However, traditional composites do not have built-in damage detection. That limitation can create safety risks, especially in demanding service environments. Self-sensing polymer composites with in situ structural health monitoring (SHM) capabilities address this issue by allowing materials to detect strain, damage, and failure as they occur.1-5
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Why Do We Need Self-Sensing Polymer Composites?
Polymer composites are valued for mechanical performance, but most of these materials rely on external inspection methods to identify damage. In many applications, internal cracks, delamination, or interfacial damage can develop before visible failure appears.
Self-sensing polymer composites help close that gap. By integrating conductive fibers, metallic nanoparticles, or conductive nanofillers into the composite, these materials can convert mechanical deformation into measurable electrical signals.
With this property structural health monitoring becomes possible without relying entirely on separate embedded electronics or external sensor systems.1-5
Carbon Fiber-reinforced Polymer Composites (CFRP)
In 1989, researchers used CFRP’s piezoresistive effect for the first time to detect tensile damage. Since then, carbon fiber has been used as an in situ strain sensor in polymer composites under flexural and tensile loading.1
For example, randomly embedded short carbon fibers in epoxy showed a significant change in electrical resistance under tension, with gauge factor values of at least 500 depending on loading conditions and content. This behavior was linked to changes in proximity between neighboring carbon fibers as strain developed.1
Studies have also investigated the unidirectional CFRP’s electromechanical behavior under cyclic tension, impact, bending, and compression. During cyclic tensile testing, fractional change in resistance (ΔR/R0) decreased as tensile strain increased, provided the stress amplitude remained below the fiber breaking stress. This was attributed to strain-induced improvement in fiber alignment.
After a certain number of cycles, the resistance change became irreversible because of fiber breakage. Similarly, in the out-of-plane through-thickness direction, CFRP laminate resistance decreased as compression strain increased because the contact area between corrugated carbon fibers grew. This irreversible conductivity change suggested irreversible microstructural damage in the interfacial or interlaminar region during cyclic loading.1
CFRP bending studies showed a similar pattern. In the elastic region, compressive surface resistance decreased reversibly, while oblique and tensile surface resistances increased. Once the material entered the nonlinear region, notable damage occurred, and the oblique and compression surface resistances increased irreversibly and abruptly before the tension surface resistance.1
This matched experimental observations showing crack initiation at the compression surface before propagation toward the tension surface.1
Various drop-weight impact energies also caused differences in electrical resistivity in the CFRP laminates, associated with the degree of internal and surface damage. For instance, fractional changes of 0.70 %, 0.21 %, and 0.32 % in resistance were observed for the oblique, bottom, and top surface resistances, respectively, after a 4.11 J impact. Upon impact, the CFRPs’ oblique resistance showed greater sensitivity owing to their interlaminar damage.1
Metallic Nanoparticle-modified FRP
Image Credit: AlexandrinaZ/Shutterstock.com
Metallic nanoparticles such as nickel, copper, silver, and zinc oxide (ZnO) have also been used to modify electrically insulating fibers before they are embedded in polymer composites for in situ damage detection and strain measurement.
One study compared the electromechanical responses of nickel-modified CFRP composites using dry nickel nanostrands (NiNs), insulated NiNs/silicone, and NiNs/epoxy nanocomposite patches embedded directly as piezoresistive sensors. Among these options, embedded NiN/epoxy patch samples showed the best stability, with no significant changes in nominal resistance even after 5000 cycles.1
A more recent study embedded nickel-coated carbon fiber (Ni-CF) tows into the second and third fabric layers of a glass fiber-reinforced plastic (GFRP) laminate. These were identified as GFRP/1’ Ni-CF and GFRP/2’ Ni-CF samples. The results showed that embedding the Ni-CF tow closer to the laminate’s upper surface improved damage detection sensitivity.
The GFRP/2’ Ni-CF laminate also showed nearly 100 % reliability at a 1.5 safety factor, as determined by statistical analysis, making it especially suitable for composite structures with demanding safety requirements.1,2
In another study, conductive silver nanoparticles were deposited onto nylon yarn via electroless plating to produce flexible nylon/silver strain sensors with gauge factors of 21-25. These sensors were then embedded into the bottom, middle, and upper plies of a GFRP laminate for cyclic three-point bending and flexural electromechanical testing. The embedded sensors detected structural damage and distinguished failure behavior from the electrical signal response.1
Self-Sensing Smart Plastics
Recent work from researchers at the University of Glasgow highlighted a new class of three-dimensional (3D)-printed smart plastics that can sense damage and strain in real time. These materials were developed for demanding applications, including aerospace structures and medical implants.3,4
The researchers used polyetheretherketone (PEEK), a high-performance plastic known for its low weight, toughness, biocompatibility, and engineering relevance. They combined this material with auxetic design principles to create structures that deform in unusual but predictable ways and produce an electrical response under stress.
In work published in Materials Horizons, the researchers showed that additive manufacturing could be used to create self-monitoring materials with programmable properties, including strain sensitivity, stretchability, and strength.3,4
Auxetic materials behave differently from ordinary materials because they become wider when stretched instead of thinner. This behavior can improve energy absorption and damage tolerance. To make use of these effects, the researchers 3D-printed complex auxetic lattices from PEEK-based feedstocks, including versions infused with carbon nanotubes.
The nanotubes provided electrical conductivity, allowing the lattices to act as sensors. As the structures deformed under mechanical strain, their internal electrical resistance changed measurably. This allowed the materials to self-sense compression, tension, and impact without the need for embedded electronics.4
The auxetic lattice designs used repeating double-ended Y-shaped units arranged in a branch-stem-branch layout. This geometry enabled the researchers to adjust each structure’s mechanical and electrical behavior by varying angles, thicknesses, and spacings.
The result was a catalog of materials with varying levels of auxeticity, strength, stiffness, and strain- or damage-sensitivity. Researchers also developed a computational model that predicted how these materials would behave under different loading conditions.
The model accurately captured the changes in electrical resistance during mechanical loading, enabling optimization of material performance before printing a physical sample. This work built on earlier research published in Additive Manufacturing, where the same group used polylactic acid (PLA) filled with carbon black to create 56 auxetic lattice structures.4,5
Table 1: Self-Sensing Polymer Composite Systems and Their Monitoring Functions
| Material system |
Sensing approach |
Key response |
Main advantage |
Applications |
| CFRP |
Carbon fiber piezoresistive effect |
Resistance changes under tension, bending, compression, and impact |
In situ strain and damage detection without separate sensors |
Aerospace and structural composites |
| Nickel-modified FRP |
Embedded nickel nanostrands or nickel-coated carbon fiber |
Stable electromechanical response and damage detection |
Improved signal stability and sensitivity in insulating laminates |
GFRP monitoring in high-safety structures |
| Silver-modified GFRP |
Silver-coated nylon yarn strain sensors |
Electrical signal changes during cyclic bending and flexural loading |
Can identify structural damage and distinguish failure behavior |
Flexible embedded sensing layers |
| PEEK auxetic smart plastics |
Conductive nanotube-filled printed lattices |
Quantifiable resistance changes during deformation |
Programmable strain sensitivity, stretchability, and damage response |
Aerospace parts and medical implants |
More on adaptive sensors here!
Applications Across Industries
The potential applications of self-sensing polymer composites span several industries. In aerospace, they can support lightweight components that monitor strain and damage during service. In automotive and marine engineering, they can improve reliability while helping maintain low structural mass.
In civil engineering, these materials could be used in load-bearing components where early damage detection is important for maintenance planning and long-term safety. In the biomedical field, smart PEEK-based materials may support implants and devices that respond to mechanical stress in real time.1-5
Conclusion
Self-sensing polymer composites are extending the role of composite materials beyond strength and durability alone. By integrating conductive fibers, metallic nanoparticles, and auxetic lattice designs, these materials can detect strain and damage in real time while still delivering the lightweight performance expected from advanced composites.
Developments in CFRP, nanoparticle-modified FRP, and 3D-printed PEEK systems show that structural health monitoring can now be built directly into the material itself. As additive manufacturing and multifunctional material design advance further, self-sensing polymer composites are becoming a practical option for safer, smarter structures in aerospace, biomedical, civil, and broader engineering applications.
References and Further Reading
- Tao, Y. et al. (2025). A comprehensive review on fiber-based self-sensing polymer composites for in situ structural health monitoring. Advanced Composites and Hybrid Materials, 8(5), 339. DOI:10.1007/s42114-025-01413-y, https://link.springer.com/article/10.1007/s42114-025-01413-y
- Zhao, Y. et al. (2022). In-situ structural health self-monitoring and diagnosing of glass fiber reinforced plastics with embedded nickel coated carbon fiber. Composites Part B: Engineering, 228, 109440. DOI:10.1016/j.compositesb.2021.109440, https://www.sciencedirect.com/science/article/abs/pii/S1359836821008088
- University of Glasgow Engineers Develop 3D-Printed Self-Sensing Smart Plastics [Online] Available at https://glasgowcityofscienceandinnovation.com/university-of-glasgow-engineers-develop-3d-printed-self-sensing-smart-plastics/ (Accessed on 08 April 2026)
- Schneider, J., Utzeri, M., Krishnamurthy, V. R., Akleman, E., & Kumar, S. (2025). Topology-engineered piezoresistive lattices with programmable strain sensing, auxeticity, and failure modes. Materials Horizons, 12(19), 8012-8032. DOI:10.1039/D5MH00884K, https://pubs.rsc.org/en/content/articlelanding/2025/mh/d5mh00884k
- Schneider, J., Ebert, M., Tipireddy, R., Krishnamurthy, V. R., Akleman, E., & Kumar, S. (2024). Concurrent geometrico-topological tuning of nanoengineered auxetic lattices fabricated by material extrusion for enhancing multifunctionality: Multiscale experiments, finite element modeling and data-driven prediction. Additive Manufacturing, 88, 104213. DOI:10.1016/j.addma.2024.104213, https://www.sciencedirect.com/science/article/pii/S2214860424002598
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