Abstract:

This review summarizes recent progress on the application of elastomeric thermal-insulation materials under the extreme conditions of rocket flight.First，the paper outlines the critical role of such materials in the thermal protection of solid rocket motors and their capacity to withstand very high temperatures as well as erosion by high-pressure，high-velocity gas flows.Subsequently，the paper focuses on four representative matrix systems-nitrile butadiene rubber（NBR），ethylene-propylene-diene monomer（EPDM）rubber，silicone rubber，and thermoplastic polyurethane（TPU），and analyzes their modification strategies.These strategies include fiber reinforcement，synergistic nano-fillers and surface treatments，aimed at improving ablation resistance and mechanical properties.In parallel，the paper discusses carbon layer formation mechanisms and the influence of multiscale fillers on thermal-protection performance.Finally，the paper summarizes the challenges faced under extreme thermal loads （corresponding to surface temperatures 3 000 ℃），such as carbon layer spallation，interfacial debonding，and insufficient environmental sustainability.Future elastic thermal insulation materials will undergo continual innovation， aiming to enhance their performance in extreme environments and ensure the safety of rocket flights.

Abstract:

Carbon fiber reinforced polymer （CFRP），owing to its corrosion resistance and high specific strength，is often stacked with metallic alloys to form hybrid laminates for aerospace and other state-of-the-art applications.Owing to the disparate machinability of the two materials，the drilling process of such laminated structures is prone to interfacial damage，including burrs，burning，chip accumulation，and inconsistent hole diameters at the interface.This damage significantly impacts the service life of the laminated structure.This paper provides a systematic review of interface damage during hole drilling in CFRP/alloy laminates.Regarding the machining characteristics at the laminate interface，the drilling process of laminated structure and the formation and evolution of chips，thrust force，and drilling temperature are described.Regarding the machining mechanism at the laminate interface，the drilling process and the formation and variation of chips，axial force，and drilling temperature are described.Concerning the formation of interface damage，the influencing factors based on the drilling mechanism of laminate hole formation are analyzed.Regarding interface damage suppression strategies，effective approaches are outlined from three perspectives：machining parameters，drilling tools，and machining methods.Finally，future research trends for suppressing interface damage during drilling of CFRP/alloy laminated materials are projected.

Abstract:

Using the Abaqus finite-element software，a finite-element drilling simulation model for a CFRP/Ti stack composite was established.The three-dimensional Hashin failure criterion was coded into a VUMAT subroutine and used as the damage criterion for the CFRP laminate.The axial force and strain evolution during drilling of the CFRP/Ti stack composite with a YG8 cemented-carbide drill were analyzed.The effects of cutting speed， feed per revolution，and drill point angle on drilling-induced defects in the CFRP/Ti stack structure were further investigated， and drilling experiments were conducted for validation.The simulation and experimental results show that a spindle speed of 750 r/min，a feed of 0.025 mm/r，and a drill point angle of 140° produce the best entry quality on the CFRP side.Under conditions of low speed，low feed and a large point angle，the axial force is smaller and the hole quality in the stack is higher.Standard rake angle drill are not suitable for machining such laminates.

Abstract:

Woven prepregs were increasingly employed in the thermos-compression molding of helicopter rotor blades，and accurate characterization of their mechanical behavior was critical for predicting and controlling forming quality.This study focuses on investigating the influence of different temperatures and loading rates on the in-plane fiber-direction tensile，in-plane shear，and out-of-plane bending mechanical behaviors of CF3052/3238A carbon fiber/epoxy woven prepreg during thermos-compression.The results show that the tensile modulus of CF3052/3238A varies little with temperature or loading rate.By contrast，shear deformation becomes less sensitive to loading rate as temperature increases，accompanied by a pronounced reduction in shear modulus；moreover，the shear modulus increases with loading rate.For a fixed loading rate，the prepreg''s bending stiffness decreases as temperature rises，whereas at a fixed temperature the bending stiffness increases with loading rate.Building on these observations，based on its in-plane uniaxial tensile，shear deformation，and out-of-plane bending deformation characteristics，a mixed shell-membrane elements is employed to fully decouple the prepreg''s in-plane tensile deformation from its out-of-plane bending deformation.Accounting for the material’s true bending stiffness，a non-orthogonal constitutive model with accurately tracked fiber directions was used to describe the behavior of the woven prepreg.Simulations of in-plane shear deformation and the forming of a hemispherical part confirm the effectiveness and fidelity of the proposed forming model.

Abstract:

To optimize the process parameters of inertia friction welding for small，thin-walled annular workpieces and to investigate the relationships between these parameters and joint geometry as well as axial shortening，a two-dimensional axisymmetric，thermo-mechanically coupled finite-element model was developed in ABAQUS.Using the tensile strength of the welded part as the response variable，a Box-Behnken experimental design was employed within a response surface methodology（RSM） to construct a regression prediction model，which was subsequently validated by experiment.The results show that the quadratic polynomial regression model fitted via RSM is statistically sound，with a significance P-value0.000 1 and a lack-of-fit value 0.05.The optimized parameters are an initial speed of 380 r/min，a friction pressure of 268.93 MPa，and a moment of inertia of 350 kg·m².The discrepancy between experimental measurements and model predictions is within 5%.

Abstract:

Using nanoindentation technology combined with finite element simulation and dimensional analysis，the parameters of the power-law constitutive model for single-crystal germanium were inverted.Nanoindentation tests were conducted on the（111）crystal plane of single-crystal germanium to obtain load-displacement data.A dimensionless functional relationship corresponding to the experiments was established based on finite element simulation，and the specific parameters of the power-law constitutive model were determined through fitting.The experimentally obtained load-displacement curves exhibited high consistency with finite element simulation results， validating the reliability of the inversion process.The results indicate that the power-law constitutive model obtained through this method effectively describes the elastic-plastic mechanical behavior of single-crystal germanium during nanoindentation.And it provides a reliable basis for mechanical modeling of such type of material at the micro-nano scale.

Abstract:

Winding CFRP grinding wheels exhibited high circumferential strength but relatively low radial strength，and are prone to interlaminar delamination，which limits their performance.A multi-ring interference fit assembly can effectively enhanced the radial strength of grinding wheels.In this study， an analytical model was established via theoretical analysis to guide the selection of interference fit for anisotropic wheels.Using finite element modeling and deformation measurement experiments，it analyzed the effects of different parameters（interference fit amount，individual ring thickness，and number of assembled rings） on the structural performance of multi-ring interference fit assembled winding grinding wheels with dimensions Φ360 mm×120 mm×16 mm.The results indicate that increasing the number of assembly rings leads to a more uniform stress distribution and reduces the risk of debonding between rings.Decreasing the thickness of each ring raises the radial stress it sustains and reduce the risk of delamination；when ring thickness is graded to increase progressively from the inner to the outer ring，the total deformation is minimized and overall performance improves.The allocation of interference fit between any given pair of adjacent rings has little effect on the stress levels in the other rings；for the pair itself， larger interference fit reduces the tendency to delaminate.By tuning the interference fit between adjacent rings to adjust the radial stress state at their interface，delamination during rotation can be mitigated，thereby improving grinding-wheel performance.

Abstract:

Graphite oxide （GTO） and graphene oxide （GO） were prepared from two graphite raw materials with two particle sizes using three wet chemical methods.The obtained different GTO and GO were qualitatively analyzed by XRD，IR，and SEM and TEM characterization in terms of layer spacing，surface functional groups，structural integrity，and microscopic morphology，etc.Meanwhile，the concept of D-peak origin in Raman characterization was introduced，and the degree of defects introduced into the graphite structure during the chemical reaction，which was the proportion of oxygen-containing functional groups on the surface，was analyzed semi-quantitatively based on the I_D/I_G ratios of different samples.The results show that graphene oxide with different functional group states and properties can be obtained by controlling the synthesis method and graphite particle size.The degree of oxidation of graphite by chemical methods is in the order of：HydrothermalHummers≈ Staudmaier.The smaller the size of the graphite raw material，the more rapid and pronounced the oxidation process becomes.

Abstract:

Silica-based aerogels were materials with outstanding properties，but their poor mechanical performance and cumbersome drying methods severely limited their practical applications.Here，using terephthalaldehyde and 3-aminopropyltrimethoxysilane as precursors，combined with methyltrimethoxysilane and dimethyldimethoxysilane as co-precursors，a novel bridged silica aerogel via a sol-gel process and atomspheric pressure drying method was produced.The effect of the molar ratio n（H₂O/Si） on aerogel performance was investigated and the density，shrinkage，hydrophobicity，mechanical properties，and thermal characteristics of the prepared crosslinked aerogels were detailed.The results show that at n（H₂O/Si）=4，the aerogel exhibits low density（82 mg/cm³） and thermal conductivity ［29 mW/（m·K）］，high hydrophobicity（contact angle150°），and excellent flexibility（E=40 kPa）；under 50% compressive strain，the stress decreases by only 10% after 100 loading-unloading cycles.Thermogravimetric analysis indicates superior thermal stability，with mass loss 5% at 380 ℃ under nitrogen.

Abstract:

To reduce the manufacturing cost of conductive rubber and enhance its engineering applicability，a graphene oxide/silver/polyaniline（GAP）composite was synthesized via an in situ route，and GAP-reinforced electrically conductive silicone rubber was prepared.Characterization by SEM shows that，using graphene oxide as a template，Ag⁺ ions and aniline monomers grew in situ into silver nanoparticles and dendritic polyaniline，forming the GAP composite.The GAP powder disperses effectively within the silicone-rubber matrix to yield a reinforced elastomer.At a loading of 100 phr，the silicone rubber exhibites a tensile strength of 4.67 MPa，an elongation at break of 430%，a tensile modulus of 0.76 MPa，and a volume resistivity of 8.1 mΩ·cm，and comparable to Ag-powder-filled silicone rubber（control values：4.89 MPa，422%，0.72 MPa，and 5.4 mΩcm）.The Shore A hardness of the GAP-reinforced silicone rubber is 64，a 15.8% reduction relative to the Ag-powder-filled counterpart（76）.These results indicate high practical utility for engineering applications，with the prospect of reduced manufacturing costs.

Abstract:

For Fe-20Mn-6Al-1.5C-5Cr steel（designation：ZG-6），the effects of different solution treatment and aging processes on microstructure and hardness were investigated using optical microscopy（OM），scanning electron microscopy（SEM），transmission electron microscopy（TEM），and physicochemical phase analysis.Solution treatments were performed at 1 050，1 100，and 1 150 °C.The results show that with increasing solution temperature， carbides dissolve and the hardness increases；a single-phase austenitic microstructure is obtained at solution temperatures≥1 150 °C.On this basis，the steel solution-treated at 1 150 °C is aged at various temperatures（450～525，550，and 650 °C，2 h each）.At 550 °C，the intragranular κ phase content reaches saturation and the hardness attains a peak value（316 HB）.At 650 °C，lamellar κ′ carbides form and the hardness decreases.After aging at 650 °C for 16 h，κ′ carbides at grain boundaries become saturated and grow into the grains.

Abstract:

This study investigates the properties of flame-retardant vinyl ester resins for vacuum-assisted resin infusion（VARI）processes，providing data support for the application of resins.Characterization methods including viscometer，differential scanning calorimeter（DSC），dynamic mechanical analyzer（DMA），oxygen index tester，and universal testing machine were employed to evaluate the resin system''s process adaptability，heat resistance，flame retardancy，and the mechanical properties of both the resin and its composites.The results show that the gel time at 20-30 ℃ exceeds 30 min，and the viscosity at 25 ℃ remains around 400 mPa·s for extended periods，indicating good processability.Curing-kinetics analysis yields the gelation，cure，and post-cure temperatures of the system.The resin exhibits excellent thermal and flame-retardant performance：the heat deflection temperature reaches 114.3 ℃，the glass-transition temperature reaches 134 ℃，and the limiting oxygen index exceeds 27%， meeting the criterion for"hardly combustible"materials.The neat-resin casting and its composites show outstanding mechanical properties；the flexural strength of the casting reaches 156 MPa.Overall，the resin demonstrates superior performance and provides a solid basis for subsequent application-oriented research.

Abstract:

To meet the urgent demand of low-density adhesives in next-generation satellite structural platforms，this study employed a silane coupling agent to surface-modify hollow glass microspheres.A low-density adhesive was prepared using a blending method，followed by testing of mechanical properties，space environment resistance，pull-out strength of embedded anchors in honeycomb sandwich structures，and adhesive density.The results show that the new low-density adhesive has a density of 0.67 g/cm³，46% lower than that of the J-133 adhesive，a shear strength of 26.2 MPa，and a pull-out force of 5.1 kN for M4 potted inserts in honeycomb sandwich panels.After high/low-temperature thermal shock testing，the mechanical properties changed little，and both the total mass loss（TML）and collected volatile condensable materials（CVCM）are reduced compared with J-133.The adhesive thus exhibits excellent mechanical performance and space-environmental resistance，and can meet the requirements of future spacecraft for low-density adhesives.

Abstract:

Composite rectangular tubes were widely used in aerospace and related fields and often served as critical load-bearing and functional components，imposing stringent requirements on dimensional accuracy and surface quality that conventional pultrusion and filament-winding processes struggle to meet.Integrating the advantages of compression molding and soft-mold（compliant-tool）expansion，this paper investigated a high-precision molding-thermal-expansion process for fabricating composite rectangular tubes and detailed the workflow of material selection，tooling design，and manufacturing.In the proposed scheme，the matched female and male dies are made of Invar steel，while the core mandrel is aluminum alloy；by exploiting the large mismatch in their coefficients of thermal expansion，parts with high-quality inner and outer surfaces are obtained，and the dimensional accuracy meets the specified targets.This work offers a viable approach for the molding and fabrication of similar composite rectangular tubes.

Abstract:

Cutting force and cutting heat were both critical factors in machining of propellant grain.Two single-factor experiments were first designed to analyze the evolution of cutting force and cutting temperature during machining，followed by an orthogonal array cutting experiment to optimize the process parameters.The results show that increasing the feed rate causes the main cutting force，thrust force，and feed force to rise.Among the tools evaluated，polycrystalline diamond（PCD）tools yield the smallest main cutting and thrust forces.The feed rate has little influence on temperature，and PCD tools yield the lowest cutting temperature.After optimizing the process parameters of cutting，the overall minimum main cutting force and temperature are obtained at V_c=65 m/min，V_f=30mm/min，a_p=0.5 mm，γ₀=20°，α₀=15°.

Abstract:

Short-circuit and open-circuit faultswere the two most common failure modes in electronic components；in most cases，a failed device manifests only one of two modes.This paper analyzes a solid-state relay（SSR） that exhibited both short-and open-circuit behavior simultaneously.Based on test results，failure investigations are conducted separately for each mode.The root cause is ultimately identified as a cold solder joint at the internal gate connection of the solid-state relay.This defect prevents proper gate drive and block the release of gate charge，resulting in both open-circuit and short-circuit phenomena.

Abstract:

Based on the project development requirements of Fast，Intelligent，and Cheap for satellite subsystems，research was conducted on assembly process technology for an onboard ultra-high-frequency MCM （Multi-Chip Module）receiver component.Through structural layout，selection of materials and devices，and process-flow design，and together with targeted advances on key steps such as connector sintering，substrate sintering，and die attach，a viable manufacturing route for spaceborne EHF products was established.The approach resolves the thermal mismatch between the RF insert and the aluminum housing，achieving an assembly accuracy of 50 μm.Relative to conventional spaceborne MCM modules，the product’s cost is reduced to one-fifth，production efficiency is doubled， and the automation level reaches 90%，thereby meeting the goals of Fast，Intelligent，and Cheap development. The product has been successfully deployed on satellites and has entered mass production.