More destructive testing to answer your questions about concrete.
Concrete’s greatest weakness is its tensile strength, which can be less than 10% of its compressive strength. So, we often reinforce it to create a composite material strong against all types of stress. This video briefly touches on conventional rebar and prestressed/post-tensioned reinforcement.
What’s the difference between concrete and cement?
Concrete is the most important construction material on earth and foundation of our modern society. At first glance it seems rudimentary, but there is a tremendous amount of complexity involved in every part of designing and placing concrete. This video is meant to be a bare-bones introduction to the topic, with a cool demonstration of concrete strength using a hydraulic press.
Materials scientists are always on the look out for new composites, materials comprising two or more different substances that combine to bring together the useful properties of each component and to overcome the limitations of any. Moreover, some composites might also work synergistically so that the useful properties of one component enhance those of the other and vice versa. Often, computation and modeling can be used to work out the likely outcomes of combining certain components.
New research published in the International Journal of Computational Materials Science and Surface Engineering reveals a mathematical model that can be used to optimize a novel composite for tensile strength. The composite is made from the synthetic polymer, polyester, and human hair as a reinforcing component.
Divakara Rao and Udaya Kiran of the J.B. Institute of Engineering and Technology, in Hyderabad, and Eshwara Prasad of the Jawaharlal Nehru Technological University also in Hyderabad, prepared polymer-based composites using chopped fibers of human hair at between 5 and 25 percent by weight and with fiber lengths of 10 to 50 millimeters. Data from tensile strength testing of these experimental composites were used to build a model that might then be used to optimize the formulation of new composites.
Physicists and materials scientists from Peter the Great St.Petersburg Polytechnic University (SPbPU) analyzed the structures in nanomaterials made of ceramic and graphene plates, in which cracks appear most frequently. The results of the first trial of the model, that describes this regularity, were published in the Mechanics of Materials Journal. This model will help in creation of crack-resistant materials. The research was supported by the Russian Science Foundation grant.
Graphene is the lightest and strongest carbon composite. Moreover, it has a very high electrical conductivity. Because of these characteristics graphene is often included in the composition of new ceramic-based materials. Ceramics are resistant to high temperatures, and, if carbon modifications are added, the composites become multifunctional. In the future they can be used in production of flexible electronic devices, sensors, in construction and aviation.
It is known from many experimental studies of such composites that their mechanical characteristics are set by the graphene proportion in the composition and by the size of graphene plates allocated in the ceramic matrix. For example, in the case of low graphene concentration, high crack resistance was achieved with the help of long plates. However, in one of the recent experiments of synthesis of materials from alumina ceramics and graphene, the opposite effect was shown: as the plates were bigger, the crack resistance was weaker. The researchers from Saint Petersburg have developed a theoretical model that explains this paradox.
Sand Castle Holds Up A Car! – Mechanically Stabilized Earth
Dirt is probably the cheapest and simplest construction material out there, but it’s not very strong compared to other choices. Luckily geotechnical engineers have developed a way to strengthen earthen materials with almost no additional effort – Mechanically Stabilized Earth (aka MSE or Reinforced Soil). If you look closely, you’ll see MSE walls are everywhere. Thanks for watching, and let me know what you think!
This week, we’re celebrating National Composites Week, which CompositesWorld says is about shedding some light on how “composite materials and composites manufacturing contributes to the products and structures that shape the American manufacturing landscape today.”
What exactly are composites and why are we talking about them?
Composites are building materials that we use to make airplanes, spacecraft and structures or instruments, such as space telescopes. But why are they special?
Composites consist of two or more materials, similar to a sandwich. Each ingredient in a sandwich could be eaten individually, but combining them is when the real magic happens. Sure, you could eat a few slices of cold cheese chased with some floppy bread. But real talk: buttery, toasted bread stuffed with melty, gooey Gouda makes a grilled cheese a much more satisfying nosh.
With composites—like our sandwich—the different constituent parts each have special properties that are enhanced when combined. Take carbon fibers which are strong and rigid. Their advantage compared to other structural materials is that they are much lighter than metals like steel and aluminum. However, in order to build structures with carbon fibers, they have to be held together by another material, which is referred to as a matrix. Carbon Fiber Reinforced Polymer is a composite consisting of carbon fibers set in a plastic matrix, which yields an extremely strong, lightweight, high-performing material for spacecraft.
Composites can also be found on the James Webb Space Telescope. They support the telescope’s beryllium mirrors, science instruments and thermal control systems and must be exquisitely stable to keep the segments aligned.
We invest in a variety of composite technology research to advance the use of these innovative materials in things like fuel tanks on spacecraft, trusses or structures and even spacesuits. Here are a few exciting ways our Space Technology Mission Directorate is working with composites:
Deployable structures on small spacecraft
We’re developing deployable composite booms for future deep space small satellite missions. These new structures are being designed to meet the unique requirements of small satellites, things like the ability to be packed into very small volumes and stored for long periods of time without getting distorted.
A new project, led by our Langley Research Center and Ames Research Center, called the Advanced Composite Solar Sail System will test deployment of a composite boom solar sail system in low-Earth orbit. This mission will demonstrate the first use of composite booms for a solar sail in orbit as well as new sail packing and deployment systems.
Nano (teeny tiny) composites
We are working alongside 11 universities, two companies and the Air Force Research Laboratory through the Space Technology Research Institute for Ultra-Strong Composites by Computational Design (US-COMP). The institute is receiving $15 million over five years to accelerate carbon nanotube technologies for ultra-high strength, lightweight aerospace structural materials. This institute engages 22 professors from universities across the country to conduct modeling and experimental studies of carbon nanotube materials on an atomistic molecular level, macro-scale and in between. Through collaboration with industry partners, it is anticipated that advances in laboratories could quickly translate to advances in manufacturing facilities that will yield sufficient amounts of advanced materials for use in NASA missions.
Through Small Business Innovative Research contracts, we’ve also invested in Nanocomp Technologies, Inc., a company with expertise in carbon nanotubes that can be used to replace heavier materials for spacecraft, defense platforms, and other commercial applications.
Nanocomp’s Miralon™ YM yarn is made up of pure carbon nanotube fibers that can be used in a variety of applications to decrease weight and provide enhanced mechanical and electrical performance. Potential commercial use for Miralon yarn includes antennas, high frequency digital/signal and radio frequency cable applications and embedded electronics. Nanocomp worked with Lockheed Martin to integrate Miralon sheets into our Juno spacecraft.
Composites for habitats
At last spring’s 3D-Printed Habitat Challenge the top two teams used composite materials in their winning habitat submissions. The multi-phase competition challenged teams to 3D print one-third scale shelters out of recyclables and materials that could be found on deep space destinations, like the Moon and Mars.
After 30 hours of 3D-printing over four days of head-to-head competition, the structures were subjected to several tests and evaluated for material mix, leakage, durability and strength. New York-based AI. SpaceFactory won first place using a polylactic acid plastic, similar to materials available for Earth-based, high-temperature 3D printers.
This material was infused with micro basalt fibers as well, and the team was awarded points during judging because major constituents of the polylactic acid material could be extracted from the Martian atmosphere.
Second place was awarded to Pennsylvania State University who utilized a mix of Ordinary Portland Cement, a small amount of rapid-set concrete, and basalt fibers, with water.
These innovative habitat concepts will not only further our deep space exploration goals, but could also provide viable housing solutions right here on Earth.
We work with composites in many different ways in pursuit of our exploration goals and to improve materials and manufacturing for American industry. If you are a company looking to participate in National Composites Week, visit: https://www.nationalcompositesweek.com.
The tests displayed and documented (through my exhibition and publication) attempt to critically interrogate and explore the material possibilities of charcoal as a biocomposite, while also evidencing the often futile and frustrating inconsistencies of results. Some turned out to be nothing more than a sticky black tar-like mess, unable to be pulled out of the mould, while others had a pleasing and tactile aesthetic, able to be rolled, shaped or moulded into a form. During the testing phase, I created a series of interrogation prompts – cut it, stack it, mould it, bend it, crumple it, tear it, break it, pour it etc. This allowed me to push the techniques, and to gain some new skills, so that I wouldn’t settle at the first pleasing outcome. All in all, I created over 30 samples.
On the table, you will find an array of successful and failed material experiments that fit together as a harmonious configuration. It’s been an important step for me to be able to acknowledge that it’s ok to let go and show development ‘warts and all’. I want the viewer to be able to manoeuvre around the objects; to feel and touch them. To see the variety of the outcomes, from matt to shiny, flexible to hard. The textures and tactile qualities are some of the main properties that I am trying to convey to the audience. Displaying the material in this varied and ‘unfinished’ way invites the viewer to consider its potentialities for themselves.
I feel pleased with how I have situated the materials, learning from AP1, letting the elements breath and have some connection to each other, understanding and testing what refinement means, but also being less precious and not trying to over engineer the elements – that is certainly the case with a hand printed book. It’s also been good to collaborate and learn new skills from other people, which I will do much more of going forward into major project.
This is certainly a stepping stone. I am only just discovering and getting a feel for the properties of charcoal, and I am already planning a much more ambitious casting of forms that will allow for happenstance and unpredictability in the pour. It’s an exciting phase and I’m looking forward to seeing how the next step unfolds.
A recent study, published in Advanced Materials, shows that native viruses can be employed as a scaffold to immobilise photoactive molecules to potentially oxidise organic pollutants present in wastewater, under visible light irradiation
A research team from Aalto University has developed a novel strategy to create virus-based materials for catalysis. The project, which is framed within the Horizon 2020 Marie Skłodowska-Curie actions, aims to pave the way towards the application of optically active biohybrid materials—a combination of biomolecules and synthetic moieties—in topics ranging from nanomedicine to green organic synthesis or environmental sciences.
“Our first challenge was to select the right photosensitizer,” says Eduardo Anaya, postdoctoral researcher at Aalto University, “We decided to employ phthalocyanines, a synthetic derivative of hematoporphyrin (the dye responsible for the colour of blood), due to their outstanding properties as a reactive oxygen species generator. However, the use of this kind of dyes in aqueous media presents several challenges that affect their performance. Therefore, careful design was necessary to maintain their properties`.
Back in May after an initial tour in April, I applied to Steamhouse to help me with the development of the biomaterials. Even though I’m still very much in an inception phase, I’m hoping to explore the possibilities of biomaterials and product innovation and I feel SH is the best place for these developments to happen. My application to join Steamhouse was successful and as soon as I’d got the induction completed I have been in the studios. My over arching aims is to explore the application of a charcoal material composite for marketable lifestyle products – so this is what I’m going to experimenting with over the coming weeks.
My first outcome is to make moulds for casing/packaging or product forms. Not moving too far away from my previous bio tests, I decided to use the ground mussel shells. In the previous tests the shell lost a lot of the iridescent qualities within the grind, so this was something I was conscious of showing off to a greater degree by using larger pieces of shell. I set about creating a terrazzo = tile/coaster using a mix of jesmonite and shells. I have tried a few different methods and recipes – the most successful looking tile had all of the ingredients mixed in, when it’s sanded back using a wet and dry paper reveals the shell detail. Next up, I laced the moulds with the shells top and bottom, and poured in the mixture. This creates pockets, air holes and uneven surfaces, which have a beautiful quality to it, revealing the curious overlapping structures. Following on from this I started experimenting with dyes and waste wood chips from the woodwork room. The dyes and coloured jesmonite chips worked really well, especially when mixed with the mussel shells, the wood chips not so much, but I do intend to find the right use for them at some point.
One observation to be noted, even though the mussel shells lost their slight hint of fishy smells, it seems to have returned with the mixing of materials, even when dry there is a slight overtone.
High-performance biomass-based nanocomposites are emerging as promising materials for future structural and functional applications due to their environmentally friendly, renewable and sustainable characteristics. Bio-sourced nanocelluloses (a kind of nanofibers) obtained from plants and bacterial fermentation are the most abundant raw materials on earth. They have attracted tremendous attention recently due to their attractive inherent merits including biodegradability, low density, thermal stability, global availability from renewable resources, as well as impressive mechanical properties. These features make them appropriate building blocks for spinning the next generation of advanced macrofibers for practical applications.
In past decades, various strategies have been pursued to gain cellulose-based macrofibers with improved strength and stiffness. However, nearly all of them have been achieved at the expense of elongation and toughness, because strength and toughness are always mutually exclusive for man-made structural materials. Therefore, this dilemma is quite common for previously reported cellulose-based macrofibers, which greatly limited their practical applications.