Transverse Compressive Loading Research Articles

Modification of the model for calculating the long SiC fibre-reinforced metal matrix composites transverse strength and study for interfacial influences

The transverse strength of long SiC fibre-reinforced metal matrix composites is superior to its longitudinal strength owing to interface factors. To accurately predict the transverse strength of long SiC fibre-reinforced metal matrix composites, a micro-mechanics representative volume element (RVE) model was developed; periodic boundary conditions were applied to the model to ensure its displacement and stress continuity. Taking into account the influence of the stress concentration coefficient of the matrix, the failure strength of long SiC fibre-reinforced metal matrix composites under transverse tensile loads and compressive loads were calculated, where the error between the calculation results of the model and the test results was found to be large. A novel calculation method based on the interfacial cohesion model is proposed herein, to improve the accuracy of the RVE model. It was found that the accuracy of the corrected model calculation has been improved through a comparison with the experimental values. The stress/strain relationship between interfaces of different strengths under tensile and compressive loads was analysed, the failure index of interface strength was extracted, and the relationship between the influence of interface strength on failure was determined.

Laser-Welded Corrugated-Core Sandwich Composition—Numerical Modelling Strategy for Structural Analysis

Laser-welding technology has recently enabled the production of corrugated-core steel sandwich panels (CCSSPs) as an innovative large-scale, lightweight structural solution in maritime and infrastructure applications. Detailed numerical analyses, specifically weld-region stress prediction in the presence of transverse patch loading and supports, are computationally challenging and time-consuming for their optimal design. This paper introduces an efficient, simplified combined sub-modelling approach for accurately predicting the detailed structural response of welded corrugated-core steel panels. The approach rests on the homogenisation of the three-dimensional (3D) panel into a two-dimensional equivalent orthotropic single layer (EOSL), where the effect of transverse compressive loads and local support conditions are captured separately via different 2D and 3D sub-modelling techniques, together with a model introduced for calculation of the weld region’s equivalent spring stiffnesses. A laser-welded corrugated-core steel sandwich panel (CCSSP), as a future generation of the steel bridge deck, was examined using different modelling approaches. It was shown that the proposed combined sub-modelling approach can accurately predict stresses and displacements in all the constituent members of the cross-section, including the welds, in a reasonable calculation time when compared with a 3D reference model, unlike the conventional homogenisation approaches.

Influence of Axial Strain and Transverse Compressive Load on Critical Current of Nb3Sn Wires for the FCC

Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn superconducting wires are under consideration for producing high field accelerator magnets for the proposed Future Circular Collider (FCC) due to their high critical field. R&D studies are ongoing worldwide with a target non-Cu critical current density ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> ) of 1500 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K, 16 T. As an accomplishment of this R&D, one of the conductor manufacturers, JASTEC, has developed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires with non-Cu <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> higher than 1100 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 16 T, 4.2 K by a distributed-tin (DT) method. In high field Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn magnets, degradation of performance has been frequently reported due to the brittleness of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn and the high electromagnetic force. To realize more robust Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn accelerator magnets, electro-mechanical properties of the conductors should be deeply understood. In this study, the variation of the critical current with mechanical loading is evaluated for a DT Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire in two configurations, i.e. under axial strain and under transverse compression.

Numerical simulation of mechanical behaviors and intergranular fracture of polycrystalline Nb3Sn and superconducting filaments

Given the importance of large-scale engineering applications of the superconducting compound Nb3Sn, both its use and performance under certain operating conditions have attracted the interest of applied superconductivity researchers and material scientists for several years now. Huge efforts are directed toward understanding the response to applied loads and predicting fracture damage within their internal microstructure; this is fundamental in the design of superconducting coils and magnets which must meet stringent requirements in terms of maximum thermal and electromagnetic loads. In this paper, the fracture behaviors in polycrystalline Nb3Sn and Nb3Sn filaments with composite structures are investigated using the micromechanical finite element (FE) models with Voronoi tessellation. First, the 2D and 3D Voronoi FE models of the polycrystalline Nb3Sn tensile tests are developed and validated to provide insight into the cracking behavior in the intergranular brittle fracture of polycrystalline Nb3Sn. A cohesive zone model is used to simulate crack propagation at the grain level model including grain boundary zones. It is found that the pre-existing cracks of polycrystals and martensitic phase transformation of grains significantly impact the fracture properties in polycrystalline Nb3Sn. Second, detailed FE models of powder-in-tube (PIT) and bronze route filaments with Voronoi structures for fracture analysis are then developed on the basis of experimental observations of sectional morphologies. The mechanism of crack initiation and propagation under tensile load have been investigated by analyzing the mechanical properties of each component and the characteristics of multi-scale composite structures of filaments. Furthermore, the damage situation is investigated in PIT filaments undergoing transverse compressive load. The proposed simulation method in this paper can be extended to the fracture and damage analysis of Nb3Sn superconducting wires with different layouts and fabrication processes.

Degradation of I c due to residual stress in high-performance Nb3Sn wires submitted to compressive transverse force

Future particle colliders in search for new physics at the energy frontier require the development of accelerator magnets capable of producing fields well beyond those attainable with Nb-Ti. As the next generation of high-field accelerator magnets is presently planned to be based on Nb3Sn, it becomes crucial to establish precisely the mechanical limits at which this brittle and strain sensitive superconductor can operate safely. This paper reports on the stress dependence and the permanent reduction of the critical current under transverse compressive loads up to 240 MPa in state-of-the-art restacked-rod-process (RRP®) and powder-in-tube Nb3Sn wires. Single-wire experiments were performed at 4.2 K in magnetic fields ranging between 16 T and 19 T on resin-impregnated samples to imitate the operating conditions of a wire in the Rutherford cable of an accelerator magnet. Depending on the wire technology, we measured irreversible stress limit values—defined as the transverse stress value, leading to a permanent reduction in the critical current of 5%, assessed by convention at 19 T—ranging between 110 MPa and 175 MPa. This permanent reduction of the critical current after mechanical unload can occur for two reasons, which can be concomitant: the plastic deformation of the Cu matrix that produces residual stresses on the Nb3Sn lattice and the formation of cracks. We developed a method to identify the dominant degradation mechanism in our experiments that allowed us to predict the fraction of critical current lost due to residual stresses. Interestingly, we found that in the RRP® wires the measured reduction of Ic after unload from stresses as high as 240 MPa can be fully ascribed to residual stresses. An independent confirmation of this conclusion coming from a study combining x-ray tomography and deep learning Convolutional Neural Networks is also reported.

Experimental and Numerical Investigation of the Mechanical Properties of a CFRP Tendon-Wedge Assembly Loaded under Transverse Compressive Loading.

Carbon-fiber-reinforced polymer (CFRP) tendons have become a viable alternative to steel cables in cable roof structures owing to their high tensile strength, low weight, and resistance to corrosion. However, the effective anchoring of CFRP tendons is a challenge because of their poor transverse mechanical properties. Therefore, the mechanical properties of CFRP tendons and a tendon-wedge assembly under transverse compression were investigated by simulating the force environment of the CFRP tendon inside an integrated-wedge anchorage. The deformation of and local damage to CFRP tendons under transverse compression were explored using load-strain curves and full-field strain measured using digital image correlation. The experimental and numerical results show that large-diameter CFRP tendons with a length in the range of 90-110 mm had better cross-sectional deformation resistance and more stable transverse mechanical properties. Longer CFRP tendons with larger diameters have lower contact compressive stress and local maximal shear stress under the same transverse compressive load. Based on the analysis of the experimental and numerical results, we propose design suggestions for tendon size selection and integrated-wedge design details, such as the manufacturing materials of the wedge, the radius through the gap of the wedge, and the radial difference of the groove, to improve the anchoring properties and efficiency of the integrated-wedge anchorage.

Investigations on the influence of load width on web compression buckling strength of wide-flange steel members

A comprehensive study on web-compression buckling strength of wide-flange steel members subjected to concentric transverse loads spread over lengths longer than member section depth is presented in this paper. Calculation methodologies previously developed for web-compression-buckling strength of wide-flange steel members were established for use in beam-to-column moment connections, where the load width is relatively very narrow compared to the depth of the section, therefore does not include load width as a parameter in strength equations. More recently developed calculation procedures that account for load widths are typically limited to member section depth and are merely based on numerical models, and lack experimental evidence that validates these models. This study presents experimental research on steel wide-flange members subjected to transverse compression loading by having the load length as the primary variable. Experiments were conducted on specimens with measured imperfection levels and provided results on the buckling strength, displacement, and strain variation of the web portion during testing. The experimental program also investigated the potential of creep under sustained loading on web compression buckling strength of wide flange members at load levels near buckling strength. Benchmark numerical models using the finite element method were developed using the test results to obtain insights into the observed behavior and were employed in conducting numerical parametric studies to investigate the sensitivity of results due to load width and the angle of the applied load for various cross sections. The results obtained from the experimental and numerical studies were compared with the calculation methods provided in the North American and European design codes to evaluate their accuracy. The parametric study results were also used to develop an analytical calculation procedure for estimating the web-compression-buckling strength of steel wide-flange shapes subjected to vertical and inclined loading.

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.

Study of manufacturing defects on compressive deformation of 3D-printed polymeric lattices

This paper studies theoretical, numerical, and experimental studies on static compression behaviour of polyamide 12 body-centred cube (BCC) lattices manufactured using the selective laser sintering (SLS) method. In the analytical formulation, the influence of imperfections that happened during 3D printing such as material overlapping in the vicinity of filament joints is considered to provide predictions of mechanical properties of a macro lattice structure. Finite element (FE) models of the BCC lattices are performed to predict the compressive behaviour and deformation localisation of filaments. In order to determine a material model and input parameters for FE simulation of the lattice cubes, an individual 3D-printed filament is subjected to transverse compressive loading utilising a custom-made filament compression rig. Then, true experimental stress and strain data are generated that are imported into an inverse calibration technique using MCalibration software to determine the material parameters for the FE simulation. A series of BCC lattice cubes were printed using the SLS method. Compression experiments were conducted utilising digital image correlation (DIC) techniques in order to determine localisation of deformations and strains and validate the material properties obtained by the analytical modelling and numerical simulations. Good agreements are observed among the analytical, numerical, and experimental results. The results show that effect of filament defects should be taken into account to find the accurate responses in analytical model and FE simulation.

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.

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

A Novel Deep Learning Model to Predict Ultimate Strength of Ship Plates under Compression

The evaluation of ship strength during the hull structure design stage is essential for structural safety. Additionally, plate is one of the basic structural members of the hull, it is important to analyze and predict the ultimate strength. The curved plate used for shipbuilding must be able to withstand repeated axial loads and complex loads, and stability needs to be confirmed through ultimate strength analysis. In general situations, the magnitude of the transverse compression is smaller than that of the longitudinal and combined loads, but transverse compression causes different physical behaviors from the longitudinal load state, which affects the ultimate strength, so study on the ultimate strength of the curved-plate under transverse compression is essential. Therefore, in this paper, a curved plate under transverse compressive load was selected as a subject, and the ultimate strength of the curved plate under the corresponding compression condition was predicted using a deep learning model. To obtain the training data for the deep-learning model, 4050 cases were selected and analyzed using the ANSYS. The accuracy of the model was verified by comparing the results predicted by the model and empirical equations with those of the FEM analysis. The study shows that it is possible to consider the ultimate strength more efficiently in the initial design stage of the ship.

Experimental analysis of polymer matrix composite microstructures under transverse compression loading

Strengthening the fundamental understanding of micromechanical methods in continuity is a critical aspect in developing and designing future composite systems. Virtual testing has provided additional understanding of the behavior of materials on a microstructural scale. However, experiments must be executed to determine their validity. Modeling realistic microstructures under realistic loading conditions could help develop physically based micromechanical constitutive laws needed to predict their intrinsic failure. In this study, a micropillar with varying sizes was manufactured out of continuous fiber reinforced composites and transversely compressed to observe micromechanical phenomena. The fiber shape, size, and distribution were recorded as well as stress vs strain curves for each size of micropillar. The specimens were speckled to perform 2D digital image correlation (DIC) to analyze displacement and strain contours of the surface. The results from this study provides basic knowledge of microstructural instabilities, effects of nanovoids, interfacial debonded and matrix crack formation while under transverse compressive loading.

Nonlinear dynamics and active control of smart beams using shear/extensional mode piezoelectric actuators

In this work, the nonlinear dynamics and active control of smart beams are investigated using the shear mode and extensional mode piezoelectric actuators. The numerical analysis is performed considering two smart beams for separate use of the two kinds of piezoelectric actuators. These smart beams are considered to operate under the transverse or axial compressive harmonic load while the actuators are activated by supplying the external electric field according to the velocity feedback control law. The dynamics of the smart beams is analysed numerically by deriving the geometrically nonlinear electro-elastic incremental equations of motion in the finite element (FE) framework. The FE equations of motion are solved using Bathe time integration method for evaluation of the transient responses while the frequency responses are evaluated by implementing the harmonic balance method in conjunction with a numerical continuation technique. The results for the transverse harmonic load reveal that both the actuators are capable of attenuating the large amplitude vibration of the smart beams; however, the application of the shear/extensional mode actuator is mainly limited to a certain extent of the load-amplitude. Under the axial compressive harmonic load, the dynamics of the smart beams in the pre-buckled state appears through the parametric instabilities. However, once the buckling occurs, the smart beams undergo complex nonlinear dynamics due to the appearance of the snap-through periodic motion and the chaotic motion through the symmetry breaking, period-doubling/demultiplying and saddle-node bifurcations. The presented results mainly reveal the suitability of the shear mode and extensional mode piezoelectric actuators in active control of such dynamic instabilities and the associated complex nonlinear dynamics of the smart beams.

AISC Provisions for Web Stability under Local Compression Applied to HSS

The relevant limit states for local compression loading on the webs of a rectangular HSS member are reviewed, and the 2016 AISC Specification Chapter J provisions are adapted from their normal application to the single web of a W-shape or I-section to this case. Two recent laboratory tests on matched-width, rectangular HSS-to-HSS cross-connections are described to illustrate the behavior of such connections under branch axial compression. The data from these tests are supplemented by experimental results from a further 76 cross-connection tests, with the branches being either welded plates or welded HSS. From this 78-test database, the existing provisions for local yielding of the chord sidewalls, local crippling of the chord sidewalls, and buckling of the chord sidewalls, are evaluated. Recommendations are made for handling transverse compression loading on HSS webs in the AISC Specification, and a design example is given to illustrate the approach.

Structural Finite Element Evaluation of Twisted Stacked-Tape Cable Under Cyclic Lorentz Loads

Structural finite element analysis (FEA) was performed on a straight 40-tape Twisted Stacked-Tape Cable (TSTC) surrounded with a solid copper core to investigate the stress state of the tape-stack under cyclic transverse compressive Lorentz loads up to the tenth cycle. Two worst-case stack orientations, 45 degree and 90 degree, were investigated. In addition, the stack was modeled as simply placed into the core or soldered to the core. Since annealing of the copper core can occur during machining; the stress state of the stack was studied as a function of yield strength of the copper. The results showed that if the copper was strong enough, the stress state of the stack remained unaltered and low up to 300 kN/m cyclic transverse compressive loading. However, when the copper was fully annealed, the plastic deformation accumulated from cyclic loading more significantly affected the stress distribution in the stack. If the tape-stack was simply placed into the core, the tapes can move and slide after each loading cycle. The averaged stress went down for the first few cycles, and then plateaued. However, when the stack was soldered to the core, the stack had less room to move, and therefore the stress state remained at higher values and was less affected by cyclic loading. Additionally, when producing the stack, the tapes at the edge may not align perfectly, and this would introduce additional stress concentration. The misalignment of the stack was studied, and the results showed that this effect caused higher stress in the stack. The numerical modeling presented provides a technique to simulate cyclic loading of TSTC cable. Besides, the information on the stress state of the tape-stack can be used to investigate the behavior of more recently developed cable designs and optimize future configurations.

Suppression of the critical current degradation under the compressive stress on the internal reinforcement bronze processed Nb3Sn wire using Cu-Sn-In ternary bronze alloy matrix

Typical large current capacity conductors for fusion magnet are often manufactured by the Cable-In-Conduit (CIC) method. The CIC conductor is fabricated by twisting multiple Nb3Sn strands and pure Cu wires, and huge local stress/strain concentration alike the point contact was observed in each twisted Nb3Sn strand applied to transverse compressive load based on the electromagnetic force. These concentrations caused to the Nb3Sn filament breakage and it was also a major factor of the current sharing temperature (Tcs) and critical current density (Jc) degradation on CIC conductor. Mechanical strength improvement of the Nb3Sn strand is required to realize superconducting magnet under higher electromagnetic force for a future DEMO. Recently, we succeeded to fabricate the internal matrix reinforcement bronze processed Nb3Sn multifilamentary wire using a Cu-Sn system ternary alloy matrix containing Indium (In) element.In this study, critical current (Ic) property with the in-situ compressive stress on the internal matrix reinforcement Nb3Sn wire was evaluated. The compressive stress obtained to the Ic deterioration of 5% on the internal matrix reinforcement Nb3Sn wire was confirmed at 150 MPa, and this stress was 3 times higher than Nb3Sn wire without reinforcement. We found that the internal matrix reinforcement was one of the great advantage methods to suppress the Ic degradation by the compressive stress.

Compressive failure due to kink band formation in the presence of transverse loading, and accounting for mesoscale and microscale misalignment

Compressive strength of fiber reinforced laminates is limited by kink banding failure of the axial (0∘) plies. Motivated by observations of compressive failure in laminated composite bolted joints, the kink banding failure in axial plies is analyzed in the presence of transverse compressive loading, a condition that is found in a laminated composite bolted joint. A micromechanics model is utilized to understand the influence of microscale and mesoscale fiber misalignment and their influence on compressive stiffness, strength and post-kinked response. The results of this study show the myriad of parameters that can influence compressive strength in fiber reinforced composites, therefore providing insight to the scatter that is to be expected in assessing compressive strength of fiber reinforced composites.

Experimental Damage Evaluation of Honeycomb Sandwich with Composite Face Sheets under Impact Load

Aerospace structures are highly vulnerable to impact loads whose damage tolerance, and its resistance vary over the range of impact velocity. Honeycomb sandwich structures are used in aerospace industries where mass efficient and impact resistant structures are needed. However, the structural integrity of these structures is reduced by impact load due to tool drop, runway debris, hailstones and improper handling of the structure. A thorough investigation of the damage behaviour of honeycomb sandwich under low-velocity impact and the post-impact residual strength determination is required to design a crashworthy lightweight structure. This paper presents the experimental evaluation of specific energy absorption using Charpy impact, residual compressive strength by compression after impact and damage evaluation of honeycomb sandwich structures having composite face sheets. Parametric studies on composites and honeycombs are carried out by varying the cell size, cell thickness, core height, impact velocity, thickness and orientation of lamina. Densely packed thick honeycombs provide higher fracture energy. Under transverse compressive loading, the honeycomb core undergoes cell wall buckling, crushing and densification. Load-displacement history under in-plane compression and compression after impact for different impact energies is observed. The present study contributes for the understanding how various parameters affect the characteristics of face sheet indentation and plastic buckling of honeycomb sandwich structures with composite face sheets, thereby providing useful guidelines for its potential applications in impact engineering.

The effect of strain rate on the orientation of the fracture plane in a unidirectional polymer matrix composite under transverse compression loading

Transverse compression tests on a unidirectional composite were performed under quasi-static and high-rate loading conditions using servo-hydraulic machines as well as a direct impact Hopkinson bar. Aside the expected increase of compressive strength with increasing loading rate, a change of fracture plane orientation was observed. For quasi-static loading conditions, the fracture angle was 54.5°, for high rate-loading conditions this increased to 65°. Assuming a Mohr-Coulomb type of fracture for unidirectional composites under transverse compression loading, the change of fracture plane orientation indicates a rate dependency of the internal friction angle ϕ, which has not previously been reported for composite materials.