In-plane Shear Tests Research Articles

Mechanical Performance on Flax Fibre Epoxy Composites Filled with Montmorillonite Nanoclay for Lightweight Applications

The objective of this study is to investigate the mechanical performance on develop flax/epoxy composite filled with montmorillonite nanoclay for lightweight applications. For this purpose, firstly, nanoclay at different weight percentages montmorillonite nanoclay such as 0.5, 1, 1.5 was dispersed homogeneously into epoxy resin with the help of ultrasanitization process. For better nanoclay distribution in composite, the montmorillonite nanoclay concentration higher than 1.5% was not analyzed. Secondly, using this mixture, flax fiber based composites were produced by vacuum bag molding process. Finally, the mechanical properties of flax/epoxy composites filled with different percentages montmorillonite nanoclay were determined with tensile, flexural, and in-plane shear test. From the experimental results obtained, the addition of montmorillonite nanoclay indicate positive effect on the performance of the composites compared with the neat composite samples, if the montmorillonite nanoclay distribute homogeneously in the epoxy. The composites added with 0.5 wt.% nanoclay showed the highest tensile modulus and tensile strength. Moreever, the elasticity modulus of composite samples with 0.5% nanoclay addition is approximately 87% higher than the pure composite. Also, the composite samples loaded with 1.5 wt.% of montmorillonite nanoclay performs better under flexural loading conditions.

Experimental investigation of buckling and post-buckling behaviour of repaired composite laminates under in-plane shear loading

The performance of Ramped Scarf (RS) and Stepped Scarf (SS) repair schemes for highly loaded composite structures has been extensively studied under compressive, tensile, and flexural loadings. However, there is a lack of research on the buckling and post-buckling behaviour of RS and SS repairs under in-plane shear loading, which is critical for aerostructures. This paper addresses this gap by investigating the buckling and post-buckling performance of these repair schemes. Pristine (P) laminates, RS repairs with a scarf angle of 3°, and SS repairs with an overlap step length of 1/60 were manufactured and tested. The quality of the scarf repairs was inspected using artificial intelligence-based machine vision. Mechanical in-plane shear testing was conducted to evaluate the buckling and post-buckling behaviour of P, RS, and SS laminates. The experimental results indicate that RS repairs demonstrated an average of 35 % higher maximum displacement and 12 % higher failure load compared to pristine laminates. SS repairs showed 19 % higher maximum displacement, and 5 % higher failure load compared to pristine laminates. RS repairs excelled in all key mechanical performance indicators, including buckling load, Hooke's stiffness, maximum displacement, and failure load, compared to SS repairs. The failure modes of P, RS, and SS laminates were similar. However, RS repairs exhibited greater susceptibility to repair patch detachment compared to SS repairs.

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.

Experimental and numerical investigation on the in-plane performance of nail-laminated timber floor

Existing research has shown that the nail-laminated timber (NLT) floor has the potential to achieve considerable out-of-plane flexural performance at a relatively lower cost. However, though the in-plane performance of structural floors greatly impacts the seismic resistance of the overall structure, research on the in-plane behavior of NLT floors is still insufficient. In this paper, an in-plane shear test was carried out on twelve NLT floor specimens of four subgroups. A finite element model (FEM) method was established and verified using the experimental results. A parametric analysis was performed based on the FEM method to quantify the influence of sheathing nails on the in-plane performance of the NLT floor in both planar directions. Experimental results indicate that sheathing nail spacing and loading direction showed significant influence on the in-plane performance of NLT, while the orientation of sheathing did not. Main failure modes include dislocation of adjacent sheathings, sheathing nail failure, and lamina nail failure. Verification of the proposed FEM method showed good agreement with the experimental results, both on performance characteristics and deformation patterns. Parametric result indicates that the elastic stiffness and shear strength were linearly correlated to the quantity of sheathing nails.

Efficiency of FRPU strengthening of a damaged masonry infill wall under in-plane cyclic shear loading and elevated temperatures

This paper presents results of in-plane shear tests carried out at the ZAG laboratory in Ljubljana (Slovenia) on a RC frame with masonry infill made of clay blocks (KEBE OrthoBlock). The frame was loaded with constant vertical loads at the top of the columns and then by gradually increasing horizontal cyclic loads at the top beam level. Acquired forces and measured displacements allowed capturing hysteretic behavior for determination of dissipation energy. In addition, two Digital Image Correlation (DIC) systems, Aramis and the CivEng Vision, were used to visualize the behavior of the tested specimens, with an emphasis on computing locally required information about the behavior of highly deformable interfaces. Three types of specimens were tested in-plane: the reference specimen in form of plain RC frame, the reference specimen with constructed masonry infill without any strengthening and the specimen, previously damaged and then strengthened on both sides using glass mesh bonded to the infill and the RC frame using flexible adhesive made of polyurethane matrix (Glass Fiber Reinforced PolyUrethane - GFRPU system). The strengthening process, allowed the specimen to withstand additional cyclic loads, reaching a maximum drift of 3.6 % without serious damage disqualifying the structure from further exploitation. The GFRPU strengthening system was found to be highly effective in preventing infill collapse of damaged masonry infill wall during in-plane loading. Additionally, the results of extended thermal analysis of PU are presented as polymers are, in general, a material, poorly resistant to heat. However, the analyzed PU manifested stable properties up to 200 degrees Celsius, which makes this material promising in civil engineering applications at elevated temperatures.

Length Scale Insensitive Phase-Field Fracture Methodology for Brittle and Ductile Materials

We present length scale insensitive phase-field fracture models for brittle and ductile fracture to address the deficiencies of widely implemented models which over-estimate crack dissipation. An approach is proposed to attain a regularization length scale insensitive mechanical response, which considers a continuous approximation of a crack boundary with a function of infinite support. This is in contrast to previous approaches to attain a length scale insensitive response which exploited approximations of the crack boundary with functions of finite support. The choice of these functions with finite support creates implementational challenges which are avoided in the presented quasi-brittle and ductile fracture models with infinite support of the phase-field. The capability of these models is demonstrated in several benchmarks with attention given to the sensitivity of the structural response with respect to the choice of regularization length scale. The models are validated against a three-point bending test on a concrete specimen and an in-plane shear test on a steel specimen.

In-plane shear performance and damage evolution of FRP connectors for composite sandwich panels

This study investigated the in-plane shear responses of four types of connectors (single-strand truss, double-strand truss, grid-type, and I-shaped) in precast concrete sandwich panels (PCSPs). The influence of connector type, connector arrangement, and wythe material on the shear performance was discussed through in-plane shear tests and finite element analysis. The failure modes and test results of the four types of connectors were closely related to their shear resistance mechanisms. Changing the connector arrangement method from continuous along the length to discrete arrangement improved connector damage extent and toughness index (TI). The substitution of ordinary concrete with ECC or UHPC in wythes can prevent the wythes failure and enhance peak load (Pm). The finite element (FE) model using the Hashin damage model and randomly generated fibers can accurately capture the shear response of the connectors within PCSP. The damage factor was introduced for quantitative analysis of the damage processes in connectors and wythes and corresponding damage evolution model was developed. Furthermore, the damage evolution model was applied to characterize the degradation of shear stiffness in the load-slip curve, and a load-slip theoretical model that accounted for the progressive development of damage was established.

In-plane shear failure behavior and mechanical properties of SiC/SiC Composites

Fiber-reinforced ceramic matrix composites, especially SiC/SiC composites, have the characteristics of lightweight, high strength, high-temperature resistance, etc., which are ideal structural candidates for aerospace vehicle components, in-plane shear performance is one of the important indicators to characterize the mechanical properties of materials and component assessment, this paper designs and processes the in-plane shear test pieces and test devices and methods to study the shear mechanical behavior under the mechanical properties and failure behavior of SiC/SiC ceramic-based fiber bundle composites are studied under shear mechanical behavior. The results show that matrix cracking and fiber fracture are the main failure modes, and there are two obvious phases in the specimen shear force-displacement curves, and fiber fracture is the main cause of strain in the specimen.

In-plane testing and hysteretic modeling of steel-spline cross-laminated timber diaphragm connection with self-tapping screws

ABSTRACT This study examines experimentally and numerically the in-plane behavior of a steel-spline Cross-Laminated Timber (CLT) connection with self-tapping screws. Although this connection is a strong, rapid, and cost-effective alternative suitable for CLT diaphragms of tall timber-concrete buildings, no previous cyclic/monotonic testing has been documented. Two specimens were tested under axial and in-plane shear loads, where a ductile failure mode was observed due to bending and withdrawal of screws, and deformation and buckling of the strap. Mechanic properties, such as strength capacity, stiffness, ductility, energy dissipation, equivalent viscous damping, stiffness/strength degradation, and damage index characterize the joint. Furthermore, the yield point and ductility were calculated with the EEEP, CEN, and Yasumura–Kawai methods, the last approach most accurate, with a mean ductility of 7.25 and 5.50 for the axial and in-plane shear tests, respectively. Overstrength factors of about 2.6 and 1.9 were also estimated for respective tests by comparing analytical expressions from timber codes and literature. Finally, three numerical models (SAWS, DowelType, and ASPID) were assessed to measure their epistemic uncertainty, showing an adequate force and dissipated energy history simulation, with a normalized root mean square less than 8.8% and 4.5%, and R 2 over 87% and 97%, respectively.

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.

Effect of the loading-rate and stress state on the constitutive modelling and fracture of 2205 Duplex stainless steel

Shear cutting is a high-speed forming process where material separation is involved. The nature of the process leads to high strain rates and temperatures on the sheared zone of the material subjected to the operation. In this work, the mechanical behavior in terms of flow stress, plastic deformation and fracture of a 2205 Duplex stainless steel sheet is determined. Uniaxial tension, uniaxial compression, stack compression, plane strain tension and simple shear tests at different angles with respect to the rolling direction of the metal sheet are performed to determine the anisotropic behavior of the material. Strain rate and temperature dependence of the flow stress and the plastic behavior of the material is determined through notched tensile tests performed under various temperatures (20°C, 100°C, 300°C and 500°C) and strain rates (0.001 s-1, 10 s-1 and >100 s-1). Finally, fracture behavior under various stress states is determined through notched tensile, central hole, in-plane shear and plane strain tests. The temperature and strain rate dependence of the fracture behavior is determined through notched tensile, in-plane shear and plane strain tests performed under various temperatures (20°C, 100°C, 300°C and 500°C) and strain rates (0.001 s-1, 10 s-1 and >100 s-1). The anisotropic behavior and work hardening of the material are modelled by the Hill48 yield function and Swift-Hockett-Sherby hardening law, respectively. Among the two ductile fracture models tested, Hosford-Coulomb model showed the best agreement and is therefore used to account for the temperature and strain rate effects on the fracture behavior. By combining these three models, an accurate reproduction of the mechanical behavior of the 2205 Duplex stainless steel sheet is achieved.

Thermomechanical characterisation of reprocessable, siloxane-based, glass-fibre-reinforced vitrimers

Polymer composites have been extensively used for the last 30 years in the automotive, green-energy, maritime and aerospace industries. While the demands of composites' applications are increasing, complications are arising regarding their sustainability. In this work, a siloxane-based vitrimer with fast stress-relaxation, and its Glass-Fibre-Reinforced Vitrimer (GFRV) were manufactured and mechanically characterised as a sustainable alternative to thermoset composites produced by infusion. Dynamic mechanical analysis and differential scanning calorimetry were performed to identify the ageing effect on the glass-transition temperature of the materials. Tensile and in-plane shear tests were executed to investigate the materials’ performance at elevated temperature. The results were compared to the ones of a thermoset benchmark and showed that after ageing and up to 50 °C, both the neat vitrimer and its corresponding composite exhibited a thermomechanical performance comparable to their thermoset counterparts. GFRV specimens were then successfully reprocessed by hot-pressing up to two consecutive cycles. The GFRV specimen was thermoformed into an omega-stiffener profile by the first hot-pressing cycle, while its flat profile was restored during the second cycle. Finally, the reprocessing results were evaluated by optical microscopy, demonstrating that the newly developed advanced GFRV is indeed a viable, sustainable alternative.

Reinforcement of Traditional Wood-Frame Tabique Walls Using Wood-Based Panels

ABSTRACT In many regions of Portugal wooden-frame walls, known as tabique walls, are commonly found in old buildings. This type of wall is a traditional building element made of raw materials such as earth, wood and stone. These walls are generally used as non-structural elements (partitions) but are also used as structural solutions. Their maintenance in service must be based on the comprehension of their construction system and the materials involved, as well as sustainable reinforcement solutions. This study presents a reinforcement solution based on the application of wood-based panels (MDF and plywood) applied to their faces (sheathing). To assess this solution (reinforced and unreinforced), wall specimens were subjected to in-plane shear testing. The results showed a substantial increase in rigidity, even in cases where the reinforcement takes place after the wall has suffered some damage.

In-plane Shear Behaviour of Novel Thick Stitched Textile Reinforcements Part II: Quantitative Analysis of Shear Locking Angle

A quantitative analysis of the in-plane shear test results reported in PhD thesis of Hafeth Bu Jldain was preformed in this paper. Analysis of the results was conducted from experimental and analytical bases. It was conducted experimentally through comparing the results obtained for uO-APT samples with the results obtained for samples made from an industrial fabric manufactured by GmbH Saertex. The analytical validation was conducted through systematic Taguchi plans. These plans investigate, the effect of the type of reinforcement (A and B), the effect of the number of layers, and the effect of stitching setup (R-45, R+45, R0 and R90) on the behavior of the reinforcements. The plans primarily analyzed the extent to which the reinforcement may shear and the force required to do so.Shear test results for stitching orientation R-45 and R+45 show the ability of the new fabric to shear under lower shear forces, which ranged between 0 N and 25 N needed to shear uO-APT reinforcements to shear angles ranging from 50° to 55° before wrinkling was observed.

Investigation of mechanical properties and damage types of E-glass fiber reinforced epoxy matrix composites under various loadings

This study presents a comprehensive experimental investigation to determine the elastic material properties of a unidirectional E-glass fiber/epoxy composite. Tension, compression, in-plane shear, and flexural tests were conducted in both longitudinal and transverse directions. The composite laminates were manufactured using vacuum-assisted resin transfer molding (VARTM) with a 65% fiber weight fraction. Mechanical tests were performed according to ASTM standards, and special fixtures were used for shear and compression tests. The damage mechanisms were interpreted for each test, revealing fiber splitting in tension and kink band failure in compression were dominant damage modes. The findings provide valuable insights into the behavior and performance of the composite under various loading conditions, which may help in its application in different engineering fields.

Mechanical properties of stone masonry set in mud mortar and contained by steel wire mesh

The mechanical properties of semi-dressed stone masonry set in mud mortar and contained within steel wire mesh are reported. Two-wythe thick masonry was laid in a semi-layered configuration as is typically found in the earthquake-affected areas of the 2015 Gorkha (Nepal) earthquake. An experimental testing program was undertaken that included direct compression, diagonal tension (shear), and in-plane quasi-static cyclic shear tests of masonry wallettes that were both uncontained (without containment mesh) and contained (with containment mesh). The results of the experimental testing indicated that the provision of containment enhanced the strength, deformability, and energy dissipation capacity of the masonry. Findings from the experimental testing are presented, including a comparison of the performance of stone masonry set in mud mortar when either uncontained or contained.

Analysis of the efficiency of advanced methods of in-plane shear testing of highstrength CFRP specimens

The mechanical testing performed to determine shear characteristics of advanced carbon fiber-reinforced plastics (CFRP) can involve significant problems. First of all, this is due to the difficulties in providing uniform distribution of shear stresses in the working area of the specimens, particularly in determining the strength characteristics of advanced polymer composite materials based on high-modulus or highstrength carbon fibers with the ± 45° layup, where the material properties depend not only on the matrix but also on the fiber properties, unlike unidirectional composites. In addition, one can mention a large number of shear test methods and related standards of in-plane shear testing. At the same time, the results of the tests performed according to various standards generally do not comply with each other. In this study the analysis of CFRP shear characteristics obtained from various test methods was performed. The calculated and experimental data of stress-strain distribution for various specimen types were obtained. The experimental results of determining the strength and elastic characteristics of CFRP in the in-plane shear were obtained during the testing of 125 flat specimens made of four brands of CFRP reinforced with the ± 45° plies. None of the standard methods discussed in this study was found to provide uniform distribution of shear stresses in the working area of the test specimen. The strength values closest to the predicted ones were obtained from the specimens made according to ASTM D7078 (GOST R 57207) based on the method of V-notch plate distortion. At the same time, the method of plate distortion in the four-bar linkage (GOST 24778, ASTM D2719) and the losipescu method (ASTM D5379, GOST R 56799) cannot definitely be used to reliably determine the shear strength characteristics of advanced CFRP reinforced with the ± 45° plies.

A comparison study on experimental characterization of unidirectional fiber reinforced composites using strain-gauges and virtual extensometers

Abstract The aim of this study is to characterize E-glass/epoxy unidirectional fiber reinforced composites using the digital image correlation method with virtual extensometer, which is a less laborious method than strain gauges, compare the results and investigate whether virtual extensometers can be used instead of strain gauges. Measurements in tensile and Iosipescu shear tests were made with both strain gauge and virtual extensometer. Unlike full-field strain measurements in literature, the strains were measured using virtual extensometers. Tensile test and in-plane shear test results gave very consistent results. The differences between the strain gauge and the virtual extensometer for the tensile and in-plane shear tests were less than 3% in the linear region. However, the out-of-plane shear test showed a larger difference of 8.6%. This study showed that the 2D digital image correlation method with virtual extensometers is highly sufficient to find the elasticity moduli and shear moduli in tensile and shear tests in the linear region. In addition, after the damage has started, more measurement data can be obtained with virtual extensometers than with strain gauges.

Effect of MWCNTs on mechanical properties of woven cross ply GFRP laminates

The impact of multiwalled carbon nanotubes (MWCNTs) on the structural integrity of woven cross ply glass fiber reinforced polymer (GFRP) has been examined in this study. Eight-ply laminates of fiber orientation (0˚/90˚) with neat epoxy GFRP, 0.5 wt% and 1.0 wt% MWCNTs modified GFRP were manufactures by using vacuum supported hand layup technique. According to ASTM standards, rectangular samples were cut from the prepared composite laminates for mechanical testing such as three-point bending test, tensile test, interlaminar shear strength test, in-plane shear and compression test. Addition of 0.5 wt% and 1.0 wt% of MWCNTs in cross ply GFRP laminates enhanced the ultimate tensile stress, compressive stress, bending stress, interlaminar shear stress and in-plane shear stress.

Recent advances in the in-plane shear testing of Mg alloy sheets

Recent advances in the in-plane shear testing of Mg alloy sheets