In-plane Shear Deformation Research Articles

A hyperelastic model considering the coupling of shear-compression for the forming simulation of 3D orthogonal composite preforms

The shear-compression coupling phenomenon is vital in the forming process of complex 3D woven composite components, but has not been effectively considered in existing macroscopic material models. A hyperelastic material model considering shear-compression coupling is developed here. Firstly, in-plane shear tests on pre-compressed specimens and compression tests on pre-sheared specimens were carried out, respectively. The results show that pre-compression can hinder and promote the in-plane shear deformation before and after shear locking occurs in the fabric, respectively. In-plane shear can contribute to compression. Then, a nonlinear hyperelastic constitutive model is presented and implemented in an Abaqus/Explicit user subroutine. Finally, a simulation study of the hemispherical forming of 3D orthogonal woven fabric was conducted using this model. The simulation results considering shear-compression coupling show more accurate in-plane shear angles and edge shapes compared to those without considering coupling. Moreover, since the shear-compression coupling is considered, the friction between the fabric and the tool needs to be reasonably discussed in the moulding simulation.

Microstructure and texture evolution in AZX311 Mg alloy during in-plane shear deformation

The current study examined the deformation mechanisms, microstructure, and texture evolution in AZX311 Mg alloy sheets subjected to in-plane shear (IPS) deformation. Different levels of shear strains, with values 0.05, 0.10, and 0.15, were applied along the rolling direction (RD) using a specialized in-plane shear testing jig. The strain measurement for the applied shear deformation was conducted utilizing the digital image correlation (DIC) technique. The strain distribution was found to be nearly homogeneous over sufficiently large areas, thereby allowing the microstructural measurements to yield relevant statistical data. A thorough microstructural examination across the thickness using electron back-scattered diffraction (EBSD) revealed that the application of IPS strain led to the formation of a significant number of tensile twins (TTWs) in the sheet. This was evidenced by the emergence of two satellite peaks at the periphery of the pole figures. As the shear strain increased, the proportion of TTWs in the material also increased, encompassing the entire parent grain and leading to the formation of what has been termed as “all-twinned microstructure”. The microstructural and texture investigation after IPS deformation revealed that TTWs were the dominant deformation mechanism that defined the microstructure and texture under IPS deformation, while dislocation slip activity was dominated by prismatic slip, as evidenced by the resolved shear stress analysis in this study. Consequently, this research highlights the effect of IPS deformation on the microstructure and texture evolution throughout the thickness of an Mg alloy sheet and elucidates the underlying mechanisms.

Advanced analysis of the bias-extension of woven fabrics with X-ray microtomography and Digital Volume Correlation

The bias-extension test is widely used to study the mechanics of woven fabrics undergoing large deformation. Standard analyses focus on the in-plane shear deformation, but rarely on other deformation modes. Here, the bias-extension of a basalt fiber twill was performed inside a X-ray microtomograph to get 3D in situ observations. The 3D images were used in a dedicated Digital Volume Correlation procedure that enabled relevant 3D strain invariants to be estimated. Coupled with important in-plane shear and moderate tension along the yarns, significant 3D compaction was observed as a complex combination involving out-of-plane auxetic expansion and in-plane compaction. The transition between sheared regions extends to 2–3 unit cells of the fabric, highlighting the role of the fibrous micro and mesostructures. This unique 3D experimental database enriches the knowledge on the mechanics of woven fabrics and provides valuable information for the development of generalized continuum approaches to model their mechanical behavior.

Numerical investigation into vibration damping in woven composite structures

This study numerically investigates the mechanism of vibration damping in woven composite structures using a decoupled multi-scale simulation scheme that considers the macroscopic woven structure consisting of bundles and resin-rich regions, as well as the microscopic structure in the bundles made of fiber and resin. For efficient macroscopic modeling of complicated woven structures, the embedded element technique is introduced to utilize separate meshes for bundles and resin regions. A special treatment is introduced for volumetric integration in the mesh overlapped between bundle and resin regions, which is required to calculate the strain energy and modal damping ratio of the entire woven structure. Using the developed scheme, the natural frequencies and damping ratios of braided and laminated composite cylinders are investigated. By comparing the vibration properties of two braided composites with different braided angles and two unidirectional laminates with different fiber volume fractions, the effects of the fiber volume fraction, braided angle, and out-of-plane waviness on vibration properties are discussed. Based on the mode shape and resultant energy dissipation within each bundle and resin-rich region, the braided composite with a large braided angle exhibited the best damping properties, mainly owing to the in-plane shear deformation in the crimped braided bundles.

Shear response behavior of SSE/Kevlar composite fabric before and after shear interlocking effect

Shear stiffening gel (SSG) material was obtained by high-temperature polymerization with boric acid and hydroxyl silicone oil, shear stiffening elastomer (SSE) material was enhanced by vulcanization, and the rheological properties were analyzed. SSG and SSE/Kevlar composite fabric was obtained by “dip–dry” and “hot-pressing” process, and a picture frame test was performed on neat fabric and composite fabrics under three loading rates. The in-plane shear deformation behaviors of the fabrics were characterized by the DIC marker method, and the shear deformation mechanism of braided cells was analyzed theoretically. The results show that the SSG material has superior shear stiffening characteristics, whereas the SSE material has a much higher initial degree of crosslinking and does not have cold-flow characteristics. The fabrics experience typical shear interlocking behavior in shear deformation, and different shear deformation stiffness and energy absorption capacity before and after the shear interlocking was observed, which is caused by the different resistance mechanisms of braided cell to external shear force. The strain rate phase-change characteristics of SSG and SSE materials make the composite fabric have higher shear deformation stiffness and energy absorption at high speed, and SSE material significantly reduces the contact force between adjacent yarns after shear interlocking.

Experimental characterization and numerical modelling of bending behavior of carbon fiber unidirectional thermoset prepregs

To enhance the prediction accuracy of forming simulations of carbon fiber unidirectional (UD) thermoset prepregs, particularly the wrinkle predictions, bending behavior of UD prepregs in the forming process needs to be accurately characterized and modelled. In this paper, an improved bending test system was proposed to characterize the bending behavior of UD prepregs at different forming temperatures and loading rates. It is found that both the temperature and the loading rate have significant impact on the bending stiffness of UD prepregs. An obvious nonlinear bending behavior can be noted in the fiber direction. The loading rate sensitivity of bending stiffness in the fiber direction decreases with temperature increasing. To simulate the bending deformation, a superimposed membrane-shell element model was employed to achieve the decoupling of tensile-bending deformation. Membrane element simulated the in-plane tensile and in-plane shear deformations of UD prepregs, while shell element primarily accounted for the bending deformation. Fiber orientation dependent nonlinear bending stiffness was accounted in the model. Deformation simulations were conducted for vertical cantilever bending, horizontal cantilever bending, and compression wrinkling of UD prepregs. Good agreement is noted between simulation and experiment, demonstrating efficiency of the model and validity of measured bending stiffness.

Experimental characterization and numerical modeling of in-plane shear behavior of woven prepreg composite fabrics

In-plane shear deformation is a highly important mechanic that controls the formation of wrinkles during the forming of textile composites. This paper presents two computational formulations that describe the in-plane shear behavior of woven thermoset prepreg fabric. The bias-extension characterization test was used to validate the computational models. One of the two computational models presented is based on linear visco-elasticity and the other is based on visco-hyperelasticity. The comparison of simulation and experiments shows that a visco-hyperelastic model is necessary to accurately capture the behavior of woven composite prepregs. This paper also compares the experimental measurements with calculations based on the pin-jointed net theory to develop a criterion that helps to determine the range of the bias-extension experiment data that can be used to validate and calibrate computational models.

An optimization strategy for the shear specimen with cutouts considering the coordinated deformation of multiple regions

To expand the use of shear specimens with cutouts, proposed by Shouler and Allwood (2010), for the investigation of in-plane shear-induced fracture, an optimization strategy considering the coordinated deformation of the multiple deformation regions was proposed. The effects of aspect ratios of different deformation regions on the ratio of average equivalent strain between these regions were investigated to prevent the out-of-plane buckling instability during the shear deformation. On this basis, the geometries of one-sided specimens under uniaxial tensile test, symmetric specimens under uniaxial tensile test, and symmetric specimens under Nakajima test for an 0.3 mm-thick interstitial-free (IF) steel were determined. Successful in-plane shear deformation without out-of-plane instability was experimentally achieved on the optimized specimens using uniaxial tensile test and Nakajima test, and near pure shear states were obtained.

Features of Nonlinear In-Plane Shear Deformation of a Unidirectional and Orthogonally Reinforced Polymer Sheets of Composite Materials

Features of Nonlinear In-Plane Shear Deformation of a Unidirectional and Orthogonally Reinforced Polymer Sheets of Composite Materials

Enhanced stretch formability of AZ31 magnesium alloy sheet by secondary regulation of initial twin orientation

• Simple shear deformation is introduced to regulate twinning texture. • The twin orientation rotates away from the transverse direction, due to shear deformation. • The regulated twin orientation still exists after annealing. • Based on the modification of grain orientation, the formability is greatly improved. To modify the basal texture and improve the formability of the magnesium alloy sheet, in-plane shear deformation is introduced into the pre-twinned AZ31 Mg alloy sheet. The twinning orientation is secondary regulated and rotates away from the transverse direction about 20° after shear deformation. After annealing, the recrystallized grains inherit the grain orientation of rotating twins. Thus, the basal texture is significantly weakened. Compared with the received sample, the average fracture elongation of sheared and annealed sample improves from 15.3 % to 28.5 %. The Erichsen value increases from 2.79 mm to 5.63 mm due to the secondary regulation of initial twin orientation (SRITO).

Anisotropic deformation mechanism of {110} hexagonal dislocation networks in BCC Iron

Molecular dynamics simulation was performed to study the anisotropic mobility behavior of hexagonal dislocation networks (HDNs) in a series of bicrystalline pure Fe samples under a force-control in-plane shear deformation test. It is found that the mobility of HDN is mainly controlled by the characteristic features of <001> dislocations, which formed in the vicinity of ½<111> dislocations lying at the HDN. Furthermore, we elucidate the underlying mechanism of shearing in HDN as the variation of the length and the core energy of <001> dislocation lines with HDN misorientation angle. The energy barrier analysis of kink activities on the HDN plane is used to address the contribution of these geometrical and structural features to the in-plane shearing anisotropy of the HDN.

Experimental characterisation of large in-plane shear behaviour of unidirectional carbon fibre/epoxy prepreg tapes for continuous tow shearing (CTS) process

The continuous tow shearing (CTS) process is an advanced tape placement technique with the ability to steer unidirectional prepreg tapes by in-plane shear deformation without the presence of tape buckling, gaps and overlaps. However, the inherent fibre misalignment within the tape can induce fibre waviness during the shearing process, which is further affected by processing parameters such as temperature, shear rate and fibre tension. In this paper, the effect of those parameters on the shear behaviour of two different unidirectional carbon/epoxy prepreg tapes was experimentally investigated. A bespoke test fixture was designed to shear the tape specimens at various shear rates and fibre tensions. Digital image correlation (DIC) was used to obtain full-field strains of the specimens to investigate the fibre realignment during shearing. Experimental results showed that both temperature and fibre tension significantly affect the uniformity of the fibre realignment. Moreover, the responses of the two prepreg tapes under the same shearing condition were different due to their different impregnation characteristics.

Reinforced Effect on Brick Wall Using Timber Wall as a Retrofitting Method

The purpose of this study is to utilize timber material to enhance the in-plane shear strength and deformation capacity of a brick wall. The proposed strengthening method is light-weight and easy to assemble and includes a timber frame, plywood panel, M12 threaded rod with chemical epoxy, and the hold-down anchor. To evaluate the effectiveness of the reinforced brick wall, three walls were tested under a cyclic horizontal load and static compression stress: the brick wall (BW wall), the reinforced brick wall with timber (BW-T wall), and the reinforced brick wall with timber and the hold-down anchor (BW-TA wall). The proposed prediction method of the Kamiya and Inayama Murakami models assessed the BW-TA wall. The rocking was caused by the failure of BW and BW-T walls. However, because the BW-T wall failed in the lowest part of the wall, the timber part retained the original shape of the brick wall. When the diagonal on the BW-TA wall failed, the horizontal load at maximum load increased by 22%, and the drift angle calculated from the diagonal measurement increased 4.6 times.

In-plane behaviour of masonry walls embedding with steel welded wire mesh overlay with mortar

ABSTRACT This paper presents an experimental study of the structural behaviour of masonry walls strengthened with steel-welded wire mesh (WWM) overlay with mortar to improve their in-plane shear strength and deformation capacity. The experimental programme consists a compression testing of masonry prism and a diagonal compression testing of 15 wall specimens made of clay brick strengthened with four different WWM systems: (i) embedding WWM along the bed joint, (ii) embedding WWM along the bed joint and a strip diagonally crossing on wall surface, (iii) WWM alternately embedding along the bed joint and continue to the surface of wall and (iv) WWM fully cover on wall surface. The experimental results show that the adopted WWM-strengthening solutions produce a beneficial increase of compressive strength, shear resistance, ductility and energy dissipation capacity making them suitable for seismic strengthening.

In-Plane Shear Characterization of Unidirectional Fiber Reinforced Thermoplastic Tape Using the Bias Extension Method

Through an improved characterization methodology, this work contributes to better prediction quality in composite forming simulations for unidirectional thermoplastic composites. A better understanding of the forming behavior will aid in the adoption of these lightweight materials in aerospace applications. The bias extension method was implemented and applied to cross-ply laminates from unidirectional carbon fiber reinforced thermoplastic materials to characterize the in-plane shear deformation resistance of the molten material. Two commercially available materials were characterized at three rates and three temperatures. The shear deformation was measured directly on the specimen throughout the test using a video extensometer, avoiding the use of the pin-jointed net assumption to relate deformation to the clamp displacement. In addition, the distribution of shear deformation over the specimen surface was characterized after the test using image analysis. The observed deformation was similar to the typical deformation for woven materials, with some agreement to the pin-jointed net assumptions but also some identified deviations. Localization of shear deformation along the fiber direction of the outer ply was observed to occur at approximately 15° shear angle. The proposed bias extension method directly relates the measured force to the deformation on the specimen, ensuring the characterization of the correct deformation mechanism. This key benefit of the bias extension method solves a common issue found in other characterization methods for in-plane shear on the molten material.

Characterizing the macroscopic response and local deformation mechanisms of a unidirectional non-crimp fabric

The macroscopic response and local deformation mechanisms of a warp stitched heavy-tow unidirectional non-crimp fabric (UD-NCF) was characterized. Quasi-static uniaxial tests captured the fabric in-plane longitudinal, transverse, and shear deformation response where digital image correlation was employed. The fabric bending response was captured through modified cantilever tests. Off-axis extension tests conducted along 30°, 45° and 60° bias directions revealed that extension and contraction of the polyester stitching web and resulting transverse compression of the carbon fiber tows and inter-tow sliding were the dominant local deformation mechanisms. At a bias angle of 30°, the extent of inter-tow sliding increased when compared to a bias angle of 45° leading to earlier onset of fabric shear locking, while at a bias angle of 60° shear locking also occurred sooner. Shear angle maps and strain profiles at different bias angles further revealed the notable inter-dependency between the fabric shear, longitudinal and transverse deformations, which was governed by the interactions between the stitching and carbon fiber tows. The distinct out-of-plane bending behavior of the fabric reinforcement along longitudinal and transverse directions was also captured and quantified. The study provided a comprehensive characterization of the UD-NCF, which is critical for the development of constitutive models.

In-Plane Shear and Interlaminar Fracture Toughness Properties of MWCNT stitch Para-aramid/Phenolic Nanocomposites

In-plane shear and mode‒II interlaminar fracture toughness properties of three-dimensional nanostitch para-aramid/phenolic composites were experimentally studied. Introducing the nanostitching yarn into nanocomposites slightly enhanced their shear strengths and the interlaminar fracture toughness (GIIC) due to the through-the-thickness reinforcement which was provided by micro filament TOWs and nanotubes. In-plane shear failure mode was predominantly irregular shear hackle marks in the phenolic resin and fibrillar peeling on the fiber due to in-plane shear deformation. However, the failure mode of interlaminar fracture toughness was mainly shear hackles in the interlayer region of the nanostitch composite. Carbon nanotubes in the phenolic resin and filament TOWs probably reduced the stress clustering via friction-debonding-pull-out-sliding as a form of stick-slip. These failure mechanisms probably arrested the crack growth and suppressed delamination in the through-the-thickness fiber reinforced zone. As a result, nanostitch aramid composite showed damage tolerance characteristic.

Analysis of the Mechanical and Preforming Behaviors of Carbon-Kevlar Hybrid Woven Reinforcement

Carbon-Kevlar hybrid reinforcement is increasingly used in the domains that have both strength and anti-impact requirements. However, the research on the preforming behaviors of hybrid reinforcement is very limited. This paper aims to investigate the mechanical and preforming behaviors of carbon-Kevlar hybrid reinforcement. The results show that carbon-Kevlar hybrid woven reinforcement presents a unique “double-peak” tensile behavior, which is significantly different from that of single fiber type reinforcement, and the in-plane shear deformation demonstrates its large in-plane shear deformability. Both the tensile and in-plane shear behaviors present insensitivity to loading rate. In the preforming process, yarn slippage and out-of-plane yarn buckling are the two primary types of defects. Locations of these defects are closely related to the punch shape and the initial yarn direction. These defects cannot be alleviated or removed by just increasing the blank holder pressure. In the multi-layer preforming, the compaction between the plies and the friction between yarns simultaneously affect the quality of final preforms. The defect location of multi-layer preforms is the same as that of single-layer, while its defect range is much wider. The results found in this paper could provide useful guidance for the engineering application and preforming modeling of hybrid woven reinforcement.

Experimental Behavior of a Full-Scale Housing Section Built with Cold-Formed Steel Shear Wall Panels under Horizontal Monotonic and Cyclic Loading

This paper presents the results of an experimental study on the behavior of the cold- formed steel shear wall panel (CFSSWP) with fibrocement panels as sheathing, when it is subjected in-plane shear deformations and flexural deformation under perpendicular monotonically increasing horizontal loads on the longest plane. A full-scale housing section was built with three walls and a ceiling using commonly used construction details in El Salvador. The strength and stiffness of the experimental specimen tested overcame significantly critical demand imposed by the technical design standards in this country. Additionally, a simplified finite element model was defined with the objective to analyze stresses in the components. The results of the numerical model were similar to the experimental model tested.

Anisotropic elastic behavior of a hydrogel-coated electrospun polyurethane: Suitability for heart valve leaflets

Although xenograft biomaterials have been used for decades in replacement heart valves, they continue to face multiple limitations, including limited durability, mineralization, and restricted design space due to their biological origins. These issues necessitate the need for novel replacement heart valve biomaterials that are durable, non-thrombogenic, and compatible with transcatheter aortic valve replacement devices. In this study, we explored the suitability of an electrospun poly(carbonate urethane) (ES-PCU) mesh coated with a poly(ethylene glycol) diacrylate (PEGDA) hydrogel as a synthetic biomaterial for replacement heart valve leaflets. In this material design, the mesh provides the mechanical support, while the hydrogel provides the required surface hemocompatibility. We conducted a comprehensive study to characterize the structural and mechanical properties of the uncoated mesh as well as the hydrogel-coated mesh (composite biomaterial) over the estimated operational range. We found that the composite biomaterial was functionally robust with reproducible stress–strain behavior within and beyond the functional ranges for replacement heart valves, and was able to withstand the rigors of mechanical evaluation without any observable damage. In addition, the composite biomaterial displayed a wide range of mechanical anisotropic responses, which were governed by fiber orientation of the mesh, which in turn, was controlled with the fabrication process. Finally, we developed a novel constitutive modeling approach to predict the mechanical behavior of the composite biomaterial under in-plane extension and shear deformation modes. This model identified the existence of fiber–fiber mechanical interactions in the mesh that have not previously been reported. Interestingly, there was no evidence of fiber–hydrogel mechanical interactions. This important finding suggests that the hydrogel coating can be optimized for hemocompatibility independent of the structural mechanical responses required by the leaflet. This initial study indicated that the composite biomaterial has mechanical properties well-suited for replacement heart valve applications and that the electrospun mesh microarchitecture and hydrogel biological properties can be optimized independently. It also reveals that the structural mechanisms contributing to the mechanical response are more complicated than what was previously established and paves the pathway for more detailed future studies.