This research investigates the integration of fiber optic (FO) strain sensors into Large Format Additive Manufacturing (LFAM) components to enable real-time structural health monitoring (SHM) for civil infrastructure. The study addresses four fundamental questions: (1) Can embedded fiber optics reliably identify structural events and usage patterns? (2) Is adequate interfacial bonding achieved between the fiber optic sensor and polymer matrix? (3) How does the embedding process affect strain measurement accuracy? (4) What impact does sensor integration have on the mechanical performance of printed components? Twenty short carbon fiber-reinforced PLA specimens were fabricated in two configurations, neat and fiber-optic-embedded, and subjected to quasi-static tensile testing to failure and displacement-controlled cyclic fatigue testing. The embedding process leveraged LFAM’s layer-by-layer deposition and relatively low processing temperatures to place optical fibers between print layers without modifying standard print parameters. X-ray computed tomography revealed a fiber-to-matrix contact percentage of 58.2%, indicating that interfacial porosity introduced during embedding partially limits strain transfer and that absolute FO strain measurements should be interpreted alongside an independent reference measurement. Under cyclic fatigue loading, embedded FO sensors demonstrated strong qualitative agreement with load-cell-reported stress measurements, faithfully resolving cycle peaks, valleys, and transitions in real time. Quantitative differences between FO-measured strain and crosshead-derived applied strain were attributed to the limitations of crosshead displacement as a proxy for material strain, incomplete fiber-matrix contact, and local material heterogeneity. Across both testing regimes, the influence of FO embedment on bulk mechanical performance was inconsistent, with no systematic reduction in peak force or displacement, although inherent variability in the printed material limited definitive conclusions. These results demonstrate that fiber optic sensors can be embedded into LFAM components without meaningful disruption to fabrication or a consistent mechanical penalty, supporting the broader vision of self-sensing structural components with built-in monitoring capabilities. Further development is needed to improve fiber-matrix contact quality and expand the experimental test matrix for practical deployment in civil infrastructure applications.

The ability to monitor variations in seismic or acoustic wave velocity is of major interest in many applications like Structural Health Monitoring (SHM), near surface geophysics, the security in an underground context or oil industry.

The use of buried sensors is particularly suited to this goal, as it provides information about the internal properties of the probed medium. Fiber Optic Sensors (FOS) offer some advantages in buried contexts, such as their low intrusiveness (due to their small diameter) and their immunity to electromagnetic interferences. In particular, Fiber Bragg Gratings (FBGs) sensors can be used to measure dynamic strain fields caused by mechanical waves. The primary information that can be gathered from these measurements is the travel time of a P-wave between a source and a buried receiver.

Here we attempt to measure P-wave travel time variations in order to image a local change in the mechanical properties of the probed medium. A differential inversion approach is used to convert travel time differences into an image of the relative velocity variations.

To validate this method, a combination of numerical studies and laboratory experiments is used. To this end, a polyurethane resin mock-up is made, in which FBGs sensors are embedded and used as ultrasonic sensors. Then, the local changes in P-wave velocity between a reference state and two disturbed states of the mock-up is map, based on the inversion of P-wave travel time differences. The results of differential inversions demonstrate that the imaging method developed can be used to monitor a local P-wave velocity contrast using embedded FBGs as ultrasonic sensors.

Self-sensing concrete (SSC) can support structural health monitoring by turning the bulk electrical response of cementitious material into a sensing channel. This paper evaluates simple, training-free resistivity-derived features under monotonic destructive tests (MDT) and ramp--hold--ramp monitoring (NMT-RHR).
Graphite--milled carbon fibre concrete cubes were tested while resistance, strain, and force were recorded. The electrical response was processed into fractional resistivity change ($\kappa$), its time-rate ($\beta_t$), and supporting strain-normalised variants. Low-load segments were treated as conservative internal references for feature comparison rather than as verified damage-free states.
Across the retained MDT specimens, $\kappa$ provided the clearest sustained deviation from the initial reference segment, while $\beta_t$ highlighted abrupt late-stage transitions. Across NMT hold segments, $\kappa$ showed the strongest sustained response as load severity increased, whereas $\beta_t$ behaved as a more transient companion indicator. The strain-normalised variants were less stable and are best treated as secondary comparison features.
These results indicate that sustained and rate-sensitive electrical features provide complementary information: $\kappa$ is more suitable for tracking persistent offsets, while $\beta_t$ is more suitable for identifying short transitions.
Overall, the study provides a comparative basis for selecting simple electrical features under controlled compression loading, with the reported detections interpreted as reference-relative changes in the electrical response.

Clay-based composites have been emerging as strain-sensors despite the current challenges in incorporating conductive fibers within them. These fibers must resist firing conditions between 900 °C and 1100 °C, which can typically only be withstood by metallic fibers such as steel fibers. Nevertheless, a recent study has demonstrated that graphitic pyroproteins with conductive characteristics can be incorporated into clay-based composites, also known as smart bricks, exhibiting gauge factors comparable to those of carbon/cement-based composites. To evaluate such piezoresistive properties, loading tests in combination with the biphasic approach (10 V at low frequency, <100 Hz) were implemented using a low-cost acquisition system named the Smart Materials Electrometer (SME). This hardware demonstrated significant accuracy in piezoresistive and piezocapacitive measurements in comparison with high-cost systems in the market. In this occasion, a multichannel version of SME (see Figure 1) demonstrated the strain-sensing capabilities of carbon/clay-based bricks. This new generation of smart bricks was embedded in medium-scale walls as piezoresistive sensors to address damage detection and strain-monitoring, paving the way for future applications in structural health monitoring.