Transverse Compressive Stress Research Articles

Effect of transverse compressive stress applied at room temperature on Nb3Sn Rutherford cables

The accelerator magnets for the high luminosity upgrade of the large Hadron collider use Nb3Sn conductor to achieve the required in-field performance. To sustain the Lorentz forces during operation, a pre-compression is applied to the coils during the fabrication of the magnet. This can lead to an irreversible degradation of the Nb3Sn conductor due to its mechanical sensitivity. In this study, the impact of the pre-compression applied to the conductor at room temperature is investigated using a reacted double-stack specimen made of two Nb3Sn Rutherford cables. The cables have a keystone angle and are stack with a non-inverted configuration, without compensating the angle. The rectangular specimen is submitted to increasing transverse compressive stresses at room temperature applied perpendicularly to its width. The non-inverted configuration and the rectangular shape of the total specimen can thus lead to stress concentration. The pressure applied covers the range from 130 MPa to 190 MPa with a 10 MPa step increase. After each cumulated stress level, transport current measurements are performed in liquid helium and in background fields of up to 9.6 T in the FReSCa test station at CERN Metallographic analyses of several samples are made at selected stress levels. Monotonic and cumulated stresses are applied and the impact of mechanical cycling is analyzed. Procedures are specifically developed to minimize surface damage during samples’ preparation. The observations are compared with the electrical measurements in order to correlate the irreversible effect of the transverse pressure with the A15 damage state in the cross section. The transport current measurements of the double-stack specimen show degradation of critical current and n-value starting at respectively 170 MPa and 160 MPa cumulated loadings. However, cracks in the A15 phase are already observed in a metallographic sample subjected to 140 MPa.

Buckling resistance of stiffened panels subjected to constant transverse compression stresses

AbstractIn a box girder cross‐section with inclined web panel, transverse compression may be introduced into the bottom panel from both sides in addition to constant longitudinal compressive stresses. In EN 1993‐1‐5, the only analytical method for determining the resistance of panels to biaxial compression is the Reduced Stress Method (RSM). However, the current rules were mainly derived for longitudinal stresses. Due to missing rules, in practice the longitudinal stiffeners need being verified according to flexural member buckling considering the transverse updrift forces.Therefore, in order to assess the real behaviour, a large parametric study of stiffened panels with closed longitudinal stiffeners under transverse compressive stresses was carried out using a verified numerical model. LBA and GMNIA are performed for each case. To apply the RSM, all critical buckling stresses were determined considering the torsional stiffness of stiffeners. According to EN 1993‐1‐5, the support of the edges of the panels parallel to the load direction should be set free when determining the critical stress for column‐like behaviour. In the case of a longitudinally stiffened panel under transverse stresses, it is not clear whether the support of the plate and the stiffeners or only the plate should be released. In this paper, these interpretations are discussed and results are compared. Finally, a simplified procedure to determine the global reduction factor of plate buckling for transverse stresses in a single step is proposed.

Onset of Mechanical Degradation due to Transverse Compressive Stress in Nb3Sn Rutherford-Type Cables

In the framework of the High Field Magnets program at CERN, lower limits of degradative mechanical loads on reacted and impregnated Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford-type cables are being studied with the goal of optimizing the pre-stress applied at room temperature on the accelerator magnets. Coils are loaded during assembly, for instance when transverse load is applied by using a collaring press or the bladder and key technique. Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn is susceptible to transverse compressive stress, which is the loading condition investigated for this study. The purpose of this work is to identify the maximum pressure that can be applied, at room temperature, to reacted cables without generating cracks in the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn subelements and to quantify the crack propagation with increasing pressure. Metallographic techniques are used to examine the onset and evolution of damage in the transverse planes of impregnated double-stacked Rutherford-type cable specimens with increasing stress. The damage pattern observed at subelement, strand and cable levels is described. Two reaction heat treatment cycles are analyzed.

Mechanism and Control Scheme of Central Defects in Cross Wedge Rolling of Railway Vehicle Axles

Faced with a great demand for railway axles, the cross wedge rolling (CWR) process has the advantages of high efficiency and material saving, and good forming quality of axles is significant for railway transportation safety. The stress inside the railway axle of CWR was analyzed by the finite element method. It was found that the center of the rolled piece is subjected to tensile stress in transverse and axial directions and compressive stress in radial direction, making it more prone to defects. By simulating the evolution of micro voids in the center of the CWR piece, it was found that the presence of voids makes the strain around them significantly large and concentrated and the material between the voids deforms intensely. When voids expand relative to the rolled piece and the internal necking between voids is significant, void coalescence is easy to occur, and central defects are formed. The influence of process parameters on void evolution was analyzed. The scheme of detaching die was proposed to avoid central defects of the CWR piece and the optimal parameter conditions of CWR of railway axles were determined, which proved that the quality of railway axles formed with optimized parameters meets the technical requirements of railway vehicle axles.

Analysis of residual stresses in electron beam welding with filler wire of Ti62A alloy

Residual stress significantly affects the performance of the welded joints and the tensile residual stress easily leads to the joint fracture and failure. A three dimensional nonlinear transient thermo-mechanically coupled finite element model of Ti62A alloy electron beam welding (EBW) with filler wire was established. The influence of the welding parameters, such as welding power, groove angles and number of welding layers on the temperature and residual stress evolutions was predicted and verified against existing literature data. The calculated results indicate that the high tensile stress of heat affected zone is very likely to induce the failure of the welded joints. When the welding power is 2600 W, the longitudinal residual stress along the welding direction is more symmetrical on both sides, and the force and deformation of the weldment will be more uniform. As the groove angle decreases, the transverse residual compressive stress on the joint surface becomes larger, which results in the low risk for cracking tendency of the joint. Increasing the number of welding layers reduces the weld reinforcement and the residual stress. In addition, the decline magnitude of residual stress decreases with the increase in the number of welding layers. Both the smaller groove angle and the multi-layer welding can effectively reduce the residual stress of weldments and improve the joint performance. The findings of this study will provide a good theoretical basis for optimizing welding process.

Measurement and simulation of thermal-induced residual stresses within friction stir lapped Al/steel plate

Welding residual stress and distortion usually affect the assembly accuracy, product performance, and service life, with no exception for the Al/steel hybrid structure. The lapped joint of 5052 Al alloy and DP590 steel was made by friction stir welding (FSW) at various rotation speeds. A subsequentially coupled computational modeling approach based on the in-house software JWRIAN combining an efficient hybrid solution method was developed to predict the temperature field, the residual stress distribution and the warpage deformation. Based on the simulation, a higher welding temperature with subsequently a higher average cooling rate was created at a high rotation velocity, leading to the area extension of the longitudinal tensile stress and transverse compressive stress near the weld zone. The thermal expansion coefficient mismatch leads to the mirroring distribution of the near interfacial residual stress on both sides, particularly for transverse residual stress. With the increasing rotation speed, the longitudinal residual stress on the steel side near the interface was changed from compressive to the tensile state. The maximum warpage deformation in the Al plate border became larger at a higher rotation speed. The surface residual stress was measured by X-ray diffusion method and the internal residual stress was reconstructed by the contour method with the aid of elastic FE analysis. The comparisons of temperature history, residual stress and deformation indicated satisfactory agreements between simulation and experiment ones.

Investigating the effect of transverse compressive loads on the electromagnetic performance of superconducting CORC® cables

High-temperature superconductor (Re)Ba2Cu3O x (ReBCO) conductor on round core cable (CORC®) has a large current carrying capacity for high field magnets. Lorentz forces acting on CORC conductors, cause a reduction of the critical current, or even permanent degradation of their performance when exceeding critical values. Transverse compressive stress is one of the principal mechanical stresses when CORC cables are bundled to cable-in-conduit conductors (CICC) conductors capable of operating at currents up to 100 kA in magnetic fields of up to 20 T. In this research, a mechanical-electromagnetic model is developed to study the effect of transverse compressive loads on the electromagnetic performance of CORC cables. A mechanical transverse load on the cable is implemented to simulate the electromagnetic force. A comparison of numerical simulations with experiments for a three-layer CORC cable is first performed to validate the model’s reliability, with particular attention to critical current reduction during the transverse compression process. A novel feature of this paper is that the model developed can analyze both mechanical response under transverse compressive loads and electromagnetic performance under applied AC magnetic fields with low amplitudes. On this basis, the model investigates the effects of winding parameters on the axial strain and critical current reduction of the ReBCO layer in a single-layer CORC cable. The numerical analysis shows that increasing the winding angle can reduce the axial strain and critical current reduction of the ReBCO layer in the contact area. Subsequently, a detailed comparative study is carried out studying the axial strain of the ReBCO layer in the non-contact area with and without taking the winding core into account. In addition, a sudden increase in the magnetization loss is explained when the transverse compressive load reaches a certain level. Finally, a six-layer CORC cable’s electromagnetic analysis is performed, and each tape layer’s critical current reduction is investigated and discussed. The comparison of magnetization loss and current density between six- and single-layer CORC cables in the no-strain case is also given. This finite element model can guide optimizing a cable design for specific application conditions.

Formation and propagation of cracks in RRP Nb3Sn wires studied by deep learning applied to x-ray tomography

This paper reports a novel non-destructive and non-invasive method to investigate crack formation and propagation in high-performance Nb3Sn wires by combining x-ray tomography and deep learning networks. The next generation of high field magnet applications relies on the development of new Nb3Sn wires capable to withstand the large stresses generated by Lorentz forces during magnets operation. These stresses can cause a permanent reduction of the transport properties generated by residual deformation of the Nb3Sn crystal lattice as well as the formation of cracks in the brittle Nb3Sn filaments. Studies for the development of the high luminosity LHC (HL-LHC) upgrade showed that nominal transverse compressive stresses above 150 MPa may be sufficient to generate cracks in the wires. In the case of fusion magnets, wires experience periodic bending due to the electro-magnetic cycles of the reactor which over time may induce wire deformation and filament cracks. Therefore, it has become essential to develop a quantitative method for the characterization of crack formation and propagation under compressive loads. The x-ray tomographic data of a series of restacked-rod-process (RRP) Nb3Sn wires was acquired at the micro-tomography beamline ID19 of the European Synchrotron Radiation Facility (ESRF), after intentionally inducing a broad spectrum of cracks in the Nb3Sn sub-elements. The samples were submitted to transvers compressive stresses, with and without epoxy impregnation, at different pressures, up to 238 MPa. The resulting tomographic images were analysed by means of deep learning semantic segmentation networks, using U-net, a convolutional neural network (CNN), to identify and segment cracks inside the wires. The trained CNN was able to analyse large volumes of tomographic data, thus enabling a systematic approach for investigating the mechanical damages in Nb3Sn wires. We will show the complete three-dimensional reconstruction of various cracks and discuss their impact on the electro-mechanical performance of the analysed wires.

Jc Performance Under Transverse Compressive Stress of Internal Matrix Reinforced Nb3Sn Multifilamentary Wires Using Various Ternary Bronze Alloys

We approached internal matrix reinforcement using Cu-Sn-Zn and Cu-Sn-In ternary bronze alloy matrices for enhancing the effective mechanical strength of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire. In this study, we evaluated the critical current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> ) degradation due to transverse compressive stress on internal matrix reinforced Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn multifilamentary wires using these ternary bronze alloy matrices, and the effects of both Zn and In solute element on the changes of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> property under compressive stress was investigated. In the cases of internal matrix reinforced Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires using the Cu-Sn-Zn and Cu-Sn-In ternary alloy matrices, no <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> degradation was observed within 100 MPa of the transverse compressive stress. The (Cu, Zn) and (Cu, In) solid solution matrices contributed to suppressing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> degradation by the compressive stress. In addition, the In element was the more effective solute element in the ternary alloy matrix on the internal matrix reinforcement based on the irreversible compressive stress estimated by the loading-unloading test.

Quasi static compressive behavior of aluminum foam

Closed-cell AL foams’ indentation response under quasi-static loading and uniaxial compression at varied strain rates (from 3.333e-4 to 0.1333 s-1) were studied experimentally in this study. The indentation deformation was found to be nearly entirely contained inside a compressed zone within cap of spherical shape below the indenter. The strength due to indentation for aluminum foam with closed cell is higher than its uniaxial compressive strength due to effort needed in ripping cell walls along indenter circumference & friction. Under transverse uniaxial compressive stresses, the aluminum foam (closed cell type) shows an elastoplastic behavior. Metal foam is an excellent energy absorber, as seen by a long plateau Stress VS Strain curve. In contrast, plastic strength appears to grow linearly with strain rate, but metals with higher density appear having just a linear behavior. The sensitivity of foam to strain was shown to be dependent on strain and strain rate, just as that of metals with higher density.

A novel variable curvature clamping anchor for the multilayer CFRP plate cable: Concept, numerical investigation, and design proposals

This paper proposed a novel variable curvature clamping anchor (VCCA) for the multilayer carbon fiber-reinforced polymer (CFRP) plate cable and systematically evaluated the anchor performance using the finite element (FE) method. The design concept of the anchor, function of variable curvature waveform, anchor configuration and components design were first presented, then the stress distribution of the CFRP plate with different layers and failure mode of the anchor system were investigated. The six parameters affecting the anchor performance were also studied, including the number of waveforms, bolt preload, anchor length, thickness of ear plate, thickness of clamping plate, and thickness of clip. Finally, the design proposals of the anchor were given. The results indicate that the peak compressive stress has been successfully transferred from the loading end to the back of the anchor, and the interfacial shear stress of the CFRP plate was small and less than one-sixth of the shear strength. In addition, the failure of the anchor system occurred in the cable body part and not inside the anchor. The number of waveforms and the thickness of the clip slightly affected the peak transverse compressive stress, whereas the bolt preload, anchor length, ear plate thickness, and clamping plate thickness had an important influence on the axial stress distribution and peak transverse compressive stress. The novel VCCA proposed in this paper has essential engineering value and significance, filling the gap of the anchor for the multilayer CFRP plate cable, contributing to promoting the application of large-tonnage CFRP plate cable in bridges and space structures, and landing a solid foundation for subsequent experiments.

The effect of transverse compressive stresses on tensile failure of carbon fibre/epoxy composites

A novel test configuration has been developed to induce combined stress-states of in-plane longitudinal tension and transverse compression in thin-ply, unidirectional (UD) composite layers. Three different multi-directional laminates have been designed incorporating UD carbon/epoxy plies embedded in angle-ply blocks of the same material. The scissoring deformation of the angle-ply blocks induces transverse compression in the central UD layers when the composite is strained in the 0° fibre direction. The amount of transverse compressive stress was estimated from the measured surface strain of the laminates to be up to about 140 MPa. Negligible effect was found on the tensile failure strain despite the very high in-plane transverse compressive strains generated in the laminates. These were much higher than those typically attained in multi-directional laminates, exceeding the strain at which compressive failure would occur in any 90° plies. The results of this study suggest that in practice fibre direction tensile failure is unlikely to be significantly affected by transverse compressive stresses.

Fracture toughness-based models for web-crippling of pultruded GFRP profiles

This paper presents a numerical study on the web-crippling failure of pultruded glass fibre reinforced polymer (GFRP) profiles, under external-two-flange (ETF) and internal-two-flange (ITF) configurations. The numerical study is validated through experimental tests recently conducted by the authors on four I-section profiles and one U-section profile, obtained from four different suppliers. These web-crippling tests were simulated through shell finite element (FE) models where the transverse compressive fracture toughness of each GFRP material was implemented as a damage evolution parameter. In order to quantify the influence of material damage and instability effects on the web-crippling failure, three different analyses were implemented, accounting for (i) material damage, (ii) instability, and (iii) both effects. The results obtained through the analysis accounting for both material damage and instability effects showed a good agreement with experimental results, in terms of stiffness, failure modes and ultimate loads; moreover, the transverse compressive strain distributions obtained from the numerical models also agreed well with experimental results. Finally, the transverse compressive stresses were found to influence web-crippling the most, regarding both damage initiation and ultimate load stages.

Effect of Strain Rate on the Transverse Tension and Compression Behavior of a Unidirectional Non-Crimp Fabric Carbon Fiber/Snap-Cure Epoxy Composite.

The strain rate-dependent behavior of a unidirectional non-crimp fabric (UD-NCF) carbon fiber/snap-cure epoxy composite loaded along the transverse direction under quasi-static and dynamic conditions was characterized. Transverse tension and compression tests at quasi-static and intermediate strain rates were performed using hydraulic testing machines, while a split Hopkinson pressure bar (SHPB) apparatus was used for transverse compression tests at high strain rates. A pulse shaper was used on the SHPB apparatus to ensure dynamic equilibrium was achieved and that the test specimens deformed homogenously with a nearly constant strain rate. The transverse tensile strength at a strain rate of 16 s−1 increased by 16% when compared to that at quasi-static strain rates, while distinct localized fracture surface morphology was observed for specimens tested at different strain rates. The transverse compressive yield stress and strength at a strain rate of 325 s−1 increased by 94% and 96%, respectively, when compared to those at quasi-static strain rates. The initial fracture plane orientation for the transverse compression tests was captured with high-speed cameras and found to increase with increasing strain rate. The study provides an important data set for the strain rate-dependent response of a UD-NCF composite material, while the qualitative fracture surface observations provide a deeper understanding of the failure characteristics.

Study on the wrinkling behavior of perforated metallic plates using uniaxial tensile tests

The Yoshida buckling test (YBT) is a commonly used method to evaluate the wrinkling behavior of sheet metals; however, it is difficult to reflect the actual in-plane stresses in many sheet forming processes owing to the limited variation in the stress state. Furthermore, the test is impracticable for some low-ductility materials because fracture typically occurs before wrinkling. This paper proposes an approach for examining the wrinkling properties of sheet metals using uniaxial tension of plates with a central cut-out; a relevant wrinkling model is established using stress analysis of a finite perforated plate and an energy method. The results show that the typical stress distribution modes around the central hole before wrinkling are biaxial compression in the top/bottom domains and biaxial tension in the lateral domains, and the mode changes with the hole size and tensile displacement. The ratio of transverse to axial stresses increases with the diameter/width ratio; this leads to a larger influence of transverse nonuniform compressive stress, consequently decreasing the critical wrinkling stress. The wrinkling tendency in perforated sheets is more sensitive than that in a conventional YBT specimen; thus, it can be used to capture the subtle distortion of wrinkling for low-ductility materials. A second wrinkling phenomenon that occurred in plates with large holes under a large tensile displacement was observed and addressed.

Stretching Hookean ribbons part II: from buckling instability to far-from-threshold wrinkle pattern.

We address the fully developed wrinkle pattern formed upon stretching a Hookean, rectangular-shaped sheet, when the longitudinal tensile load induces transverse compression that far exceeds the stability threshold of a purely planar deformation. At this "far-from-threshold" parameter regime, which has been the subject of the celebrated Cerda-Mahadevan model (Cerda and Mahadevan in Phys Rev Lett 90:074302, 2003), the wrinkle pattern expands throughout the length of the sheet and the characteristic wavelength of undulations is much smaller than its width. Employing Surface Evolver simulations over a range of sheet thicknesses and tensile loads, we elucidate the theoretical underpinnings of the far-from-threshold framework in this setup. We show that the evolution of wrinkles comes in tandem with collapse of transverse compressive stress, rather than vanishing transverse strain (which was hypothesized by Cerda and Mahadevan in Phys Rev Lett 90:074302, 2003), such that the stress field approaches asymptotically a compression-free limit, describable by tension field theory. We compute the compression-free stress field by simulating a Hookean sheet that has finite stretching modulus but no bending rigidity, and show that this singular limit encapsulates the geometrical nonlinearity underlying the amplitude-wavelength ratio of wrinkle patterns in physical, highly bendable sheets, even though the actual strains may be so small that the local mechanics is perfectly Hookean. Finally, we revisit the balance of bending and stretching energies that gives rise to a favorable wrinkle wavelength, and study the consequent dependence of the wavelength on the tensile load as well as the thickness and length of the sheet.

Structural, magnetic and magnetoelectric investigations on CoFe2O4 prepared via various wet chemical synthesis route : A Comparative Study

Magnetostrictive materials are potential candidates for many applications such as sensors, actuators, transducers, and other magnetoelectric applications. Cobalt Ferrite (CoFe2O4) has proven to be favourable in comparison to commonly used magnetostrictive materials due to its high magnetostriction coefficient and it’s preparation being cost effective. This work deals with the preparation of CoFe2O4 (CFO) using four different wet chemical synthesis techniques in the form of autocombustion, co-precipitation, sol–gel and hydrothermal methods. Same conditions of heat treatment have been maintained for all the methods which facilitates a fair comparison of the performance of the samples prepared by various methods. The prepared CFO samples were subjected to subsequent characterization of their structural, magnetic, magnetostrictive and magnetoelectric properties. Static and dynamic magnetoelectric measurements were carried out on trilayered composites comprising of CFO synthesized by hydrothermal and sol–gel methods. Effect of in-plane and transverse compressive stress on the magnetoelectric response of CFO/PZT/CFO trilayered structure have been studied. All the experimental characterisations indicated the sample synthesized by hydrothermal method to yield better properties. The results thus reveal the importance of synthesis route towards attaining an improved magnetic, magnetostrictive and magnetoelectric properties of CFO.

A micromechanical model of carbon fiber-reinforced plastic and steel hybrid laminate composites

The fracture strain of carbon fiber-reinforced plastics (CFRPs) within CFRP/steel hybrid laminate composites is reportedly higher than that of CFRPs due to transverse compressive stress induced by the steel lamina. A micromechanical model was developed to explain this phenomenon and also to predict the mechanical behavior of CFRP/steel hybrid laminate composites. First, the shear lag theory was extended to calculate stress distributions on fibers and matrix material in a CFRP under multiaxial stress condition, considering three deformation states of matrix (elastic and plastic deformation and fracture) and the transverse compressive stress. Then, the deformation behavior of CFRP was predicted using average stress in the ineffective region and the Weibull distribution of carbon fibers. Finally, the mechanical properties of CFRP/steel hybrid laminate composites were predicted by considering the thermal residual stress generated during the manufacturing process. The micromechanical model revealed that increased transverse compressive stress decreases the ineffective lengths of partially broken fibers in the CFRP and results in increased fracture strain of the CFRP, demonstrating the validity of the current micromechanical model.

Prediction of principal stresses and strains in laminated composites using MATLAB

The present study deals with laminated composite plate modeling and analysis. Major research in the field of composite structures has been carried out in recent years due to its widespread use in aerospace as smart and even some intelligent structures. In the current analysis, classical laminated plate theory is considered for studying the failure criteria of composites, by creating MATLAB script files which assist the operator to work under safe conditions of composite laminates design. MATLAB is an ideally suited programming tool to study the mechanics of composite materials because the formulation of the mechanical behaviour of composite materials involves extensive use of matrices. The input sources required to execute the conventional based program are the properties of the material its limits, and applied load. To calculate the principal stresses and strains on each layer for two-dimensional composites, equations considering Hooke's Law were used. Via the failure theory known as Tsai-Wu failure theory, failure analysis of the framework was carried out. According to Tsai-Wu failure criterion, the laminate will fail under transverse loading σ 2 and the failure occurred at layer 2 at a stress of 3.66 MPa. Under compression loading, failure occurred either on 2nd layer or 4th layer with transverse compressive stress of 25 MPa. To prevent the failure of the composite laminate the Strength Ratio obtained should lie between the range of 1 to 1.2 so it is required to change the orientation of fiber layer and also add on the optimal number of fiber layers.

Effect of strain rate on strength of unidirectional CFRP

An analysis of the anisotropy of failure stress envelopes for unidirectional carbon fiber reinforced plastic at different strain rates, including dynamic loading, is carried out. Based on the study of transverse compressive and share strengths, a peak of the failure stress envelopes is observed, which is described by using the parabolic function approximation. It is shown that with an increase in the strain rate, not only an increase in strength but also a shift of the peaks to the area of higher transverse compressive stresses are observed.