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A carbon fiber-reinforced composite foldcore based on curved-crease origami was designed and fabricated using a hot press molding method. The fabrication process based on curved-crease origami reduces the abrupt change in fiber direction and is more suitable for continuous fiber-reinforced composites. The analytical models based on differential and integral method for predicting the compressive stiffness and strength of curved-crease origami foldcores were developed first and a three-dimensional failure mechanism map was constructed. The compressive properties and failure modes of carbon fiber reinforced composite curved-crease origami foldcores were investigated through experiments and finite element analysis (FEA). A reasonable agreement among the analytical models, experiments, and FEA results was observed. The dominant failure mode in the curved-crease origami foldcores could change from buckling to crushing with the wall thickness of foldcores increasing when subjected to compressive loads. The novel curved-crease origami design with open core channels has potential to applications for lightweight multifunctional structures, such as fuselage panels of airplane.

A series of expanded graphite (EG), hybrid fillers, and foam materials (FM) filled with epoxy resin (EP) composites were designed and fabricated to improve the thermal conductivity of neat EP composites. The effects of the particle size and volume fraction, modification of the EG, the ratio of EG (100):EG(300), the acidification of carbon nanotubes (CNTs), and the construction of 3D network structure of FM on the thermal conductivity, thermal stability and mechanical properties (tensile strength and compressive) of the composites were investigated experimentally. The thermal conductivity of the composite, which is filled with 0.2-μm copper foam, is up to 9.91 W/(m K) and almost 82 times compared to the pure EP composites.

A folding fabrication method inspired by origami for carbon fiber-reinforced composites to fabricate three-dimensional structures is presented. PMI foams serve as substrates, making it possible to manufacture this kind of origami-inspired composite sandwich materials in a single-step process. Analytical models are proposed to provide upper and lower bounds of the out-of-plane compressive strength of the origami-inspired composite sandwich materials. Finite element analysis (FEA) and experiments are conducted to characterize the compressive behaviors including the deformation history, failure mode, strength, etc., and verify the validity of the analytical models. By incorporating PMI foams, the out-of-plane compressive failure mode of the composite sandwich material at low relative density changes from buckling to wrinkling or crushing, thus greatly increasing the strength. Additionally, the energy absorption capacity is significantly enhanced due to the PMI foams and their interaction with the composite origami core. This work creates a new method to fold composites into lightweight sandwich materials with high strength and high energy absorption, paving the way for their applications in transport, energy and communication.