In-plane Shear Loading Research Articles

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.

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.

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.

Exploring in-plane shear characteristics of multilayer biaxial weft knitted fabrics through a micro-scale virtual fiber modeling

The multilayer biaxial weft knitted (MBWK) fabrics and their composites have been widely applied in fields of complex structural products due to their flexible curved deformability. The existence of stitch in MBWK complicates the deformation behavior under the in-plane shear loading. However, it has not been well explored and understood. In this study, a numerical micro-scale virtual fiber modeling was built to investigate the in-plane shear performance of MBWK by considering the micro geometric features and fiber property that are difficult to be characterized solely by experiment. The strain conditions of the stitch that determine the fabric shear behavior are discussed. The deformation behavior leads to local deformation and morphological locking of the stitch. In the early stage of the shearing, the deformability of stitch provides enough space to accommodate the rearrangement of axial yarns. In the shear locking stage, the restriction of stitch and compression within axial yarns at high shear angles restricts the axial yarns from movement in the loading direction. When the theoretical shear angle is 20°, the shear angle located in different shear regions varies. The maximum shear angle near the loading area is 19.1°, while the minimum shear angle near the fixed area is approximately 17°. The results illustrate the deformation mechanism of MBWK under in-plane shearing and provide an excellent guidance for the design of large deformation fabrics, especially for curved surfaces, thus realize the effective utilization of fabrics in engineering applications.

Kirigami beyond tension: Expanding Kirigami's versatility via shear actuation

The potential of Kirigami-based metamaterials as versatile platforms in applications where shape-morphability is desired is presently well established. Interestingly, in-plane loading under simple tension has been the predominant actuation-of-choice, with other fundamental loadings (e.g., shear, torsion) being largely overlooked. In this work, we explore the instability landscape of a simple Kirigami motif under in-plane shear loading and demonstrate how the incorporation of shear actuation effectively augments both the design and output space of Kirigami-based metamaterials. The nonlinear response of Kirigami under shear is first elucidated parametrically via nonlinear Finite Element Analysis on a subset of geometrically asymmetric motifs. The interplay between cut layout and the bidirectional nature of in-plane shear enables a variegated bifurcation landscape that includes unusual inversions and sharp kinks in the bifurcation curves. The numerical analysis is complemented with experimental validation of the out-of-plane bifurcation curves of several cases of interest by means of shadow moiré and laser displacement sensing. Together with the experimental validation, a proof-of-concept demonstration of the applicability of Kirigami-shear metamaterials as multistate electro-mechanical switches is presented. Overall, our findings add a new dimension to an already rich design space, thus opening a vista of opportunities for multimodal programmable structures, particularly appealing in sensing and actuation applications.

Experimental investigation of size effect on unreinforced concrete brick masonry walls under in-plane shear loading

The size effect is one of the primary structural characteristics exhibited in reinforced concrete (RC) members in shear. Even though numerous studies have been conducted on masonry walls under shear, very few studies have been conducted that definitively answer whether a size effect exists for masonry walls. Diagonal compression tests on two groups of masonry walls with different dimensions were conducted to investigate the size effect on concrete brick masonry walls. A total of sixty masonry wall panels were tested. Five bed-joint mortar mix properties were used for each specimen. Test results showed that four failure modes were observed: diagonal tension failure, combined failure, sliding failure, and toe-crushing failure. In particular, the diagonal tension strength was significantly related to the specimen size. The larger specimen size led to a lower shear strength. Also, the shear modulus was highly dependent on the specimen size. Through experimentation, this study demonstrated that masonry walls exhibit a size effect. Moreover, the size effect is valid only in cases of diagonal tension failure. Based on the test results, this study revealed a correlation between diagonal tension strength and wall size. Lastly, the adequacy of the predictions was compared to the existing masonry codes.

Fibre reinforced concrete under in-plane shear stresses

Steel fibres have a positive influence on the shear behaviour of concrete elements, such as beams and walls, the more so as the developments in fibre reinforced concrete (FRC) technology allow reaching increasingly higher residual post-cracking strengths. The partial, or total, replacement of shear reinforcement by steel fibres allows increasing the construction speed and reducing labour costs, potentially offering economic benefits in the context of industrialized fabrication. However, the combined behaviour of steel fibres with reinforcement in shear critical elements is still not fully understood hindering the development of consistent design procedures.In this study, a detailed mechanical model based on the Cracked Membrane Model using fixed and interlocked cracks (F-CMM) is presented, which is capable of describing the behaviour up to failure of concrete panels reinforced with both steel fibres and rebars (R-FRC) subjected to in-plane shear and axial forces. The model explicitly considers all the individual mechanical phenomena governing shear behaviour of R-FRC and can serve as the basis for the development of methodologies for shear safety verifications.The model is validated against the existing experimental results from R-FRC panels subjected to in-plane shear loading. A calculation example is used to discuss in detail the model outcomes and the impact of the spatial variability in the fibre distribution. A parametric study is developed to understand the effects of fibres on the shear strength and failure modes, and its interactions with both the reinforcements and crack shear stress transfer mechanics.

Dependence of a Steel-concrete-Steel Sandwich Structure Behavior under Pure In-Plane Shear Loading on the Reinforcement Ratio

This paper deals with failure modes of a steel-concrete-steel sandwich loaded by pure in-plane shear. Current research together with the developed models imply that increase of reinforcement ratio leads to decrease of ductility and possibly to change a failure mode from yielding of steel in tension to crushing of concrete in compression which results in brittle failure. In order to give a reader basic information about in-plane shear behavior of a steel-concrete-steel sandwich, an analytical model is introduced. Japanese experimental program that researched a behavior of SCS panels with reinforcement ratio 2.3%, 3.2% and 4.5% is also shown. In addition to the effect of changing the reinforcement ratio, the experimental program also investigated the effect of the transverse steel plate on the ductility of test panels with a degree of reinforcement of 3.2%. The next chapter describes the methodology used by the author to model the individual parts of the model, the loads, and especially the method of supporting the model. This is followed by the presentation of the results of the analysis on the calibration and extrapolation models. Finally, a discussion is conducted on the agreement of the analysis results on the calibration models with the Japanese experimental results, followed by an evaluation of the analysis results on the extrapolation models. According to the results on the extrapolation models the critical degree of reinforcement at which a change in the failure mode of the structure occurs under in-plane shear loading is around 13%.

Influence of microvascular structured void content on composites subjected to in-plane shear loads

Microvascular fiber reinforced composites can be used as multifunctional structures capable of self-healing, thermal regulation, and communication, among others. The inclusion of a small volume of microchannels generally has a minimal impact on the mechanical properties of the composites. In the current work, the in-plane shear properties of microvascular composites containing embedded stainless steel and wall-less microchannels produced through sacrificial material removal were characterized for the first time. Microvascular unidirectional composites were manufactured with precisely located microchannels both aligned with and transverse to the fiber direction, and their in-plane shear properties were tested. Microchannels aligned with the fiber direction were shown to cause a substantial (−7%) decrease in shear strength but had no effect on shear modulus or failure strain. Distortion of the laminate surface around the channels oriented transverse to the fiber axis was observed, resulting in an increase in void content (1–4%), a 9% loss in shear modulus, and a 27% loss in shear strength. The use of a caul plate made the loss in shear strength statistically insignificant, increased the shear modulus by 12–15%, and decreased the shear strain by −25% relative to the baseline composite without microchannels. Digital image correlation showed that the surface strains for transversely oriented samples were interrupted near the microchannels, but post-test x-ray computed tomography and optical microscopy do not show crack redirection. The newfound understanding of the shear response of microvascular composites provides important insights that will enable future engineering designs of multifunctional aerospace structures.

Critical load for shear-induced lateral-distortional buckling in I-section steel beams considering flexural stiffness ratio

In prefabricated buildings, lateral-distortional buckling (LDB) of I-section steel beams is a common failure mode that has garnered considerable attention. However, existing studies and design methods for lateral-distortional buckling primarily focus on members subjected to in-plane flexure and do not take into account the influence of shear forces. In this paper, a study on the elastic lateral-distortional buckling behavior of I-section steel beams under in-plane shear loads was conducted. Firstly, refined finite element (FE) models of beam webs under shear loads were established and validated against theoretical formulas for different boundary conditions. Subsequently, by combining with analytical solutions and numerical results, an accurate buckling load formula for the beam web with a free bottom edge was obtained, which can be used for further study. Based on the parametric analysis results, a formula was obtained to determine the critical flexural stiffness ratio of flange to web. When the flexural stiffness ratio exceeds the critical value, the lateral-distortional buckling of I-section steel beams can be effectively avoided. Finally, a formula that incorporates both the critical flexural stiffness ratio and the span to height ratio was proposed to calculate the elastic critical lateral-distortional buckling loads of I-section steel beams solely under in-plane shear loads.

A novel core-shell C/SiC bolt prepared by chemical vapor infiltration and its fiber strengthening mechanisms

Integrated manufacturing techniques have been extensively utilized to assemble thermal structural components made of continuous fiber reinforced silicon carbide composites (C/SiC) to fabricate large and complex components. The mechanical joint, always in terms of C/SiC bolts, become the weakest link in the components. Laminated C/SiC bolts have been invented to meet the requirements of the high temperature applications. Due to the low shear strengths of C/SiC, the threads are prone to be damaged. In order to fully employ the high tensile strength of carbon fibers, core-shell C/SiC bolt is proposed with the shell prepared by woven fiber architecture. Uniform circumferential microstructure of the threaded teeth has been obtained and the corresponding strength has been improved through fiber bridging mechanism. The results shows that the thread pull-off strength is 17.96% greater than that of the laminated thread tooth, and the stud tensile strength is slightly improved up to 2.96%. The stud shear strength is enhanced by 45.29% and 46.88% with unidirectional C/SiC rod and ZrO2 ceramic rod, respectively. The improvements are mainly caused by the fiber tension-shear coupling effects. Especially the introduction of unidirectional C/SiC rod improves the shear strength of the bolts by fully utilizing the fiber strengthening mechanisms under in-plane shear loading.

Experimental and numerical investigations of Frameless CFSCW under combined in-plane shear and axial loads

This paper presents a comprehensive evaluation of a novel Cold Form Steel Corrugated Walls (CFSCWs), named Frameless CFSCWs, under combined axial and lateral loads. A series of experimental investigations were carried out on full-scale specimens. The influence of different axial loads on the buckling-failure mode, the peak force capacity, the post-buckling stiffness, and the residual force capacity are presented. Subsequently, robust finite element models were developed to simulate the complex bucking behavior of these Frameless CFSCWs. The results of the experimental and numerical investigations revealed that the lateral force-deformation response of Frameless CFSCW is highly influenced by the axial loads. A linearized backbone curve of the Frameless CFSCWs with different axial loads is proposed. Key design parameters such as overstrength and ductility ratios of the Frameless CFSCW panels are identified. The linearized backbone curve can be used by engineer to design Frameless CFSCWs under different axial loads.

Analytical modeling of fiber–matrix interface failure in unidirectional laminae subjected to in-plane shear loads

Unidirectional laminae subjected to in-plane shear loads present complex behavior with strong nonlinear response. A novel analytical model is proposed considering a unit cell with square symmetry and circular fiber cross-section taking into account the failure on the interface between fiber and matrix. The interface failure is a shear-driven phenomenon described by a constant value during the failure process. The model validation is performed using two different approaches: the analytical estimations are compared with experimental data, and finite-element simulations are employed to evaluate the influence of fiber volume fraction. The proposed analytical model captures the main features of experimental data showing its capability and reliability to represent the complex interface debonding propagation phenomenon. Numerical simulations show in-plane shear stress–strain curves for four distinct unidirectional laminae with different fiber volume fractions. Results attest the model capability to describe composite materials with composite failure, essentially characterized by the interface behavior.

Mechanical properties and failure behaviors of T1100/5405 composite T-joint under in-plane shear load coupled with initial defect and high-temperature

The T1100/5405, a novel carbon fiber resin matrix composite, boasts superior specific strength, stiffness, and broad applicability. This study rigorously investigated the in-plane shear performance and thermally coupled damage failure mechanisms of this composite in a T-joint context under initial defects, being highly relevant for hypersonic vehicles in high-temperature environments. Experimental tests yielded mechanical property parameters and in-plane shear data for varying test temperatures (25℃, 150℃) and defect radius (0 mm, 15 mm). Compared to flawless samples at room temperature, the synergistic impact of high temperature and defects expedited the structural damage failure process, reducing load-bearing capabilities significantly. A numerical model was established based, on the inherent structural relationship of the cohesive zone model and the continuum damage mechanics of the composite, whose accuracy was confirmed by experimental data. Further analysis revealed that a high-temperature environment would exacerbate the damage failure process of initial defects. Specifically, as the temperature rose, the defect radius increased, thus diminishing the shear capacity of T-joint. The maximum structural ultimate load has been reduced by 67.54 %, which was perfectly aligned with experimental results. Consequently, the study provides practical insights for the structural design of hypersonic vehicle composite.

Buckling analysis of stiffened functionally graded multilayer graphene platelet reinforced composite plate with circular cutout embedded on elastic support subjected to in-plane normal and shear loads

Buckling analyses of orthogonally stiffened functionally graded graphene platelet reinforced composite plate with circular cutout supporting on Winkler elastic foundation is conducted according to the third order shear deformation plate theory and the finite element method to achieve the desired solutions. Material properties of the composite plate are evaluated using Rule of mixture and Halpin-Tsai approach. Graphene platelet reinforcements and Poly methyl methacrylate matrix are considered as the two components of the composite media. The material of the stiffeners is selected the same as that of the polymer matrix. In one efficient case, adding a set of stiffeners increased the critical buckling load by 41.8 % with only a 10.3 % increase in weight of the structure. Influence of broad range of factors such as GPLs nanofillers distribution pattern and weight fraction, Winkler-type elastic foundation, uniaxial and biaxial normal and shear loads, plate thickness and aspect ratio, width, height and number of longitudinal and transverse stiffeners are reported in several tabular and graphical data in detail.

A Study on Damage of T800 Carbon Fiber/Epoxy Composites under In-Plane Shear Using Acoustic Emission and Digital Image Correlation.

In addition to measuring the strain, stress, and Young's modulus of materials through tension and compression, in-plane shear modulus measurement is also an important part of parameter testing of composites. Tensile testing of ±45° composite laminates is an economical and effective method for measuring in-plane shear strength. In this paper, the in-plane shear modulus of T800 carbon fiber/epoxy composites were measured through tensile tests of ±45° composite laminates, and acoustic emission (AE) was used to characterize the damage of laminates under in-plane shear loading. Factor analysis (FA) on acoustic emission parameters was performed and the reconstructed factor scores were clustered to obtain three damage patterns. Finally, the development and evolution of the three damage patterns were characterized based on the cumulative hits of acoustic emission. The maximum bearing capacity of the laminated plate is about 17.54 kN, and the average in-plane shear modulus is 5.42 GPa. The damage modes of laminates under in-plane shear behavior were divided into three types: matrix cracking, delamination and fiber/matrix interface debonding, and fiber fracture. The characteristic parameter analysis of AE showed that the damage energy under in-plane shear is relatively low, mostly below 2000 mV × ms, and the frequency is dispersed between 150-350 kHz.

Slip and Crack Initiation Behavior of Carbon Steel Thin Films under Cyclic In-Plane Shear Loading

Slip and Crack Initiation Behavior of Carbon Steel Thin Films under Cyclic In-Plane Shear Loading

Superior flexural, interlaminar- shear and fracture performance of glass fiber/epoxy laminates employing 3-D reinforcement approach: Emphasis on through thickness functionalized CNT alignment

Owing to the absence of z-directional reinforcement in laminated glass/epoxy (GE) composites, their performance under out-of-plane normal and in-plane shear loadings are questionable. This article highlights the importance of using an electric field induced nanotube alignment along the z-direction of the laminate using pristine and functionalized CNTs (CNT and FCNT). Use of aligned FCNTs in the GE composite showed best performance as confirmed from a series of mechanical tests, i.e. flexural properties, interlaminar shear strength (ILSS), mode- I and II interlaminar fracture toughness (ILFT). The key finding of this work includes an enhancement in the critical energy release rate under crack opening mode (i.e. GIC) as high as ∼82% in case of A-0.1F-CNT-GE (0.1 wt% aligned FCNT in GE composite) over the control GE composite. Fractographic study reveals various strengthening and toughening mechanisms responsible for the improved mechanical properties of the composites due to alignment and functionalization of CNTs.

Postbuckling Strengths of Composite Laminates with a Central Circular/Elliptical Cutout Under In-Plane Combined Loads

This paper deals with the effect of cutouts (i.e., circular and elliptical) aspect ratio on the buckling and postbuckling strengths, and failure characteristics of a simply-supported quasi-isotropic composite laminate subjected to in-plane shear and uni-axial compression combined with in-plane shear loads. The present study is carried out using self developed finite element program. The finite element formulation is based on the first order shear deformation theory and von Karmans assumptions to incorporate geometric nonlinearity. The resulting nonlinear algebraic equations are solved by Newton-Raphson method. The postbuckling strength of the laminate is defined in terms of the first-ply failure load of the lamina predicted by tensor polynomial form of the 3-D Tsai-Hill criterion. It is observed that for maximum buckling and first-ply failure strengths of the laminate with a cutout, it is preferred to have elliptical shape of the cutout as compared to the circular shape of the same area. It is also found that irrespective of load conditions and cutout shapes and sizes, shear load direction has significant effects on buckling and postbuckling stiffness of the laminate; although buckling stiffness is greater under negative shear, but the laminate shows stiffer postbuckling response under positive shear load.

Response of RC shear walls with single and double layers of reinforcements subjected to in-plane cyclic loading

Reinforced concrete (RC) shear walls are primarily designed to resist lateral actions in buildings, in addition to carrying the vertical loads from above. Recent changes in the Australian concrete standard (AS 3600) enforces RC walls to have double layers of reinforcement in the horizontal and vertical directions to be considered as ductile walls, whereas RC walls with centrally placed single layered reinforcement are regarded as non-ductile walls. The in-plane behaviour of these RC shear walls under both in-plane lateral and vertical loads is complex as many parameters influence their lateral strength and deformity. To extend the knowledge on the performance of RC walls with single and double layered reinforcement, experimental testing followed by an in-depth data analysis was carried out in this study. The experimental study involved testing of two RC walls with the same percentage of reinforcement arranged either in single or in double layers under in-plane cyclic shear loading. The aim of the experimental testing was to investigate the reinforcement detailing effect between a single-layer and a double-layer configuration, while keeping other key structural parameters such as reinforcement ratio, concrete compressive strength, level of axial load, aspect ratio, and slenderness ratio constant. Experimental results revealed that the double layered RC wall possessed higher in-plane strength (by ∼30%) and displacement ductility (by ∼9.7%) than the single layered RC wall. To validate these findings, a database of the single- and double-layered RC walls using results from previous experimental studies was developed to compare the in-plane load capacities of single and double layered RC walls. Existing design provisions from the standards (AS 3600 and ACI 318–19) were employed to predict the in-plane load capacities of the single and double layered RC walls and compared with the experimental results of the database.