Fracture Damage Research Articles

Influence of corrosion on seismic performance of steel beam-to-column connections

Steel structures are not only subjected to the threaten of single hazard (e.g., earthquake), but also suffers from the coupling environmental effect such as corrosion throughout the entire service life cycle. This study explores the seismic performance of steel beam-to-column connections after corrosion. Accelerated corrosion tests were conducted on a series of practical steel beam-to-column connections, and the seismic performances of the specimens before and after corrosion were compared. A modeling method of corroded steel members that considers distribution randomness of corrosion depth was proposed. Finally, the proposed method is applied to conduct time-dependent seismic performance prediction of corroded beam-to-column connections. The results show that corrosion mainly influences the buckling and post buckling behaviors of steel beam-to-column connections. Due to earlier appearance of local buckling, more evident stiffness degradation is observed for the corroded specimen. Corrosion also induces performance degradation of the panel zone. For the corroded specimen with cover plate, multiple small cracks initiate at the junction between the cover plate and beam flange, and fracture damage is more likely to happen for the beam-to-column connections after corrosion. Both yield and ultimate load-carrying capacities of the connections decrease linearly with the increase of accelerated corrosion time, and the load-carrying capacity deterioration rate of the cover plate strengthened connection is quicker than that of the un-strengthened connection. The initial stiffness approximately degrades linearly with the increase of corrosion time. Corrosion degree also influences the energy dissipation capability of the beam-to-column connections, especially after the occurrence of local buckling.

Damage prediction and improvement method based on cutting mode of circular empty hole

Based on the theory of empty hole effect of cutting blasting, the Hopkinson effect and Saint–Venant principle are integrated to establish a two-dimensional calculation model of dynamic stress evolution of the holes wall, and then the dynamic fracture mechanism and damage distribution mode of the rock mass in the cutting area under the action of longitudinal waves are predicted. The results of the calculation and numerical simulation are verified by experiments, and the results show that: The time-varying stress function of the circular cavity wall conforms to the periodic dynamic evolution of the trigonometric function, and the theoretical calculation is consistent with the simulation results. Through the calculation of the round holes cut model and the square empty hole cut model, the change of the shape of the holes in the cut area changes the failure form of the surrounding rock mass. The circular empty hole wall is affected by the stress wave to produce "interval ring" destruction, and the effect of the reflected stretch wave is inhibited. The large range of rock mass in the square empty hole wall produces tensile and shear failure, and the rock mass collapses inward under the influence of the second stage stress. Among them, the empty space utilization rate of the square empty hole model is about 8.5 times that of the circular holes model. Vibration monitoring in the center of the cutting area shows that the vibration effect of the circular empty hole is larger than that of the square empty hole, and the proportion of rock breaking energy is lower.

Static behavior of stiffened CFST KK joints of offshore wind turbines under antisymmetric loading

This study examines the static behavior of the critical joints of the new kind of offshore jacket foundations under antisymmetric loading by employing a combination of experiments, finite element analysis (FEA), and theoretical derivation. Three tests and 35 FEAs of stiffened concrete-filled steel tubular (CFST) KK joints are described. The introduction of a novel perfobond ring rib (PRB) as a stiffener, along with using a limiting fixture during loading to consider interactions among the four braces, are novelties of this research. Experiments compare the influence of stiffener rib forms (PRB and Perfobond Leister Ribs (PBL)) on the behavior of CFST KK joints, highlighting the superiority of PRB strengthening. However, the influence of the stiffener rib form on the stiffness of the CFST KK joints can be ignored. The properties of PRB-stiffened CFST KK joints are further investigated via validated FEA models, which introduce the modified Mohr-Coulomb (MMC) criterion to realize steel fracture damage. A parametric analysis is then undertaken to explore how variations in the joint's geometrical parameters, chord material strength, and thickness and quantity of the PRBs influence the punching shear capacity of PRB-stiffened CFST KK joints. Furthermore, a formula is presented for punching shear strength in PRB-stiffened CFST KK joints by employing the superposition method. Its predictions align well with both experimental and FEA results.

Fracture characteristics and damage evolution of manufactured sand-based ultra-high performance concrete using tensile testing and acoustic emission monitoring

To address the challenges posed by the excessive exploitation of natural river sand, manufactured sand (MS) was used as a substitute material for natural sand to produce manufactured sand-based ultra-high performance concrete (UHPMC). This study aims to investigate the effects of MS replacement ratio, stone powder content, steel fiber content, and steel fiber shape on the fracture characteristics and damage evolution of UHPMC under tensile load through tensile tests combined with acoustic emission (AE) technology. The research results indicated that the stress-strain behavior of UHPMC could be divided into low strain hardening, low strain softening, and high strain softening. The tensile strength and energy absorption of the UHPMC were less correlated with MS replacement ratio. The tensile strength showed a trend of first increasing and then decreasing with the increase of stone powder content, and UHPMC with a 4% stone powder content presented the better tensile strength. The tensile damage process of UHPMC was mainly concentrated in the range of tensile strain from 0.0002 to 0.0025. The microstructure analysis of the UHPMC matrix revealed that an optimal amount of stone powder enhances the bond property between MS and mortar, thereby improving tensile performance. AE monitoring indicated that AE amplitude and AE energy provide sensitive identification capabilities for classifying the elastic state, strain hardening, and strain softening stages of UHPMC. The findings of this study contribute to understanding the fracture characteristics and damage evolution of UHPMC, promoting the engineering application of MS in ultra-high-performance concrete.

Flexural Performance of Reinforced Concrete Beams Strengthened with a Novel High-Strength and High-Toughness Epoxy Mortar Thin Layer

The flexural performance of RC beams strengthened with a novel high-strength and high-toughness epoxy mortar thin layer was investigated through four-point flexural tests on two contrast beams and two strengthened beams. The effects of this strengthening method on the failure modes, crack distribution, load–deflection curves, and bearing capacity of the RC beams with two reinforcement ratios were studied. The experimental results revealed that the contrast beams exhibited the typical bending failure modes where the failure mode of the reinforced beam is the yielding of the tensile reinforcement of the original beam and then fracture damage of the new epoxy mortar-reinforced thin layer. No debonding phenomenon was observed between the reinforced thin layer and the original concrete, and no visible cracks appeared before the tensile failure occurred in the thin layer. The cracks in the reinforced beams developed slowly, increased in number, and decreased significantly in width and spacing. The stiffness of the strengthened beam increased significantly, while its deformation ductility coefficient noticeably decreased. Compared to the corresponding contrast beams, the cracking load for strengthened beams A1 and B1 increased by 14% and 23%, respectively; the yield load increased by 32% and 40%, respectively; and the peak load increased by 18% and 17%, respectively. Finally, a calculation method for the flexural bearing capacity of RC beams strengthened with the novel epoxy mortar thin layer based on the flat section assumption was proposed. The calculated values showed a good agreement with the experimental values (with errors at −11.73% and 4.14%, respectively), providing a valuable reference for further research and application related to this kind of reinforcement method.

Computational Investigation of the Mechanical Response of a Bioinspired Nacre-like Nanocomposite under Three-Point Bending

Natural biological nanocomposites, like nacre, demonstrate extraordinary fracture toughness, surpassing their base materials, attributed to their intricate staggered hierarchical architectures integrating hard and soft phases. The enhancement of toughness in these composites is often linked to the crack-deflection mechanism. Leveraging the core design principles that enhance durability, resilience, and robustness in organic materials, this paper describes the use of computational modeling and simulation to perform a three-point bending test on a 3D staggered nanocomposite intentionally crafted to mimic the detailed microstructure of nacre. We adopted a previously proposed interfacial zone model that conceptualizes the “relatively soft” layer as an interface between the “hard” mineral tablets and the microstructure’s interlayer spaces to examine how the microstructure and interface characteristics affect the mechanical responses and failure mechanisms. By comparing the model’s predictions with experimental data on natural nacre, the simulations unveil the mechanisms of tablet separation through adjacent layer sliding and crack deflection across interfacial zones. This study offers a robust numerical method for investigating the fracture toughening mechanisms and damage evolution and contributes to a deeper understanding of the complex interplays within biomimetic materials.

High Temperature Experiments and Properties of Carbon Polyimide Composites

The interlayer shear tests of AC741/M55JB carbon fiber reinforced composite at room temperature, 400℃, 600℃ and 800℃ were carried out.The longitudinal and transverse shear tests of AC741/CCF800 carbon fiber reinforced composite were carried out at room temperature, 400℃, 600℃ and 800℃ dry conditions, as well as the experiments to calculate material property parameters. The results showed that the main failure mode of the sample in the interlayer shear test was stratified damage, and the fracture of the upper surface material was not obvious.This is due to the different types of tests, the interlayer shear pattern is short and small, and it is not easy to occur the fracture damage of the material without stratification.In addition, with the increase of temperature, the interlaminar shear strength also decreased significantly.In crossbar shear test, the maximum in-plane shear stress, maximum in-plane shear strength and in-plane shear modulus of the material gradually decrease with the increase of temperature, thus changing the bearing property of the material.

Dynamic slip behavior and off-fault damage of tension-induced fractures constrained by different grain sizes in granite

The mineralogy and texture of granite have been found to have a pronounced effect on its mechanical behavior. However, the precise manner in which the texture of granite affects the shear behavior of fractures remains enigmatic. In this study, fine-grained granite (FG) and coarse-grained granite (CG) were used to create tensile fractures with surface roughness (i.e. joint roughness coefficient (JRC)) within the range of 5.48–8.34 and 12.68–16.5, respectively. The pre-fractured specimens were then subjected to direct shear tests under normal stresses of 1–30 MPa. The results reveal that shear strengths are smaller and stick-slip behaviors are more intense for FG fractures than for CG fractures, which is attributed to the different conditions of the shear surface constrained by the grain size. The smaller grain size in FG contributes to the smoother fracture surface and lower shear strength. The negative friction rate parameter a – b for both CG and FG fractures and the larger shear stiffness for FG than for CG fractures can account for the more intense stick-slip behaviors in FG fractures. The relative crack density for the post-shear CG fractures is greater than that of the FG fractures under the same normal stress, both of which decrease with the distance away from the shear surface following the power law. Moreover, the damage of CG fracture extends to a larger extent beneath the surface compared with the FG fracture. Our findings demonstrate that the grain size of the host rock exerts a significant influence on the fracture roughness, and thus should be incorporated into the assessment of fault slip behavior to better understand the role of mineralogy and texture in seismic activities.

Modeling of viscoelastic deformation and rate-dependent fracture damage in rat bone

Bone is a complex hierarchical structural material whose organ-level response is highly influenced by its constitutive behavior at the microstructural level, which can dictate the inelastic nonlinear deformation and fracture within the organ. In the current study, a combined experimental-computational approach was sought to first obtain the local constitutive properties. Later, a multiscale modeling framework utilizing a novel rate-dependent nonlinear viscoelastic cohesive zone (NVCZ) model was used to explore the fracture behavior at the microstructure of the bone and its influence on the global scale (organ-level) response. Toward this end, nanoindentation testing was conducted within the cross-section of a rat femur bone specimen. An inverse optimization process was used to identify the isotropic linear viscoelastic (LVE) properties of cortical bone by integrating the test results with a finite element model simulation of the nanoindentation testing. Model results using different numbers of spring-dashpot units in the generalized Maxwell model showed that four spring-dashpot units are sufficient to capture the LVE behavior, while solely LVE constitutive relation is limited to fully characterize the rat femur. The LVE constitutive properties were then used along with the rate-dependent NVCZ fracture within the representative volume element (RVE), which was two-way coupled to the global scale bone. A parametric study was conducted by varying the fracture properties of the NVCZ model. The model demonstrated the capability and features to represent inelastic deformation and nonlinear fracture that are linked between length scales. This further implies that the inelastic fracture model and the two-way coupled modeling can elucidate the complex multiscale deformation and fracture of bone, while model validation and further advancements with test results remain a follow-up study and are currently in progress.

Experimental Study on Energy Release Mechanism and Crack Propagation Evolution of Sandstone under True Triaxial Loading

The instability of hard and brittle rock often leads to disastrous consequences in underground engineering. Under various surrounding rock pressure conditions, in situ stress induces corresponding deformation and damage to the floor post-mining. Therefore, it is crucial to examine the effects of mining under different confining pressures on rock disturbance, damage characteristics, and their distribution. Consequently, triaxial loading experiments under varying intermediate principal stress conditions were conducted on red sandstone specimens, using an acoustic emission monitoring system to track energy changes during rock damage and failure. This approach aids in studying crack generation, propagation, and fracture damage evolution. The results indicate that rock deformation results in axial compression and dilatancy, aligned with the direction of minimum and intermediate principal stresses. Ductility in rock failure becomes more pronounced with increased stress, primarily manifesting as shear failure. Internal cracks in the specimen lead to stress concentration and marked plastic deformation under compression, yet do not result in macroscopic surface cracks. The fracture angle θ of specimens post-failure generally exceeds 45° and varies with stress changes; at consistent burial depths, the angle of the sandstone failure surface increases with intermediate principal stress. This paper preliminarily establishes the informational linkage between rock failure and energy release, analyzing the rock samples over time and space. This research offers insights for analyzing and mitigating sudden rock instability.

Damage identification and fracture behavior of 2.5D SiCf/SiC composites under coupled stress states

Continuous fiber-reinforced silicon carbide composites have received significant attention due to their high-temperature mechanical stability. However, their widespread implementation has been hindered by intricate fracture mechanisms and limited toughness. This study presents a real-time approach for identifying damage type in 2.5D SiCf/SiC composites and highlights the significant impact of minor eccentric loading angle on the fracture behavior and mechanical properties using acoustic emission (AE). Even a slight degree of eccentric loading angle can significantly alter the fracture behaviors, leading to a significant increase in fracture toughness. The fracture damage evolution law of 2.5D SiCf/SiC under varying eccentric loading angles was investigated with the help of the AE damage identification, fracture morphology and finite element analysis. These findings provide valuable insights for multi-axis stress analysis of 2.5D high-performance composites.

Study on fracture failure behaviour of sapphire transparent window under ultra-high hydrostatic pressure

ABSTRACT Accurately predicting the fracture damage behaviour of light transmission windows is crucial in the design of deep-sea optoelectronic devices. This study proposes a simulation model based on the exponential cohesive zone law to predict the fracture failure of sapphire transparent windows (STW) under multi-dimensional load conditions. By utilising finite element simulation technology, the model accurately determine the fracture damage morphology and failure location of STW in different assembly structure schemes under a hydrostatic pressure of 127 MPa. These simulation results are then effectively validated through full sea depth pressure test experiments. Furthermore, by analyzing the simulation data, this study uncovers the internal mechanism of the fracture damage process of STW and presents a method to predict the fracture damage of STW. This research enhances the understanding of fracture behaviour in light transmission windows and offers valuable insights for the design and development of deep-sea optoelectronic devices.

Numerical modeling of fracture propagation of supercritical CO2 compound fracturing

The exploitation of shale gas is promising due to depletion of the conventional energy and intensification of the greenhouse effect. In this paper, we proposed a heat-fluid-solid coupling damage model of supercritical CO2 (SC-CO2) compound fracturing which is expected to be an efficient and environmentally friendly way to develop shale gas. The coupling model is solved by the finite element method, and the results are in good agreement with the analytical solutions and fracturing experiments. Based on this model, the fracture propagation characteristics at the two stages of compound fracturing are studied and the influence of pressurization rate, in situ stress, bedding angle, and other factors are considered. The results show that at the SC-CO2 fracturing stage, a lower pressurization rate is conducive to formation of the branches around main fractures, while a higher pressurization rate inhibits formation of the branches around main fractures and promotes formation of the main fractures. Both bedding and in situ stress play a dominant role in the fracture propagation. When the in situ stress ratio (σx/σy) is 1, the presence of bedding can reduce the initiation pressure and failure pressure. Nevertheless, it will cause the fracture to propagate along the bedding direction, reducing the fracture complexity. In rocks without bedding, hydraulic fracturing has the lengthening and widening effects for SC-CO2 induced fracture. In shale, fractures induced at the hydraulic fracturing stage are more likely to be dominated by in situ stresses and have a shorter reorientation radius. Therefore, fracture branches propagating along the maximum principal stress direction may be generated around the main fractures induced by SC-CO2 at the hydraulic fracturing stage. When the branches converge with the main fractures, fracture zones are easily formed, and thus the fracture complexity and damage area can be significantly increased. The results are instructive for the design and application of SC-CO2 compound fracturing.

Phase field modelling and simulation of damage occurring in human vertebra after screws fixation procedure

The present endeavour numerically exploits the use of a phase-field model to simulate and investigate fracture patterns, deformation mechanisms, damage, and mechanical responses in a human vertebra after the incision of pedicle screws under compressive regimes. Moreover, the proposed phase field framework can elucidate scenarios where different damage patterns, such as crack nucleation sites and crack trajectories, play a role after the spine fusion procedure, considering several simulated physiological movements of the vertebral body. Spatially heterogeneous elastic properties and phase field parameters have been computationally derived from bone density estimation. A convergence analysis has been conducted for the vertebra-screws model, considering several mesh refinements, which has demonstrated good agreement with the existing literature on this topic. Consequently, by assuming different angles for the insertion of the pedicle screws and taking into account a few vertebral motion loading regimes, a plethora of numerical results characterizing the damage occurring within the vertebral model has been derived. Overall, the phase field results confirm and enrich the current literature, shed light on the medical community, which will be useful in enhancing clinical interventions and reducing post-surgery bone failure and screw loosening. The proposed computational approach also investigates the effects in terms of fracture and mechanical behaviour of the vertebral-screws body within different metastatic lesions opening towards major life threatening scenarios.

Experimental study of fracture behaviors of granite at ultra-low temperatures

A good understanding of fracture characteristics of rocks at ultra-low temperatures is essential in selecting and designing cavernous liquefied natural gas (LNG) storage facilities. In this study, three-point bending tests on Notched Semi-Circular Bend (NSCB) granite specimens with various grain sizes and saturation levels were conducted at temperatures of 25°C, −90°C, −120°C, and −165°C, respectively. The test results show that the fracture characteristics of granite are significantly weakened at −165°C under saturated conditions. As the temperature goes low, granite’s peak strength, fracture toughness, and fracture energy increase under dry conditions. A robust linear relationship between the mode-I fracture toughness (KIC) and the fracture energy of granite at ultra-low temperatures is established in this study. This relationship demonstrates that specimens with higher fracture toughness require more energy to reach their fractures. In addition, the relationship, along with its test constraints, forms a theoretical basis that can be used to explain the fracture damage modes and the characteristics of granite at different temperatures. Furthermore, granite at ultra-low temperatures was also investigated from the view of pores with frozen water and the change of particle sizes. The data obtained from our experiments can serve as valuable parameters for simulating underground LNG storage. The research findings from this study provide a valuable foundation that can be used for designing and installing cavernous LNG storage tank facilities.

Multi-stages of Paleozoic deformation of the fault system in the Tazhong Uplift, Tarim Basin, NW China: Implications for hydrocarbon accumulation

The Tazhong Uplift is an important petroliferous secondary structure unit in the Tarim Basin and has undergone multiple structural deformation. In the current study, we use 3D and 2D seismic data to investigate the nature of the fault system in the Tazhong Uplift. The deformation of the Cambrian sedimentary rocks in the Tazhong Uplift is generally neglected but noted in this study. We found that the Lower–Middle Cambrian rocks are involved in thrust faults. NE-trending weak zones acted as accommodation faults formed at the connective positions and bends of the deep thrust faults. The Middle Cambrian compressional stress stemmed from the northeastern margin of the Tarim Block, pointed SW, and caused the uprising of the Tabei Uplift. The second deformation occurred in the Late Ordovician. In this instance, the compressional stress stemmed from the SW direction of the Tazhong Uplift, which originated from the amalgamation of the Western Kunlun Terrane and Tarim Block. The main strike–slip fault surfaces and subordinate faults developed along the weak zones generated in the Middle Cambrian. The collision that occurred in the southeast part of the Tarim Block in the Middle Silurian to Middle Devonian resulted in the third deformation. The representative structures that occurred during this compressive deformation were the intensive NEE-trending thrust faults in the southeast of the Tazhong Uplift. The three stages of deformation played different and important roles in hydrocarbon accumulation. These strike–slip faults holding the high-productivity hydrocarbon wells generally experienced early-stage Cambrian deformation, had wide fracture damage zones in the Ordovician carbonate rock strata, and had weak en echelon faults in the Silurian to Middle Devonian clastic rocks.

Experimental characterization on fracture behavior of UHPMC under small-scale sample tensile testing: Acoustic emission monitoring and digital image correlation

Manufactured sand (MS) was used to partially replace the traditional quartz sand (QS) to prepare a novel ultra-high-performance manufactured sand concrete (UHPMC). To better understand the fracture damage mechanism of UHPMC, small-scale sample tensile tests were conducted to investigate the tensile behavior of three types of UHPMC (low strain hardening, low strain softening and high strain softening). Acoustic emission (AE) and digital image correlation (DIC) are employed simultaneously to monitor and assess the damage characteristics of UHPMC. The results indicate that the classical AE characteristic parameters (ringing counts, duration and b-value) provide a satisfactory result in identifying the feature stages of low strain hardening and high strain softening. Based on the Gaussian mixture model (GMM) and support vector machine (SVM), an automatic probability classification algorithm has been developed that achieves the quantitative categorization of three UHPMC cracking types (shear or tensile cracks). Among them, tensile damage is dominant during the entire loading process, whereas shear damage, including aggregate dislocation and fiber debonding and pullout, accumulates during the hardening and softening stages. DIC visualization and AE source localization complement each other in identifying crack distribution, contributing to further revealing the tensile damage mechanism of UHPMC. The results obtained in this study can provide data and theoretical support for fracture damage characterization and health monitoring of ultra-high-performance concrete materials under tensile conditions.

Study of stress field induced by natural fracture and its influence on hydraulic fracture propagation

The change of fracture propagation direction caused by stress interference between fractures is one of the main reasons that affect shale gas productivity. Natural fractures will be damaged by the induced stress, and the induced stress field produced by natural fracture damage will in turn affect the propagation of hydraulic fractures. Previous studies usually ignored the impact of stress field variation caused by natural fracture damage, leading to inaccurate fracture propagation simulation results. A new model for simulating hydraulic fracturing-induced stress field is established with consideration of the influence of natural fracture damage. Then, the natural fracture-induced stress is analyzed in open and closed fracture states. Through superposition of stress fields of natural fractures and hydraulic fractures, the interaction among open and closed natural fractures, reservoir and hydraulic fracture, and the corresponding fracture property evolution are studied. The results demonstrate that induced stress is not affected by elastic modulus and Poisson's ratio of the rock. The induced stress difference at the fracture tip is proportional to the net pressure and the length of hydraulic fractures. The results provide guidance for the optimal design of fracturing. When the deflection angle of hydraulic fracture is less than 90°, the maximum induced stress difference at the fracture tip decreases with the reduction in the deflection angle. When the deflection angle of hydraulic fracture is smaller than 90° or the deflection angle of natural fracture is smaller than 45°, the steering of hydraulic fracture is less hindered, which is beneficial to the formation of complex fracture network.

Study on compressive performances of carbon nanotube film‐protected composite laminates after lightning strike

AbstractCompressive performances of composite structures can be significantly decreased due to the lightning strike damage, so the structures with lightning frighten must be considered lightning protection design. In this study, compressive experiments after lightning strikes were conducted on non‐protected, 12‐layer interlaminar carbon nanotube film (CNF) protected, and traditional surface silver coating (TSSC)‐protected composite laminates. A numerical analysis procedure was established, incorporating a lightning strike ablation damage simulation (LSADS) module and compressive residual strength calculation (CRSC) module. The procedure's effectiveness was verified by the experiment results. Based on this procedure, the compressive performances and the possible failure mechanism of laminates after lightning strikes were analyzed. The results show that the laminates with TSSC protection and 12‐layer interlaminar CNF protection can increase compressive residual strength compared with non‐protected laminates. The predominant compressive damages of the laminates after lightning strikes are fiber‐matrix shear damage and fiber fracture damage. Optimized one‐layer interlaminar CNF protection with a thickness of 0.36 mm can increase the laminate compressive strength but decrease the structural weight. This study offers a reference and basis for the lightning strike protection design of composite structures.Highlights CNF in lightning strike protection of composite structures. Compressive failure mechanism of composite laminates after lightning strikes. A numerical procedure to evaluate lightning damage and compressive performances. Design of interlaminar CNF protection.

Thermal shock effects on the microstructure and mechanical properties of iron-based composites reinforced by in-situ Fe2B/FeB ceramic phases

Recently, high-temperature composites reinforced with in-situ phases have been developed as a new class of composites for harsh environments. The behaviour of these composites under sudden heating and cooling conditions is greatly influenced by the type and fraction of components. The aim of this study is to investigate the microstructural properties and mechanical response of iron based composites after thermal shock cycling. The fabrication process involved in-situ powder metallurgy (IPM) sintering of Fe–B4C starting powders. The samples were subjected to thermal shock with a constant temperature differences (ΔT: 600 °C) and varied cycles (N: 1–50). Comparison of microstructural changes and mechanical behaviour before and after thermal shock has been carried out. The boron atoms released from the initial B4C generated diffusion zones in the matrix dominated by iron boride phases (Fe2B/FeB). An effective matrix-reinforcement interface has been created by in-situ powder metallurgy, where boride phases are almost homogeneously distributed in the iron matrix. While the hardness of the composites was significantly developed by the Fe2B/FeB phases, the addition of B4C resulted in a reduction in the coefficient of thermal expansion (CTE). The in-situ phases contributed in the minimisation of the coefficient mismatch by balancing the thermal expansion coefficients between iron and the initial B4C. Under the influence of thermal shock, microcracks and then macrocracks formed on the sample surfaces, increasing in width and depth with thermal cycles. This resulted in accelerated fracture damage under post-thermal loading. Both the impact and flexural strengths of the samples were significantly reduced as the number of thermal cycles increased. Although the 20% B4C reinforced composite provided maximum hardness, it showed poor resistance to thermal loading. The best results for mechanical loads were achieved by the 5% B4C reinforced composite, which showed no cracks even after 50 thermal cycling.