Mechanical Damage Research Articles

Identification, Cloning, and Characterization of Two Acupuncture-Injury-Inducing Promoters in Rice

As an important global food crop, rice is damaged by a variety of piercing–sucking pests. Identifying a broad-spectrum promoter induced by the physical signal of sucking pests and applying it to transgenic breeding to mitigate the damage caused by different sucking pests will significantly improve the efficiency of our breeding. This study compared the transcriptome changes in two rice varieties under needle-wounding stress to investigate their differential responses to mechanical damage. The results showed that the insect-susceptible variety TN1 exhibited more differentially expressed genes (DEGs) and greater changes in expression levels after needle treatment, indicating a more active internal gene regulatory network. GO and KEGG enrichment analysis further revealed that TN1 not only exhibited changes in genes related to the extracellular environment, but also mobilized more genes associated with stress response and defense. By screening the differentially expressed genes, we identified two promoters (P1 and P2) with inducible expression characteristics in both the resistant and susceptible rice varieties. These promoters were able to effectively drive the expression of the insect resistance gene OsLecRK1* and enhance the resistance of transgenic plants against the brown planthopper. This study provides promoter resources for the development of insect-resistant transgenic crops.

Combined Effects of Heavy Metal and Simulated Herbivory on Leaf Trichome Density in Sunflowers

Trichomes play a key role in both heavy metal tolerance and herbivory defense, and both stressors have been shown to induce increased trichome density. However, the combined effect of these stressors on trichome density in general, and specifically on metal-hyperaccumulating plants, has yet to be examined. The aim of this study was to test the effect of cadmium availability and herbivory on leaf trichome density and herbivore deterrence in the metal hyperaccumulator Helianthus annuus. To test this, H. Annuus plants were grown in control pots or pots inoculated with 10 mg/kg cadmium and were subjected to either no herbivory or simulated herbivory using mechanical damage and foliar jasmonic acid application. Herbivore deterrence was tested in a feeding assay using Spodoptera littoralis caterpillars. Interestingly, while the trichome density of H. annuus increased by 79% or 53.5% under high cadmium availability or simulated herbivory, respectively, it decreased by 26% when the stressors were combined. Furthermore, regardless of cadmium availability, simulated herbivory induced a 40% increase in deterrence of S. littoralis. These findings suggest that the combination of metal availability and herbivory might present excessive stress to hyperaccumulators. Moreover, they suggest that the risk of metal bioaccumulation in phytoremediation can be reduced by simulated herbivory.

Review of Reservoir Damage Mechanisms Induced by Working Fluids and the Design Principles of Reservoir Protection Fluids: From Oil–Gas Reservoirs to Geothermal Reservoirs

Various working fluids are applied during geothermal reservoir development, and geothermal reservoir damage induced by contacts between working fluids and reservoir formations are inevitable. Reservoir damage mechanisms, including solid and colloidal plugging, fluid sensitivity, stress sensitivity, and water locking, provide guidance for designing reservoir protection working fluids. In this paper, based on the design principles of reservoir protection working fluids applied in oil–gas reservoirs, four design principles of reservoir protection working fluids are proposed to eliminate potential geothermal reservoir damage for geothermal reservoirs, containing solid-free, facilitated flowback, temporary plugging, and inhibition. Solid-free is achieved by replacing solids with polymers in working fluids. Surfactant and materials with low affinity towards rock surfaces are applied for the facilitated flowback of working fluids from reservoir formations. Temporary plugging is achieved by using temporary plugging materials, some of which are polymers that also apply to solid-free working fluids. Besides, some of the temporary plugging materials, such as surfactant, are applicable for both the facilitated flowback and inhibition of working fluids. The inhibition of working fluids include the inhibition of clay minerals, which can be attributed to clay mineral inhibitors or activity regulators in working fluids, as well as the inhibition of mineral precipitations. This review aims to provide insights for geothermal reservoir protection working fluids, contributing to achieving an efficient development of geothermal resources.

Damage and failure assessment of banana/ramie/epoxy composites using acoustic emission monitoring

In recent years, Composite materials that include natural fibers have played a significant role in aerospace, automotive industries, and other engineering applications. Due to its enhancing properties, the usage of composites has owing to an increase in day-to-day life. This research aims to develop a sustainable alternative material pronounced for environmental sustainability for surpassing synthetic fibers. Therefore, real-time monitoring and detection of the damage mechanisms in natural fiber composites are indispensable. In this regard, the acoustic emission (AE) technique lends itself to identifying the microscopic damage mechanisms in composite materials. Compression tests were performed in banana/ramie/epoxy composite specimens, and following consequences, the AE parameters (frequency, amplitude, counts, duration, energy rise time, etc.) were recorded. The novelty of this article is to detect the damage evolution and failure mechanisms of banana/ramie/epoxy composites under quasi-static compression with AE signal analysis for the first time. Findings showed that the stacking of hybrid reinforcing banana and ramie fiber improves the stress distribution, leading to enhanced load-carrying capacity (30.56 %), energy absorption (26.78 %), and stiffness (35.24 the compressive strength reached the maximum strength of the banana/ramie/epoxy composites%).This increase represents a substantial 30 % increase in AE energy absorption prior to failure, suggesting that the composite specimens experienced significant damage or extensive failure mechanisms Further, the AE parameters also showed that the AE energy under compression is relatively low and that frequency disperses between 70 and 150 kHz.

Omega-3 fatty acids protect cartilage from acute injurie by reducing the mechanical sensitivity of chondrocytes

Acute cartilage injuries, such as intra-articular fractures and blunt impacts, frequently result in chondrocyte death and extracellular matrix (ECM) degradation, significantly elevating the risk of post-traumatic osteoarthritis (PTOA). Despite advances in treatment, no effective therapies currently exist to fully cure PTOA or halt its progression. This study explores the protective effects of the dietary fatty acid eicosapentaenoic acid (EPA) on human primary chondrocytes (HPCs) and cartilage explants exposed to mechanical overload and blunt trauma. HPCs were isolated and subjected to mechanical stretching using BioFlex six-well culture plates, while cartilage explants were subjected to impact loading via a customized drop tower. EPA was incorporated into the culture medium, followed by assays to evaluate cell viability, calcium (Ca²⁺) influx, apoptosis, reactive oxygen species (ROS) levels, and collagen type II alpha (Col-2a) expression. EPA treatment markedly decreased chondrocyte mechanical sensitivity, as demonstrated by enhanced cell viability and reduced lactate dehydrogenase (LDH) release. Furthermore, EPA inhibited Piezo1 activation, leading to lower intracellular Ca²⁺ concentrations, decreased apoptosis, and diminished ROS levels. In cartilage explants, EPA improved chondrocyte viability, minimized structural damage, and sustained higher Col-2a expression compared to the blunt trauma group. These results indicate that EPA effectively shields chondrocytes and cartilage explants from mechanical overload-induced damage by inhibiting Piezo1 activation and mitigating Ca²⁺ influx, apoptosis, and oxidative stress. The findings suggest that EPA supplementation could offer a promising strategy for preventing PTOA progression following acute cartilage injuries. Further research is warranted to assess the clinical applications of EPA and confirm its efficacy in larger animal models and human trials.

Numerical and experimental crack-tip cohesive zone laws with physics-informed neural networks

The cohesive zone law represents the constitutive traction versus separation response along the crack-tip process zone of a material, which bridges the microscopic fracture process to the macroscopic failure behavior. Elucidating the exact functional form of the cohesive zone law is a challenging inverse problem since it can only be inferred indirectly from the far-field in experiments. Here, we construct the full functional form of the cohesive traction and separation relationship along the fracture process zone from far-field stresses and displacements using a physics-informed neural network (PINN), which is constrained to satisfy the Maxwell-Betti's reciprocal theorem with a reciprocity gap to account for the plastically deforming background material. Our numerical studies simulating crack growth under small-scale yielding, mode I loading, show that the PINN is robust in inversely extracting the cohesive traction and separation distributions across a wide range of simulated cohesive zone shapes, even for those with sharp transitions in the traction-separation relationships. Using the far-field elastic strain and residual elastic strain measurements associated with a fatigue crack for a ZK60 magnesium alloy specimen from synchrotron X-ray diffraction experiments, we reconstruct the cohesive traction-separation relationship and observe distinct regimes corresponding to transitions in the micromechanical damage mechanisms.

Damage constitutive model of RAC under triaxial compression based on weibull distribution function

Fly ash (FA) and ground blast furnace slag (GGBS) can be used to densify the pore structure of recycled aggregate concrete (RAC). However, there remains a lack of deep exploration into the effects of confining pressure and mineral admixtures on RAC's crack formation and damage analysis. This study thus focused on investigating the combined impact of the replacement rate of recycled coarse aggregate (RCA), FA, and GGBS contents on the damage mechanisms of RAC under varying stress conditions by microscopic tests and triaxial compression tests. Results identified that increasing confining pressures enhance the peak stress, peak strain, and elastic modulus of RAC, with shear cracks predominating under triaxial compression. Whereas higher the replacement rate of RCA reduced the mechanical performance of RAC, incorporating 20 % FA and 20 % GGBS can significantly enhance its strength and modulus. Electron microscopy (ESEM) images proved that the incorporation of FA and GGBS lead to a denser internal structure compared to that of RAC without mineral admixtures. The constructed damage constitutive model agreed well with experimental data of this study and literatures, showing slower increases in damage variables (D) under triaxial stress compared to uniaxial compression. Model parameters indicated that increasing confining pressure decreased parameter m and increased F0, resulting in flatter post-peak stress-strain curves, and RAC incorporated with 20 % FA and 20 % GGBS had smaller m value under different stress states. These findings provide valuable insights for applying mineral-admixed RAC in diverse engineering scenarios, offering a robust reference for optimizing RAC formulations with FA and GGBS in practical applications.

Bayesian Inference for the Calibration of Progressive Damage Model of Dovetail Specimens from Laminated Composite Fan Blade

Abstract Composite fan blades are the preferred alternative for the fan stage of most advanced high bypass ratio turbofan engines. The ability of the dovetail to safely bear this load is one of the key points of the multi-level “test pyramid” approach of compliance demonstration for special airworthiness regulation. Debonding between adjacent layers is the main damage mode of laminated composite fan blades. However, there is difficulty in measuring the as manufactured interlaminar mechanical properties used in finite element models. In this study, tensile loading was applied to simulate the interacting centrifugal force and capture mixed mode damage evolution. Structural responses and material damages were calibrated with measured tensile loads through Bayesian inversion. Posterior probability distributions of maximum interface tractions and contact stresses were solved using Markov chain Monte Carlo sampler. Results indicated the two bilinear cohesive material models had a capacity of predicting empirical means of longitudinal reaction forces as that in test considering additional discrepancy term (0.035 kN and 0.96 kN respectively), while they made an significant impact on the prediction of tensile load history especially when two delamination cracks initiated and propagated. Interface elements provided a higher matching quality in predicting loading history and capturing damage mechanism in association with in-plane progressive damage analysis. This calibrated parameter set could be functioned as benchmark in numerically determining the ultimate tensile load of dovetail elements and reducing the necessary number of physical tests at elemental length level.

Self-Healing and Shear-Stiffening Electrodes for Wearable Biopotential Sensing and Gesture Recognition.

The achievement of flexible skin electrodes for dynamic monitoring of biopotential is one of the challenging issues in flexible electronics due to the interference of large acceleration and heavy sweat that influence the stability of skin-electrode interfaces. This work presents materials and techniques to achieve self-healing and shear-stiffening electrodes and an associated flexible system that can be used for multichannel biopotential measurement on the skin. The electrode that is based on a composite of silver (Ag) flakes, Ag nanowires, and polyborosiloxane offers an electrical conductivity of 9.71 × 104 S/m and a rheological characteristic that ensures stable and fully conformal contact with skin and easy removal under different shear rates. The electrode can maintain its conductivity even after being stretched by more than 60% and becomes self-healed after mechanical damage. The combination of the electrodes with a screen-printed multichannel flexible sensor allows stable monitoring of both static and dynamic electromyography signals, leading to the acquisition of high-quality multilead biopotential signals that can be readily extracted to yield gesture recognition results with over 97.42% accuracy. The conductive self-healing materials and flexible sensors may be utilized in various daily biopotential sensing applications, allowing highly stable dynamic measurement to facilitate artificial intelligence-enabled health condition diagnosis and human-computer interface.

Low-grade systemic inflammation in patients with long COVID: The role of imbalance of endotoxin-releasing systems and vasoconstrictor markers

Background. Currently, the pathophysiological mechanisms of acute damage to organs and systems caused by coronavirus infection have been studied quite fully, but the mechanisms underlying the clinical manifestations of long COVID have not yet been accurately described. The mechanisms of persistence of a number of symptoms in patients who have had COVID-19 and the role of systemic inflammation and endotoxemia markers in it remain a understudied aspect and a promising direction for further studying.The aim of the study. To assess the markers of systemic inflammation, endotoxin-releasing systems, intestinal permeability and endothelial dysfunction in patients with long COVID at the stage of health resort treatment.Methods. The study included 32 patients who had recovered from coronavirus infection and were undergoing health resort treatment in the pulmonology department of the I.M. Sechenov Academic Research Institute for Physical Therapy, Medical Climatology and Rehabilitation. We also selected a control group (n = 20). All patients underwent peripheral blood analysis to detect the levels of markers of systemic inflammation, endotoxin-releasing systems, intestinal permeability, endothelial dysfunction and vasoconstrictor agents: C-reactive protein (CRP), lipopolysaccharide-binding protein (LPB), tissue-type plasminogen activator (tPA), zonulin, bactericidal/ permeability-increasing protein (BPI), vasopressors of angiotensin 2 and endothelin (EDN1).Results. Patients who had recovered from coronavirus infection had a statistically significant increase in the levels of CRP (3.4 [2.56; 4.0] mg/l), LBP (18.46 [14.0; 25.5] ng/ml), tPA (0.07 [0.02; 0.32] ng/ml), angiotensin 2 (133.3 [63.0; 503.7] pg/ml) and a decrease in the level of BPI (1576 [276; 3588] pg/ml) (p < 0.05).Conclusion. A statistically significant increase in markers of systemic inflammation, endotoxinemia, and vasoconstrictor agents in patients with long COVID indicates an imbalance in endotoxin-binding and endotoxin-releasing systems in patients who have had coronavirus infection. Further study of the described markers is necessary to improve approaches to long-term personalized therapy for this category of patients.

Foodborne iron overload induces oxidative stress and causes mitochondrial damage in the liver of grass carp (Ctenopharyngodon idellus)

Iron is essential to biological processes such as energy metabolism and oxygen transport. However, excessive iron can cause iron overload and ultimately result in tissue damage. To date, the damage mechanism of foodborne iron overload in aquatic animals is still unclear. This study used grass carp (Ctenopharyngodon idellas) as the research subject to establish a chronic iron overload model by feeding diets with different iron levels, and combined in vitro experiments to investigate the mechanisms of iron overload-induced damage. The growth performance and liver HE staining indicated that a high‑iron diet led to decreased growth in grass carp, accompanied by hepatic iron deposition. ELISA and qRT-PCR analysis data revealed that a high‑iron diet disrupted the antioxidant balance and modulated the expression of genes associated with iron metabolism. CCK-8 determination results revealed that treatment of L8824 cells with ferri ammonii citras (FAC) resulted in iron overload, led to disruption of iron metabolism and enhanced the intracellular production of reactive oxygen species (ROS), and caused lipid peroxidation. Furthermore, qRT-PCR analysis results showed that the treatment of L8824 cells with FAC resulted in a significant up-regulation of genes associated with antioxidant, apoptosis, and necrosis pathways, and increased the rate of apoptosis. In addition, fluorescence microscopy observation and mitochondrial DNA detection data showed that excess iron could increase the iron accumulation in mitochondria and the production of mtROS, reduce the mitochondrial membrane potential, and finally cause mitochondria damage. In conclusion, our research offers invaluable insights that iron overload leads to disrupted intracellular iron pool stability, causing mitochondrial damage and oxidative stress, eventually causing cell death.

Perspective in the Mechanisms for Repairing Sperm DNA Damage.

DNA damage in spermatozoa is a major cause of male infertility. It is also associated with adverse reproductive outcomes (including reduced fertilization rates, embryo quality and pregnancy rates, and higher rates of spontaneous miscarriage). The damage to sperm DNA occurs during the production and maturation of spermatozoa, as well as during their transit through the male reproductive tract. DNA damage repair typically occurs during spermatogenesis, oocytes after fertilization, and early embryonic development stages. The known mechanisms of sperm DNA repair mainly include nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), and double-strand break repair (DSBR). The most severe type of sperm DNA damage is double-strand break, and it will be repaired by DSBR, including homologous recombination (HR), classical non-homologous end joining (cNHEJ), alternative end joining (aEJ), and single-strand annealing (SSA). However, the precise mechanisms of DNA repair in spermatozoa remain incompletely understood. DNA repair-associated proteins are of great value in the repair of sperm DNA. Several repair-related proteins have been identified as playing critical roles in condensing chromatin, regulating transcription, repairing DNA damage, and regulating the cell cycle. It is noteworthy that XRCC4-like factor (XLF) and paralog of XRCC4 and XLF (PAXX) -mediated dimerization promote the processing of populated ends for cNHEJ repair, which suggests that XLF and PAXX have potential value in the mechanism of sperm DNA repair. This review summarizes the classic and potential repair mechanisms of sperm DNA damage, aiming to provide a perspective for further research on DNA damage repair mechanisms.

Comprehensive mechanical properties and damage mechanisms of a new type multiphase fibers braided/phenolic resin composites

The comprehensive thermodynamic properties of polymer composites play a critical role in determining their service, and internal microscopic damage will lead to severe consequences such as product deformation and cracking. This research presents the composition parameters and preparation process of a new type 2-dimension multiphase fibers braided layered phenolic resin (2D-MFRP) composites. The mechanical property test was conducted by setting the conditions of sampling angle θ, temperature load T, and tensile rate S, which the variation patterns of different characteristics were analyzed based on the specified parameters. The experimental results show that the mechanical properties exhibit high stability within 25 °C to 300 °C, and the mechanical properties sensitivity level of the corresponding parameter is T<S<θ. Additionally, the thermo-mechanical of 2D-MFRP composites were analyzed, which used the combining thermogravimetric methods and differential scanning calorimetry (DSC). The microstructure and damage were observed by scanning electron microscope (SEM), in which the 2D-MFRP composites woven fiber/bundles layered cracks and propagation micro-damage mechanism have been revealed under the influence of angle θ and temperature T. The above research content can provide valuable insights into the thermomechanical properties of a new type 2D-MFRP composites and structural products.

A practical multiscale analysis for nonlinear RC structures using a smart substructure replacement strategy

This paper presents a novel practical multiscale analysis (MSA) method for simulating local damages in large reinforced concrete (RC) structures during seismic events. Traditional techniques like the finite element (FE) method often struggle to balance computational costs with detailed simulation. The proposed method facilitates sequential local refinement from macroscopic to mesoscopic scales of RC structures, focusing strategically on critical areas prone to damage and cracking. Key features include: (1) 'Correction forces' enable integration and collaboration among models of different refinement levels, keeping models unchanged (i.e., without additions, deletions, or further refinement of elements), streamlining analysis and independent implementation across methods, scales, and platforms. (2) A smart replacement strategy ensures smooth transitions and prevents abrupt force changes between models at different refinement levels. (3) A ‘training process’ before performing the replacement and a semi-explicit method guarantee the accuracy and efficiency of the MSA method. (4) Parallel and distributed computing is seamlessly applied, significantly accelerating the analysis at each level. Implemented in the open-source software OpenSees, this method is illustrated through three examples that efficiently capture both the macroscopic mechanical responses and detailed local damage behaviors. This approach provides a valuable tool for the refined analysis of large-scale RC structures.

Towards multi-variable tsunami damage modeling for coastal roads: Insights from the application of explainable machine learning to the 2011 Great East Japan Event

The accurate assessment of tsunami-induced damage to coastal roads is crucial for effective disaster risk management. Traditional approaches, reliant on univariate fragility functions, often fail to capture the complex interplay of variables influencing road damage during tsunami events. This study addresses this limitation by employing machine learning techniques on an extensive dataset compiled after the 2011 Great East Japan tsunami. The dataset, enriched with additional explicative variables accounting for the hydraulic features of the event and the physical characteristics at roads’ location, enables a comprehensive analysis of road damage mechanisms. Results indicate that while inundation depth remains a significant predictor, factors such as wave approach angle, road orientation and potential overflow from inland watercourses also play critical roles.

Gene Editing with Artificial DNA Scissors.

Artificial metallo-nucleases (AMNs) are small molecule DNA cleavage agents, also known as DNA molecular scissors, and represent an important class of chemotherapeutic with high clinical potential. This review provides a primary level of exploration on the concepts key to this area including an introduction to DNA structure, function, recognition, along with damage and repair mechanisms. Building on this foundation, we describe hybrid molecules where AMNs are covalently attached to directing groups that provide molecular scissors with enhanced or sequence specific DNA damaging capabilities. As this research field continues to evolve, understanding the applications of AMNs along with synthetic conjugation strategies can provide the basis for future innovations, particularly for designing new artificial gene editing systems.

Mechanical properties and damage constitutive relationship of microwave irradiation of granite under uniaxial compression

Microwaves have great potential to increase the efficiency of hard rock breakage during mechanical excavation in engineering. This study conducted uniaxial compression tests on granite specimens after microwave irradiation at 4.85 kW. The results demonstrated a linear decrease in uniaxial compressive strength and elastic modulus correlating with increasing irradiation durations. Acoustic emission data indicated increased normalized crack closure stress and decreased normalized crack initiation and damage stress, suggesting complex crack propagation and evolution patterns under microwave influence. 3D Digital Image Correlation revealed that as heating time increased, the macrocrack leading to specimen failure shifted from being load-dominated to involving both load and microwave-induced thermal cracks. A simple four-parameter damage constitutive model for granite (a 1, r 1 , a 2, and r 2) effectively described the damage evolution under the coupling effect of microwave and uniaxial load. The model accurately characterized the complete stress–strain curves, including both microcrack compaction and post-peak stages, revealing that initial damage escalates with longer heating, though the progression rate decreases.

Novel integration of PSO-enhanced damage mechanics and finite element method for predicting medium–low-cycle fatigue life in perforated structures

In this research, we introduce an innovative approach that combines the Continuum Damage Mechanics-Finite Element Method (CDM-FEM) with the Particle Swarm Optimization (PSO)-based technique, to predict the Medium-Low-Cycle Fatigue (MLCF) life of perforated structures. First, fatigue tests are carried out on three center-perforated structures, aiming to assess their fatigue life under various strengthening conditions. These tests reveal significant variations in fatigue life, accompanied by an examination of crack initiation through the analysis of fatigue fracture surfaces. Second, an innovative fatigue life prediction methodology is applied to perforated structures, which not only forecasts the initiation of fatigue cracks but also traces the progression of damage within these structures. It leverages an elastoplastic constitutive model integrated with damage and a damage evolution model under cyclic loads. The accuracy of this approach is validated by comparison with test results, falling within the three times error band. Finally, we explore the impact of various strengthening techniques, including cross-sectional reinforcement and cold expansion, on the fatigue life and damage evolution of these structures. This is achieved through an in-depth comparative analysis of both experimental data and computational predictions, which provides valuable insights into the behavior of perforated structures under fatigue conditions in practical applications.

Analysis of the mechanical behavior of asphalt pavement under multiple coupling effects

To reveal the damage mechanism of asphalt pavement caused by the spatial rotation of the stress principal axis, and the influence range of excess pore water pressure on the pavement under the coupling action of multiple fields, the finite element software was used to build the three-dimensional highway asphalt pavement models. Under the consideration of gravity's impact on dynamic computation results, the study investigated the variation patterns of the direction cosines of the principal stress axes of asphalt structural pavement elements under the action of moving loads, as well as the distribution laws of excess pore water pressure. The results indicate that the influence of gravity on dynamic computation results increases gradually with the depth of the pavement, reaching an error of first principal stress of 40.1 % at the bottom of the lower layer. During the movement of loads, the pavement elements directly under the load undergo rotation of the principal stress axes in the xy, xz, and yz planes under different physical fields. With increasing pavement depth, the angle between the first principal stress and the z-axis primarily fluctuates between −90° to 0° and 90° to 180°. The cosine of the angle between the first principal stress and the x-axis and z-axis undergoes instantaneous positive and negative conversion, which can easily lead to transverse and longitudinal cracks on the road surface. The influence widths of excess pore water pressure along the longitudinal and transverse directions of the pavement increase with the pavement depth, with maximum widths of 5.426 m and 2.075 m, respectively. These findings offer new insights into the mechanisms behind the formation of transverse and longitudinal cracks on asphalt pavement and hold significant implications for the improvement of asphalt design methods.

EXPLORING THE EFFECTS OF STITCHING PROCESS ON THE MECHANICAL PROPERTIES OF THREE- DIMENSIONAL (3D) STITCHED UNIDIRECTIONAL COMPOSITES

The stitching process has obvious effects on the out- of- plane mechanical properties of composites such as impact damage mechanism or impact energy absorption. However, the effects on the in- plane mechanical properties of composites have been under discussion and need to be clarified. In the previous studies, tensile, shear and bending behaviors of 3D stitched biaxial woven carbon composite were investigated. The unidirectional carbon woven fabrics constitute the significant part of raw materials in the composite industry. For this reason, the research study was expanded to examine the in- plane mechanics of 3D stitched unidirectional carbon woven composites. In this study, the unstitched and 3D stitched unidirectional woven carbon composites were manufactured and tested under the shear, tensile and bending loads. While the stitching process improved the tensile and shear modulus of composite, it could not create the significant difference in the bending behavior. The highest module and maximum stress values were obtained in the tensile test. The bending and shear test results follow them, respectively. Moreover, it was proven that the fabric architecture of stitched composite layer has the substantial effect on the tensile properties of 3D stitched composite.