Tough Bioinspired Composites That Self-Report Damage

Abstract

The increasing use of lightweight composite materials in structural applications requires the development of new damage monitoring technologies to ensure their safe use and prevent accidents. Although several molecular strategies have been proposed to report damage in polymers through mechanochromic responses, these approaches have not yet been translated into lightweight bioinspired composites for load-bearing applications. Here, we report on the development of bioinspired laminates of alternating polymer and nacre-like layers that combine optical translucency, high fracture toughness, and damage-reporting capabilities. The composites signal damage via a fluorescence color change that arises from the force activation of mechanophore molecules embedded in the material’s polymer phase. A quantitative correlation between the applied strain and the fluorescence intensity was successfully established. We demonstrate that optical imaging of mechanically loaded composites allows for the localized detection of damage prior to fracture. This fluorescence-based self-reporting mechanism offers a promising approach for the early detection of damage in lightweight structural composites and can serve as a useful tool for the analysis of fracture processes in bulk transparent materials.

Stress-Dependent Multicolor Mechanochromism in Epoxy Thermosets Based on Rhodamine and Diaminodiphenylmethane Mechanophores

“…Mechanochromic polymers (MCPs) capable of changing their visible or fluorescent color in response to mechanical forces (e.g., tensile or compression) have attracted extensive attention and thus have undergone significant development. − Various MCPs have shown potential for application in damage detection, − stress sensing, , and security communication. , Although promising, most mechanochromic changes in solid polymer systems have been realized in elastomers with a low modulus and high elongation at break. Realizing mechanochromism in strong structural polymers, for which damage detection capability is the most critical, remains a challenge. , …”

Mechanochromophore‐Linked Polymeric Materials with Visible Color Changes

“…Magrini et al reported a multilayered bulk composite with damage reporting ability via assembling SP cross‐linked poly(2‐hydroxyethyl methacrylate)‐poly(urethane diacrylate) with glass composite layers. [ 183 ] Fluorescence color changes upon loading were measured in the system.…”

Glow Stick‐Inspired Multilayered Composites with Damage Self‐Reporting and Self‐Healing Properties for Aquatic Environments

“…Inspired by nature, the selfreporting and self-healing materials have been developed to reduce the inspection cost and prolong the service life of materials. [2][3][4][5][6][7][8][9] By introducing dynamic covalent and noncovalent bonds into polymer matrices, self-healing properties can be imparted to the materials. [10,11] However, the self-healing polymers based on supramolecular interactions, including hydrogen bonding, metal-ligand coordination, electrostatic interactions, are generally unstable underwater because the reversible bonding reconnection during self-healing would be disturbed by water molecules.…”