The automotive industry is working towards more sustainable vehicles and lower carbon footprints. One of the ways to achieve this is by decreasing the weight of vehicle components by using composites and other lightweight materials.
Compared to commonly used metals, these futuristic materials can be more difficult to model due to more complex failure mechanics and manufacturing processes. High-density strain data can help validate models, and High Definition Fiber Optic Sensing (HD-FOS) is a tool that can provide the density of measurements required for model validation for new materials.
It is also important to gain a greater understanding of how these new materials behave under loading when integrated into a full design. A team of Luna engineers tested the versatility of the ODiSI 6000 System and its ability to make high resolution measurements even in dynamic, real-world conditions.
They instrumented a vehicle with the ODiSI system and drove while taking HD-FOS measurements in highway and gravel road conditions. The team found that HD-FOS measurements were very stable for the highway data, and turning and breaking events were distinguishable when they occurred. While driving along the gravel road and over deep pot holes, the measurements became noisier at higher vehicle speeds but always recovered. Despite the high vibration, the sensors and the system saw no damage or failures in operation.
This capability and dependability allows for analysis of new materials and components or structural health monitoring in and outside the lab to ensure that new, lightweight parts meet needed design specifications.
Check out our Engineering Brief to learn more about these tests and how the ODiSI 6000 Series makes high-resolution measurements in dynamic, real-world conditions.
When developing new technologies for use in outer space missions, companies and researchers are challenged to evaluate performance of their innovations in a space environment. Often, the only method to understand the impact of outer space temperature extremes and radiation exposure is to actually send new innovations into orbit. NASA has traditionally addressed this need by inviting researchers to include their innovations onto CubeSats that would be fixed as auxiliary payloads on future missions. A CubeSat is a miniaturized satellite that enables cost-efficient research on space technology, and through NASA’s CubeSat Launch Initiative (CSLI), researchers have included innovations on various planned NASA missions. Because of the CSLI rideshare-style format, CubeSat availability and launch opportunities for researchers are fairly limited; providing opportunities for such field testing only when and where space is available on other larger NASA missions.
This is why researchers around the world are marveling at the successful launch of Rocket Lab’s first ever Venture Class Launch Services mission! The Rocket Lab Electron successfully launched on December 16, 2018, at 06:33 UTC (01:33AM ET) from New Zealand’s Māhia Peninsula, marking the first time in history that a commercial launch vehicle has been dedicated to sending NASA CubeSats into orbit. The mission, designated Educational Launch of Nanosatellites (ELaNa-19), deployed 13 satellites to their precise, designated orbits. According to Justin Treptow, NASA ELaNa-19 Mission Manager, “With this the first launch of a Venture Class Launch Service on the Rocket Lab Electron, NASA now has an option to match our small satellite missions with a dedicated small launch vehicle to place these satellites in an optimal orbit to achieve big results.” (1)
Luna Labs, the applied research division of Luna Innovations (NASDAQ: LUNA), is grateful to have been invited by NASA to participate in this historic mission. The NASA Langley Research Center Shields-1 CubeSat is carrying a new coating technology developed by Luna’s Protective Materials research group. LUNA XP-CD Charge Dissipating Conformal Coating enables improved protection and electrostatic discharge (ESD) mitigation for spacecraft electronics. The coating offers the combined performance properties of common conformal coating protection and radiation hardening through ESD mitigation. Providing this combination of performance, in a single conformal coating, gives spacecraft designers a new tool to protect sensitive electronics from hazardous radiation environments while reducing spacecraft complexity, weight, and cost. Luna XP-CD meets the required volume resistivity of 1×108 to 1×1012 ohm-cm for ESD protection across a wide temperature range, is optically transparent, inspectable under ultraviolet light, easy to apply and repair, provides low outgassing, and has excellent adhesion and flexibility. A successful mission will pave the way for future programs to utilize Luna XP-CD for electronics protection during Geosynchronous Earth Orbit (GEO), Medium Earth Orbit (MEO), Polar Low Earth Orbit (PLEO), and Outer Planets exploratory missions. For more information about Luna XP-CD Charge Dissipating Conformal Coating, check out our blogpost here and send an inquiry to firstname.lastname@example.org.
Dedicated launches from Rocket Lab will provide several advantages for researchers including more frequent flight opportunities for CubeSats, tailored deployments to meet unique orbital requirements, and the possibility for launches on a personalized schedule. If interested in sending a CubeSat to outer space, submit an online booking request with Rocket Lab. This is certainly an exciting time for the STEM community!
In optical networks where action on a message or signal is time critical, latency becomes a critical design element. Latency in communications networks is comprised of the networking and processing of messages, as well as the transmission delay through the physical fiber. Measuring and optimizing this optical transmission delay can be critical in diagnosing latency issues in a data center or maintaining quality control in the production of precision fiber links. Fortunately, the Luna OBR 4600 can measure this latency with picosecond accuracy.
Specifically, latency is the time delay of a light signal to travel, or propagate, in an optical transmission medium. The latency is related to the length of an optical fiber by the equation
Where L is the length, c is the speed of light in a vacuum and n is the index of refraction for the optical fiber.
Because the Luna OBR can measure loss and reflections in short fiber networks with ultra-high resolution (sampling resolution of 10 µm) and no dead zones, it is straightforward to extract the exact length or latency of a segment of fiber or waveguide by analyzing the time delay between reflection events. In fact, the OBR 4600 is able to measure latency or length this way with an accuracy of <0.0034% of the total length (or latency). For a 30 m optical fiber, for example, this corresponds to an overall length measurement accuracy of better than 1 mm, which is equivalent to a latency measurement accuracy of about 5 ps for standard fiber. Note that this is the absolute accuracy; actual measurement resolution will be much higher.
The example illustrates a typical application of measuring any differences in the length or latency of two fiber segments, each approximately 50 m in length. An OBR 4600 scans both segments and the latency of each segment is indicated by the distance between the two reflections at the beginning and end connectors of the segments. In this example, the difference in latency is found to be 95 ps. For this fiber, this is equivalent to a difference of about 19.3 mm in length.
Measuring length and latency is only one application of the versatile OBR reflectometer. For an overview of the OBR and common applications for ultra high resolution optical reflectometry, be sure to download Luna’s OBR white paper.
Test panel being instrumented by Luna engineers. Two metal plates form patch repairs at previous crack test locations to remove any effects on current testing.
Luna engineers were invited to the Federal Aviation Administration (FAA) William J. Hughes Technical Center in Atlantic City to participate in testing an aircraft fuselage panel. Several issues related to the structural integrity of fuselage applications are being examined using the Full-Scale Aircraft Structural Test Evaluation and Research Lab (FASTER), including the fatigue and damage tolerance characteristics of current and emerging metallic and composite designs, performance of bonded and mechanically fastened repair technologies, assessment of conventional and emerging non-destructive inspection, and more advanced structural heath monitoring methods.
Luna engineers were able to showcase the ability of the ODiSI high-definition fiber optic sensing (HD-FOS) system to measure and map strain gradients in front of an intentional crack. The ODiSI’s measurements allowed the team to observe the strain gradients increasing at the crack front in real time as the panel was loaded biaxially in a load frame designed to replicate realistic flight load conditions.
Fiber Sensors in Front of the Crack
Straight fiber segments were laid 0.1 inches apart, perpendicular to the crack tip, in its path of propagation. This mimicked the layout of a 10-element strip strain gage sensor. Each straight section of fiber in front of the crack was approximately 2 cm in length, which is the equivalent of 30 strain gages per pass and over 300 sensors in total. Further to the right of the crack, engineers demonstrated the layout of a rosette configuration to obtain the principal strain magnitudes and directions.
Strain Gradient Peaks in Front of the Crack and Decays with Distance
The resultant strain along each fiber segment of interest at 3.7125 psi is shown as a color map of strain overlaid on a photo of the part.
Strain from the crack flows outward along its path in an arc with the highest strain occurring at the fiber nearest the crack edge. Colors indicate strain ranging from 0 to 1000 µε, note that closest to the crack measurements exceed 1000 µε.
Further details of the strain gradient profile can be seen more clearly in this plot of strain along each straight segment at four loads.
Strain is highest right in front of the crack and decays with distance away from the crack. As the panel was pressurized, the strain increased proportionally. The color scheme indicates proximity to the crack, red being closest and blue being the farthest.
The propagation of cracks can be slow at first, often taking weeks of accelerated loading before the part eventually violently fails. While the crack did not grow noticeably during Luna’s time at the FAA, the ability to detect and monitor the effects of flaws such as cracks with such a high spatial resolution and density makes HD-FOS a valuable tool for structural health monitoring.
Learn More about ODiSI strain and temperature measurement system, or Contact Us to arrange a consultation with one of our engineers to see the ODiSI in action yourself.
The Hong Kong-Zhuhai-Macau Bridge (HZMB) is designed to have a lifespan 120 years. The mega-structure, which opened October 24, is built to withstand a magnitude 8 earthquake, a super typhoon and strikes by super-sized cargo vessels.
However, the Pearl River Delta operational environment is one of the world’s most densely urbanized regions. Degradation and aging from the environment and operation, along with natural and man-made disasters, will impact the bridge’s structural health.
Active monitoring of the conditions of the HZMB bridge-tunnel system in real time is critical to the long-term safety of the system, which spans a total length of 55 kilometers, making it the longest sea-crossing link ever built, and incorporates 400,000 tons of steel, 4.5 times the amount in San Francisco’s Golden Gate Bridge.
Fiber optic sensing is widely accepted and adopted for structural health monitoring (SHM) of bridges. It provides fast, accurate and dependable measurements for large structures of any age.
Given the significant span of this complicated structure, the HZMB SHM system employs 13 si155 Optical Sensing Interrogators to acquire continuous long-term data on the strain, deformation and temperatures of the system.
Featuring new and groundbreaking capabilities, Optical Sensing Interrogators provide reliable and accurate measurements of hundreds of optical strain, temperature, acceleration and displacement sensors. These critical measurements allow bridge operators to monitor the long-term structural health of the bridge, assess its condition during extreme weather events and detect vessel impacts.
New nuclear power generation is an important non-fossil fuel option to meet future global electricity demands. To ensure public safety and maintain energy security, the new reactors must be significantly safer and more efficient than previous designs. The Gen-IV design initiative is driving the development of the next generation nuclear plants with designs such as the Molten Salt Reactor, Sodium-cooled fast reactor, Lead-cooled fast reactor, very high temperature reactor and Supercritical-water cooled reactor.
These reactors will operate at temperatures between 500-1200°C, allowing them to operate with higher efficiencies than their predecessors and provide the required heat to produce hydrogen in large quantities without producing additional CO2. The safe and efficient operations of these systems will require pressure and temperature sensors that can survive in the harsh environments of the proposed Gen-IV reactor designs.
To address this need, Luna is researching reliable, high-temperature, radiation-tolerant sensors that provide many inline temperature measurements and high accuracy pressure data using only a single optical fiber.
The research utilizes both Luna’s Optical Backscatter Reflectometer (OBR) and Micron Optics’ Hyperion interrogation systems to explore combining radiation hardened femtosecond-laser-written Fiber Bragg Gratings (fsFBG/FBG) with harsh environment Extrinsic Fabry-Perot Interferometer (EFPI) pressure sensors on a single fiber.
The figure shows the wavelength-dependent reflection coefficients for a two FBGs and one EFPI at 0°C and 100°C, with an EFPI gap of 120µm and 160µm respectively. The bottom of the figure illustrates the sensor design, showing two FBGs written in the fiber and an EFPI gap constructed at the fiber’s tip.
The FBGs strongly reflect light at a single wavelength that increases linearly with temperature. The EFPI reflection is an interference fringe pattern. As the EFPI gap shrinks due to increased pressure, the wavelength range between the fringe maxima increases. The Phase I work is featured in the U.S. Department of Energy’s Advanced Sensors and Instrumentation Newsletter (pages 16-18).
Read More about how Luna Innovations and Micron Optics solve sensing needs for utilities around the world.
As the automotive industry continues to develop new lighter weight material systems and move to electrification, new design challenges are created that will require new advanced methods for test, measurement and validation. Fiber optic sensors can reduce time to first measurement and go where strain gages and temperature sensors cannot – in tight bends, on small details and even embedded inside composite materials. In addition, they are small, lightweight and flexible, immune to electromagnetic interference and chemically inert.
High-Definition Fiber Optic Sensing (HD-FOS) provides thousands of millimeter resolution measurements per meter on one fiber optic sensor. Traditional data acquisition (DAQ) systems, on the other hand, employ discrete electrical sensors that are relatively bulky, require multiple wires and are limited to set measurement points.
HD-FOS will help automotive manufacturers speed new technologies to market while lowering the risk associated with the introduction of new materials and processes:
• High definition data helps accurately characterize high strain or thermal gradients that can only be estimated with point sensing and traditional DAQ systems. • Fiber can reach hard-to-instrument places and at only 150 microns in diameter can be embedded into components without influencing parameters under test. • Fine mesh finite element models of critical components can be validated with certitude.
At Automotive Testing Expo Oct. 23-25 in Novi, Michigan, Luna is presenting a session, “Distributed High-Definition Strain and Temperature Measurement Delivers New Testing Insight,” which will discuss how more data and more insight provided by HD-FOS results in more complete model verification, enhanced damage detection and development of smart parts.
This year at the annual the Defense TechConnect (DTC) Fall Summit, Luna will be exhibiting the capabilities of Luna Labs (the Technology Development Division of Luna Innovations). At our booth, DTC attendees have the opportunity to meet with Luna’s team and understand how Luna Labs can work with their organization to create technologies which save time, save money, and save lives. Luna can be found at booth #217 during exhibit hall hours on Tuesday October 23, 2018 4:00pm to 7:00pm ET and Wednesday, October 24 Noon to 5:30pm ET.
As part of the DTC Fall Summit, Luna Labs will be presenting several innovations from our Health Sciences Group. Join Brad Brooks of Luna on Tuesday October 23, 2018 at 2pm for his presentation of “Bioinspired Synthetic Nanoparticles as Universal Anti-venom” when he will discuss recent advances of Luna’s universal anti-venom technology. And stop by the Medical and Biotech poster sessions to learn about Luna’s exciting new methods for stabilizing open globe injuries and locally applying fentanyl to treat burn pain.
Nanofiber-Based Fentanyl Bandages for Localized Treatment of Burn Pain M. Patterson, B. Brooks, M. Skoff, J. Mao, Z. You, C. Tison, Luna Innovations, Inc., US
Nanofiber-Reinforced Hydrogels for the Stabilization of Open Globe Injuries L. Costella, B. Brooks, K. Broderick, M. Gasbarre, L. Woodard, A. Eiseman, X. Wang, C.Tison, Luna Innovations, Inc., US
Bioinspired Synthetic Nanoparticles as Universal Antivenom Y. Xu, Luna Innovations Inc, US
ABOUT DEFENSE TECHCONNECT
Entering its sixth year, the annual Defense TechConnect (DTC) Summit, co-located with the Fall SBIR/STTR Innovation Summit, brings together defense, private industry, federal agency, and academic leadership to accelerate state-of-the-art technology solutions for the warfighter and national security.
The DTC supports innovation imperatives in the new National Defense Strategy (NDS) and is a unique platform to reach thousands of public and private leaders focused on innovation and technology to support the warfighter. At last year’s Defense Innovation Summit, close to 1,000+ one-on-one meetings took place between small businesses and SBIR Federal Program Managers, 200+ booths and tabletop displays in the Exhibit Hall representing private sector companies and non-traditional innovators, and more than 30 breakout sessions focused on defense innovation areas of interest including but not limited to energy, cyber, biomedical, and command, control, communications, computers/intelligence, surveillance, and reconnaissance (C4ISR). The annual DTC is one of the most well-attended defense innovation conferences of the year. As the home to both SOCOM and CENTCOM, Tampa serves as an ideal location to link the DoD’s innovation needs with global private sector solution providers.
The use of composite materials is ever increasing due to their high strength to weight ratios, manipulative properties, multifunctional capabilities and corrosion resistance. To fabricate high-quality composite components with acceptable thermal properties, elevated temperature cure cycles are typically required. Maintaining uniform heat distribution throughout the curing composite can be critical to the performance of the resulting part.
Thermocouples are typically used to both monitor and control the cure cycle. Multiple thermocouples are necessary to measure both air and part temperature at critical locations. The logistics of installing, wiring and tracking each sensor can be cumbersome, especially with complex parts.
An alternative to multiple thermocouples is the use of High-Definition Fiber Optic Sensing (HD-FOS) to measure the temperature during the cure cycle. In combination with Luna’s ODiSI interrogator system, temperature can be measured with high spatial density (millimeter resolution) along meters-long sensors, enabling temperature profiling across an entire part as opposed to obtaining measurements only at discrete locations.
Luna is presenting a technical paper on “Measuring Uniformity of Cure Temperatures Using High-Definition Fiber Optic Sensing” at CAMX (The Composites and Advanced Materials Expo) this week in Dallas, Texas. The subject of this paper was an initial investigation into the application of HD-FOS temperature sensors to the thermal uniformity of heat pads used for the composite cure cycle of an Out of Autoclave (OOA) prepreg system. HD-FOS sensors were applied in a serpentine pattern in three layers of composite laminates during lay-up and monitored during application of heat via heat pads. The work demonstrates the ability to measure spatially dense temperature distribution on, inside and under a composite panel during the cure process.
Measuring the return loss along a fiber optic network, or within a photonic integrated circuit, is a common and very important technique when characterizing a network’s or device’s ability to efficiently propagate optical signals. Reflectometry is a general method of measuring this return loss and consists of launching a probe signal into the device or network, measuring the reflected light and calculating the ratio between the two.
Spatially-resolved reflectometers can map the return loss along the length of the optical path, identifying and locating problems or issues in the optical path. There are three established technologies available for spatially-resolved reflectometry:
• Optical Time-Domain Reflectometry (OTDR)
• Optical Low-Coherence Reflectometry (OLCR)
• Optical Frequency-Domain Reflectometry (OFDR)
The OTDR is currently the most widely used type of reflectometer when working with optical fiber. OTDRs work by launching optical pulses into the optical fiber and measuring the travel time and strength of the reflected and backscattered light.
These measurements are used to create a trace or profile of the returned signal versus length. OTDRs are particularly useful for testing long fiber optic networks, with ranges reaching hundreds of kilometers. The spatial resolution (the smallest distance over which it can resolve two distinct reflection events) is typically in the range of 1 or 2 meters. All OTDRs, even specialized ‘high-resolution’ versions, suffer from dead zones – the distance after a reflection in which the OTDR cannot detect or measure a second reflection event. These dead zones are most prevalent at the connector to the OTDR and any other strong reflectors.
OLCR is an interferometer-based measurement that uses a wideband low-coherent light source and a tunable optical delay line to characterize optical reflections in a component. While an OLCR measurement can achieve high spatial resolution down to the tens of micrometers, the overall measurement range is limited, often to only tens of centimeters. Therefore, the usefulness of the OLCR is limited to inspecting individual components, such as fiber optic connectors.
Finally, OFDR is an interferometer-based measurement that utilizes a wavelength-swept laser source. Interference fringes generated as the laser sweeps are detected and processed using the Fourier transform, yielding a map of reflections as a function of the length. OFDR is well suited for applications that require a combination of high speed, sensitivity and resolution over short and intermediate lengths.
Luna’s Optical Backscatter Reflectometers (OBRs) are a special implementation of OFDR, adding polarization diversity and optical optimization to achieve unmatched spatial resolution. An OBR can quickly scan a 30-meter fiber with a sampling resolution of 10 micrometers or a 2-kilometer network with 1-millimeter resolution.
This graphic summarizes the landscape of these established technologies for optical reflectometry. By mapping the measurement range and spatial resolution of the most common technologies, the plot illustrates the unique application coverage of OBR.