Uniaxial Compression Experiments Research Articles

A periodic micromechanical model for the rate- and temperature-dependent behavior of unidirectional carbon fiber-reinforced PVDF

The rate- and temperature-dependent mechanical behavior of unidirectional carbon fiber-reinforced polyvinylidene fluoride (PVDF) is investigated through uniaxial tension and compression experiments under various off-axis loading conditions. To improve the understanding of the behavior of the composite, a 3D micromechanical model is developed. Microscopic analyses are used to characterize the geometrical properties of the UD composite at the fiber length-scale. These properties are used to construct a periodic 3D representative volume element (RVE). In combination with periodic boundary conditions, uniaxial macroscopic deformation (in any possible direction) is applied to the RVE to accurately and efficiently model off-axis loading. The rate- and temperature-dependent behavior of the PVDF matrix is accurately described using an elasto-viscoplastic constitutive model. The finite element simulations of uniaxial tension and compression tests are compared to the experimental data and the micromechanical response is analyzed. The micromechanical model accurately describes the rate-dependent macroscopic behavior of unidirectional carbon fiber-reinforced PVDF for various off-axis loading directions at different temperatures. Analysis of the local matrix response in the RVE reveals the influence of the matrix on the macroscopic behavior of the composite.

A two-step modeling method for constructing 3D negative Poisson’s ratio materials with high specific strength based on common lattice structures

The traditional negative Poisson’s ratio (NPR) structure was basically designed based on concave or rotational mechanisms, resulting in relatively low specific strength and limiting its application. This paper proposed a two-step modeling method to establish a connection between the common lattice structures and NPR structures, which can obtain NPR structures with high specific strength. The models with different triaxial compression ratios were obtained through triaxial compression FE simulation to the selected initial configuration. Then, the mechanical properties of these models were studied through uniaxial compression FE simulation and experiments. In the research scope of this paper, the results demonstrate that the lattice structure can get NPR through the two-step modeling method when the Maxwell’s number is less than or equal to zero. The specific strength of the NPR structure obtained through the two-step modeling method was at most 1.5 times higher than that of the traditional 3D star-shaped NPR structure. Due to the high designability and excellent mechanical properties of lattice structures, this work provides a novel method for the manufacture of NPR structures with high specific strength.

Study on the size effect of rock burst tendency of red sandstone under uniaxial compression

The study of rock burst tendency of rock masses with different sizes plays a key role in the prevention of rock burst. Through theoretical analysis, it is proposed that uniaxial compressive strength and deformation modulus ratio are the key mechanical parameters affecting rock burst occurrence. In order to find out the size effect of uniaxial compressive strength and deformation modulus ratio, theoretical analysis and uniaxial compression experiment are carried out on rock samples with different heights, different cross-sectional areas and different volumes. The results show that the smaller the uniaxial compressive strength is, the larger the deformation modulus ratio is, and the more likely rock burst are to occur. On the contrary, rock burst is still not easy to generate. The uniaxial compressive strength of rock samples with different heights, different cross-sectional areas and different volumes increases with the increase of rock sample size. The deformation modulus ratio of rock samples with different heights and different volumes shows an upward trend on the whole, while that of rock samples with different cross-sectional areas shows a downward trend on the whole. The fracture forms of rock are analyzed using the energy conversion law in the process of deformation and failure for three kinds of rock with different shapes and sizes.

Influence of primary interface characteristics on mechanical properties and damage evolution of coal-rock combination

Indirect fracturing technology of coal seam roofs is a crucial method to enhance coalbed methane extraction efficiency in broken soft coal seams. The cracks formed significantly increase permeability by extending from the rock-coal interface into the coal seam. The structural features of the coal-rock interface are pivotal in determining the path of crack propagation, highlighting the importance of studying the mechanical properties and damage evolution in coal-rock combinations. Industrial CT, three-dimensional (3D) reconstruction, and 3D printing technology are utilized to create physical models with authentic interface structure features. Subsequently, coal-rock combination samples exhibiting smooth and original interface characteristics are produced through a layered pouring method. Uniaxial compression experiments are conducted on various interface feature combinations to examine the impact of primary interface structure characteristics on the mechanical properties and damage evolution of the combinations. Real-time monitoring is performed using acoustic emission (AE) equipment. The results show that the compressive strength of coal-rock combinations treated with glue and pouring is significantly higher than those treated with vaseline, while the axial strain shows an opposite trend. The presence of an interface constraint effect weakens the strength of the rock near the coal-rock interface, while enhancing the strength of the coal. The damage in coal-rock combinations initially occurs in the middle and lower parts of the coal, then progresses towards the interface and rock. Finally, a uniaxial compression model considering the interface constraint effect explains and theoretically demonstrates the phenomenon observed in the experiment, where more complex coal-rock interface structures result in higher compressive capacities of samples. It provides insights for further investigation into fracture trans-media expansion and permeability enhancement during the indirect fracturing of coal seam roofs.

Traction resistance analysis and cutting state recognition of shearer based on numerical simulation

Accurate identification of the shearer cutting state is essential for the intelligent control of the shearer. In addition to the coal-rock strata conditions, the operational parameters of the shearer also influence the shearer cutting state. To analyze the factors on the shearer cutting state and accurately identify its cutting state, the characteristics of shearer traction resistance are analyzed under various working conditions using discrete element numerical simulation. A method of the shearer cutting state recognition based on traction resistance and traction speed is proposed. Firstly, the mechanical properties of coal and rock are obtained through uniaxial compression experiments. The joint simulation model is developed to analyze the change in traction resistance under different traction speeds. The functional relationship between traction resistance and traction speed is obtained. Then, the influence of gangue thickness and position on traction resistance is analyzed. The time domain and frequency domain analysis of traction resistance is conducted to more accurately describe the characteristics of shearer traction resistance. Finally, simulation and experimental data are used to verify the reliability of the proposed method. The recognition accuracy of simulation and experimentation reaches 100 % and 97.1 %, respectively. This indicates that the proposed method can effectively recognize the shearer cutting state.

Traction resistance analysis and cutting state recognition of shearer based on numerical simulation

Accurate identification of the shearer cutting state is essential for the intelligent control of the shearer. In addition to the coal-rock strata conditions, the operational parameters of the shearer also influence the shearer cutting state. To analyze the factors on the shearer cutting state and accurately identify its cutting state, the characteristics of shearer traction resistance are analyzed under various working conditions using discrete element numerical simulation. A method of the shearer cutting state recognition based on traction resistance and traction speed is proposed. Firstly, the mechanical properties of coal and rock are obtained through uniaxial compression experiments. The joint simulation model is developed to analyze the change in traction resistance under different traction speeds. The functional relationship between traction resistance and traction speed is obtained. Then, the influence of gangue thickness and position on traction resistance is analyzed. The time domain and frequency domain analysis of traction resistance is conducted to more accurately describe the characteristics of shearer traction resistance. Finally, simulation and experimental data are used to verify the reliability of the proposed method. The recognition accuracy of simulation and experimentation reaches 100 % and 97.1 %, respectively. This indicates that the proposed method can effectively recognize the shearer cutting state.

Damage evolution, acoustic emission and electromagnetic radiation of rock under uniaxial cyclic loading

Uniaxial cyclic loading compression experiments are conducted with synchronous monitoring of acoustic emission (AE) and electromagnetic radiation (EMR). The AE and EMR characteristics of rocks during cyclic loading are analyzed. Subsequently, the Kaiser and Felicity effects of AE and EMR are disclosed. Moreover, the b-value and fractal dimension are calculated to explore the cracking mechanism of rock materials. These results show that the AE and EMR are active during the 1st and 2nd loading cycles, and sparse during the 3rd and 4th loading cycles where the AE and EMR are only generated when the stress exceeds the previous peak stress due to the Kaiser effect. In the 5th loading cycle, AE and EMR accelerate and peak at rock failure. The variation of EMR-based FR is consistent with that for AE under cyclic loading. Hence, the FR associated with EMR is also well correlated with stress memory. The AE and EMR-based FR is greater than 1 in the 2nd-4th loading cycles, and less than 1 in the 5th cycle, indicating that FR can be used to reflect the damage evolution of rocks. The b-value and fractal dimension increase in the 1st-4th loading cycles, and turn to decrease in the 5th loading cycle. This pattern serves as a precursor to identify the rock failure.

Rate-independent mechanism of deformation twinning in single crystal magnesium

The dynamics of {101¯2}〈101¯1〉 extension twins in a single crystal of pure magnesium are studied through uniaxial compression experiments coupled with direct optical imaging. The experiments covered a seven orders of magnitude strain rate, between 10−5−102s−1, covering all rates of engineering applications of magnesium and its alloys. Under uniaxial compression along a direction perpendicular to prismatic planes, only two variants of extension twins are activated, facilitating in-situ tracking of individual twin boundaries throughout the deformation process. Across the entire strain rate range, the twinning transformation evolves in a self-similar pattern of twin nucleation and thickening. Deformation fronts initiate at the edges of the sample and propagate toward the center, creating parallel twins with characteristic thicknesses and distances from each other. The velocity of the deformation fronts scales linearly with the imposed external strain rate and a nearly uniform resolved shear stress is measured over the entire strain rate range. We show that this unique process is attributed to the constant ratio between the nucleation rate and sideways velocity of individual twin boundaries, where both processes are proportional to the imposed strain rate. These findings indicate that, within the large strain rate range investigated in this study, the evolution mechanism of extension twinning is practically rate-independent.

An adaptive phase field approach to 3D internal crack growth in rocks

Modeling the 3D internal crack under compression entails complex fracture mechanics (mode I-II-III fracture), resulting in substantial computational costs and challenges in characterizing fracture morphology characterization for Phase Field Method (PFM) simulations. In the present paper, we developed a 3D adaptive crack propagation model integrated into the PFM to study the internal cracks in rocks. The proposed locally refined solution was implemented within the isogeometric analysis (IGA) framework, utilizing PHT-splines and employing the phase field variable as an error indicator to accurately capture non-smooth crack surfaces. The simulation begins with a coarser mesh, and the spatial discretization is adaptively refined in real-time as the computation progresses and the phase variable threshold is reached. By comparing our results with previous numerical tests, we validated the effectiveness of our model in simulating crack growth. Notably, a smaller length scale parameter led to a higher peak force in notched square plates under tension, and our adaptive PFM successfully reduced errors caused by length scale parameters. We further validated our model by comparing it with uniaxial compression experiments on 3D-printed resin samples with internal penny-shaped cracks, achieving good agreement with the experimental data. Using the 3D adaptive PFM, we predicted changes in crack morphology and fracturing mechanisms by varying the inclination angles of internal penny-shaped cracks. Our numerical results showed that as the inclination angle increased, wing cracks initiated closer to the end tips of the original crack, and their length decreased due to the wings wrapping effect. The corresponding fracturing mechanisms transition from mode I-III fracture (0°) to mode I-II-III fracture (30°, 45°, 60°), and eventually to mode I fracture (90°) as inclination angles increase. Comparing 2D and 3D models, we found that the growth of wing cracks in 3D was significantly influenced by the intermediate principal stress. We conclude that the extended 3D adaptive PFM-based model accurately predicted complex mechanical behavior and crack growth patterns in rock.

Multiscale Dynamic Diffusion Model for Ions in Micro- and Nano-Porous Structures of Fly Ash: Mineralization Experimental Research

The leaching concentration of alkaline ions plays a crucial role in the efficiency of the CO2 mineralization reaction in fly ash. The multi-scale structural characteristics of micro–nano pores in fly ash are the primary factors that control the leaching and diffusion rate of alkaline ions. However, the existing theoretical models do not account for the multi-scale pore structure, leading to challenges in accurately describing the ion diffusion in fly ash and predicting the reaction rate and efficiency of CO2 mineralization. To address this issue, a multi-scale dynamic diffusion model of ions was developed based on the micro–nano pore structure of fly ash. This model established the relationship between the ionic leaching rate and pore structure, as well as macroscopic changes over time, which were validated through experiments. Mineralization experiments with varying soaking times and uniaxial compression experiments on mineralized specimens were conducted to investigate the relationships among soaking time, ion leaching concentration, mineralization degree, and mechanical strength. The results elucidated the impact of alkaline ion concentration on the mineralization degree and mechanical strength of fly ash materials, offering theoretical insights to enhance mineralization and material properties.

The mechanical responses of SiC-coated carbon-bonded carbon fiber composites under quasi-static cyclic compressive loading

SiC-coated carbon-bonded carbon fiber composites (CBCFs), serving as novel thermal protection materials for hypersonic vehicles, are manufactured to investigate their mechanical properties concerning reusability. Comprehensive analyses are performed on their microstructures, including the fiber arrangement and the morphology of individual fibers and interconnecting bonds. The results demonstrate that SiC-coated CBCFs exhibit higher elastic moduli and strengths in both typical directions compared to bare CBCFs. To evaluate their durability in repeated use scenarios, a series of quasi-static uniaxial cyclic compressive experiments are conducted with emphasis on the variations of deformation recovery, load bearing and energy dissipation. The results indicate that SiC-coated CBCFs exhibit stable deformation recovery ability in the OP direction after the 25th cycle, with a decelerating decline in their load-bearing capacity observed over subsequent cycles. The energy loss coefficient initially decreases with increasing cycle number, and higher compression loads enlarge the amount of energy that is dissipated in the first cycle. These insights elucidate critical correlations between the mechanical properties of SiC-coated CBCFs and the number of compressive cycles, contributing to the optimization of their practical utilization in reusable scenarios.

Microfabrics impact on rock salt geomechanical diversity – an experimental investigation

Geomechanical studies of rock salt serve as the foundation for designing and ensuring the long-term stability of storage caverns. Research conducted in recent years has shown that rock salt exhibit highly variable mechanical parameters. Even macroscopically similar rock salt samples from the same formation have very different mechanical parameters in standard strength tests. In this paper, the effect of microfabrics on the mechanical behaviour of rock salt was studied using a uniaxial compression device with simultaneous observation under a microscope. The tests were carried out on rock salt samples, previously tested on standard uniaxial compression (UCS). Tested samples showed different strength values despite macroscopic similarity and similar anhydrite content. The tests revealed that the microfabrics, such as fluid inclusions and anhydrite crystals distributed along the halite grain boundaries, play a significant role in the strength of a rock salt sample. Four types of grain boundaries were recognized in both group of samples: (1) dominated by anhydrite crystals with a small number of fluid inclusions (FIs), (2) with FIs prevailing over anhydrite crystals, (3) only with FIs, and (4) without anhydrite crystals or FIs. The experimental uniaxial compression tests in microscale (mUCS) showed that the damage process is initiated by FIs activity at the halite grain boundaries and consists of three main stages. The samples dominated by anhydrite crystals at halite grain boundaries were characterised by the highest mUCS. Conversely, if FIs prevail at the grain boundaries the lowest mUCS values were registered. Therefore, anhydrite crystals located along halite grain boundaries influenced the mechanical behaviour and deformation process. On the contrary, anhydrite crystals dispersed within halite grains had no impact on failure and mechanical parameters. The experiment showed that apart from impurity content, the distribution of these impurities within halite grains should be examined during geomechanical evaluation of rock salt samples. Thus, the overall strength of rock salt samples determined in standard test results from the local variations of petrological features in micro- and macro scale.

Design and analysis of a conical origami tube (COT) composed of quadrilateral unit cells

Kresling origami is a topic that is constantly being researched, especially when it comes to the cylindrical mechanisms made up of special quadrilateral units. It’s also fascinating that the conical mechanisms based on the Kresling pattern are gaining more attention lately. However, designing conical mechanisms with stable behavior and solving the stress concentration in crease areas for practical engineering applications remains less researched. Therefore, this study considers quadrilateral unit cells as the research object, designs a conical origami tube (COT), and establishes a theoretical model with five variables to systematically investigate the COT. Based on this, the design domain related to the design variables is proposed, and the COT is analyzed in three cases. We further explored the influence of η (conical degree) on the COT. In addition, this study implements a cutting design on each crease vertex to reduce the impact of stress concentration on the nonlinear response through finite element shell models and uniaxial compression experiments. The findings of this study reveal that the setting of η and the crease-cutting design have a remarkable impact on the mechanical properties and stability behavior.

Experimental investigation into grain size effect on failure behavior and nonlinear time-varying acoustic emission series of granite

This study aims to investigate the grain size effect on mechanical properties and failure mechanisms of hard rock. Thus, a series of uniaxial compression experiments were carried out on granites with various grain sizes, and acoustic emission (AE) signals were synchronously collected in the experimental process for further nonlinear analysis. The results show that the four characteristic stresses of granite (σcc, σci, σcd, and σc) significantly decrease with the increase of grain size. The ratio of σcd/σc basically remains a constant of 0.8; the ratio of σci/σc increases gradually from 0.6 to about 0.7; the ratio of σcc/σc also shows a rising trend overall. With the increase of grain size, the AE energy level rises; the proportion of high-frequency tensile signals is reduced; the multi-fractal parameters Δα (non-uniformity of signals) and Δf (frequency difference between minimum and maximum signals) decrease. During the loading process, the time-varying value of Δα changes between 0.0 and 0.35, and that of Δf changes within the range from −0.2 to 0.5, showing a ‘rise-fall-rise-fall’ mode. The grain size effect on the influence of crack evolution is further discussed based on the nonlinear time-varying AE analysis. All these results reflect the mechanisms of grain size effect on granite. Large grain size weakens grain boundaries, facilitating shear slip along weak planes between crystal particles. In addition, the enhanced local stress concentration and initial defects in rock with large grain size could activate the crack coalescences of intra-crystalline cracks and weak boundary planes more easily in a relatively low-stress state.

Research on anisotropic characteristics and energy damage evolution mechanism of bedding coal under uniaxial compression

Bedding structures are commonly present in the underground coal mine pillar rock mass, posing a certain threat to its stability. In order to gain a deeper understanding of the damage, destruction, and energy conversion of bedding coal, uniaxial compression experiments were conducted on bedding coal samples. The research results reveal that the compressive strength of coal is highest when the bedding dip angle is 0° (28.74 MPa), followed by 30° and 90° (15.03 and 14.02 MPa), and lowest at 60° (10.03 MPa). The damage evolution curve of coal at a bedding dip angle of 60° exhibits an early sharp increase, indicating that macroscopic damage is easily induced along the bedding planes under this condition. As the bedding dip angle increases from 0° to 90°, the degree of damage to coal under energy drive exhibits a pattern of difficulty-ease-difficulty. When the bedding dip angle is 0°, the coal sample fractures steadily as cracks expand. At 30°, the failure process involves a gradual and steady expansion of cracks followed by an unstable extension. At 60° and 90°, the fractures result in sudden and unstable damage. Furthermore, this study explores the inherent mechanisms of anisotropy and the evolution models of damage in bedding coal.

Mesoscopic simulation of uniaxial compression fracture of concrete via the nonlocal macro–meso-scale consistent damage model

To capture the uniaxial compression fracture of concrete composite is still a great challenging problem. To this end, the newly proposed nonlocal macro–meso-scale consistent damage (NMMD) model is extended to simulate uniaxial compression fracture of concrete composites. In the NMMD model, a mesoscopic structure composed of material point pairs is attached to each material point. A decomposition scheme suitable for masonry-like materials is adopted to decompose the elongation quantity of point pairs. The topologic damage is defined as the weighted summation of mesoscopic damage in neighboring material point pairs driven by the decomposed elongation quantity. The physically-based energetic degradation function is employed to bridge the geometric discontinuity in solids and the energy dissipation, and thus the topologic damage is integrated into the framework of continuum damage mechanics. The Monte-Carlo method and two-phase random field model are employed to generate stochastic circular and irregular aggregates representing the meso structure of concrete, respectively. The interface transition zone is prescribed by reducing the critical value of interface point pairs. Numerical results indicate that both the crack patterns and stress–strain curves of the uniaxial compression experiments on concrete panels can be well captured by the proposed NMMD model without mesh size sensitivity. The influence of horizontal constraints on the top and bottom surfaces is investigated and shown to have an effect on the crack patterns, strength and deformation capability of the specimen. The necessity of decomposition is also illustrated.

Experimental Study on Strength Enhancement and Porosity Variation of 3D-Printed Gypsum Rocks: Insights on Vacuum Infiltration Post-Processing

AbstractThree-dimensional printing (3DP) technology has shown great potential in rock mechanics and mining engineering due to its ability to create complex and customized objects with high precision and accuracy. At present, an emerging research focus is improving the mechanical properties of 3D-printed samples, which originally has low strength and stiffness, to match those of natural rocks. The objective of this study was to investigate the effectiveness of different post-treatments on the strength enhancement of 3D-printed gypsum samples. To achieve this goal, 3D-printed gypsum samples were subjected to different post-treatments including dipped infiltration treatment and vacuum infiltration treatment using different infiltrants: water, saltwater, ColorBond, and StrengthMax. Subsequently, each sample was subjected to ultrasonic wave velocity testing and uniaxial compression experiments to characterize their mechanical properties, CT scans to investigate their microstructural characteristics. Additionally, X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) tests were conducted to explore the underlying reasons for changes in macroscopic strength. Finally, the physical characteristics and mechanical properties of untreated and post-processed 3D-printed gypsum samples were compared with natural rocks. The results showed that the strength of samples treated with water and saltwater was much lower than that of those treated with ColorBond and StrengthMax, while the porosity was the opposite. In water-treated and saltwater-treated samples, water or saltwater treatment can alter particle characteristics, but weak adhesive bonding and numerous pores result in low mechanical strength. Samples treated with Colorbond or StrengthMax exhibit improved strength due to effective gap filling and cohesive structure formation, with StrengthMax-treated samples showing higher strength despite having more pores than Colorbond-treated ones. Moreover, the physical and mechanical properties of these treated samples matched a wider range of natural rock types compared to the untreated samples.

Soil condition determines how crop residues affect soil compressive characteristics

AbstractExcessive soil compaction is a major cause of environmental problems and reduced agricultural soil productivity. Soil conditions can affect soil compressive characteristics. The application of organic materials reduces soil susceptibility to compaction. However, the direct effect of incorporated organic matter and interactions among soil conditions and incorporated organic materials on soil compressive characteristics are poorly understood. In this study, uniaxial compressive experiments were conducted to determine the compression curves of repacked brown earth from Northeast China. The effect of variable levels of incorporated corn straw (20, 40, 60, 80, and 100 g kg−1) and soil conditions (moisture content 0.14, 0.18, and 0.22 g g−1, and bulk density 1.20, 1.30, 1.45, and 1.60 g cm−3) on the compressive characteristics were investigated. The results showed that compressive characteristics were directly affected by soil conditions and corn straw‐derived organic matter (p < 0.01). Compressive characteristics were also significantly influenced by the interaction between soil conditions and corn straw‐derived organic matter (p < 0.01). By constructing a Entropy Weight Method (EWM) Technique for Order Preference by Similarity to Ideal Solution model (EWM‐TOPSIS), the conflicting indicators of soil resistance was comprehensively evaluated. The evaluation results indicated that moisture content at 0.14 g g−1, bulk density at 1.30 g cm−3 and corn straw‐derived organic matter at 34 g kg−1 was the optimal mode for soil resistance in our experiment. The results suggested that the interaction of soil conditions and incorporated organic matter should be considered to evaluate the susceptibility to compaction in the fields accurately.

Constitutive model of viscoelastic dynamic damage for the material of gas obturator in modular-charge howitzer

In order to investigate the mechanical response behavior of the gas obturator of the breech mechanism, made of polychloroprene rubber (PCR), uniaxial compression experiments were carried out by using a universal testing machine and a split Hopkinson pressure bar (SHPB), obtaining stress-strain responses at different temperatures and strain rates. The results revealed that, in comparison to other polymers, the gas obturator material exhibited inconspicuous strain softening and hardening effects; meanwhile, the mechanical response was more affected by the strain rate than by temperature. Subsequently, a succinct viscoelastic damage constitutive model was developed based on the ZWT model, including ten undetermined parameters, formulated with incorporating three parallel components to capture the viscoelastic response at high strain rate and further enhanced by integrating a three-parameter Weibull function to describe the damage. Compared to the ZWT model, the modified model could effectively describe the mechanical response behavior of the gas obturator material at high strain rates. This research laid a theoretical foundation for further investigation into the influence of chamber sealing issues on artillery firing.

Microscopic analysis of mechanical anisotropy and damage evolution of 3D printed rock-like samples under uniaxial compressive tests

Three-dimensional printing (3DP) offers valuable insight into the characterization of natural rocks and the verification of theoretical models due to its high reproducibility and accurate replication of complex defects such as cracks and pores. In this study, 3DP gypsum samples with different printing directions were subjected to a series of uniaxial compression tests with in situ micro-computed tomography (micro-CT) scanning to quantitatively investigate their mechanical anisotropic properties and damage evolution characteristics. Based on the two-dimensional (2D) CT images obtained at different scanning steps, a novel void ratio variable was derived using the mean value and variance of CT intensity. Additionally, a constitutive model was formulated incorporating the proposed damage variable, utilizing the void ratio variable. The crack evolution and crack morphology of 3DP gypsum samples were obtained and analyzed using the 3D models reconstructed from the CT images. The results indicate that 3DP gypsum samples exhibit mechanical anisotropic characteristics similar to those found in naturally sedimentary rocks. The mechanical anisotropy is attributed to the bedding planes formed between adjacent layers and pillar-like structures along the printing direction formed by CaSO4·2H2O crystals of needle-like morphology. The mean gray intensity of the voids has a positive linear relationship with the threshold value, while the CT variance and void ratio have concave and convex relationships, respectively. The constitutive model can effectively match the stress–strain curves obtained from uniaxial compression experiments. This study provides comprehensive explanations of the failure modes and anisotropic mechanisms of 3DP gypsum samples, which is important for characterizing and understanding the failure mechanism and microstructural evolution of 3DP rocks when modeling natural rock behavior.