Progress in Self‐Healing Fiber‐Reinforced Polymer Composites

Abstract

With the potential for small-scale damage to grow or coalesce under subsequent loading, FRP structures incorporate high safety factors to account for this defect sensitivity to ensure they will remain load bearing throughout their service life. This paradigm has resulted in many research groups worldwide exploring and developing the concept of self-healing or selfrepair being applied to FRPs, with the aim of achieving autonomous structural recovery via an embedded functionality, to address damage formation in its early stages before the integrity of the structure is compromised. In principle, this could reduce the structural redundancy and fully realize the mass saving associated with using FRP composite materials. This paper sets out to review the current state of the art in applying self-healing/self-repair to high-performing advanced fiber-reinforced polymer composite materials. Our definition of an advanced fiber-reinforced polymer composite material for this work is as follows:Our review discusses what has been achieved to date, the ongoing challenges which have arisen in implementing selfhealing into FRPs, how considerations for industrialization and large-scale manufacture must be considered from the outset, where self-healing may provide the most benefits (with respect to current FRP approaches to design), and how a functionality like self-healing can be validated for application in real structures.A significant proportion of self-healing studies have focused on assessing the healing efficiency of the system in bulk polymers, liquid (or low fiber volume) polymers, particulate composites, or low-volume fraction fiber-reinforced materials with inferior mechanical properties. [1,2] Comparatively, limited research has been undertaken on self-healing in advanced FRP composite materials, specifically based on systems commonly used in industry or those that possess high-performance characteristics.Two broad categories of self-healing systems can be found in the available literature: [3] i) intrinsic self-healing systems, which can heal a crack through interactions (physical or chemical) at the molecular level; ii) extrinsic self-healing systems, which This paper sets out to review the current state of the art in applying selfhealing/self-repair to high-performing advanced fiber-reinforced polymer composite materials (FRPs). A significant proportion of self-healing studies have focused so far on developing and assessing healing efficiency of bulk polymer systems, applied to particulate composites or low-volume fraction fiber-reinforced materials. Only limited research is undertaken on self-healing in advanced structural FRP composite materials. This review focuses on what is achieved to date, the ongoing challenges which have arisen in implementing self-healing into FRPs, how considerations for industrialization and large-scale manufacture must be considered from the outset, where selfhealing may provide most benefits, and how a functionality like self-healing can be validated for application in real structures. ...

Materials as Machines

“…The processability of this PU SMP formulation enables its straightforward reconfiguration into numerous form factors, which, at the time opened up new opportunities for SMPs 341,342. Today, countless reports detail the integration of SMPs of a range of compositions and network chemistries into end uses spanning from deployable space structures343–345 to medical implants346–349…”

“…While SMPs are not competitive with the energy densities achievable with SMA actuators, these materials have other distinct attributes: compositional variation, processability, and morphological diversity that differentiate their use and motivate integration in robotic devices. Foremost of these benefits is the considerable weight savings associated with the density of SMPs (polyurethanes—1.25 g cm ‐3 ) when compared to SMAs (Nitinol—6.4 g cm ‐3 ) 349,351. Another key advantage of SMPs in robotics is their tolerance of large deformations during shape memory cycling.…”

Self‐Healing Materials are Coming of Age

“…Collage of self‐healing materials addressed in the current Special Issue. Reproduced with permission …”

Low Temperature‐Based Flexural Properties of Carbon Fiber/Epoxy Composite Laminates Incorporated with Carbon Nanotube Sheets

“…Meanwhile, some other literatures also reported that the G IC , G IIC , ILSS, and flexural strengths of the FRPs can be improved by 98-150%, [16,17] 30-200%, [16,17] 10-69%, [18][19][20][21] and 8-26%, [22][23][24][25] respectively, by incorporating with CNTs-based resin films or coating interleaves. Obviously, previous studies have already demonstrated that the CNTBP-based interleaf shows significant reinforcing effect on the interlaminar performance of the FRPs, but these researches are usually carried out at room temperature and how the CNTBP affects the mechanical properties under low temperature is rarely considered.Due to the high strength, rigidity, thermal conductivity, and corrosion resistance, carbon FRPs (CFRPs) are increasingly utilized in high-tech engineering applications, such as airframes, space shuttles, satellites, cryogenic fuel tanks, [26,27] in which, some CFRP structures would undergo low-temperature environments such as ranging from 0 to −60 °C (e.g., airframes), and others might be exposed to cryogenic environment such as reaching −250 °C (e.g., liquid hydrogen tank). [28] On the Carbon Nanotubes This study introduces carbon nanotube buckypaper (CNTBP) into the easily fractured sites of [0°] 16 and [0°/90°] 4S composite laminates, and comparatively explores how the CNTBP affects the flexural properties of the laminates at 25, −15, and −55 °C.…”

“…Due to the high strength, rigidity, thermal conductivity, and corrosion resistance, carbon FRPs (CFRPs) are increasingly utilized in high-tech engineering applications, such as airframes, space shuttles, satellites, cryogenic fuel tanks, [26,27] in which, some CFRP structures would undergo low-temperature environments such as ranging from 0 to −60 °C (e.g., airframes), and others might be exposed to cryogenic environment such as reaching −250 °C (e.g., liquid hydrogen tank). [28] On the Carbon Nanotubes This study introduces carbon nanotube buckypaper (CNTBP) into the easily fractured sites of [0°] 16 and [0°/90°] 4S composite laminates, and comparatively explores how the CNTBP affects the flexural properties of the laminates at 25, −15, and −55 °C.…”