Resistance-foil strain-gage technology as applied to composite materials
A general review of existing strain-gage technologies as applied to orthotropic-composite materials is given. The specific topics addressed are gage-bonding procedures, transverse-sensitivity effects, errors due to gage misalignment, and temperature-compensation methods. The discussion is supplemented by numerical examples where appropriate. It is shown that the orthotropic behavior of composites can result in experimental error which would not be expected based on practical experience with isotropic materials. In certain cases, the transverse sensitivity of strain gages and/or slight gage misalignment can result in strain-measurement errors exceeding 50 percent.
Evaluation of Advanced Conductive Nickel Materials for Strain Sensing in Carbon Fiber Reinforced Polymers
Evaluation of Advanced Conductive Nickel Materials for Strain Sensing in Carbon Fiber Reinforced Polymers Michael Koecher Department of Mechanical Engineering, BYU Master of Science Due to their unique properties, carbon fiber reinforced polymers (CFRP) are becoming ever more prevalent in today’s society. Unfortunately, CFRP suffer from a wide range of failure modes and structural health monitoring methods are currently insufficient to predict these failures. It is apparent that self-sensing structural health monitoring could be advantageous to protect consumers from catastrophic failure in CFRP structures. Previous research has shown that embedded nickel nanostrand nanocomposites can be used to instantaneously measure strain in carbon fiber composites, but these methods have been severely limited and can induce high stress concentrations that compromise the structural integrity of the carbon fiber structure. In this research the strain sensor material and the connective circuitry to the sensor are analyzed to improve the practicality of in situ strain sensing of carbon fiber structures. It has been found that the use of nickel nanostrands embedded directly onto carbon fiber as a strain sensor material has no advantages over a carbon fiber strain sensor alone. Additionally, it has been shown that the circuitry to the strain sensor plays a critical role in obtaining a strong, consistent piezoresistive signal that can be related to strain. The use of nickel coated carbon fiber in the circuitry has been evaluated and shown to reduce the noise in a piezoresistive signal while allowing for remote strain sensing from greater distances away from the strain location. The piezoresistive strain sensing utilized in the tested sensor designs relies on electrons tunneling through an insulting barrier between two conductors. This phenomenon is known as quantum tunneling. T wo factors tunneling barrier height and gap distance affect the probability of quantum tunneling occurring. Thus, to accurately model and predict the piezoresistivity of nanocomposites these two parameters must be known. T hrough the use of dielectric spectroscopy the gap distance can be determined. U sing nanoindenting, the barrier height for various polymers was also determined. The measured values can be used, in future work, to improve the modeling of nickel nanostrand nanocomposite.
First Insights into the Draft Genome Sequence of the Endophyte Paenibacillus amylolyticus Strain GM1FR, Isolated from Festuca rubra L.
ABSTRACT Paenibacillus amylolyticus strain GM1FR is an endophyte isolated from aerial plant tissues of Festuca rubra L. Here, we report the draft genome sequence (7.3 Mb) of GM1FR containing 6,241 protein-coding genes, some of which are potentially involved in plant growth promotion and biocontrol.