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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.

A methodology for designing cylindrical origami with different patterns and different cross-sectional shapes is presented. Planar and cylindrical origami with curved-crease patterns are designed and proved to be foldable and developable regardless of the type of crease line. Specifically, cylindrical origami structures with arc-Miura pattern and circular cross section, arc pattern and circular cross section, arc-Miura pattern and triangular cross section, arc pattern and triangular cross section are designed. The relationships between the two-dimensional (2D) crease lines in a sheet and three-dimensional (3D) spatial origami structures are derived. Fabrications of cylindrical origami by a folding process are performed to validate the design theory for 2D crease lines. This work paves the way for applications for cylindrical origami in engineering, such as energy absorption.

Origami offers a novel design possibility for periodic sandwich cores. The curved-crease origami is adopted to enhance the anti-buckling performance and reduce the abrupt change of the carbon fibers in the origami sandwich cores. CFRP curved-crease origami sandwich structures were fabricated using a hot press molding method. Analytical models were developed for predicting the shear stiffness and strength concerning different failure modes including debonding, compressive and shear buckling, tensile, compressive and shear fracture in both transverse and longitudinal directions. The shear deformation histories, failure modes, strength and stiffness of the sandwich structures were investigated through experiments and finite element analysis (FEA). The analytical models, experiments, and simulations agree with each other reasonably. The origami sandwich undergoes buckling failure when the wall thickness of the origami core is sufficiently thin. With the increase of the wall thickness, debonding between the face sheets and the origami cores usually occurs instead of fracture. The exploration of the shear behaviors lays the foundation for the applications of the origami sandwich structures in the lightweight construction fields.