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Macroscopic 3D graphene has become a significant topic for satisfying the continuously upgraded smart structures and devices. Compared with liquid assembling and catalytic templating methods, laser‐induced graphene (LIG) is showing facile and scalable advantages but still faces limited sizes and geometries by using template induction or on‐site lay‐up strategies. In this work, a new LIG protocol is developed for facile stacking and shaping 3D LIG macrostructures by laminating layers of LIG papers (LIGPs) with combined resin infiltration and hot pressing. Specifically, the constructed 3D LIGP composites (LIGP‐C) are compatible with large area, high thickness, and customizable flat or curved shapes. Additionally, systematic research is explored for investigating critical processing parameters on tuning its multifunctional properties. As the laminated layers are stacked from 1 to 10, it is discovered that piezoresistivity (i.e., gauge factor) of LIGP‐C dramatically reflects an ≈3900% improvement from 0.39 to 15.7 while mechanical and electrical properties maintain simultaneously at the highest levels, attributed to the formation of densely packed fusion layers. Along with excellent durability for resisting multiple harsh environments, a sensor‐array system with 5 × 5 LIGP‐C elements is finally demonstrated on fiber‐reinforced polymeric composites for accurate strain mapping. [ABSTRACT FROM AUTHOR]

Abstract Carbon nanomaterials (CNM) based technology has offered a variety of promising strategies for self-sensing and diagnosing functionalities in polymeric composites. In comparison with studies about detecting deformations and cracks, monitoring the manufacturing stage of composites using CNMs is rather limited. Based on continuous fabrication, we systematically investigated carbon nanotubes (CNTs) coated, graphene coated and carbon fiber sensors for monitoring complete molding process of composites through the real-time resistance change. Comparing to graphene-coated and carbon fibers with densely and continuously packed graphitic structures, the CNT fiber sensor with entangled and loosely packed porous network shows far superior performance for sensing different processing stages of composites, including resin infusion, gelation and curing. The resistance decay of the CNT sensor agrees well with curing kinetics measured by differential scanning calorimetry. Versatile capabilities of the CNT sensor were further explored for identifying various flowing defects such as dry spots and partially infiltrated areas. [ABSTRACT FROM AUTHOR]

Abstract: With glass, polyaramid, nylon and polyethylene terephthalate as the fiber substrate, a continuous spray coating and winding process was developed for fabricating SWCNT-FibSen sensor – single-walled carbon nanotube (SWCNT) thin film enabled 1D fiber sensor. The microstructures of the SWCNT-FibSen and its piezoresistive behavior were respectively characterized by scanning electron microscopy and Raman spectroscopy and evaluated by the coupled electromechanical tensile test. With embedding the SWCNT-FibSen sensor in the fiberglass prepreg laminates at different orientations and locations, its use for multipurpose sensing in life-long (from manufacturing to failure) structural health monitoring of high-performance polymeric composites was demonstrated. During the manufacturing process, the sensor was able to provide valuable local resin curing information. After the manufacturing process, the sensor was useful in mapping the stress/strain states of the host composite under different deformation modes – tension, bending, compression and failure. The integrity of the sensing performance of the embedded SWCNT-FibSen sensor was demonstrated upon a 10,000-cyclic coupled electromechanical test. [Copyright &y& Elsevier]

Carbon nanomaterials have gradually demonstrated their superiority for in-line process monitoring of high-performance composites. To explore the advantages of structures, properties, as well as sensing mechanisms, three types of carbon nanomaterials-based fiber sensors, namely, carbon nanotube-coated fibers, reduced graphene oxide-coated fibers, and carbon fibers, were produced and used as key sensing elements embedded in fabrics for monitoring the manufacturing process of fiber-reinforced polymeric composites. Detailed microstructural characterizations were performed through SEM and Raman analyses. The resistance change of the smart fabric was monitored in the real-time process of composite manufacturing. By systematically analyzing the piezoresistive performance, a three-stage sensing behavior has been achieved for registering resin infiltration, gelation, cross-linking, and post-curing. In the first stage, the incorporation of resin expands the packing structure of various sensing media and introduces different levels of increases in the resistance. In the second stage, the concomitant resin shrinkage dominates the resistance attenuation after reaching the maximum level. In the last stage, the diminished shrinkage effect competes with the disruption of the conducting network, resulting in continuous rising or depressing of the resistance. [ABSTRACT FROM AUTHOR]

Carbon nanomaterials enabled fibers have been witnessed as a promising technology for in situ structural health monitoring of polymeric composites. Self-sensing composites were enabled with varied integration strategies, including carbon nanotube (CNT) coated fibers (CNTF), reduced graphene oxide (RGO) coated fibers (RGOF) and carbon fibers (CF). Piezoresistive response of varied sensors was disclosed and showed that gauge sensitivity of RGOF is the highest with a clear two-stage performance from linear to non-linear, while CNTF consistently shows well-organized signal before final fracture. Resin infiltration theory was raised to explain the observed structure–property relationship. For CNTF, resin molecules are permeable to its porous network and form integrated CNT/resin nanocomposites. Comparatively, RGO with large lateral dimension and surface conformability forms the noninvasive network from resin penetration. Based on results analysis and mechanism study, CNTF is more suitable for status recognition and long-term purposes; RGOF is more feasible for early warning of structural damages. [ABSTRACT FROM AUTHOR]

Laser-induced graphene (LIG) has provided a facile and effective strategy for graphene formation via one-step laser scribing on polymer structures. However, the direct utilization of LIG toward multifunctionalization for high-performance fiber-reinforced polymeric composites (FRPs) is rarely explored. Aiming to integrate the laser-induced graphitic structure (LIGS) with FRPs through the most facilitated approach, herein, we innovatively report a self-converted strategy for manufacturing multifunctional LIGS-hybridized FRP-composites (LIGC). By incorporating the laser irradiation process on either pristine or fully-cured epoxy prepregs at different stages of composite manufacturing, two paths of LIGS formation have been naturally developed to respectively implant the designable graphitized patterns interlaminarly or superficially. Benefiting from systematic processing-dependent-structural analysis, diversified properties of LIGC can be modulated for simultaneously achieving the optimized electrical conductivity (~0.74 kΩ/sq) as well as the negligible mechanical degradation (<1.58%) compared with neat composites. By virtue of bimodally selectable processes along with tunable properties, the novel LIGC structure is highly advantageous with multifunctions, including sensing (monitoring resin-cure, mechanical-deformations, & hazardous liquids), self-defensing (de-icing & fire retardancy), and energy-harvesting (supercapacitors). Image 1 [ABSTRACT FROM AUTHOR]