The importance of materials testing cannot be underestimated. Across every major industry, manufacturers, developers and operators of critically important systems, products and components need to be assured that the materials employed in forming their equipment are up to their intended tasks. That’s why the most diligent method of verifying that the materials companies use in manufacturing processes will perform to expectations and adhere to all applicable regulations is through reliable materials testing.
Advanced Composite Materials (ACMs) have broad, proven applications, in the aircraft, aerospace, and sports equipment sectors. Even more specifically ACMs are very attractive for aircraft and aerospace structural parts. ACMs have been developing for NASA’s Advanced Space Transportation Program, armor protection for Army aviation and the Federal Aviation Administration of the U.S.A., and high-temperature shafting for the Comanche helicopter. Additionally, ACMs have decades of history in military and government aerospace industries. However, much of the new technology is now being developed for secondary or commercial markets, and the technology of advanced composites manufacture is continually evolving.
The intent of arc resistance testing is to distinguish between solid electrical insulating materials. It examines the specimen’s ability to resist an arc with high voltage and low current exposed to the material’s insulating surface. The ASTM arc resistance test for dry and uncontaminated materials centers on the time elapsed until tracking paths form.
Comparative tracking index (CTI) is used to assess the relative resistance of insulating materials to tracking. The CTI expressed as that voltage which causes tracking after 50 drops of 0.1 percent ammonium chloride solution have fallen on the material. The results of testing the nominal 3 mm thickness are considered representative of the material’s performance in any thickness.
Dielectric Constant is used to determine the ability of an insulator to store electrical energy. The dielectric constant is the ratio of the capacitance induced by two metallic plates with an insulator between them to the capacitance of the same plates with air or a vacuum between them. Dissipation factor is defined as the reciprocal of the ratio between the insulating materials capacitive reactance to its resistance at a specified frequency. It measures the inefficiency of an insulating material. If a material were to be used for strictly insulating purposes, it would be better to have a lower dielectric constant.
Differential scanning calorimetry (DSC) measures Specific Heat Capacity, Heat of Transition, and the Temperature of Phase Changes and Melting Points. DSC measures the rate of heat flow, and compares differences between the heat flow rate of the test sample and known reference materials. As a sample undergoes a transition (melting, crystallization, etc.), heat is absorbed or emitted. This change in heat flow is then measured by the system and can be analyzed. The difference determines variations in material composition, crystallinity and oxidation.
Gravelometer testing is designed to evaluate the resistance of vehicle surface coatings (paint, clear coats, metallic plating, etc.) to chipping caused by the impacts of gravel and other flying objects in accordance with SAE and ASTM standards. The primary usage of this test is to simulate the effects of the impact of gravel or other debris on automotive parts. Test samples are typically mounted in the back of the Gravelometer, and air pressure is used to project 1 pint (approximately 300 pieces) of gravel at the sample. The test sample is then removed and gently wiped off with a clean cloth. Tape is then applied to the entire tested surface. Removal of the tape then pulls off any loose fragments of the coating. The appearance of the tested sample is then compared to standard transparencies supplied by SAE to determine the chipping ratings. Visual examination can also be used to describe where in the coating/substrate system that the failure has been induced.
High-Current Arc Ignition (HAI) performance is expressed as the number of arc rupture exposures (standardized to the electrode type and shape and electric circuit) that are necessary to ignite a material when they are applied at a standard rate on the surface of the material. The number of arc rupture exposures necessary to ignite a material when they are applied at a standard rate on the surface of the material. Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.
The High Voltage Tracking Resistance (HVTR) test method is used to assess the susceptibility to tracking of insulating materials that are exposed to high voltages outdoors. Insulators installed in the open are often at the mercy of humidity. Their electrical insulation properties can deteriorate to such an extent as a result that tracking paths are formed on the insulator surface. This test determines the tracking resistance that defines the dielectric strength of the insulating material surface and the maximum allowable leakage current (tracking).
Advanced Polymers & Rubbers Materials have broad, proven applications, in the aircraft, aerospace, and sports equipment sectors. More specifically, APMs are very attractive for aircraft and aerospace structural parts. APMs have continued to develop due to NASA’s Advanced Space Transportation Program. Additionally, advanced polymer materials have decades of history in military and government aerospace industries. However, much of the technology is now being developed for secondary or commercial markets, as the technology of advanced plastics manufacture is continually evolving.NTS has the capabilities to assess the mechanical strength and integrity of these materials and provide you with the data required to evaluate the performance of the product applications.
Thermo Gravimetric Analysis (TGA) is a thermal analysis technique used to measure changes in the weight (mass) of a sample as a function of temperature and/or time. TGA is commonly used to determine polymer degradation temperatures, residual solvent levels, absorbed moisture content, and the amount of inorganic (noncombustible) filler in polymer or composite material compositions.
TMA is used to characterize linear expansion, glass transitions, and softening points of materials by applying a constant force to a specimen while varying temperature. For expansion measurements, a probe rests on a sample on a stage with minimal downward pressure. Other constant force experiments include measurement of penetration, bending, tension, shrinkage, swelling, and creep (sample motion measured as a function of time under an applied load).
Volume resistivity represents an insulating material’s resistance to leakage current through its body. It calculates the ratio of the potential gradient in relation to the current in a material with the same density. A direct-current resistance between opposing faces of a one-meter cube of the material numerically equates to volume resistivity in SI (Ohm-m).
The importance of materials testing cannot be underestimated. Across every major industry, manufacturers, developers and operators of critically important systems, products and components need to be assured that the materials employed in forming their equipment are up to their intended tasks. That’s why the most diligent method of verifying that the materials companies use in manufacturing processes will perform to expectations and adhere to all applicable regulations is through reliable materials testing.
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