Carbon Fiber Prepreg Research Articles

Comparative applicability of strength of materials approach to laminated composites with glass and carbon fibre prepregs

Comparative applicability of strength of materials approach to laminated composites with glass and carbon fibre prepregs

In-situ acoustic emission based technique for damage detection and identification and failure mode prediction in scarf repaired composite structures

One of the great challenges facing adhesively bonded repair procedures in the industry is the absence of a reliable structural health monitoring technique to ensure that the repaired region is intact during service. To this end, this paper proposes a novel in-situ acoustic emission-based methodology to detect and identify damages as well as to predict failure modes at early stages. In this essence, two tapered-scarf repaired plates are produced with different patch materials. The first patch consists of neat carbon fiber prepregs whereas in the second thermally exfoliated graphene oxide integrated carbon fiber prepregs are utilized. Testing the constituents of the repair system individually while monitoring their acoustic activity makes it possible to separate each damage type precisely. Hence, when the specimens of the repaired panel are tested, very detailed information is revealed regarding the current structural status of the specimen and probable failure scenarios. The effectiveness and robustness of the proposed methodology in detecting and identifying damages of varying severity in addition to predicting the failure scenario are verified in the composite panels repaired with pristine and graphene integrated patches.

Preparation of continuous carbon fiber reinforced PA6 prepreg filaments with high fiber volume fraction

High-performance continuous carbon fiber prepreg filaments have been a research hotspot in the field of additive manufacturing in recent years, and are considered to be an effective option for improving the mechanical strength of thermoplastic composite parts. However, the effect of fiber volume fraction on the microstructure and tensile properties of 3D printed prepreg filaments remains miss. Therefore, this study selected suitable impregnation processes and materials to prepare prepreg filaments with different fiber volume fraction and investigated their mechanical properties and microscopic morphologies. The results show that the increase of fiber volume fraction effectively promoted the interface bonding between fiber and resin, and increased capacity for load transfer. When the fiber volume fraction was 54.0 %, the tensile strength of the prepreg filaments and specimens reached 1977 MPa and 334 MPa, respectively. This study can provide a process optimization strategy for the preparation of more types of continuous fiber prepreg filaments with high fiber volume fraction, as well as a data reference for the preparation of high-performance 3D-printed thermoplastic composites.

Design, simulation and manufacture of a flexible frequency selective surface based on aramid/carbon fiber woven fabric

Frequency selective surfaces (FSSs) are significant for the efficient and accurate transmission of microwave signals due to its ability to selectively shield electromagnetic (EM) waves of different frequencies. In some special scenarios, mechanical properties are vitally required. Herein, a flexible frequency selective fabric (FSF) is proposed. Different from traditional FSSs or reported FSFs, aramid/carbon fiber woven fabric serve as the flexible substrate in which carbon fiber provides functionality instead of metallic materials, and patches made of carbon fiber prepreg are periodically applied for property reinforcement. Equivalent circuit model is used to guide the basic determination of patch’s geometry, and it is further optimized via full-wave simulation software HFSS. A simulation model that reasonably reflect the correlation between structure and frequency-selection characteristic is provided, and structural factors affecting the characteristic are analyzed and discussed. Further, an FSF sample is prepared and its frequency response is measured. Measurement revealed the FSF selectively shields EM waves in the frequency range of 8.9 GHz to 11.4 GHz, and is of the bandpass-bandstop-bandpass characteristic. Benefit from EM property and flexibility, the proposed FSF has advantages in applications pursue lightweight, high strength, and require excellent EM functionality, such as aerospace and structure-EM function integrated products.

Measurement of the water absorption on hybrid carbon fibre prepreg waste composite and its impact on flexural performance

Carbon fibre (CF) prepreg, essential to composites and aircraft, generates waste known as carbon fibre prepreg waste (CFW) due to its limited lifespan. This study investigates recycling CFW through hybridization, milling it into powder and mixing it with epoxy resin and alumina to form hybrid composites. Using Minitab software, optimal compositions were determined from 13 and 20 experimental designs for CFW-EP and CFW-EP-AL, respectively. Results identified 2.5 wt% CFW and 97.5 wt% epoxy resin as optimal for CFW-EP, and 2.5 wt% CFW, 2.5 wt% alumina, and 95 wt% epoxy resin as optimal for CFW-EP-AL. Samples of epoxy resin polymer (EP), carbon prepreg waste reinforced composite (CFW-EP), and carbon prepreg waste reinforced with alumina composite (CFW-EP-AL) were fabricated and tested for moisture absorption and flexural strength, revealing noticeable deterioration over time. These findings highlight the importance of compositional analysis in developing sustainable materials with optimal flexural strength for various applications.

Pseudo‐ductility behavior of carbon/glass hybrid composites with unidirectionally arrayed chopped strands: Experimental and numerical research

AbstractAlthough lightweight fiber‐reinforced polymer (FRP) composites are widely used in various engineering fields due to their high specific strength and modulus, the mutual exclusion of strength and toughness is one of the bottlenecks in the field of FRP design because of the inherent brittleness of fiber themselves. In this research, discontinuous fiber structures with vertical and bi‐angled slits are introduced into the thin‐ply carbon fiber prepreg. The fracture energy and delamination degree of the center carbon fiber layer could be controlled by adjusting the structural parameters to design the pseudo‐ductility of carbon/glass (C/G) hybrid laminates and obtain the higher pseudo‐yield stress. The hybrid specimens with 20 mm slits exhibit obvious pseudo‐ductility, and the pseudo‐ductility strain increases as the C/G ratio increases, while the plateau stress decreases. The larger slit distance provides sufficient propagation space for the delamination damage, which dissipates tensile energy and results in a smoother plateau area of the stress–strain curve. The stress–strain curve of the specimen with a smaller slit exhibits a noticeable rapid load decrease caused by the transient propagation of delamination damage. The peak stress of hybrid laminate with bi‐angled slits shows the highest pseudo‐yield stress. The present finite element model successfully analyzed the pseudo‐ductile damage propagation of C/G hybrid laminates with vertical slits, and the results are in good agreement with the experiments.Highlights Revealed the pseudo‐ductility behavior of carbon/glass hybrid composites. The pseudo‐ductility of carbon/glass hybrid composites is controllable. The pseudo‐ductility strain increases with the increase of C/G ratio.

Research on Automated Fiber Placement Surface Defect Detection Based on Improved YOLOv7

Due to the black and glossy appearance of the carbon fiber prepreg bundle surface, the accurate identification of surface defects in automated fiber placement (AFP) presents a high level of difficulty. Currently, the enhanced YOLOv7 algorithm demonstrates certain performance advantages in this detection task, yet issues with missed detections, false alarms, and low confidence levels persist. Therefore, this study proposes an improved YOLOv7 algorithm to further enhance the performance and generalization of surface defect detection in AFP. Firstly, to enhance the model’s feature extraction capability, the BiFormer attention mechanism is introduced to make the model pay more attention to small target defects, thereby improving feature discriminability. Next, the AFPN structure is used to replace the PAFPN at the neck layer to strengthen feature fusion, preserve semantic information to a greater extent, and finely integrate multi-scale features. Finally, WIoU is adopted to replace CIoU as the bounding box regression loss function, making it more sensitive to small targets, enabling more accurate prediction of object bounding boxes, and enhancing the model’s detection accuracy and generalization capability. Through a series of ablation experiments, the improved YOLOv7 shows a 10.5% increase in mAP and a 14 FPS increase in frame rate, with a maximum detection speed of 35 m/min during the AFP process, meeting the requirements of online detection and thus being able to be applied to surface defect detection in AFP operations.

Energy absorption characteristics of a bio-inspired prepreg carbon fiber crash box under quasi-static axial compression

Reducing vehicle weight is crucial for enhancing fuel efficiency and reducing emissions in transportation. Traditional composite materials offer improved energy absorption over metals yet are limited by brittleness. This study introduces an innovative approach, inspired by the mantis shrimp's natural defense mechanisms, to enhance the crashworthiness and energy absorption of composite structures, optimizing safety and performance. Utilizing a bio-inspired design, we developed corrugated Carbon Fiber Reinforced Polymer (CFRP) crash box structures, aiming to optimize their energy absorption capabilities and crash force efficiency (CFE) for potential applications in transportation safety. Through a series of quasi-static axial compression tests, the corrugated structures' performance was evaluated against traditional crash box designs. The experimental results demonstrate that the bio-inspired configurations improved crashworthiness characteristics. Strategic manipulation of layer numbers and corrugations led to superior CFE values, indicative of safer, more controlled collision behavior. The “7N-6L” configuration featuring seven corrugations with six layers of CFRP demonstrated the highest efficacy, achieving an optimal CFE of 1.08. This configuration demonstrated a Specific Energy Absorption (SEA) of 1.56 J/g and an Energy Absorption (Ea) of 42.56 J. Furthermore, compared to conventional steel crash boxes, the CFRP crash box with 7N-6L corrugated structure showcased competitive energy absorption capabilities with significantly reduced mass, absorbing 2850 J with a CFE of 0.91, nearly matching the ideal CFE and highlighting its superior lightweight performance. These results underline the potential of integrating bio-inspired designs to develop robust, lightweight structures for improved crashworthiness, paving the way for safer and more sustainable transportation solutions.

Performance Evaluation of Out-of-Spec Carbon Prepregs for Upcycling Purposes.

In view of exploring the possibility of upcycling aerospace scrap, cure characteristics of out-of-spec carbon fiber prepregs are investigated in this study. The cure behavior of the prepreg is examined in the form of the mechanical cure conversion state of the material using a Dynamic Mechanical Analyzer (DMA). Cure kinetics is modeled by comparing the storage modulus at the start of the reaction (E'0) and instantaneously (E't) during isothermal experiments with those of the fully cured material (E'∞) obtained from dynamic scans. The glass transition temperature Tg and the extent of reaction before gelation are modeled using the DiBenedetto model, where the Tg of each laminate is determined in a DMA, per standard ASTM D7028. The mechanical properties, the extent of cure, and the glass transition temperature of the cured laminates were determined according to industry and international standards. The maximum conversion at temperatures between 100 °C and 140 °C is approximately 80% (±5%). The modeled rate of conversion shows a reasonable match with the experimental data, exhibiting a maximum reaction rate at about 30-40% of the cure conversion. The predicted evolution of the Tg as a function of cure conversion using the DiBenedetto model provides a 94% match with the experimental data. The multi-stage cure cycle based on the models offers shorter cycle times and high-quality laminates. The mechanical test results indicate approximately a 13% and 15% decrease in tensile strength and modulus, respectively, compared to pristine ones. The experimental extent of cure of the cured laminates (95.4%) is in close agreement with that predicted by the model (97%). The porosity in the laminates is estimated to be approximately 2.4%, which is acceptable in several industries.

Multi‐physics field coupling modeling and simulation to study the stress evolution during HTCLS curing process

AbstractHybrid titanium carbon laminates (HTCLs) are a new type of fiber metal laminates, that are attracting extensive attention due to their comprehensive mechanical and physical properties. The curing stress is an important factor affecting the manufacturing performance of HTCLs. Based on viscoelastic mechanics and temperature variation characteristics of materials in this work, the multi‐physics field coupling modeling and simulation are conducted, and the stress evolution mechanism during HTCLs curing process is investigated. Furthermore, the interlayer interfacial damage of HTCLs induced by the curing stress is analyzed combined with the microscope images. Results show that the restriction of metal layers and the stacking sequence of carbon fiber prepregs are the primary reasons for generating significant stress during HTCLs curing. The secondary insulation stage of HTCLs curing process has a positive effect on suppressing the curing stress, by which the interfacial stress between the different metal layers and prepregs layers can decrease by 10.53%, 4.06%, 10.24%, and 1.11%. From the beginning of cooling to the end of curing, the residual stress in HTCLs increases rapidly, and the maximum can increase by 197%. Stress concentration is easily generated on the edges of HTCLs, and the interfaces near the bottom of HTCLs are more prone to forming cracks and delamination.Highlights A multi‐physics field coupling model for HTCLs curing process is established. The viscoelastic mechanics and the temperature variation characteristics of materials are considered in this model. The stress evolution mechanism during HTCLs curing is studied. The interface damage of HTCLs induced by the curing stress is analyzed combined with experiments.

Performance Analysis of Helical Milling and Drilling Operations While Machining Carbon Fiber-Reinforced Aluminum Laminates

Being a difficult-to-cut material, Fiber Metal Laminates (FML) often pose challenges during conventional drilling and require judicious selection of machining parameters to ensure defect-free laminates that can serve reliably during their service lifetime. Helical milling is a promising technique for producing good-quality holes and is preferred over conventional drilling. The paper compares conventional drilling with the helical milling technique for producing holes in carbon fiber-reinforced aluminum laminates. The effect of machining parameters, such as cutting speed and axial feed, on the magnitude of cutting force and the machining temperature during conventional drilling as well as helical milling is studied. It was observed that the thrust force produced during machining reduces considerably during helical milling in comparison to conventional drilling at a constant axial feed rate. The highest machining temperature recorded for helical milling was much lower in comparison to the highest machining temperature measured during conventional drilling. The machining temperatures recorded during helical milling were well below the glass transition temperature of the epoxy used in carbon fiber prepreg, hence protecting the prepreg from thermal degradation during the hole-making process. The surface roughness of the holes produced by both techniques is measured, and the surface morphology of the drilled holes is analyzed using a scanning electron microscope. The surface roughness of the helical-milled holes was lower than that for holes produced by conventional drilling. Scanning electron microscope images provided insights into the interaction of the hole surface with the chips during the chip evacuation stage under different speeds and feed rates. The microhardness of the aluminum layers increased after processing holes using drilling and helical milling operations. The axial feed/axial pitch had minimal influence on the microhardness increase in comparison to the cutting speed.

Impact response characteristics and damage mechanism of continuous carbon-fiber-reinforced magnesium matrix composite materials

The continuous carbon-fiber-reinforced magnesium matrix composite (C_f/Mg) is a new type of composite material made of a magnesium alloy sheet and carbon-fiber-reinforced composite material with alternating layers. It has the advantages of high damage tolerance, light weight, and corrosion resistance, and has become the first choice of lightweight materials in aerospace, transportation, and other fields. Because impact-resistance serves as an important index for its structural design and performance stability, a continuous carbon-fiber-reinforced magnesium matrix composite with indirect bonding using a modified epoxy resin was designed in this study. Moreover, C_f/Mg was chosen to be the object of research through the selection of constituent materials such as magnesium alloys, carbon fibers, resins, and other properties, which matched the aim of realizing a lightweight material. With the help of hot-compression molding technology, dynamic impact mechanical behavior, and damage analysis technology, the structural design and preparation process optimization of epoxy resin carbon-fiber prepregs and magnesium alloy layer materials, as well as the dynamic impact mechanical response characteristics and damage evolution process under different impact energy conditions, were studied. Accordingly, through a combination of low-velocity impact experiments and numerical simulations, the effects of continuous multiple impacts at the same location with the same impact energy, as well as impacts with the same impact energy and different punch diameters, on the low-velocity impact damage behavior and dynamic impact response characteristics of C_f/Mg were investigated. The results of this study show that when the 5J impact is applied four times consecutively, the peak impact load gradually increases with the increasing number of impacts. Moreover, the peak impact loads of the second, third, and fourth impacts increase by 6.09%, 10.7%, and 14.5%, respectively, compared with the results of the first impact.

BEHAVIOR OF BIKE HANDLEBARS MADE OF BRAIDED CARBON FIBRE

The mechanical design of a bike handlebar made of carbon fibre is presented. Usually carbon fibre handlebars are constituted by unidirectional (UD) carbon fibre prepreg. That configuration usually leads to a light design of the piece but fragile. The proposed design allows the handlebar to withstand as high efforts as a steel bar could. On the contrary the carbon handlebar presents a weight much lower. This can be achieved thanks to the selected carbon braiding. Design, manufacturing on cheap PolyLactic Acid (PLA) 3D printed moulds, FEM calculation and testing of the developed carbon fibre handlebar are shown in this paper. Keywords: handlebar, carbon fibre, numerical simulation, test, braiding

Transformation of waste carbon fiber prepreg into sustainable composites: Application in the automotive industry components

AbstractCarbon fiber (CF) prepregs are employed in the manufacture of many different aeronautical structural and non‐structural components. Following the cure of the prepregs in molds, trimming is generally used to give the final shape to the components. Considering the aircraft's vast surface area and the use of multiple prepreg layers in each component, an extensive amount of carbon fiber prepreg is discarded. The unique characteristics of carbon fibers render this CF waste highly valuable and requires its efficient recycling. Cured waste CF prepregs were milled and processed in this research to produce chopped carbon fibers for use in the novel composite development. The matrix material used in the composites was selected as recycled polypropylene sourced from old surgical masks, which highlighted the sustainability of the developed composites. To enhance the quality of the fiber‐matrix interface and improve the impact resistance of the composites an anhydride‐grafted polyethylene (Fusabond) was employed in small quantities. From mechanical characterizations, synergistic effects of the fillers were observed. Besides, compositions containing CF and Fusabond are found more impact resistant than neat matrix. In addition, the use of carbon fibers increased fracture toughness of the matrix through various mechanisms including fiber bridging, fiber pullout, and matrix plastic deformation identified by scanning electron microscopy fractography. Thermomechanical characterizations using dynamic mechanical analysis revealed that carbon fiber raises the neat matrix's glass transition temperature. The developed materials are intended to be employed in the automotive industry to produce inner fender liners, with an optimal composition determined by an optimization research.Highlights Carbon fiber (CF) derived from aerospace fresh scraps significantly improved the mechanical properties of the polymer matrix. Anhydride‐grafted polyethylene incorporation remarkably enhanced the impact resistance of the polymer. CF demonstrated a bridge effect and improved the fracture toughness of the composites. The use of recycled CF presents encouraging prospects in the automotive industry for the production of inner fender liners.

Study on projectile impact resistance of carbon-glass hybrid bioinspired helical composite laminate

Mantis shrimp dactyl clubs have excellent impact resistance due to their special helical structure. Meanwhile, hybrid fibre has become increasingly popular to improve the mechanical properties of composite materials. Based on the helical structure of the periodic region of mantis shrimp dactyl clubs and hybrid fibres, in this study, a hybrid fibre helical lay-up laminate (HHL) is designed. The laminates are prepared using unidirectional carbon fibre prepregs and unidirectional glass fibre prepregs. To study the protective performance and damage process of HHL, a light gas gun impact test and numerical simulation calculations were carried out on the specimens. The harvested protective capability of the HHL specimen was then compared with those of carbon fibre unidirectional lay-up laminate (CUL), carbon fibre helical lay-up laminate (CHL), and hybrid fibre unidirectional lay-up laminate (HUL) specimens. The ballistic protection capability of HHL at different helical lay-up angles was also explored. The testing results show that HHL has the best ballistic protection performance. HHL’s ballistic limiting velocity is 228.5 m/s, which is 49.5%, 30.8%, and 19.9% higher than those of CUL (152.8 m/s), CHL (174.7 m/s), and HUL (190.5 m/s), respectively. Finally, hybrid fibres with a 90° interlaminar helix angle were found to have the highest ballistic limiting velocity. The reason is that the larger interlaminar angle allowed more fibres to be involved in the protection, increasing the energy loss of the projectile and enhancing the protection of the laminate.

Fabrication and bending performance of ultra-low-density all-composite honeycomb sandwich shell based on stretching process

A sandwich shell with an ultra-low-density honeycomb core was designed and manufactured from a carbon-fibre prepreg via a stretching process. Subsequently, the bending bearing limits of the sandwich shell corresponding to five possible failure modes (shear buckling, shear fracture, intracellular dimpling, face fracture, and core debonding) were obtained through theoretical predictions. Failure mechanism maps were generated to reflect the possibility of each failure mode intuitively. In addition, three-point bending tests were performed on specimens with different shell thicknesses to acquire as many of these typical failure modes as possible. Moreover, the competition mechanism between different failure modes was revealed. The research results provide theoretical guidance for parameter optimisation and applications in advanced engineering fields for ultra-low-density carbon-fibre honeycomb sandwich shells.

Ultrasonic welding of lap joints of PEI plates with PEI/CF-fabric prepregs

In this study, ultrasonic welding (USW) of lap joints of polyetherimide (PEI) plates (adherends) with carbon fiber (CF) prepregs impregnated with PEI was investigated. No energy director (ED) was used, so binder contents were varied in the prepregs to compensate for the lack of the polymer in the fusion zone. In addition, the effect of the USW parameters on the structure and the mechanical properties of the lap-joints were analyzed. The most homogeneous macrostructure, the maintained structural integrity of both the CF-fabric in the prepregs and the lap-joined PEI adherends, as well as the maximum strength properties (tensile strength) were revealed for the USW joints with the minimum polymer content in the prepreg. In this case, rising the USW time from 400 up to 800 ms radically changed the macrostructure of the fusion zone, while the strength properties did not vary significantly (shear stresses were 42–48 MPa). Computer simulation of the influence of the PEI/CF-fabric ratios in the prepregs on the deformation response of the USW joints showed that the prepreg thicknesses and, accordingly, the PEI/CF ratios did not exert a noticeable effect on the strain–stress (tensile) diagrams, while the determining factor was the adhesion level.

Real-time in-situ process monitoring method based on the self-conductivity of carbon fiber prepreg for automated fiber placement (AFP)

Real-time online monitoring is of great significance for the manufacturing of carbon fiber reinforced composites, contributing to improving and ensuring the quality of the final manufactured part. An in-situ real-time process monitoring method based on the conductivity of continuous carbon fiber reinforced thermoplastic matrix prepreg was proposed for automated fiber placement (AFP). The detection capability of several different defects was investigated, including foreign object debris, tape breakage, weak edge bonding, gaps/overlaps, and even debonding. In addition, the influence of placement speed and laser power on the detection capacity was also discussed. The number, position, length, and width of various interlayer defects were detected through the resistance change between the current placement layer and the laid layers. Furthermore, accurate detection of defects in different layers was also achieved, indicating the detection capability of existing defects. This method of timely defect detection during the manufacturing process allows for an early manual intervention to improve the quality of manufactured structures and the intelligence of AFP technology.

An integrated nanofiller spray and nanosecond pulse electrically-assisted method for synergistically interlaminar toughening and in-situ damage monitoring of CFRP composites

Nanomaterials have already been explored their potential for interlaminar toughening and crack-monitoring capabilities within the field of composite materials. However, efficient enhancement of interlaminar fracture toughness remains an unresolved challenge. Herein, a novel integrated filler spray and nanosecond pulsed electric field (nsPEF)-assisted curing technique is proposed for the fabrication of high-performance composite material system for the first time. The spraying technique proves to be an effective approach for depositing fillers, including carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon nanofibers (CNFs), onto carbon fiber prepreg. Meanwhile, the nsPEF-assisted technique is utilized to enhance the wettability of resin to fiber, thus reducing void defects. The efficacy of this integrated technique is evidenced by the particularly low content of fillers (0.047 wt%). The experimental results show a substantial reduction of porosity in the composite by 49.36% (from 1.56% to 0.79%). Meanwhile, the mode I initiation and steady-state toughness of samples with CNTs and GNPs are remarkably improved by up to 47% and 82%, respectively, compared to the baseline. This represents the most significant improvement reported to date for non-functionalized CNTs and GNPs at such low concentrations. Moreover, the relative electrical resistance variation (ΔR/R0%) of CNT/GNP sensors used for in-situ damage sensing increased by ∼ 14%. This work pioneers the investigation of the synergistic effects of two promising techniques for preparing composite materials, offering advantages in terms of simplicity, multifunctionality, and the potential for industrial scalability.

Investigation of the stress–strain state of a composite blade in ANSYS WorkBench

In this paper, the static strength of a UAV blade made of composite material was calculated. Composite materials have an advantage over traditional materials (metals and alloys) in the field of aviation - gain in weight, low sensitivity to damage, high rigidity, high mechanical characteristics. At the same time, the identification of vulnerabilities in a layered structure is a difficult task and in practice is solved with the help of destructive control. Composite materials available in the ANSYS materials library were used in the modeling: Epoxy Carbon Woven (230 Gpa) Prepreg woven carbon fiber in the form of a semi–finished prepreg impregnated with epoxy resin carbon fiber with Young's modulus E=230 GPa and Epoxy Carbon (230 Gpa) Prepreg is a unidirectional carbon fiber prepreg impregnated with epoxy resin with a Young's modulus E=230 GPa. Modern software products, such as ANSYS WorkBench, allow comprehensive investigation of the layered structure. Several variants of blade designs with different fillers as the median material were investigated. The forward and reverse destruction criteria based on the Tsai-Hill theory were used. The influence of gravity was not taken into account. It is shown that the developed blade design meets the requirements. Balsa wood, pine, aspen and polyurethane foam were chosen as the middle material of the blade. Pine and aspen wood were selected according to the criteria of their availability and having the lowest density. The materials library of the ANSYS WorkBench software package used does not have characteristics for all of them, so the characteristics of the selected materials (pines and aspens) were added manually. For modeling and calculations in the ANSYS WorkBench program, such characteristics as density, axial elastic modulus, Poisson's coefficients, shear modulus and tensile and compressive strength limits are required.