highlighting the importance of contact geometry in the analytical model, used in the inverse identification of the fiber’s apparent transverse elastic modulus ET. Experimental results show that a misalignment of 1° between the platens produces a variation of more than 35% on the identified ET, compared to a compression with parallel platens. Given the importance of platen misalignment angle an experimental setup and protocol are designed in order to maintain this angle below 0.1°, thus keeping the error on ET below 5%.

Prediction of transverse mechanical performance of UD CFRP composite lamina considering high-temperature properties of epoxy

A comprehensive computational micromechanics has been presented to predict the transverse mechanical properties and failure envelop of bi-axial stress in a 22-33 plane at high temperatures. First, a paraboloidal elasto-plastic damage model considering the temperature effect of epoxy has been employed. Then, in order to rapidly create the random fiber distribution of the representative volume element (RVE), a simple and effective algorithm of fiber placement and an auto modeling and calculating python script have been developed, where the thickness size effect of RVEs has been discussed. Finally, the transverse tension/compression and out-of-plane shear properties and the corresponding failure envelop of RVEs are analyzed systematically by means of finite element simulations. The results show that the in-plane shear strength exists strongly thickness size effect, and high temperature can significantly weaken the transverse strength, especially for transverse compression, and the temperature effect of modulus can be depicted by a specific Gaussian function. In addition, Hashin and Tsai-wu criteria may be more appropriate to predict the bi-axial failure envelop of at high temperature, and Tsai-Wu criterion is better and more suitable than Hashin and Catalanotti criteria for considering bi-axial compression.

A parameterised model of maize stem cross-sectional morphology

Stalk lodging, or failure of the stalk structure, is a serious problem in the production of maize (corn). Addressing this problem requires an understanding of the parameters that influence lodging resistance. Computational modelling is a powerful tool for this purpose, but current modelling methods have limited throughput and do not provide the ability to modify individual geometric features. A parameterised model of the maize stalk has the potential to overcome these limitations. The purposes of this study were to (a) develop a parameterised model of the maize stalk cross-section that could accurately simulate the physical response of multiple loading cases, and (b) use this model to rigorously investigate the relationships between cross-sectional morphology and predictive model accuracy. Principal component analysis was utilised to reveal underlying geometric patterns which were used as parameters in a cross-sectional model. A series of approximated cross-sections was created that represented various levels of geometric fidelity. The true and approximated cross-sections were modelled in axial tension/compression, bending, transverse compression, and torsion. For each loading case, the predictive accuracy of each approximated model was calculated. A sensitivity study was also performed to quantify the influence of individual parameters. The simplest model, an elliptical cross-section consisting of just three parameters: major diameter, minor diameter, and rind thickness, accurately predicted the structural stiffness of all four loading cases. The modelling approach used in this study model can be used to parameterise the maize cross-section to any desired level of geometric fidelity, and could be applied to other plant species. • The maize stalk geometry was decomposed to create a parameterised model. • The parameterised model allows control over geometric shape and fidelity. • The maize stalk was shown to be well-approximated by an ellipse. • This method can be used to control the shape of the maize stalk in future models.

Characterization and modeling of continuous carbon fiber-reinforced polycarbonate under multiaxial loads

The presented work considers the characterization of a continuous fiber-reinforced thermoplastic (FRTP) with unidirectional plies under quasi-static, multiaxial loading conditions and the modeling of the non-linear mechanical behavior. For the experimental investigation, hoop wound tubular specimens fabricated from carbon fiber-reinforced polycarbonate (CF-PC) tape were tested on an electromechanical static testing machine with an axial and torsional drive. The multiaxial material response was determined for an extensive set of tests performed at several load ratios of in-plane shear to transverse stress. For modeling the non-linear mechanical response, an elasto-plastic framework is used which is kept preferably simple in order to facilitate the application in numerical analysis. Based on the generated experimental data, suitable criteria for fracture and yielding are proposed. The defined yield criterion respects the special characteristics of a FRTP such as the different mechanical behavior under transverse tensile and compressive loading as well as a linear material response in the direction of the fiber reinforcement . Furthermore, the implementation of the proposed model as a user-defined material (UMAT) routine for implicit finite element analysis (FEA) using Abaqus /Standard is described and the calibration of the plasticity approach using only the data of the in-plane shear and transverse compression tests is discussed. The model predictions for multiaxial loads are validated using the determined biaxial material data. • Multiaxial experimental data for a continuous fiber-reinforced thermoplastic • Full dataset of the arithmetic mean stress–strain curves is provided • Selection of a suitable fracture criterion and definition of a yield criterion • Development and implementation of a non-linear elasto-plastic material model • Calibration and validation of the material model using the determined multiaxial data