Riveted steel bridges, which were built in the early 20th century require their regular structural integrity assessment to avoid any catastrophic failure. This paper presents continuous strain monitoring of a single riveted lap joint, which is a representative critical element of riveted steel bridges through an optical frequency domain reflectometry (OFDR) based distributed fibre optic sensor (DFOS). The aim of this study was to instrument a DFOS on a single riveted lap joint for monitoring the surface and critical strains experienced by the rivet joint under two fatigue loading conditions, and also to compare the strain transfer between the two commonly used adhesives for bonding the DFOS. Initially, through finite element analysis (FEA) a location for installing the DFOS was identified and also a strategy was developed for monitoring the critical location of the joint during fatigue loading. Subsequently, the DFOS was instrumented on the riveted joint at the identified location in two segments, where similar strain levels were expected with the aid of two types of adhesives: Cyanoacrylate and Epoxy. The strains on the rivet joint were monitored under high cycle fatigue (HCF) for up to 2 × 106 loading cycles with constant stress amplitude and followed by low cycle fatigue (LCF) loading with increasing stress amplitude until the failure of the specimen. The results showed that the DFOS could continuously sense the cyclic peak strain of -223 με under HCF conditions and a peak maximum strain of -1244 με under LCF conditions. Furthermore, the internal critical strain on the rivet joint during loading could be monitored with the application of the developed damage monitoring strategy and DFOS strain data. Finally, the DFOS segment bonded using cyanoacrylate measured marginally high strains than epoxy adhesive during the HCF test.

Substantial range, handling and acceleration improvements in high-performance vehicles can be achieved by weight reduction. An important area for weight reduction on a car is the wheels. A novel prototype carbon fibre/epoxy wheel has been developed using a combination of automated fibre placement (AFP) and hand layup for the Sunswift 7 solar car. A three-piece wheel design that utilises each process where best suited has been analysed and optimised using the ANSYS ACP PrepPost suite, manufactured, and mechanically tested. The wheel disc was produced using AFP and featured selective reinforcement in the form of spokes. The AFP fibre paths for the disc have been optimised using CGTech’s VERICUT VCP and VCS to minimise gaps and overlaps, resulting in a 98.9% reduction in overlaps when compared with the unoptimised layup. The rim and tyre mounting region of the wheel have been manufactured using hand layup and adhesively bonded to the disc. This hybrid manufacturing approach has demonstrated an advancement in the feasibility of combining traditional and automated composite manufacturing. The final wheel weighed 3352 g, and the wheel deflection under a compressive load has been experimentally verified within 3% of the theoretical value.

Fibre reinforced composites materials offer a pathway to produce passive shape adaptive smart marine propellers, which have improved performance characteristics over traditional metallic alloys. Automated fibre placement (AFP) technology can provide a leap forward in cyber-physical automated manufacturing, which is essential for the implementation and operation of smart factories in the marine propeller industry towards Industry 4.0 readiness. In this paper, a comprehensive structural health monitoring routine was performed on an AFP full-scale composite hydrofoil to gain confidence in its dynamic and structural performances through a number of active and passive sensors. The hydrofoil was subjected to constant amplitude flexural fatigue loading in a purpose-built test rig for 10 ⁵ cycles. The hydrofoil was embedded with distributed optical fibre sensors, traditional electrical strain gauges and linear variable displacement transducers. Both microelectromechanical system and piezoelectric accelerometers were used to conduct experimental modal analyses to observe changes in the modal response of the hydrofoil at regular intervals throughout the fatigue program. The hydrofoils modal response, as well as the stiffness measured using both displacements and strains, remained unchanged over the fatigue loading regime demonstrating the structural integrity of the hydrofoil. The optical fibre sensors endured the fatigue test cycles showing their robustness under fatigue loads. Furthermore, the sensing systems demonstrated the potential of being utilised as a useful maintenance tool combining their adaptability with automated manufacturing during manufacturing through integration within the hydrofoil, a structural test framework for performance measurement, data acquisition and analytics for visualisation, and the prospect of decision making for maintenance requirement during any onset in structural performance.

Distributed fibre optic sensors (DFOS) are popular for structural health monitoring applications in large engineering infrastructure because of their ability to provide spatial strain measurements continuously along their lengths. Curved paths, particularly semicircular paths, are quite common for optical fibre placement in large structures in addition to straight paths. Optical fibre sensors embedded in a curved path configuration typically measure a component of strain, which often cannot be validated using traditional approaches. Thus, for most applications, strain measured along curved paths is ignored as there is no proper validation tool to ensure the accuracy of the measured strains. To overcome this, an analytical strain transformation equation has been developed and is presented here. This equation transforms the horizontal and vertical strain components obtained along a curved semicircular path into a strain component, which acts tangentially as it travels along the curved fibre path. This approach is validated numerically and experimentally for a DFOS installed on a steel specimen with straight and curved paths. Under tensile and flexural loading scenarios, the horizontal and vertical strain components were obtained numerically using finite element analysis and experimentally using strain rosettes and then, substituted into the proposed strain transformation equation for deriving the transformed strain values. Subsequently, the derived strain values obtained from the proposed transformation equation were validated by comparing them with the experimentally measured DFOS strains in the curved region. Additionally, this study has also shown that a localised damage to the DFOS coating will not impact the functionality of the sensor at the remaining locations along its length. In summary, this paper presents a valid strain transformation equation, which can be used for transforming the numerical simulation results into the DFOS measurements along a semicircular path. This would allow for a larger scope of spatial strains measurements, which would otherwise be ignored in practice.

Grouts have numerous applications in construction industry such as joint sealing, structural repair, and connections in precast elements. They are particularly favoured in rehabilitation of structures due to penetrability and convenience of application. Grouts for repair applications typically require high-performance properties such as rapid strength development and superior shrinkage characteristics. Sometimes industrial by-products referred as supplementary cementitious materials (SCM) are used with neat cement due to their capabilities to provide binding properties at delayed stage. Micro silica, fly ash and metakaolin are such SCMs, those can modify and improve properties of cement products. This study aims at investigating long-term mass loss and linear shrinkage along with long-term compressive and flexural strength for grouts produced from ultrafine cement and SCMs. A series of mixtures were formulated to observe the effect of SCMs on these grout properties. Properties were determined after 365 days of curing at 23^oC and 55% relative humidity. The effect of SCMs on the properties are characterised by statistical models. Response surfaces were constructed to quantify these properties in relation to SCMs replacement. The results suggested that shrinkage was reduced by metakaolin, while micro silica and fly ash had positive effects on compressive and flexural strength, respectively.