Longitudinal Compressive Load Research Articles

Investigation and calculation of the longitudinal compressive strength of unidirectional glass fiber reinforced polymer considering the fiber orientation distribution

In this study, undulations and their influence on the longitudinal compressive strength of a unidirectional glass fiber reinforced polymer (GFRP) composite are investigated theoretically and experimentally. The objective of this research is to explore the failure mechanisms in FRP and to characterize the mechanical properties of FRP as a function of fiber orientation. For this purpose, a multiscale material model is developed that considers a stochastic fiber orientation distribution (FOD) and models matrix fracture-initiated failure. The relationship between compressive strength and undulation is investigated experimentally on standardized specimens made of unidirectional GFRP. The fiber orientations are measured using X-ray computed tomography and ImageJ image analysis, resulting in a binormal distribution of fiber orientations in the series of samples tested. To examine the failure process in detail, the compression tests are simulated using finite element analysis (FEA). Both the FEA results and the measured compressive strengths confirm the model assumption of matrix fracture-initiated failure under longitudinal compressive loading. The presented analytical model realistically represents the correlation of compressive strength with the FOD.

Pilot study of lattice endoprosthesis buckling by compression in-situ using X-ray tomography

Take into account additive manufacturing while design lattice implant can improve load-bearing properties and decrease construction weight. The usage of lattice structure and biomaterials makes it possible to solve the main problem of arthroplasty – preservation of the implant after surgery in the patient's body. Unfortunately, nowadays biomaterials do not have the necessary strength capacity. In spite of this, a lot of researches are directed towards to develop new design methods or improve the existing ones. There are number of articles focused on in-situ testing and quality control of lattice structures. The study is devoted to investigate the buckling of lattice structures under uniaxial compression with synchronous X-ray computed tomography scanning. In the article an experimental study of lattice structures of two kinds has been carried out. Edges of hexagonal bipyramid were a basic cell of the samples. The distribution of basic cells in the first type of construction was uniform, and was non-uniform in the second type. The studied samples were manufactured by laser stereolithography method. The lattice structures were loaded step-by-step with a longitudinal compressive load. The loading of the specimens was carried out in cooperation with their scanning by X-ray computed tomography. As a result, the displacement fields of structures at each step of loading were obtained. The general and local buckling of lattice structures was revealed. The general buckling occurred at the second loading step for each type of structure. Local buckling was observed at the third loading step. The influence of the architecture of the lattice structures on the buckling process was revealed. The effect of interruption of the buckling process was observed in the specimen with non-uniform distribution of basic cells. And because of that the structure continued to work in compression. In other words, the lattice architecture "dampened " the bending components of the displacement vector.

Micromechanics based analytical model for composites subjected to combined torsion-compression loading

A micromechanics based analytical model under combined loading for unidirectional composites has been developed. The peak compressive load predicted from the combined loading analytical model is compared with the experimental results of carbon epoxy pultruded rod having a volume fraction 60%. The specimens were subjected to torsional load under rotational control and longitudinal compressive load using displacement control. The model captures the compressive strength of the composite subjected to remotely applied shear stress. It is observed that the peak compressive strength of the composite decreases linearly with an increase in shear stress. The analytical modeling results are in good agreement with the experiment data. The analytical model and the experimental results are used to find the effect of shear stress on longitudinal compressive loading. The peak compressive strength caused in the presence of applied shear stress and compressive load and the effect of shear on the compressive strength are predicted using a 2D analytical model in this study. The model results are confirmed using experimental data from combined loading.

Experimental Investigations on the Mechanical Performances of Auxetic Metal-Ceramic Hybrid Lattice under Quasi-Static Compression and Dynamic Ballistic Loading

In recent years, there have been increasing research interests in investigating the compression and ballistic responses of metal-ceramic hybrid structures, mainly making use of the synergistic effects of conventional metal honeycomb structures and infilled ceramic matrix materials. In this paper, a novel hybrid auxetic re-entrant metal-ceramic lattice is designed and manufactured to overcome the intrinsic conflicts between the strength and toughness of architected mechanical metamaterials, synergistic effects of auxetic re-entrant metal honeycombs and infilled ceramic materials are experimentally and numerically studied, and auxetic deformation features and failure modes are characterized with the digital image correlation (DIC) technique as well. It was found that (1) the infilled ceramic matrix of conventional honeycomb frames only endure longitudinal compression or impact loading along the external loading direction, while auxetic metal re-entrant honeycomb components endure both longitudinal and transverse loading due to the negative Poisson′s ratio effect and (2) the collaborative effects of infilled auxetics and the constraint frames’ hybrid structure dramatically moderate the stress concentration state and improve the impact resistance of single-phase ceramic materials. Our results indicate that the auxetic hybrid design exhibits promising industrial application potentials for blast protection engineering.

The body of a dynamometer wagon for special technical purposes

The development of new and improvement of existing railway rolling stock wagons is an urgent task of our time, providing for cost reduction, both in the process of creation and operation, and in the maintenance of the wagon fleet. The purpose of the work is to modernize the body of a dynamometer wagon for special technical purposes using modeling. To determine the loading of the structural elements of a dynamometer wagon, a calculated three-dimensional model of the wagon body was developed, the reinforcement points of the wagon frame were determined. Compression/tensile strength tests of the wagon were performed on a stand for loading the frames of wagons and elements of coupling devices. The stress-strain state of the wagon structure is determined when statically applied longitudinal test loads are applied to it. The test results and the stress-strain state of the design of the prototype wagon, under the action of statically applied longitudinal compressive and tensile test loads, showed that the proposed design of the wagon meets the established strength requirements, while no visible damage and residual deformations were found in the design of the prototype wagon. The developed design of the dynamometer wagon body can be included in both freight and passenger trains, which solves the problem of efficient and safe use of locomotives when operating trains on mountainous sections of railways of the Republic of Uzbekistan.

Time-and temperature-dependent compressive behavior of woven carbon fabric reinforced polyamide composite laminate

Plain woven carbon fabric reinforced polyamide (CF/PA) composite laminate was developed using hot-pressed processing with a vacuum-assisted system. Temperature-dependent mechanical properties of the CF/PA composite laminate under longitudinal compressive loading were examined. The compressive mechanical properties of the composite laminate decreased considerably with increasing the temperature to 120°C. The compressive strength and strain at maximal stress reduced rapidly below 80°C, while the compressive modulus declined slightly underneath 50°C. The glass transition temperature of the CF/PA composite was found to be about 50°C by the differential scanning calorimetry, which almost corresponded to the slight reduction of the elastic modulus at temperatures below 50°C. The time-dependent creep behavior of the CF/PA laminate under compressive loading at isotherms between 25°C and 50°C was studied. Creep strains of the CF/PA composite samples increased with rising temperature. The smooth creep compliance master curve of the CF/PA composite was obtained by shifting short-term creep compliance curves using the time–temperature superposition principle. The master curve provided a creep prediction to 961.6 days with the measured data in only 12.5 days.

A facile 3D bio-fabrication of customized tubular scaffolds using solvent-based extrusion printing for tissue-engineered tracheal grafts.

Tracheal implantation remains a major therapeutic challenge due to the unavailability of donors and the lack of biomimetic tubular grafts. Fabrication of biomimetic tracheal scaffolds of suitable materials with matched rigidity, enhanced flexibility and biocompatibility has been a major challenge in the field of tracheal reconstruction. In this study, customized tubular grafts made up of FDA-approved polycaprolactone ( ) and polyurethane ( ) were fabricated using a novel solvent-based extrusion 3D printing. The printed scaffolds were investigated by various physical, thermal, and mechanical characterizations such as contact angle measurement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), radial compression, longitudinal compression, and cyclic radial compression. In this study, the native goat trachea was used as a reference for the fabrication of different types of scaffolds (cylindrical, bellow-shaped, and spiral-shaped). The mechanical properties of the goat trachea were also compared to find suitable formulations of . Spiral-shaped scaffolds were found to be an ideal shape based on longitudinal compression and torsion load maintaining clear patency. To check the long-term implantation, in vitro degradation test was performed for all the 3D printed scaffolds and it was found that blending of with reduced the degradation behavior. The printed scaffolds were further evaluated for biocompatibility assay, live/dead assay, and cell adhesion assay using bone marrow-derived human mesenchymal stem cells (hMSCs). From biomechanical and biological assessments, of spiral-shaped scaffolds could be a suitable candidate for the development of tracheal regenerative applications.

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.

Design and evaluation of three–dimensional axisymmetric mechanical metamaterial exhibiting negative Poisson's ratio

Mechanical metamaterials are generally two-dimensional periodic structures or three-dimensional cellular structures that exhibit mechanical properties beyond the ordinary. Due to size and boundary effects, three-dimensional mechanical metamaterials typically display anisotropic changes even if they are isotropic in construction and composition. However, in this study, the comprehensive design and fabrication of a three-dimensional axisymmetric auxetic structure that exhibits uniform and axisymmetric transverse deformation under longitudinal compression loading are proposed. Extending the concept of two-dimensional periodically perforated auxetic sheet structures to the third dimension, the design of the metamaterial was generated by revolving a two-dimensional parabolic curve along the axis of rotation and subsequently perforating the structure periodically with elliptical voids varying in size longitudinally along the curvature of the structure in order to promote the exhibition of isotropic negative Poisson's ratio. Furthermore, this study elucidates the significance of the perforations by comparing the metamaterial structure to a so-called plain structure.

Artificial Neural Network-Based Failure Pressure Prediction of API 5L X80 Pipeline with Circumferentially Aligned Interacting Corrosion Defects Subjected to Combined Loadings.

Conventional pipeline corrosion assessment methods produce conservative failure pressure predictions for pipes under the influence of both internal pressure and longitudinal compressive stress. Numerical approaches, on the other hand, are computationally expensive. This work provides an assessment method (empirical) for the failure pressure prediction of a high toughness corroded pipe subjected to combined loading, which is currently unavailable in the industry. Additionally, a correlation between the corrosion defect geometry, as well as longitudinal compressive stress and the failure pressure of a pipe based on the developed method, is established. An artificial neural network (ANN) trained with failure pressure from FEA of an API 5L X80 pipe for varied defect spacings, depths, defect lengths, and longitudinal compressive loads were used to develop the equation. With a coefficient of determination (R2) of 0.99, the proposed model was proven to be capable of producing accurate predictions when tested against arbitrary finite element models. The effects of defect spacing, length, and depth, and longitudinal compressive stress on the failure pressure of a corroded pipe with circumferentially interacting defects, were then investigated using the suggested model in a parametric analysis.

Approximate closed-form solution for buckling of orthotropic plates with longitudinal edges elastically restrained against rotation

A simple trigonometric series is first introduced to satisfy the longitudinal edges with the clamped-simply supported (CS) condition, while the deformation shape function along the transverse direction is uniquely constructed through a weighted combination of three kinds of trigonometric series to meet the arbitrarily elastically restrained boundary condition against rotation. Approximate closed-form solution for buckling behavior of the orthotropic plates under compression, in-plane shear or combined shear and compression is further presented based on the Galerkin​ method. The transverse edges of the considered orthotropic plates are simply supported, while the opposite longitudinal edges are arbitrarily elastically restrained against rotation to different degree. In particular, the explicit closed-form buckling solutions for the long orthotropic plates under the respective pure in-plane shear and pure compression are obtained. The validity study demonstrates that the relative error of compressive buckling load with a maximum difference of 7% decreases with the increasing of the transverse vs. longitudinal compression load parameter (κ21), while the relative error of critical shear buckling load with a maximum difference of 10% decreases with an increase in the longitudinal compression vs. shear load (κ13) and transverse compression vs. shear load (κ23) parameters. The present approximate closed-form solution is effective and relatively accurate for performing the buckling analysis of orthotropic plates with the longitudinal edges arbitrarily elastically-restrained against rotation, and it can be used in simplified discrete plate analysis of thin-walled composite structures to predict their local buckling strength.

STRENGTH OF SHIPS’ GRILLAGES UNDER LATERAL LOAD AND IN-PLANE COMPRESSION

The paper deals with strength of a grillage loaded by lateral load and in-plane compression load (in one direction). It consists of a system of prismatic girders crossing under 90°. The compression load is taken by the longitudinal girders that are elastically fixed on rigid supports. The system of aggregated differential equations is derived for solution of the problem using the Lagrange method. It allows for replacement of the system of aggregated differential equations by a system of independent differential equations. These equations for the case of simultaneous action of lateral and longitudinal compression load have the form of differential equations for bending of prismatic girders laying on elastic foundation and loaded with lateral and longitudinal compression forces. When only lateral load exists, the form of these equations coincides with the form of differential equations for bending of girders laying on elastic foundation and loaded with lateral load alone. When only longitudinal compression load exists, the form of these equations coincides with the form of differential equations for buckling of girders laying on elastic foundation.
 Solutions are given for bending of a grillage (the first two problems). Formulas are derived for calculation of the parameters of longitudinal girders’ bending when girders’ end sections are elastically fixed. Also, formulas are derived for calculation of the reaction forces at cross-points of transverse and longitudinal girders. When only longitudinal compression load exists (third problem), a solution is given for the connection between the coefficient of elastic foundation’s rigidity and the Euler force. Results obtained by using the proposed method are compared with FEA simulations.

A strain gradient strategy to quantifying longitudinal compression behavior in slender fibrous assembly structures

Slender fibrous assembled structures can easily buckle under longitudinal compressive load. The limitation in characterizing the longitudinal compression behavior poses a significant challenge to the mechanics optimization of such structures. To address this challenge, we use one-dimensional yarns as a model system, and the yarns are deformed in bending to form a strain gradient, from tension to compression, along the radial direction of the yarns. The compression modulus as a function of compression strain is calculated based on bi-moduli elastic theory. The evolution of the fiber arrangement and the position of the neutral layer in the yarn is interpreted along with the change of compression modulus. Also, the local stress distribution in the bent yarn was determined by finite element simulation, and it is remarked that the bending property of yarns is sensitive to the compression modulus. The present study offers insights on the modeling and simulation of fabrics and garments in drape and bending deformation. Results from such investigations can provide effective guidance for the mechanical and structural design of textiles and textile-based composites.

Empirical Assessment Method of Ultimate Capability of Steel Stiffened Panel under Longitudinal Compressive Load

The hull block erection network process, which is performed during the master production planning stage of the shipyard, is frequently delayed because of limited resources, workspace, and block preparation ratio. In this study, a study to predict the delay with respect to the block erection schedule is conducted by considering the variability of the block preparation ratio based on the discrete event simulation algorithm. It is confirmed that the variation of the key event observance ratio is confirmed according to the variability caused by the block erection process, which has the minimum lead time in a limited resource environment, and the block preparation ratio. Furthermore, the optimal pitch value for the key event concordance is calculated based on simulation results.

Experimental Study and Development of Design Formula for Estimating the Ultimate Strength of Curved Plates

The curved plate has been extensively used as a structural member in many industrial fields, especially the shipbuilding industry. The present study investigated the ultimate strength and collapse behavior of the simply supported curved plate under a longitudinal compressive load. To do this, experimental apparatuses for evaluating the buckling collapse test of the curved plates was developed. Then, a series of buckling collapse experiments was carried out by considering the flank angle, slenderness ratio, and aspect ratio of plates. To examine the fundamental buckling and collapse behavior of the curved plate, elastoplastic large deflection analysis was performed using the commercial finite element analysis program. On the basis of both the experimental and FE analysis, the effects of the flank angle, slenderness ratio, and aspect ratio on the characteristics of the buckling and collapse behavior of the curved plates are discussed. Finally, the empirical design formula for predicting the ultimate strength of curved plates was derived. The proposed empirical formula is a good indicator for estimating the behavior of the curved plate.

Study on compression moulding characteristics of carbon fibre materials in sports equipment

In order to more clarify the compression moulding characteristics of carbon fibre materials, this research carried out research on the compression moulding characteristics of carbon fibre materials in sports equipment. Obtain the stress curve of the carbon fibre material, and provide the parameter basis for the carbon fibre compression experiment. A 1 × 1 plain weave carbon fibre material was selected as the experimental sample material to study the compression moulding characteristics of the carbon fibre material. The experimental results show that when the hot pressing temperature is below 300°C, the sample material is prone to compression fracture, and the crack appears in a fixed area of the fibre distribution direction; with the continuous increase of the transverse and longitudinal compression load, the material splits in the carbon fibre distribution direction. The material is divided into several strands; the pre-yielding and post-yielding curves have a good agreement.

In-situ quantification of microscopic contributions of individual cells to macroscopic wood deformation with synchrotron computed tomography

Wood-based composites hold the promise of sustainable construction. Understanding the influence on wood cellular microstructure in the macroscopic mechanical behavior is key for engineering high-performance composites. In this work, we report a novel Individual Cell Tracking (ICT) approach for in-situ quantification of nanometer-scale deformations of individual wood cells during mechanical loading of macroscopic millimeter-scale wood samples. Softwood samples containing > 104 cells were subjected to controlled radial tensile and longitudinal compressive load in a synchrotron radiation micro-computed tomography (SRµCT) setup. Tracheid and wood ray cells were automatically segmented, and their geometric variations were tracked during load. Finally, interactions between microstructure deformations (lumen geometry, cell wall thickness), cellular arrangement (annual growth rings, anisotropy, wood ray presence) with the macroscopic deformation response were investigated. The results provide cellular insight into macroscopic relations, such as anisotropic Poisson effects, and allow direct observation of previously suspected wood ray reinforcing effects. The method is also appropriate for investigation of non-linear deformation effects, such as buckling and deformation recovery after failure, and gives insight into less studied aspects, such as changes in lumen diameter and cell wall thickness during uniaxial load. ICT provides an experimental tool for direct validation of hierarchical mechanical models on real biological composites.

Ultimate strength of stiffened panels with a crack and pits under uni-axial longitudinal compression

ABSTRACT An experimental programme and nonlinear finite element analysis are carried out to examine the ultimate strength characteristics of stiffened panels with a crack and pits, under uni-axial longitudinal compressive loads. The test results are used to validate the finite element models. A series of nonlinear finite element analysis is performed with the validated models to illustrate the ultimate strength reduction by varying the relative position between crack and pits, length of crack and pit characteristics. The present results are compared with the earlier results with either crack or pits, confirming the complexity of stiffened panel collapse behaviour. Including the effect of the crack and pits on the plate and column slenderness ratio, a formula has been introduced to predict the ultimate strength of the stiffened panel with the average error less than 10%.

Micromechanical modelling of the longitudinal compressive and tensile failure of unidirectional composites: The effect of fibre misalignment introduced via a stochastic process

Initial fibre misalignment is recognised to be one of the precursors leading to longitudinal compressive failure in fibre-reinforced composites. Thus, to properly model their mechanical behaviour, an accurate spatial representation of the fibrous reinforcements must be assured. This work presents a three-dimensional micromechanical framework that is capable of analysing in detail the longitudinal tensile and compressive failure mechanisms which are inherent in unidirectional composites. This is achieved through the incorporation of initial fibre waviness via a combination of a stochastic process and an optimisation procedure. A robust micro-scale framework is developed by assigning, to both constituents and their interface, proper thermodynamically consistent damage models. Several microstructures having different degrees of misalignment are modelled and a clear trend is observed for the longitudinal compressive load case, i.e. by increasing initial fibre misalignment, the overall performance of the material decreases. In contrast, the models subjected to longitudinal tension exhibit a similar overall response, despite the misalignment. However, local mechanisms seem to change with the degree of friction and fibre misalignment, but these smaller-scale mechanisms do not play a decisive role on the overall longitudinal tensile performance of the material.

Collapse Behaviours of Stiffened Panels Under Longitudinal Compression Considering Heating and Cooling Processes

The fire accidents casually happen during operation of ship, which would influence the load carrying capacity of stiffened panel of ship structures due to the thermal load. The present paper aims to understand the influence of thermal loads on the collapse behaviour of stiffened panels under longitudinal compressive load. Considering the heating and cooling down processes, the collapse behaviours of the stiffened panels under combined in-plane displacement and heat loads representative of fire accident are simulated in the FE (finite element) analysis herein. Firstly, the thermal load is considered to investigate the stress state of the stiffened panels during heating and cooling processes. It is found that the stiffened panels would collapse during thermal loads for the structure with large heated zone. After that, the longitudinal compression loads are applied to assess the collapse strength of the stiffened panels. The parametric studies including different geometrical dimensions and areas of heat zone are performed in detail to quantify the effects of heat loads on the collapse behaviours of stiffened panels. It is found that the expansion could produce biaxial stress state that depends on not only in-plane stiffness but also collapse modes, and for stiffened panels with various heated area the cooling down to room temperature induce similar ultimate strength to that without considering heat loads.