No 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. ...

The current state‐of‐the‐art in applying self‐healing/self‐repair concepts to structural high‐performing fiber reinforced polymer composite materials relies on several approaches: Inserting healing capsules (left), vascules (middle), or using intrinsically healing matrices (right). Achievements, processing routes, resulting structural properties, healing assessment methods and challenges for industrialization are reviewed by Amaël Cohades, Ian Bond, Véronique Michaud and co‐workers in article number https://doi.org/10.1002/admi.201800177.

A new approach to self-healing systems is presented that aims to overcome the inherent drawbacks of conventional liquid resin based healing systems within composites. Finite embedded systems offer limited healing potential for small volume delaminations and as such cannot effectively heal large damage volumes often associated with shear damaged sandwich panel structures or debonding between skin and core. An expanding polymer based approach aims to overcome such limitations. The mechanical and physical properties of a prepared polyepoxide foam are investigated and how the inclusion of a carbon fibre reinforcement within the foam affects processability and performance. The healing efficiency of different polymer foams to heal damaged structures is also investigated. A secondary investigation is also presented that aimed to overcome the drawbacks associated with the requirement for stoichiometric mixing of two part healing agents, or for healing agent to come into direct contact with a catalyst embedded within the matrix material. Different approaches were taken to develop a self-healing system that once deployed required no additional mixing or stimuli for healing to occur.