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The vibration pretreatment–microwave curing process can achieve high-quality molding under low-pressure conditions and is widely used in the curing of resin-based composites. This study investigated the effects of the vibration pretreatment process parameters on the void content and the fiber weight fraction of T700/TRE231; specifically, their influence on the interlaminar shear strength and impact strength of the composite. Initially, an orthogonal experimental design was employed with interlaminar shear strength as the optimization target, where vibration acceleration was determined as the primary factor and dwell time as the secondary factor. Concurrently, thermogravimetric analysis (TGA) was performed based on process parameters that corresponded to the extremum of interlaminar shear strength, revealing a 2.17% difference in fiber weight fraction among specimens with varying parameters, indicating a minimal effect of fiber weight fraction on mechanical properties. Optical digital microscope (ODM) analysis identified interlaminar large-size voids in specimens treated with vibration energy of 5 g and 15 g, while specimens subjected to a vibration energy of 10 g exhibited numerous small-sized voids within layers, suggesting that vibration acceleration influences void escape pathways. Finally, impact testing revealed the effect of the vibration pretreatment process parameters on the impact strength, implying a positive correlation between interlaminar shear strength and impact strength. [ABSTRACT FROM AUTHOR]

The primary challenge during the secondary bonding process of full-height honeycomb sandwich structures is the aramid honeycomb core's height shrinkage. This paper systematically investigated the height evolution behavior of the honeycomb core by using a creep testing machine. The results showed that the out-of-plane compression deformation curve of aramid honeycomb cores is mainly divided into three stages: the dehumidification stage, the pressurization stage and the creep stage. Under conditions of high temperature and pressure, height shrinkage was attributed to the dehydration caused by moisture infiltration, and the compression creep resulted from the slippage of polymer molecular chains. Dehydration shrinkage is stable, whereas compression creep reflects typical viscoelastic polymer characteristics. By employing the viscoelastic Burgers mechanical model and applying the nonlinear surface fitting method, the total height shrinkage deformation behavior of the aramid honeycomb core during the curing process can be accurately predicted by summing the above three stages. This research contributes valuable insights for the manufacturing process of honeycomb sandwich structures. [ABSTRACT FROM AUTHOR]

The integrated manufacturing of aerospace composite cryogenic tanks is crucial for enhancing payload efficiency, reducing costs, and leading the aerospace industry upgrade. Composite segmented tool, which balances internal support and mold surface, must not only meet the requirements of disassembly and demolding but also ensure sufficient stiffness without deformation under loads like winding tension and curing shrinkage during tank formation. This article addresses the challenge faced by composite tool with uniformly thick ply stacking schemes, where the weight increases significantly with the rocket body diameter, rendering functions such as disassembly and demolding unfeasible. A global–local optimization approach aimed at achieving variable‐thickness ply stacking designs for composite tooling was proposed. Starting with a defined segmented tool design for the Φ3.35 m tank, models for calculating winding tension under complex service conditions and finite element models for curing shrinkage were established. Optimization of ply shapes, dimensions, and sequences using OptiStruct was conducted, which achieved a weight reduction of 34.48% while ensuring that deformations under loading met design standards. Subsequently, the engineering trials for the composite melon petal and wallboard corresponding to the Φ600 mm tank were conducted based on the optimized scheme. The maximum deformations for the two components were 0.43 mm and 0.15 mm, respectively, meeting the manufacturing requirements for engineering applications. The results provide a lightweight, high‐stiffness, and detachable tool design scheme for achieving the integrated manufacturing of extra‐large (Φ10 m) composite tanks. Highlights: The external load was analyzed through theoretical and simulation approaches.The weight of composite tool was significantly reduced after optimization.The engineering prototypes of the segmented tools were achieved. [ABSTRACT FROM AUTHOR]

Compared to composite components prepared by traditional thermal process, microwave‐cured laminates exhibit superior mechanical properties under the same heating cycle, indicating a unique heating mode that differs from air circulation. To progressively replace the thermal curing process with microwave technology in the aerospace composites manufacturing field, it is crucial to elucidate the heating mechanism of microwave‐cured composite materials. In this study, the microwave absorbing performance of both carbon fibers and epoxy resins was systematically compared and revealed. Drawing upon principles of organic chemical reaction and Fourier transform infrared spectroscopy, the results demonstrated the swift response of carbon fibers to microwaves, which facilitated heightened functional group transformation and more complete curing reactions at the fiber‐matrix interface. Notably, as indicated by the results of the three‐point bending tests and fiber push‐in tests, microwave‐cured laminates displayed enhanced interlaminar and interfacial bonding properties in comparison to thermally cured counterparts, resulting in a 10.74% increase in interlaminar shear strength (ILSS) and a 20.23% rise in interfacial shear strength (IFSS). Highlights: Carbon fibers exhibits a more pronounced ability to absorb microwaves than resins.Microwave‐cured laminate achieves a higher degree of curing reaction.Microwave curing enhances the ILSS and IFSS of composite materials. [ABSTRACT FROM AUTHOR]