The present work aimed to study the quasi-static compression behaviors of 3D printed continuous ramie fiber reinforced biocomposite corrugated structures (CFCSs) with excellent shape memory effects. The in-plane compression test was conducted to evaluate the effects of cell shapes, fiber volume fraction ( f _v ) and addition of fiber on the compression behaviors and energy absorption (EA) characteristics of the corrugated structures. The results showed that the compression property and EA capacity of the 3D printed CFCSs increased with decreasing f _v and the addition of continuous ramie yarn. The 3D printed continuous ramie fiber reinforced biocomposite with inverted trapezoid cell shape corrugated structures (CFITCSs) outperformed other cell shapes in the compression strength and specific EA. The analytical model for the in-plane compression strength of CFITCSs was derived, and predictions were in good agreement with measurements. In addition, continuous natural fiber reinforced composite structure for shape memory was proposed for the first time. The shape recovery testing results demonstrated that 3D printed CFCSs had the potential to be a key element of lightweight programmable smart systems.

Composite materials are increasingly required to operate in cryogenic environments, including liquid hydrogen and oxygen storage, deep-space structures, and polar infrastructures, where long-term strength, toughness, and reliability are essential. This review provides a unique contribution by systematically integrating recent advances in understanding cryogenic behaviour into a unified multi-scale framework. This framework synthesises four critical and interconnected aspects: constituent response, composite performance, enhancement mechanisms, and modelling strategies. At the constituent level, fibres retain stiffness, polymer matrices stiffen but embrittle, and nanoparticles offer tunable thermal and mechanical functions, which collectively define the system-level performance where thermal expansion mismatch, matrix embrittlement, and interfacial degradation dominate failure. The review further details toughening strategies achieved through nano-addition, hybrid fibre architectures, and thin-ply laminates. Modelling strategies, from molecular dynamics to multiscale finite element analysis, are discussed as predictive tools that link these scales, supported by the critical need for in situ experimental validation. The primary objective of this synthesis is to establish a coherent perspective that bridges fundamental material behaviour to structural reliability. Despite these advances, remaining challenges include consistent property characterisation at low temperature, physics-informed interface and damage models, and standardised testing protocols. Future progress will depend on integrated frameworks linking high-fidelity data, cross-scale modelling, and validation to enable safe deployment of next-generation cryogenic composites.

The present work aimed to examine the tensile and flexural behaviors of biocomposites reinforced with continuous plant fibers, utilizing a range of polylactic acid (PLA) matrix materials and varying fiber content. These biocomposites were fabricated using an in situ-impregnated fused filament fabrication (FFF) technique. The study incorporated three different PLA matrix materials, namely PLA, PLA-Matte (PLA-Ma), and PLA-ST, each with distinct mechanical properties. The effect of different linear densities of continuous ramie yarns on the biocomposites was also investigated. The results show that adding continuous ramie yarn significantly enhances both the tensile and flexural strengths, as well as the modulus, of the matrixes. Furthermore, there was a positive correlation between the content of ramie yarn and the increases in strength and modulus. Moreover, the introduction of ramie yarns altered the fracture behavior of the biocomposites, shifting towards brittle fracture. This change significantly impacted the fracture toughness of the matrixes and resulted in a convergence of elongation at the point of breakage.

In recent years, innovations in 3D/4D printing techniques for continuous fiber-reinforced polymer composites (CFRPCs) have opened new perspectives for the integrated design and manufacture of composites with customized functions. This paper reviews the current state of 3D/4D printed functional composites, including the materials, shape memory/changing effects, self-monitoring/healing behaviors, and challenges surrounding additive-manufactured functional composites. Specifically, continuous fibers and matrices that provide functional roles are classified and discussed in detail. 4D printed shape memory and changing CFRPCs can retain their original shapes from a designed shape upon exposure to different external stimuli, including heat, electricity, humidity, and multi-stimuli activation. Furthermore, self-monitoring of structural health is achieved through the piezoresistive features of reinforced fibers in 3D printed CFRPCs. Finally, this review concludes with an outlook on the future research opportunities for 3D/4D printed functional CFRPCs.

The intralaminar crack propagation of the carbon/epoxy two-dimensional plain woven composite material has been experimentally investigated. It was found that the propagation direction is insensitive to pre-crack tip locations. The propagation path direction is aligned along the intersecting position of warp fibers and weft fibers weaving, and the extends forward along the crack tip until the final fracture failure. The crack propagation process has two major stages, the maximum energy accumulation stage (stage A) and the gradual release of energy stage (stage B). In stage B, there are many single or several fiber bundles breakage during these stages due to the characteristics of reinforcing fibers woven from multiple fiber bundles. The warp fiber bundles gradually break under the axial tensile loading. Analysis of the images obtained by the optical microscope and scanning electron microscope, the fracture surfaces of the specimens are all sawtoothed, the fracture damage of the plain woven single-layer laminate is mainly fiber bundles separation, breakage of the fiber, and debonding of the fiber and the matrix. In addition, the validity of the intralaminar crack propagation mechanisms is further verified by multi-layer laminate experiments.