Damage Location Sensing in Carbon Fiber Composites Using Extrusion Printed Electronics

Structural Health Monitoring (SHM) uses sensors in advanced engineering structures to evaluate integrity and detect damage or deformation affecting structural performance, e.g., cracks, holes, or corrosion. Carbon fiber textile composites are commonly used to reinforce structures such as aircraft, vehicles, or bridges due to their high tensile strength to weight ratio, chemical resistance, and thermal and electrical conductivity. Printing electronics on textiles is a scalable manufacturing technology combining the physical properties of textile materials with the added functionality of electronic elements making them self-sensing. Extrusion printing is a contactless digital printing method to print electrical conductors and passive circuit elements. This paper proposes to combine conventional carbon fiber composite manufacturing processes with printed conductors to create self-sensing carbon fiber textile composites. Damage is sensed by measuring resistance changes in a carbon fiber sheet. Contacts are extrusion printed directly on woven carbon fiber sheets using silver flake ink. A multiplexed Kelvin Double Bridge circuit is the read-out interface. This allows small resistance changes due to damage to be measured in a 4-point configuration. The circuit is connected to the printed contacts on the carbon fiber sheet through multiplexers to detect damage in different locations. This 2D digital sensor can detect the location and size of damage holes for SHM. The resolution of the sensor is controlled by the location and spacing of the silver electrodes, which were studied experimentally and by simulation. The resolution is 26 mm in the current direction and 16 mm in the orthogonal direction. The threshold of detectable damage is 4 mm2. Simulation of the sensor as an isotropic 2D conductor shows good agreement with experimental results for the orthotropic fabric. The resultant sensing device could be integrated into many composite structures as one of its layers or simply printed on the surface to create smart structures.

Dynamic failure and crash simulation of carbon fiber sheet moulding compound (CF-SMC)

Carbon fiber sheet moulding compounds (CF-SMC) are a promising class of materials with the potential to replace aluminium and steel in many structural automotive applications. In this paper, we investigate the use of CF-SMC materials for the realization of a lightweight battery case for electric cars. A limiting factor for a wider structural adoption of CF-SMC has been a difficulty in modelling its mechanical behaviour with a computational effective methodology. In this paper, a novel simulation methodology has been developed, with the aim of enabling the use of FE methods based on shell elements. This is practical for the car industry since they can retain a good fidelity and can also represent damage phenomena. A hybrid material modelling approach has been implemented using phenomenological and simulation-based principles. Data from computer tomography scans were used for micro mechanical simulations to determine stiffness and failure behaviour of the material. Data from static three-point bending tests were then used to determine crack energy values needed for the application of hashing damage criteria. The whole simulation methodology was then evaluated against data coming from both static and dynamic (crash) tests. The simulation results were in good accordance with the experimental data. Graphic abstract

VO2(B)@Carbon Fiber Sheet as a Binder-free Flexible Cathode for Aqueous Zn-Ion Batteries

With the increase in the demand for future deformable and wearable applications, flexible aqueous zinc-ion batteries are deemed to demonstrate promise as a flexible electronic power supply. In this study,...