Compressive Failure Research Articles

Phenomenological failure criteria analysis of a composite bolted joint under multi-axial loading using the finite element method

Carbon Fiber Reinforced Polymer Composites (CFRP) are commonly used in various sectors due to their excellent properties. However, they present complex failure modes, particularly in bolted joints, which are widely used in the aeronautical industry due to their ease of assembly and disassembly. Phenomenological failure criteria can be used to evaluate failure modes analytically and reduce the number of experimental tests. It is important to determine the criterion that best reflects reality. The Hashin, Puck, and LaRC04 failure criteria were evaluated using a finite element method software - FEMAP 2021.2 educational version - through simulation. Numerical simulations were conducted on a 2D model of a carbon/epoxy composite bolted joint under multiaxial loads, following ASTM D5661 dimensions. The failure criteria were compared to determine the most appropriate one for this type of component. Among the evaluated criteria, the Hashin criterion showed an intermediate level, while the Puck criterion was the most conservative and the LaRC04 criterion was the least conservative. It is recommended to use the Hashin criterion for general analyses. For analyses that require a detailed examination of compression failure modes, it is recommended to use the LaRC04 criterion. The Puck criterion is suggested for more conservative analyses.

Compressive strength and compressive failure mechanism of high-modulus carbon fibers from polyacrylonitrile and mesophase pitch

Compressive strength and compressive failure mechanism of high-modulus carbon fibers from polyacrylonitrile and mesophase pitch

Surgical Treatment of the Bony Mallet Injuries with Augmented Extension Block Technique: Clinical Outcomes of a New Modification

Surgical Treatment of The Bony Mallet Deformity with Augmented Extension Block Technique: Clinical Outcomes of a New Modification Introduction: Mallet finger deformity is a common pathology and the ‘Extension Block Technique’, is one of the most popular surgical techniques for the treatment of this condition. However, several complications may occur with this method such as fixation failure, compression failure of the dorsal part and loss of reduction. In the current study, it is aimed to report the result of our modification which is augmented extension block technique. Materials & Method: The medical records of patients, who were operated with the diagnosis of bony mallet finger between 2015 and 2021, were evaluated retrospectively. Demographic data, mechanism of trauma, duration of operation, time from injury to surgery, follow-up period, implant removal time, and postoperative complications were collected from hospital records. Patients aged between 18 - 65 years who had been operated with augmented extension block technique with a minimum follow-up period of 6 months were included in the study. A total of 10 patients who met these criteria constituted the study group. Radiological evaluation of the cases was performed with anteroposterior and lateral radiographs. Range of motion and presence of pain were questioned and these data were evaluated according to Crawford criteria. Results: The mean age of the all patients was 40.2 ± 10.9 (range, 24-56) years. The mean follow-up period was 39.6 ± 26.7 (range, 13-76) months. Complete union was achieved in all patients on the final follow-up radiographs. According to Crawford evaluation criteria, the results were ‘excellent’ in six of the patients and ‘good’ in four of them. There were no patients with loss of flexion however, 5° extension loss was observed in four of the subjects. Discussion: This study demonstrates that the augmented extension block technique is a suitable option for the surgical treatment of bony mallet cases with lower complication rate and successful functional results. This modification can be considered as an alternative option for traditional extension block technique which avoids some related complications as postoperative reduction loss, rotational instability and extension loss. Keywords: Mallet finger, Bony mallet, Extension Block

Biaxial compression failure of brittle foams: A transfer learning-based strategy

The work describes a numerical procedure to study biaxial compression failure in brittle foams. The foam is modelled as 3D interpenetrating structure of spherical pores with pore size distribution identical to a real ceramic foam studied by micro-computed tomography scans. Multiple realizations of artificial foam microstructures are generated through a novel microstructure reconstruction algorithm for a given value of porosity and pore size distribution. A boundary value problem is solved for each microstructure realization to determine effective compression stress-strain behavior through finite element simulations. This work focusses on biaxial compression failure in which a strain-based loading is applied along two orthogonal directions on a 3D model. For different loading conditions, damage initiation and propagation mechanisms are studied in multiple microstructure realizations. The study of number of damaged regions as the loading is increased reveals interesting mechanisms of macroscopic fracture. Lastly, a neural network based surrogate model is developed that predicts the effective compression stress-strain behavior for different loading conditions. It is shown that the neural network-based prediction for a given size of foam volume element is improved if it is informed by a neural network of a smaller sized volume element. Since the computational expense for generating data on a smaller sized volume element is much lesser, the overall accuracy of the model is considerably improved at minimum increase in computational expense.

Delamination Behavior of Dyneema Composite Laminate due to High Velocity Impact using LSDYNA

Failure of composite not only includes tensile or compression failure of fiber matrix, but also the delamination between plies. The current study investigates a methodology for the Ply-Delamination of Dyneema material due Ballistics impact using LSDYNA. A new methodology was implemented in order to effectively capture the ply delamination and the damage caused due to the impact for different velocities. Numerical results obtained were correlated with previous existing simulation results.

Characteristic stress and strain precursor information for fine-grained granite during failure process under triaxial loading and unloading conditions

The unloading effect by excavation may cause irreversible and severe damage to the surrounding rock masses in underground engineering. In this paper, both conventional triaxial compression (CTC) tests and triaxial unloading confining pressure (TUCP) tests were conducted on fine-grained granite to study its triaxial compression failure processes due to unloading. Based on the crack volumetric strain (CVS) method, the crack axial strain (CAS) method and crack radial area strain (CRAS) method were proposed to identify the failure precursor information (including stress thresholds and axial strain at the initiation point of crack connectivity stage) during the rock failure processes. The results of the CTC tests show that the stable crack development stress σsd, unstable crack development stress σusd, and crack connectivity stress σct identified by the CAS method are 6%, 74%–84%, and 86%–97% of the peak stress, respectively. For the TUCP cases, as the confining pressure increases, the stress thresholds, axial pressure at failure and axial strain at the start of the crack connectivity stage increase, while the time ratio of the crack connectivity stage to the entire unloading stage decreases. This indicates that fine-grained granite is prone to generate more cracks and leads to fail suddenly under high confining pressure. Furthermore, this new method demonstrates that the point at which the derivative of the radial crack area strain transitions from stable to a sudden increase or decrease is defined as the precursor point of rock failure. The results of axial strain at the starting point of the crack connectivity stage are very close to those predicted by the AE method, with β1 no more than 11%.

Characterizing compressive failure mechanisms and their transitions in woven composites under on and off-axis loading

The compressive failure of fiber-reinforced composites is complex, occurring via multiple mechanisms depending on the loading angle with the fiber directions. This work is aimed at the detailed characterization and understanding of this dependence in a 2 × 2 epoxy/carbon twill woven composite. Reported are the results of a variety of on-axis and off-axis compressive tests with loading angles ranging from 0°to 45°, carried out as per ASTM standards. The tests show that for angles from 0°to 10°, no appreciable change in compressive strength occurs. Failure in the load aligned tows is dominated by out of plane shear failure and out of plane fiber kinking. The behavior is very brittle, consisting of a sharp peak load immediately dropping to a non-zero residual stress plateau. Extensive micro-cracking in the transverse tow is also observed. Between 10°and 25°many transitions occur, including increased ductility, pre-peak non-linearity, increasing width of the out-of-plane fiber kink band, more gradual post-peak load decrease, and an increase in the residual stress. The lowest strength occurs at 45°where the behavior is completely ductile and failure occurs by in-plane fiber kink band formation. A correlation between the in-plane shear stress and kink band width appears to exist. The maximum stress based strength envelope theory captures this loading angle dependence of strength. The findings are crucial for designing multi-directional woven composite laminates subjected to compressive loading, and for the validation of computational models.

Strain-dependent-deformation property of Gyeongju compacted bentonite buffer material for engineered barrier system

This study aims to investigate the strain-dependent-deformation property of Gyeongju bentonite buffer material. A series of unconfined compressive tests were performed with cylindrical specimens prepared at varying dry densities (ρd = 1.58 g/cm3 to 1.74 g/cm3) using cold isostatic pressing technique. It is found that as ρd increase, the unconfined compressive strength (qu), failure strain, and elastic modulus (E) of Gyeongju compacted bentonite (GCB) increases. Normalized elastic modulus (Esec/Emax) degradation curves of GCB specimens are fitted using Ramberg-Osgood model and the elastic threshold strain (εe,th) is determined through the fitted curves. The strain-dependency of E and Poisson's ratio (v) of GCB were observed. E and v were measured constant below εe,th of 0.14 %. Then, E decreases while v increases after exceeding the strain threshold. The Esec/Emax degradation curves of GCB in this study suggests wider linear range and higher linearity than those of sedimentary clay in previous study. On top of that, the influence of ρd is observed on Esec/Emax degradation curves of GCB, showing a slight increase in εe,th with increase in ρd. Furthermore, an empirical model of qu with ρd and a correlation model between qu and E are proposed for Gyeongju bentonite buffer materials.

Identifying the fracture characteristics that control deformation localization and catastrophic failure in fluid-saturated crystalline rocks in upper crustal conditions

Previous studies show that the total volume of fractures increases non-linearly during loading as rocks approach failure in triaxial compression at stress and temperature conditions representative of the upper crust. However, the factors that control the critical volume of fractures or the critical spatial organization of the fracture network that trigger macroscopic failure remain unclear. To identify the fracture characteristics that determine the timing of macroscopic failure and localization of the fracture networks, we analyze data from six X-ray tomography experiments on Westerly granite with varying confining stress, fluid pressure, and amounts of preexisting damage. We develop machine learning models to predict 1) the timing of failure, 2) the localization of the fracture networks as measured with the Gini coefficient of the fracture volume, and 3) the change in localization from one differential stress step to the next. When the models only have access to individual fracture characteristics, the fracture length produces the best predictions of the distance to failure. When the models have access to the fracture length and sets of other characteristics, the fracture volume, aperture, and distance between fractures produce the best predictions of the distance to failure. The characteristics that describe the time or loading in the experiment, the axial strain and differential stress, produce some of the best predictions of the Gini coefficient. The results are generally consistent among the different experiments, suggesting that the fracture characteristics that determine the timing of macroscopic failure, and the localization of the fracture network, are independent of the range of confining stress, fluid pressure, and amount of preexisting damage tested here. Our results are consistent with the idea that monitoring the spatial distribution of deformation and changes in the seismic wave properties indicative of fracture growth may improve forecasting efforts of failure in the crust.

Experimental study on eccentric compressive behavior of precast concrete double-faced superposed shear walls

With the growing application of prefabricated building structural systems, precast concrete double-faced superposed shear wall (PCDSSW) structures have gained increasing popularity in multi-story and high-rise buildings. However, limited research on the eccentric compressive performance of PCDSSWs could lead to severe consequences. To address this issue, this study conducted eccentric load tests on seven full-scale PCDSSW specimens with steel truss connectors and one full-scale cast-in-place reference specimen. The influence of various design parameters, including truss web diameter, trusses layout, connection locations and methods between steel trusses and distribution reinforcement on the eccentric compressive performance of PCDSSWs was analyzed and discussed. The results revealed that both cast-in-place and PCDSSW specimens exhibited similar failure modes characterized by large eccentric compression failure. PCDSSW specimens showed no noticeable laminated interface separation and can achieve the design objective of "comparable performance to cast-in-place". Moreover, the diameter of truss web reinforcement and the layout of steel trusses had minimal impact on the eccentric compression performance of PCDSSW. While employing welded connections could boost the load-bearing capacity and cracking stiffness of PCDSSW, it also led to a marginally faster stiffness degradation rate and reduced deformation capacity. Additionally, the existing design standards yield conservative predictions for the load-bearing capacity of PCDSSWs. Furthermore, the model proposed by GB 50010–2010 is advocated due to its reliability and accuracy.

Failure behavior of steel dual-angle with cruciform welding filler plates under compression

This paper focuses on the failure behavior of steel dual-angle with cruciform welding filler plates (DA-CWP) under compression. A total of three DA-CWP specimens were fabricated and tested under axial compression, where different slenderness ratios (i.e., 45, 60, 75) were considered for comparison. The failure performance was experimentally investigated from different perspectives, such as failure mode, ultimate capacity and strain development. Subsequently, numerical simulation was performed to further reveal the effect of slenderness ratio and filler plate type on the failure behavior of DA-CWP. Finally, A theoretical method to distinguish the compressive failure mode of DA-CWP was proposed, and the bending-torsion transition slenderness ratio calculated by theoretical method was compared with the one from simulation for verification. The results demonstrate that the failure mode of DA-CWP changes from torsion to bending as the slenderness ratio increases, gradually decreasing its ultimate capacity. Due to the lower torsion stiffness of steel dual-angle with alternate plates (DA-AP), the torsion instability is more prone to occur for DA-AP, resulting in larger deformations of DA-AP compared to DA-CWP under identical compression. The theoretical method proposed in this study provides a good prediction for the bending-torsion transition slenderness ratio of DA-CWP under axial compression, which can provide reference for ultimate capacity design.

Cyclic shear loading test for grout-sleeve joints in precast concrete shear wall structure

The reinforcement sleeve splicing technique has been utilized extensively in precast concrete shear wall structures, as it allows for achieving similar lateral capacity and deformation ability with cast-in-place (CIP) walls. However, investigation on shear behavior of the horizontal joint using this vertical connection is limited. In this study, six specimens of grout-sleeve (GS) joints designed for precast shear wall structures with single-row distributed reinforcements were subjected to cyclic loading tests under pure shear conditions, accompanied by three companion concrete-to-concrete (CC) joint specimens. The study investigated the influence of interfacial reinforcement ratio and surface roughness on the seismic performance of GS joints with different design details, aiming to understand their shear failure mechanism. The joint behavior under cyclic shear loading, including transverse dilation, strain development, and energy dissipation, was analyzed. Experimental results indicated that all specimens exhibited a significant pinching effect and strength degradation in hysteretic curves. Two types of shear failure, sliding failure along the grout-concrete interface with minimal wall cracking and diagonal compression failure with extensive concrete crushing above the grouted layer, are observed due to the roughness of the grout-concrete interface. This roughness also affects the curvature profile of interfacial reinforcement. A larger interfacial reinforcement ratio or a roughened interface can significantly increase the shear strength of the horizontal joints. However, although the GS joint and CC joint have similar failure modes, the variation in cracking patterns resulted in a reduction of up to 10.6 % in shear strength for the grout-sleeve joint. Nonetheless, it exhibited relatively ductile shear behavior compared to the concrete-to-concrete joint. A comparison of shear strength evaluation between five existing codes shows that Eurocode 2 gives the closest result to the test values.

Investigation on damage behavior of composite T-shaped stiffened panels under compression after multi-point impact considering impact positions

Considering the randomness and non-uniqueness of the impact damage distribution of composite structures, both experimental and numerical simulation methods are employed to systematically explore the multi-point impact damage and compression-after-impact damage behavior of composite T-shaped stiffened panels under three types of impact positions. Non-destructive testing, and numerical simulation methods are used to examine the morphology of multi-point impact damage. The compression failure process of the impacted specimens and the intact specimens (reference group) is investigated by the electrometric method. In addition, the impact failure mechanism and compression failure mechanism is further studied by combining with the numerical simulation method. The results demonstrate that impact position B (the edge of each stiffener flange), the type of impact damage is more complex, in addition to fiber/matrix damage, it contains skin/stiffener debonding damage/layer fracture damage. Especially layer fracture damage, which significantly affects the compression damage behavior of structures.

Analysis of the mechanical behavior of bolted joints with slotted-in steel plate considering the move path of rotation center for single-layer timber reticulated shell

The mechanical behavior of the bolted joints with slotted-in steel plate plays an important role in maintaining the stability of single-layer timber reticulated shell, yet methods to estimate the mechanical behavior of the bolted joints still remains to be improved. Assuming that the ductile failure of the bolted joints and the compressive failure of the glulam beam end occurred, the move path of the rotation center was obtained through theoretical derivation and used to determine the ultimate moment and rotational stiffness of the bolted joints. The equations for calculating the ultimate moment of the bolted joints were derived based on the European Yield Modes, t. Moreover, employing the beam on elastic foundation theory, a simplified equation of slipping stiffness was obtained and used to calculate the rotational stiffness. Experimental investigations on bolted joints for single-layer timber reticulated shell were conducted to verify the accuracy of the proposed theoretical methods. The results showed the rotational stiffness and ultimate moment obtained from theoretical calculation were consistent with the results of experimental tests. Furthermore, by calculating the move path of the rotation center, it was found that the rotation center started from the geometrical center of bolts at earlier loading stage and moved towards the compressive region of the glulam beam end with the increase of the external force. And the moment-rotation curves predicted by the linear model was in good agreement with the moment-rotation curves obtained from experimental tests, showing a convenient and reliable way to the design of bolted joints for single-layer timber reticulated shell.

Study on Mechanical Properties of Cement–Jute Fiber Modified Weak Expansive Soil

Sixteen groups of comprehensive tests were undertaken to examine the modifications in the mechanical characteristics of weak expansive soil resulting from the inclusion of a composite material comprising cement and jute fibers. The aim of the tests was to analyze the unconfined compressive strength and shear strength. The results reveal that (1) as the modified material content increased, the stress–strain curve of the modified soil progressively became steeper, with a more pronounced peak value. Under the same strain condition, the stress variation increased accordingly. After the stress reached its maximum, a sudden phenomenon of brittle axial compression failure occurred. (2) With the increase in cement content, the unconfined compressive strength and shear strength of the modified expansive soil gradually increased, reaching the highest shear strength when the cement content was 8%. With the increase in jute fiber content, the unconfined compressive strength and shear strength of modified expansive soil increased first and then decreased, reaching the highest value when the content was 0.5%. (3) The cohesion of modified expansive soil increased with the increase in cement content. When the cement content was 8%, the cohesion of the soil sample was as high as 298.29 kPa. The cohesion of modified expansive soil increased first and then decreased with the increase in fiber content. When the jute fiber content was 0.5%, the cohesion reached the maximum value. (4) The internal friction angle of the modified expansive soil increased with the increase in cement content. When the cement content was 8%, the internal friction angle of the soil sample increased by 2.64°. The cohesion of modified expansive soil increased first and then decreased with the increase in fiber content. When the jute fiber content was 0.5%, the internal friction angle reached the maximum value.

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.

Effect of hygrothermal aging on compression behavior of CFRP material with different layups

This study investigates the mechanical degradation mechanism and statistical analysis of residual compressive strength of three lay-up laminates under more than one-year seawater environment. Fick and Langmuir model were used to describe the moisture absorption process with a maximum moisture equilibrium content of 3.78% and various characterization methods were used to reveal the microstructural evolution of CFRP during aging. Experimental results demonstrate that the multiple fiber directions in the MD specimens provide additional moisture absorption channels, leading to a stronger wicking effect and a higher equilibrium moisture content. The layups can significantly affect the compression failure mode after long-term aging. The compressive strength of the cross-ply and multidirectional laminates decreased by 50% while that of unidirectional laminates decreased by 28%, and surface cracking is easily observed in the aged specimens. An empirical prediction model based on the Langmuir model and experimental data was proposed and verified by the data from the literature, with at least a 10% improvement in prediction accuracy. Meanwhile the three-parameter Weibull distribution was used to describe the residual compressive strength after hygrothermal aging and tested by Kolmogorov-Smirnov test. It is expected to provide insight for the application of CFRP in seawater environment.

X-ray computed tomography study of compressive failure in a notched unidirectional glass fiber-reinforced composites

An experimental study on the axial compressive failure of a notched unidirectional (UD) glass fiber-reinforced composites has been performed to better understand the failure mechanisms in three dimensions (3D). A sequence of failure initiation and propagation has been monitored based on X-ray computed tomography (CT) images of the sample during failure. The CT images have shown that fiber kinking failure is the main failure mechanism, and there are two different types of kink bands, classified as type 1 and type 2 by final geometric form. The type 1 kink band, which has an X shape, extends outward from the notch along the width direction before finally creating a shear type 2 kink band at a distance from the notch. The novelty of this work involves observing the nucleation and propagation of fiber kink bands in three-dimensional space, as well as defining and quantifying kink band variables.

Dynamic Compressive Properties and Failure Mechanism of the Laser Powder Bed Fusion of Submicro-LaB6 Reinforced Ti-Based Composites.

In this study, lanthanum hexaboride (LaB6) particle-reinforced titanium matrix composites (PRTMCs, TC4/LaB6) were successfully manufactured using the laser powder bed fusion (LPBF) process. Thereafter, the effect of the mass fraction of LaB6 on the microstructure and the dynamic compressive properties was investigated. The results show that the addition of LaB6 leads to significant grain refinement. Moreover, the general trend of grain size reveals a concave bend as the fraction increases from 0.2% to 1.0%. Furthermore, the texture intensity of prior β grains and α grains was found to be weakened in the composites. It was also observed that the TC4/LaB6 have higher quasi-static and dynamic compressive strengths but lower fracture strain when compared with the as-built TC4. The sample with 0.5 wt.% LaB6 was found to have the best strength-toughness synergy among the three groups of composites due to having the smallest grain size. Furthermore, the fracture mode of TC4/LaB6 was found to change from the fracture under the combined action of brittle and ductility to the cleavage fracture. This study was able to provide a theoretical basis for an in-depth understanding of the compressive properties of additive manufacturing of PRTMCs under high-speed loading conditions.

Characterization of Failure Behavior in Unidirectional Fiber-Reinforced Polymer via Off-Axis Compression on Small Block Specimens.

An experimental investigation was focused on the failure behavior of unidirectional fiber-reinforced polymers when subjected to combined longitudinal/transverse compression and in-plane shear due to off-axis loading. Block-shaped and end-loaded specimens, spanning ten different fiber orientations (0°, 5°, 10°, 15°, 20°, 30°, 45°, 60°, 75°, and 90° with respect to the loading direction), were loaded to ultimate failure using a dedicated fixture. Different failure modes, including longitudinal compression, in-plane shear, and transverse compression, were identified, along with distinctive characteristics of the corresponding failure envelopes. Four physically based failure theories-Hashin, Camanho, Puck, and LaRC05-were subjected to a comparative analysis. Criteria derived from the concept of the action plane consistently outperformed in describing matrix-dominated failures, providing both qualitative and quantitative predictions of failure stresses and fracture plane orientation. However, for fiber-dominated failures, these theories seem to fall short in providing satisfactory predictions, particularly in accurately describing the influence of shear on fiber compression failure. Although criteria based on fiber-kinking theory can reasonably explain the formation of kink bands, they tend to yield overly conservative results. Recalibrations and minor refinement based on experimental results were implemented, leading to an improved agreement. Finally, the constructive role of off-axis compression tests in characterizing the failure behavior of unidirectional composites is discussed.