Non-destructive evaluation of an infusion process using capacitive sensing technique

In this study, a capacitive sensing based non-destructive evaluation technique is applied to a vacuum assisted resin infusion process for the fabrication of glass fibre reinforced composites, as such different steps of the fabrication process (the injection of resin, the curing and the post curing) can be better understood to increase the quality of the fabricated part and reduce the fabrication costs. An interdigital coplanar capacitive sensor was designed, fabricated, and embedded in the glass fibre reinforced composites. Experimental data clearly shows different stages of the resin infusion process: wetting of the glass fibres marked by rapid increase of capacitance; domination of ionic conduction at the early stage of the cure when the resin is still in a liquid state; the vitrification point, indicating a transition of the resin from a gelly state to a glassy state, marked by the relatively big decrease in capacitance; further polymerization during post-curing, marked by a peak in capacitance at the beginning of post-curing cycle, and finally the completion of the cure marked by the saturation of capacitance to a final value. The different phenomena observed during the experiment can be used as a tool for in situ on-line monitoring of composites cure

High-Sensitivity Magnetic Sensors Based on GMI Microwire-SAW IDT Design

This work presents a design approach for a highly sensitive, miniaturized magnetic sensor. The design makes use of GMI microwires and a multi-electrode SAW IDT. The use of SAW IDTs allows for the magnetic effect of the GMI microwire to be measured through the transduction process. This approach permits simultaneous measurement at different frequencies of operation, enabling highly sensitive measurement over a wide range of magnetic fields. This technique may find application in magnetic sensing for non-invasive battery SOC measurement

Deformable microsystem for in situ cure degree monitoring of GFRP(Glass Fibre Reinforced Plastic)

Fibre Reinforced Polymer (FRP) is becoming a valid alternative to many traditional heavy metal industries because of its high specific stiffness over the more classical construction metals. Recent trend of more complex geometry of composites is causing increasing difficulty in composite manufacturing. A method to optimize the manufacturing process is thus imposed to ensure and improve the quality of manufactured parts. Because of the irregular 3D shapes of the composites, traditional flat sensor system is becoming unfavorable and nonpractical for monitoring purpose. In this work, the current development status of a deformable microsystem for in situ cure degree monitoring of a glass fibre reinforced plastic is presented. To accommodate the non-flat shape of the composites, the proposal is to interconnect non-deformable functional island, which contains the capacitive sensor for cure degree monitoring, with meander-shaped deformable interconnections. The developed sensor system is able to withstand the manufacturing process where change of pressure and internal strain, thus force exerted on the sensor system, is involved

Detection of chemical vapors using oscillator with Surface Acoustic Wave

Senzori sa površinskim akustičkim talasima (PAT) ispoljavaju superiornu osetljivost pri detekciji hemijskih agenasa. Zbog nepostojanja pokretnih delova i izrade kompatibilne sa modernim tehnologijama, PAT hemijski senzori su veoma pouzdani. Senzor je modelovan kao dvoportni uređaj čiji su delovi predstavljeni ekvivalentnim kolima. Izračunata je promena izlazne frekvencije u funkciji koncentracije gasa. Projektovano je oscilatorno kolo sa PAT senzorom u grani povratne sprege. PAT senzor se koristi za modifikovanje frekvencije oscilacija. Prisustvo hemijskih isparenja se onda direktno detektuje praćenjem ovog frekvencijskog pomaka.Surface Acoustic Wave (SAW) sensors demonstrate superior sensitivity in detection of chemical agents. Due to their solid state design and fabrication compatible with modern technologies, SAW chemical sensors are extremely reliable. The sensor is modeled as a two-port device with parts represented by equivalent circuits. Change of output frequency as a function of vapor concentration is calculated. The oscillator circuit with SAW sensor in the feedback loop is designed. The SAW sensor is used for modifying the oscillator frequency. The presence of chemical vapor is then detected by monitoring this frequency shift

Detection of chemical vapors using oscillator with Surface Acoustic Wave

Senzori sa površinskim akustičkim talasima (PAT) ispoljavaju superiornu osetljivost pri detekciji hemijskih agenasa. Zbog nepostojanja pokretnih delova i izrade kompatibilne sa modernim tehnologijama, PAT hemijski senzori su veoma pouzdani. Senzor je modelovan kao dvoportni uređaj čiji su delovi predstavljeni ekvivalentnim kolima. Izračunata je promena izlazne frekvencije u funkciji koncentracije gasa. Projektovano je oscilatorno kolo sa PAT senzorom u grani povratne sprege. PAT senzor se koristi za modifikovanje frekvencije oscilacija. Prisustvo hemijskih isparenja se onda direktno detektuje praćenjem ovog frekvencijskog pomaka.Surface Acoustic Wave (SAW) sensors demonstrate superior sensitivity in detection of chemical agents. Due to their solid state design and fabrication compatible with modern technologies, SAW chemical sensors are extremely reliable. The sensor is modeled as a two-port device with parts represented by equivalent circuits. Change of output frequency as a function of vapor concentration is calculated. The oscillator circuit with SAW sensor in the feedback loop is designed. The SAW sensor is used for modifying the oscillator frequency. The presence of chemical vapor is then detected by monitoring this frequency shift

Apparatus for measuring a sorbate dispersed in a fluid stream

A sensitive, miniature apparatus was designed for measuring low concentrations of a sorbate dispersed in a fluid stream. The device consists of an elongated body having a surface capable of sorbing an amount of the sorbate proportional to the concentration in the fluid stream and propagating acoustic energy along its length. The acoustic energy is converted to an electrical output signal corresponding to the concentration of sorbate in the fluid stream. The device can be designed to exhibit high sensitivity to extremely small amounts of sorbate dispersed in a fluid stream and to exhibit low sensitivity to large amounts of sorbate. Another advantage is that the apparatus may be formed in a microminiature size and at a low cost using bath microfabrication technology