polymerguru

Today's KNOWLEDGE Share: History of fiberglass The use of fiberglass dates back to 1836 when Ignace Dubus-Bonnel received the world’s first patent on a method of making them. At the time, fiberglass was hard to make thin enough to be completely flexible, and no reliable method of mass production existed.  These problems would only be solved in 1932 by Dale Kleist, a graduate student who was working part-time at Owens-Illinois as a researcher. The company wanted to make glass blocks for architectural use, and its researchers were looking for a way to seal the two halves of a block together so that moisture couldn’t get inside.  He decided to try a metal-spraying gun with molten glass instead of bronze and discovered that it created a shower of ultrafine, thread-like glass fibers. Owens-Illinois immediately recognized that this was an excellent way to make glass wool for insulation and that it might be adaptable for other applications.  Four years and the researchers were turning out

Today's KNOWLEDGE Share: Valve Liner Cracking I recently wrapped up a failure analysis on a valve liner that had cracked while in service. The valve liner had been machined from perfluoro alkoxy (PFA). In this case, almost no background information was available on the valve application. My client was several steps removed from the installation. This can significantly hamper the failure analysis, limiting the ability to interpret test results. The visual examination revealed a significant level of rust and adherent gritty debris on the valve liner. A circumferential crack was present within a design corner of the plastic liner. The cracking exhibited a continuous irregular crack pattern indicative of multiple radial cracks, not a circumferential crack. No signs of macro ductility were apparent, and the observed features were characteristic of brittle fracture. The fracture surface displayed features indicating multiple individual cracks initiating at the liner design corner. The cr

Today's KNOWLEDGE Share: Nanoparticle in carbon fiber composites Check out this amazing microscopy!  This picture shows residues of a nano particle toughened epoxy matrix adhering to a fractured carbon fiber!  Source: Leibniz-Institut Für Verbundwerkstoffe #managingcomposites Visit MY BLOG http://polymerguru.blogspot.com #composites #carbonfiber #epoxy #microscopy

Today's KNOWLEDGE Share: Failure Analysis of Electrical Connectors The metal leads on low voltage electrical connectors cracked during outdoor exposure testing. Initially, a metallurgical failure analysis was performed, concluding that the leads failed due to pitting and stress corrosion cracking (SCC). As part of the metallurgical analysis, the lead wires were identified as a 65% Cu/35% Zn yellow brass with an exterior silver plating and a nickel underplating. These results were verified as part of the continued evaluation I performed through SEM-EDS analysis and elemental mapping. The plastic base material was specified as an unfilled polypropylene, formulated with tetrabromobisphenol A bis(dibromopropyl ether) a brominated flame retardant; and antimony oxide a synergistic flame retardant additive. This was confirmed through Fourier transform infrared spectroscopy (FTIR) and EDS. Visual and microscopical examinations confirmed the cracked leads. The connectors also showed the pre

Today's KNOWLEDGE Share: How thin are carbon fibers?  The answer is pretty simple, carbon fibers have a diameter between 5 and 10 micrometers. But that is kind of hard to visualize, right? So let's compare them to something all humans have (some more than others), hair! Luckily, we have a very nice picture that makes it very easy to draw a comparison. Crazy to realize how carbon fibers are thin, right? In case you are wondering, a human hair is about 40-120 microns in diameter.  But if you think that human hair is a very weak material, you are wrong! It consists almost entirely of a protein called Keratin which has about half of the ultimate tensile strength of steel (200 MPa). If you are tensile testing a single strand, you will only measure about 100 grams of force.  Going back to carbon fibers, it is crucial for them to have small diameters, because it allows greater graphite content. This way, the probability of having a concentration of defects in the 3D structure is consi

Today's KNOWLEDGE Share: The first composite ski!  The first successful all-fiberglass ski was the Toni Sailer ski in 1959. Art Molnar and Fred Langendorf invented and built the ski in nearby Montreal. There had been other attempts to build all fiberglass (plastic) skis starting as early as 1952, but none had made it into production. This type of construction quickly replaced both wood and aluminium construction for most recreational skis. Within ten years it was the industry standard.  Let's learn more about its inventors:  Langendorf was an engineer who specialized in fiberglass and I have not uncovered much subsequent information about him. However, Art Molnar has a long resumé in the ski and snowboard world: Molnar fled Hungary during the 1956 Revolution and landed a job working for Langendorf in Montreal. Molnar designed the first Sailer ski and then in 1963 designed a later model with a ribbed fiberglass core where the ribs were separated by air channels. This latter desi

Today's KNOWLEDGE Share: Elemental Analysis of Debris The madison Group has completed a project with the objective of analyzing the composition of debris. Upon opening a gaylord of resin, a collection of contaminant debris was apparent interspersed within the plastic molding pellets. Contamination can pose a significant problem if molded into plastic parts, and can lead to premature failure. The debris was sampled, and subsequent visual and microscopic examinations revealed exclusively metallic-looking particles. The debris material was analyzed via energy dispersive X-ray spectroscopy (EDS) in conjunction with a scanning electron microscopic (SEM) examination. Energy dispersive X-ray spectroscopy is a nondestructive chemical microanalysis technique. The technique provides relative elemental concentrations for elements having an atomic weight of 5 and greater. The SEM inspection revealed that the debris consisted primarily of spherical particles. Some distortion, suggestive of pa