For the special-shaped structure of plain weave composites, the differences of multi-scale computational results obtained by two homogenization methods, including the stiffness spatial average method and uniform strain boundary condition method, are analyzed in the conditions of ply-direction tensile displacement loading and force loading. The results are compared with the reference results obtained using the whole mesoscopic model. Moreover, the influence of the number of partitions on multi-scale computational results is also analyzed. It is shown that the σ_y stress distribution trend of the two homogenization methods are consistent with same multi-scale model, and the results are in agreement with the fine model. In the displacement load, the maximum errors between the Mises/σ_y of multi-scale results and the fine results are only 9.5% and 3.3%, and the errors decreased gradually with the increase of the number of partitions. However, the errors of the results in force loading are bigger, and it does not decrease with the increase of the number of partitions. And the results of uniform strain boundary condition are generally larger than the results of stiffness spatial averages. Finally, the partitioning method of multi-scale models will destroy some structural features and affect the multi-scale results to some extent.

For the damage identification problem of composite plywood structure, the traditional damage identification indexes are too rough in describing its damage, and the number of material-level damage parameters is huge and difficult to identify, so the unit-level damage index is introduced, which can reflect the in-plane and out-of-plane damages of the plywood. In order to improve the efficiency of damage identification, a two-step regularized damage identification method for unit-level damage indicators is proposed. Through the progressive failure analysis of composite laminated plate structure, the unit-level damage index is equivalent to the material-level damage index based on stiffness degradation, and the unit-level damage index based on combined stiffness coefficient is constructed, and its correlation is analyzed, which provides prior information for subsequent damage identification. Then the damage parameters are quantitatively analyzed by step-by-step regularization, that is, the first step provides preliminary damage identification results by using the prior information provided by L2 regularization and correlation, and the second step solves for the damage variables using the L1 regularization method based on the first step to obtain finer identification results. Numerical simulation and experimental results show that the proposed step-by-step regularization method can effectively realize the damage identification of composite laminates, and the effects of noise pollution and modal order on the identification results are also explored.

In this paper, mechanical properties of hybrid composites composed of sheet molding compound (SMC)/unidirectional fiber (UD) were studied. Monte Carlo method was used to randomly generate fiber sheets at the mesoscopic level, and a modeling method to inhibit interference effect was proposed, which could effectively improve the overlap rate between fiber sheets. Periodic boundary conditions are applied to the mesoscopic representative elements to obtain the elastic parameters of the hybrid composites. The predicted elastic modulus of the model is in good agreement with the experimental results. Furthermore, the effects of fiber sheet size, volume fraction and layering mode on the elastic modulus of the hybrid composite were discussed. The results show that the dimension of the representative body changes with the increase of the aspect ratio, and the elastic modulus of the hybrid composite increases. The elastic modulus of the composite increases with the increase of the volume fraction of the fiber sheet. The layup design of hybrid composites can make them not only have the formability of SMC composites, but also have the same elastic modulus as quasi-isotropic materials.

A composite fatigue residual stiffness prediction model is proposed to address the problem of incomplete consideration of influencing factors in the construction of existing residual stiffness prediction models, which simultaneously considers the combined effects of maximum stress, initial stiffness, critical residual stiffness, cycle life, and constant amplitude fatigue life. The results indicate that the proposed model conforms to the three-stage performance degradation law and can be used to describe the residual stiffness degradation of composite materials with high accuracy; the model exhibits higher prediction accuracy in the region of higher stress than that in the region of lower stress, which is related to the concentration of test data in the higher stress region; compared with existing model, the model proposed in this paper has high prediction accuracy and applicability for the fatigue residual stiffness of composite materials as a whole.

To predict the strength of composite bolt connections, tensile tests were designed and the ultimate loads were recorded. The test variables were quantified as input parameters for the neural network model. A BP neural network was used to train the model. Three reserved test results were used to validate the model’s accuracy. The prediction errors for the three test groups were 6.13%, 1.63%, and 3.34% respectively. The composition of the training groups was adjusted and the model was retrained. The results showed that the model had excellent predictive ability for new variable values. Finally, a finite element analysis model was established for comparison with the neural network. The results indicated that compared to the finite element method, the neural network approach could predict the strength of composite bolt connections more quickly with the same precision.

The thermal expansion coefficient of TG300/epoxy uniaxial fiber reinforced composites at -100~120 ℃ was measured according to GB/T 2572—2005. The longitudinal and transverse thermal expansion characteristics of uniaxial composites with temperature are presented. The axial and radial thermal expansion coefficients of TG300 carbon fiber in the temperature range of -100~120 ℃ were obtained through parametric inversion analysis, which would provide material performance data for composite materials design when focus on thermal expansion characteristics. Further, the thermal expansion coefficients of uniaxial CFRP and biaxial CFRP were calculated, and the effects of temperature, fiber volume fraction, fabric structure, structure parameters and fiber buckling on the thermal expansion performance of the composite were analyzed, which provided a theoretical basis for the structural design and optimization of zero thermal expansion composite.

Axial compression tests were conducted on the 150 mm composite skirt of a solid rocket motor case formed by autoclave process. A progressive damage FEM analysis incorporating viscous behavior and the three-dimensional Hashin failure criterion was validated with test data such as failure mode, failure location, and axial compression load for both the composite skirt and the composite case with the skirt. Then a layup optimization model based on Random positive algorithm with layup limitation of composite skirt was established to obtain the optimal layup sequence and angle of composite skirt that meets design requirements. Subsequently, based on the optimal layup, the impact of different overlap angles and lengths on the load pattern was analyzed, determining the optimal overlap angle and length. Finally, The axial compression test results confirm that with a layup of [90/0/45/0/90/90/-45/-45/45/0], the composite skirt buckles before reaching the material strength limit, meeting design requirements. As the overlap angle increases, the buckling load rose steadily while the load increment increases initially and then decreases. Ultimately, it was determined that the optimal lap angle and length are 3° and 20 mm, respectively. The final axial compression test buckling load for the composite case with skirt is 29.77 kN, differing by 6% from the simulation. The failure position at the tip of the composite skirt aligns with simulation results.

In this paper, the curing deformation of aramid fibre-honeycomb sandwich U-shaped leading edge structure is investigated by a combination of finite element simulation and experimental verification. The simulation models of curing temperature field and curing deformation field of the U-shaped leading edge were established by considering the curing heat release, thermo-mechanical coupling and chemical shrinkage of the resin. In the test preparation, the forming process of pre-curing outer skin, then combining with honeycomb core, adhesive film and foam glue, and finally laying the inner skin and gluing and curing again was adopted. The results show that the curing deformation of the wide side and narrow side of the component predicted by the simulation model is in good agreement with the actual, which can provide guidance and basis for the subsequent mold modification of the leading edge component.

In the actual damage detection process of composite materials, the baseline data is difficult to obtain and inevitably affected by the operation and environmental conditions, which makes the detection more difficult. Based on the symmetry failure principle of Lamb wave space inversion, the non-baseline method was used to locate the multi-damage of composite plate structures. Through the exchange excitation to receive the transducer sequence, the direct wave packet in the forward-back propagation Lamb wave was obtained, and the difference of signal amplitude and phase was analyzed, the damage path was extracted effectively. Then the defect was located by DBSCAN and K-means cluster algorithm. The effectiveness of the method was verified by experiments, and the traditional probabilistic imaging algorithm was compared with the clustering algorithm. The results show that, compared with the probabilistic imaging algorithm, the positioning accuracy is obviously improved. In addition, the problem of blind area in the detection area is effectively solved by optimizing the parallel array, and the single defect and double defect location of the composite plate is realized by combining the D-K algorithm.

The absorption performance analysis of honeycomb sandwich structures with variant Poisson’s ratio and optimization design of honeycomb configuration with given reflectivity were carried out, by classifying of hexagonal honeycomb configurations using Poisson’s ratio and establishing a parameterized finite element model of honeycomb cells based on homogenization theory. The results show that under the condition of 2~18 GHz electromagnetic wave normal incidence, reducing the length and increasing the height of the honeycomb can effectively improve the absorption performance. The change of angle that causes the Poisson’s ratio to approach zero can improve the absorption performance, and there is an optimal coating thickness that matches the geometric parameters of the honeycomb to obtain the optimal absorption performance. Compared to the initial schemes of regular hexagonal honeycomb with positive Poisson’s ratio, semi-re-entrant hexagonal honeycomb with zero Poisson’s ratio, and re-entrant hexagonal honeycomb with negative Poisson’s ratio, the absorption bandwidth of the three optimized honeycomb designs with reflectivity of -10 dB increased by 56.8%, 35.2%, and 52.5%, respectively, while the absorption bandwidth of the three optimized honeycomb designs with reflectivity of -20 dB increased from zero to 4 GHz, 2.3 GHz and 0.5 GHz, respectively. Among the three types of Poisson’s ratio honeycomb, the positive Poisson’s ratio honeycomb has the best optimization adaptability potential. The research results provide a reference for the honeycomb configuration design of multifunctional honeycomb absorbing structures.

In the study of green manufacturing technology for high-performance carbon fiber reinforced resin matrix composites (CFRPs), electron beam (E-Beam) curing at room temperature is considered a promising out-of-autoclave curing method due to its small residual stress and fast curing speed. Focusing on the high-energy E-Beam curing process of CFRPs, the paper comparatively studied the impact of E-Beam doses rangingfrom 20 kGy to 200 kGy on the curing degree of prepreg tapes under two radiation methods of radiating a single-layer prepreg tapes or radiating laminates, and clarified the evolution trend of the curing degree increasing with the increase in dose. The influence of radiation dose rate on the curing degree was tested and analyzed, and the mechanism of temperature rise effect to promote curing was clarified. Combined with the microscopic morphology of interlayer damage, the synergistic influence of dose and dose rate on interlaminar shear strength (ILSS) was explored. This paper provides a process optimization method to obtain high-performance laminate preparation.

Based on the study of the propagation characteristics of laser-induced shock waves in materials and the underlying principles of material delamination, there exists potential for the development of a non-destructive testing technique for interface bonding strength utilizing laser-induced shock waves. Such an advancement holds significant importance in investigating the dynamic mechanical response characteristics of composite materials under the influence of lasers with varying pulse widths. This study entailed the measurement of particle velocities on the backside of composite laminates subjected to laser shock with diverse pulse widths. Additionally, a finite element model was constructed for carbon fiber reinforced composite laminates subjected to laser shock, allowing for an exploration of the coupling laws governing stress wave propagation within the laminates under both single-sided and double-sided laser shock scenarios with differing pulse widths. The findings indicate that as the pulse width of the laser shock load increases, under single-sided laser shock, there is an escalation in the maximum tensile stress within the laminate. Moreover, the position of the maximum tensile stress shifts towards the surface subjected to laser shock. Double-sided laser shock results in a more concentrated distribution of maximum tensile stress both temporally and spatially within the target plate. Furthermore, under double-sided laser shock, prolonging the delay time of laser shock on one side of the target plate leads to a notable displacement of the position of maximum tensile stress towards the opposite side.

The performance of carbon fiber composites is greatly affected by the use environment. In this paper, the effects of different aging environments (distilled water, sulfuric acid solution with mass fraction of 10% and sodium hydroxide solution) at the same temperature (70 ℃) on the compressive properties and compressive properties of the materials with impact damage of T700 carbon fiber/epoxy resin matrix composites were studied. The mass change, surface morphology, fourier transform infrared spectroscopy (FTIR) and dynamic mechanical properties before and after aging were studied and analyzed. The results show that in distilled water and acid solution, the moisture absorption rate curve conforms to FICK’s second law. The greater the rate of mass change, the greater the decrease of compressive properties, compressive properties of the materials with impact damage and glass transition temperature, and the more serious the damage of surface morphology; in the alkali solution, the sample is seriously damaged, and the resin also had a chemical reaction, the properties and glass transition temperature of the material are not only affected by moisture absorption, but also by the chemical reaction of the resin. This research results have important engineering practical significance for the use and storage of T700 carbon fiber/epoxy resin matrix composites in more complex environment.

In CMH-17G, the calculation process for the B-base value single-point method has been comprehensively updated, mainly focusing on the selection of statistical models and the correction of discrete coefficients. In order to study the statistical method of B-base value, two kinds of open-hole tensile tests of T800 carbon fiber resin matrix composites with two ply ratios are planned, and their open-hole tensile strength values in room temperature dry state and low temperature dry state are obtained. By studying the calculation flow of B-base value under normal distribution, Weibull distribution and log normal distribution respectively, the B-base value of composites under different statistical models are obtained. The research results show that the B-base value calculated by normal distribution is on average 3% higher than that calculated by Weibull distribution. By using the discrete coefficient correction method specified in CMH-17G compared to the uncorrected discrete coefficient, the average B-base value decreased by 9%, compensating for the variability that was not manifested in the identification test and further ensuring the safety of composites structures.

In this paper, a kind of composite thin-type frangible launch case cover with channel size of 650 mm×650 mm was designed, it can bear large internal pressure and small bursting load, the internal pressure converted to point load is 7 times the bursting load, proposed a structure design scheme of weak area and strengthening piece. The frangible cover was made and subjected to pressure and bursting tests. The result of test show that the structure of frangible cover is reasonable, it can withstand the internal pressure of 0.055 MPa, and the maximum deformation at the center point of the frangible cover is 19.83 mm, but only 3.03 kN of load is required to burst the frangible cover. In the paper, the finite element models of pressure and bursting test of the frangible cover were established respectively. The error between the analysis results and the test results is 12.7% and 8.0%, it can accurately predict the deformation and strength of the frangible cover. Based on the finite element model, the influence of the number of strengthening piece at different positions and the different thickness on the deformation of the frangible cover was analyzed, the deformation is decrease when the number of strengthening piece in zone Ⅱ, Ⅲ and the thickness of frangible cover were increased. The research content of this paper can provide reference for the engineering production of the thin-type frangible launch case cover.

The safety and lightweight of new energy automobile have extraordinary significance for the sustainable development of automotives. The research of lightweight automotive based on its safety is important for reality. The application of carbon fiber reinforced composites in the car structure is an effective way to achieve a lightweight car. The engineering elastic constants of six unidirectional single ply composites with carbon fiber volume fraction of 50%, 55% and 60% were calculated via both Halpin-Tsai equation and unit cell model as the input parameters of layup. To improve the surface flexural stiffness of T-type battery box with carbon fiber reinforced composites against its deformation in service with a maximum displacement control of 1 mm, the maximum displacement and deformation of the battery box were obtained by finite element analysis. The results demonstrate that only three carbon fiber composites meet the requirement of maximum displacement less than 1 mm under loading, when the volume fraction of carbon fiber is fixed and the thickness of the battery box is no more than 3.4 mm.

Based on the optimized multi-axial lay up with regard to the integral structural performance of FRP laminates and bolted joints, this paper further investigated the effects of lay up (uni-axial lay up UD, multi-axial lay up MD1, adjacent uni-axial and multi-axial lay up MD2 and adding carbon fiber into multi-axial lay up BC) and geometric parameters (end distance and pitch) on the axial tensile behavior of pultruded FRP square tube bolted joints. The experimental results reveal that adding multi-axial fabrics (MD1 and MD2) significantly enhances the joint ultimate capacity by over 50% and improved the ultimate displacement to more than twice the UD displacement, which greatly improves the ultimate capacity and ductility of FRP tube bolted joints. MD2 bolted joint exhibits the highest ultimate capacity, while the utilization of BC don’t improve the joint ultimate capacity but increase the joint stiffness by 7%~30%. The UD bolted joints consistently exhibit shear or splitting failure modes regardless of joint geometric parameters. When the end distance-to-bolt diameter ratio reaches 4, the failure modes of multi-axial tube bolted joint begin to shift or totally transitioned to ductile bearing failure. The simultaneous bearing process of two bolts is extended with increasing pitch, resulting in the enhancement of joint ductility and ultimate capacity. It is recommended to set the end distance-to-bolt diameter ratio and pitch-to-bolt diameter ratio of the multi-axial pultruded BFRP tube bolted joint to be no less than 4 in design.

Selective laser melting (SLM) prepares aluminum-based composite materials, which improves the problems of particle agglomeration and poor interface bonding encountered by traditional manufacturing methods. This article, with a focus on laser parameters and reinforcing particles, provides an overview of microstructural features and evolution, including aspects such as microstructure, phase transformation, particle dispersion, crystal morphology, and interface bonding. The reinforcing particles act as heterogeneous nucleation sites within the matrix, promoting grain refinement and improving crystal morphology. Control of laser parameters regulates energy input to induce temperature gradients within the melt pool, optimizing microstructural aspects such as particle distribution and interface through the Marangoni effect. This article elucidates that the tensile and fatigue performance of Al-based composite materials manufactured by SLM technology outperforms that of aluminum and aluminum alloys produced using the same method, and it is supported by an analysis of influencing factors based on microfailure surface analysis. Through the optimization of laser parameters and reinforcing particles, improvements in microstructure, reduction of porosity and cracks, and enhancements in material tensile and fatigue properties can be achieved. Finally, the article summarizes the advantages and disadvantages of SLM-prepared aluminum matrix composites and provides an outlook on pending technical issues and research directions that need to be addressed in the future.

The increasing demand and waste volume of thermosetting resins and carbon fiber reinforced thermosetting resin-based composites (CFRP) have brought the issue of carbon fiber recycling to our attention. However, the permanent cross-linked networks structure of the resin matrix makes it difficult for CFRP to degrade and recycle. Under the dual carbon goal, closed-loop chemical recycling has become the key to the sustainable development of thermosetting. In recent years, dynamic adaptive networks (CANs) have become one of the preferred solutions for the design and preparation of thermosetting with closed-loop chemical recycling. The article reviews the progress in closed-loop chemical recycling and reuse of CANs polymers and carbon fiber composites containing ester bonds, imine bonds, hexahydrotriazine structures, vinylogous urethane bonds, diketoenamine structures, and disulfide bonds. The advantages and disadvantages of their respective recycling were compared from the aspects of catalyst, temperature, pH, solvents, etc. The purpose is to provide reference for the future thermosetting resin design which can be closed loop chemical recycling.