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Human bone demonstrates superior mechanical properties due to its sophisticated hierarchical architecture spanning from the nano/microscopic level to the macroscopic. Bone grafts are in high demand due to the rising number of surgeries because of increasing incidence of orthopedic disorders, non‐union fractures, and injuries in the geriatric population. The bone scaffolds need to provide porous matrix with interconnected porosity for tissue growth as well as sufficient strength to withstand physiological loads, and be compatible with physiological remodeling by osteoclasts/osteoblasts. The‐state‐of‐art additive manufacturing (AM) technologies for bone tissue engineering enable the manipulation of gross geometries, for example, they rely on the gaps between printed materials to create interconnected pores in 3D scaffolds. Herein, the authors firstly print hierarchical and porous hydroxyapatite (HAP) structures with interconnected pores to mimic human bones from microscopic (below 10 µm) to macroscopic (submillimeter to millimeter level) by combining freeze casting and extrusion‐based 3D printing. The compression test of 3D printed scaffold demonstrates superior compressive stress (22 MPa) and strain (4.4%). The human mesenchymal stromal cells (MSCs) tests demonstrate the biocompatibility of printed scaffold.

3D printing of continuous carbon fiber reinforced thermoplastic (CFRTP) composites is increasingly under development owing to its unparalleled flexibility of manufacturing 3D structures over traditional manufacturing processes. However, key issues, such as weak interlayer bonding, voids between beads and layers, and low volume ratio of carbon fiber, in the mainstream fuse deposition modeling (FDM) and extrusion suppress the applications of these techniques in mission‐critical applications, such as aerospace and defense. This communication reports a novel approach, inspired by laminated object manufacturing (LOM), for 3D printing of continuous CFRTPs using prepreg composite sheets. The prepreg sheets are successively cut based on the sliced CAD geometry, and then bonded layer upon layer using a CO2 laser beam and a consolidation roller system. The void content is low by computed tomography scans and interlaminar bonding strength is as high as conventional autoclave method by lap shear strength tests. The excellent interfacial bonding strength and high volume ratio of continuous carbon fiber contribute to the highest reported tensile strength (668.3 MPa) and flexural strength (591.16 MPa) to date, for all 3D printed CFRTPs. Moreover, the proposed technique also enables controlling the alignment of carbon fiber in printed layers. CFRTPs with unidirectional [0°]s, cross‐ply [0/90°]s, and [0/‐45/0/45°]s fiber reinforcement are produced and evaluated for mechanical properties. The proposed 3D printing method is broadly beneficial for industries requiring high performance and lightweight structural materials with complex geometries.

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Continuous carbon fiber reinforced polymer composites (CFRPCs) exhibiting superior mechanical properties have emerged as high-performance engineering materials for various industrial applications. Additive manufacturing (AM) of CFRPCs enables production of customized structures with superior mechanical properties at a low cost and has gained tremendous popularity. In the present study, a novel AM technique namely laser-assisted laminated object manufacturing (LA-LOM) is proposed for producing CFRPCs using prepreg sheets with continuous carbon fiber reinforcement. The interfacial properties of the bonded prepreg sheets are critical for the performance of the additively manufactured CFRPCs. We further introduce graphene as a modifier between the prepreg sheets to improve the mechanical properties of the CFRPCs. It is shown that low porosity (0.38%), high concentrations of continuous carbon fibers (63 wt. %), and improved interfacial bonding strength contribute to excellent mechanical properties. For the composite structure ([0 ]s fiber arrangements), in which 0.5 mg/ml graphene is introduced as interface modifier, the lap shear strength, tensile strength, and tensile modulus are 18 MPa, 2940 MPa, and 170 GPa, respectively, and the flexural strength and modulus are 1310 MPa and 140 GPa, respectively.The tensile strength and modulus outperform all AM-produced structures reported in literature, including carbon fiber composites and metals and metal alloys. Meanwhile, the increases are observed in the lap shear strength by 25%, flexural strength by 10%, and flexural modulus by 27%, as well as tensile strength by 7% and modulus by 6%, compared to specimens without graphene reinforcement. This composite architecture design, involving laminated continuous carbon fiber reinforced prepreg sheets and graphene-modified interfaces, provides a readily scalable manufacturing method toward excellent properties and this method can be further explored in industrial applications.

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