Stress and structural damage sensing piezospectroscopic coatings validated with digital image correlation

Abstract

The piezospectroscopic effect, relating a material’s stress state and spectral signature, has recently demonstrated tailorable sensitivity when the photo-luminescent alpha alumina is distributed in nanoparticulate form within a matrix. Here, the stress-sensing behavior of an alumina-epoxy nanoparticle coating, applied to a composite substrate in an open hole tension configuration, is validated with the biaxial strain field concurrently determined through digital image correlation. The coating achieved early detection of composite failure initiation at 77% failure load, and subsequently tracked stress distribution in the immediate vicinity of the crack as it progressed, demonstrating non-invasive stress and damage detection with multi-scale spatial resolution.

Application of Stress Sensing Coatings on Metal Substrates with a Sub-surface Notch

“…An open-hole tension (OHT) carbon fiber reinforced polymer (CFRP) substrate with a PS coating consisting of 20 vol% of α-alumina nanoparticles in epoxy matrix was manufactured and tested. The coating detected internal ply damage at 76 % failure load, which was well before it surfaced at 92 % failure load as measured by digital image correlation (DIC) [9].…”

“…However, it was reported that 38 vol% of α-alumina is the maximum limit to be added to a polymer matrix to improve its mechanical properties [8]. Freihofer et al [9] demonstrated the capability of PS coatings in monitoring stress on a composite laminate substrate when it is subjected to load and detecting damage before failure occurs. An open-hole tension (OHT) carbon fiber reinforced polymer (CFRP) substrate with a PS coating consisting of 20 vol% of α-alumina nanoparticles in epoxy matrix was manufactured and tested.…”

Damage mapping with a degrading elastic modulus using piezospectroscopic coatings

“…Spatial measurements of substrate strain and PS shift were obtained simultaneously for the first time in an novel experiment [23]. The PS relationships originate from the distortion of the Ligand field around the Cr 3 þ substitutional impurity within the Al 2 O 3 lattice.…”

“…The applications of piezospectroscopy have recently been expanded by the fabrication of alumina-epoxy nanocomposites with tailorable mechanical and PS properties [20]. This produced a material which can be applied as a compliant coating to structures for stress sensing [21][22][23]. In the process of holistically understanding the multi-scale mechanics of these new materials, the solution of an effective elastic modulus of the nanocomposite with the experimental PS response was discovered [24].…”

Quantifying Alumina Nanoparticle Dispersion in Hybrid Carbon Fiber Composites Using Photoluminescent Spectroscopy

“…Specifically, a carbon fiber composite modified with additional nanoparticles is commonly referred to as a hybrid carbon fiber reinforced polymer (HCFRP). Whether in high performing composites or other applications, particle dispersion is important for many properties, including strength, modulus, and fracture toughness [12][13][14][15][16][17][18][19][20][21]. While there are a few methods to improve dispersion, such as the use of ultrasonic waves [22], achieving good dispersion of nanoparticles is known to be very difficult, with challenges such as agglomerations and sedimentation often encountered at high particle loadings [20].…”