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New & Special
Here we show you the news out of the field of testing at STFI, which can also be sometimes special.
New test devices, new procedures, modified procedures all around the testing.
Puncture test cannula
The STFI was involved in the development of a DIN SPEC for determining the puncture behavior using a cannula. The aim of DIN SPEC 91365 was to provide a test method with which materials and products can be examined with regard to their resistance to penetration by a cannula.
Perforation detection is realized via the contact of the cannula with an electrically conductive film after the test material has been completely perforated.
The ASTM F2878-10 can also be tested with this machine. The focus here is to test personal protective equipment, which should provide protection against occupational exposure to blood-borne pathogens (e.g. HIV and hepatitis).
Additional to the health sector, the process is also recommended for products in the police, waste disposal companies or garbage sorting systems. Depending on the hazard potential, gloves, aprons, sleeves or entire suits are used here.
Cutting test DIN EN ISO 13997
With the inclusion of the cutting test according to DIN EN ISO 13997 in the standard for protective gloves (DIN EN 388), the STFI expanded its testing options by purchasing a TOMODYNAMOMETER TDM-100. This is specially designed for testing the cut resistance of protective clothing. The test determines the resistance that a textile material offers when a blade is cut through. The blade is pulled once over the specimen under load until it is cut through. The aim of the procedure is to determine the load at which a cut with a length of 20 mm is created. The result can be classified according to DIN EN 388.
Adhesion is important …
Because to their characteristics, carbon fibers require special test equipment. Due to the electrical conductivity of the fibers, the test devices must be encapsulated accordingly in order to exclude defects in the electronics of the devices themselves and the electrics in the entire laboratory. Special clamps are also required for carbon fibers, because of their extreme sensitivity to lateral forces in order to exclude incorrect measurements by fiber breakage caused by the clamps.
The FAVIMAT device system from TEXTECHNO for determining fiber fineness and strength meets these requirements. In addition, the integrated software offers a significantly expanded range of evaluation options for a wide variety of parameters. The tests can be carried out and evaluated according to different standards (DIN, EN, ISO, ASTM, ...).
The module FIMABOND is a novelty. With the FIMABOND, individual fibers can be precisely embedded in a drop matrix system. Almost all common thermosets and thermoplastics can be used as matrix systems, regardless of their shape (powder, granulate, foils; fibers ...).
The pull-out-force and pull-out-lengths are tested in the FAVIMAT.
The fiber-matrix-adhesion is an important parameter for the strength of the later fiber composite. This process is used particularly in the context of improving sizing systems.
Mode I Energy release rate G
The testing options for fiber composite materials are constantly being expanded at the STFI. A new parameter in the STFI test program is the determination of the energy release rate G on composites. This parameter defines the energy that is necessary to further advance an existing crack in the laminate level.
Here, the legs of the test specimen created by the crack in the plane of the laminate are pulled further apart by means of glued-on hinges over the traverse path. A moving camera visually tracks the crack progress in the laminate. The camera recording is then synchronized with the recorded force-displacement curve and the energy release rate G is determined. The standard to be used for this is ISO 15024: 2001-12: Fiber-reinforced plastics - Determination of mode I, interlaminar fracture toughness, GIC, for unidirectionally reinforced materials.
Storage of textiles in activated sludge
Based on an inquiry about the biodegradability of textiles in an aqueous medium, a special method was developed by modifying the standard method DIN EN ISO 14851 "Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium – Method by measuring the oxygen demand in a closed respirometer".
The challenge was that various investigations, including strength, were to be carried out after storage. Due to these follow-up tests, the standard procedure had to be modified. Among other things, it was necessary to increase the volume of the medium and thus significantly enlarge the experimental setup.
Activated sludge from a municipal wastewater treatment plant was used as the inoculum. The entire experiment was carried out on an interdisciplinary basis in close and constructive coordination between the client, biologists and test personnel. The method developed allows the influence of microbiological action on textile materials to be described very well by follow-up tests, especially with regard to the practical properties required.