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Lightweight cellular materials are engineered to enhance performance attributes such as energy absorption, specific stiffness, negative Poisson's ratio, negative thermal expansion coefficient, etc. However, self‐sensing functionality of such architected materials is seldom explored. Herein, a combined experimental and numerical study on additive manufacturing (AM)‐enabled self‐sensing cellular composites processed via fused filament fabrication, utilizing in‐house engineered multiwall carbon nanotube (MWCNT)/polypropylene random copolymer (PPR) filament feedstocks, is reported. The tunable self‐sensing and enhanced mechanical performance of PPR/MWCNT lattices are experimentally demonstrated by varying their architectural parameters in addition to the MWCNT content. The lattices reveal strain and damage sensitivity gauge factors of 12 and 1.2, respectively, comparable to bulk materials' commercial gauge factors. Furthermore, self‐sensing lattices exhibit 200%, 155%, 153%, and 137% increase in stiffness, energy absorption capacity (as high as 4.7 MJ m−3), specific energy absorption (20.5 J g−1), and energy absorption efficiency (90%), respectively, compared with their non‐reinforced counterparts. The tunable multifunctional performance of AM‐enabled cellular composites demonstrated here provides guidelines for the design and development of composite lattices with advantaged structural and functional properties for an array of applications such as patient‐specific biomedical devices capable of measuring comfort in prosthetics. [ABSTRACT FROM AUTHOR]

This study is focused on carbon nanostructures (CNS), including both carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), reinforcement of medical‐grade polyetheretherketone (PEEK), and in vitro bioactivity for biomedical structural applications. CNS/PEEK scaffolds and bulk specimens, realized via fused filament fabrication (FFF) additive manufacturing, are assessed primarily in the low‐strain linear‐elastic regime. 3D printed PEEK nanocomposites are found to have enhanced mechanical properties in all cases while maintaining the desired degree of crystallinity in the range of 30–33%. A synergetic effect of the CNS and sulfonation toward bioactivity is observed—apatite growth in simulated body fluid increases by 57% and 77%, for CNT and GNP reinforcement, respectively, doubling the effect of sulfonation and exhibiting a fully‐grown mushroom‐like apatite morphology. Further, CNT‐ and GNP‐reinforced sulfonated PEEK recovers much of the mechanical losses in modulus and strength due to sulfonation, in one case (GNP reinforcement) increasing the yield and ultimate strengths beyond the (non‐sulfonated) printed PEEK. Additive manufacturing of PEEK with CNS reinforcement demonstrated here opens up many design opportunities for structural and biomedical applications, including personalized bioactivated surfaces for bone scaffolds, with further potential arising from the electrically conductive nanoengineered PEEK material toward smart and multifunctional structures. [ABSTRACT FROM AUTHOR]

Multilayered multi‐material interfaces are encountered in an array of fields. Here, enhanced mechanical performance of such multi‐material interfaces is demonstrated, focusing on strength and stiffness, by employing bondlayers with spatially‐tuned elastic properties realized via 3D printing. Compliance of the bondlayer is varied along the bondlength with increased compliance at the ends to relieve stress concentrations. Experimental testing to failure of a tri‐layered assembly in a single‐lap joint configuration, including optical strain mapping, reveals that the stress and strain redistribution of the compliance‐tailored bondlayer increases strength by 100% and toughness by 60%, compared to a constant modulus bondlayer, while maintaining the stiffness of the joint with the homogeneous stiff bondlayer. Analyses show that the stress concentrations for both peel and shear stress in the bondlayer have a global minimum when the compliant bond at the lap end comprises ≈10% of the bondlength, and further that increased multilayer performance also holds for long (relative to critical shear transfer length) bondlengths. Damage and failure resistance of multi‐material interfaces can be improved substantially via the compliance‐tailoring demonstrated here, with immediate relevance in additive manufacturing joining applications, and shows promise for generalized joining applications including adhesive bonding. [ABSTRACT FROM AUTHOR]

The carbon nanotube comprised nanocomposite further provides multifunctionality via strain-and damage-sensing, to create a multifunctional high performance lattice for a variety of applications including patient-specific smart orthopedic braces. Multifunctionality of Nanoengineered Self-Sensing Lattices Enabled by Additive Manufacturing Enhanced mechanical performance across many parameters is achieved via nanoengineering of polymer lattices realized via fused filament fabrication additive manufacturing, as described in the article number 2200194 by Shanmugam Kumar and co-workers. [Extracted from the article]

Additive manufacturing (AM) of composites, particularly continuous fiber composites as studied here, is emerging as a new paradigm for creating advanced structures. Traditional machining and joining approaches will evolve or be fully displaced by AM approaches, and here the authors introduce a seminal investigation into AM‐enabled bonding/joining of continuous fiber composite laminates/multilayers. The AM‐enabled tailoring approach volumetrically increases surface area available for bonding by ∼150% by printing lines of continuous Nylon matrix filaments at an infill density of 50% to create a porous (∼50 vol%) bonding surface, rather than the conventional/baseline solid (100 vol%) surface approach. The AM‐tailored multilayers show improvements relative to the baseline single‐lap‐joint (SLJ) multilayer, and versus the industry‐standard surface preparation approach: 550% and 145% increases in ultimate strength, 10 000% and 800% increases in toughness, respectively, while maintaining joint stiffness. Benchmark mechanical performance data is established via the AM‐tailored bonding approach for carbon, glass, and Kevlar continuous fiber reinforced additively manufactured composite SLJ multilayers. AM‐enabled enhanced joining, such as the concept demonstrated here, is critical as AM components are increasingly being joined, both to each other and to other (non‐AM, different AM, etc.) structures in advanced applications. A new additive manufacturing‐enabled surface tailoring approach demonstrated here for bonding/joining of continuous fiber composite laminates/multilayers increases the mechanical performance such as strength by 550% and 145% and toughness by 10 000% and 800%, relative to the baseline multilayer and the industry‐standard surface preparation approach, respectively, while maintaining the stiffness of the baseline multilayer. [ABSTRACT FROM AUTHOR]