![]() However, the quadratic displacement approach of a 3-node triangle requires additional strain gauges at the nodes to determine the 12 unknown coefficients of the shape function. In the results of this experiment and of the corresponding finite element simulations are presented in detailĪ quadratic displacement approach for a 3-node triangle is also presented and verified in. In addition to the experiment a finite element analysis (FEA) was performed. The simply supported plate was loaded with a single static force at the center. In order to verify this linear approach an experimental investigation of a CFS mesh applied on a 1000 mm x 1000 mm x 5 mm PMMA plate was performed. The unknown displacements u 2, u 3and v 3 of the vertex 2 and 3 can be determined by the signals of the carbon fibre sensors. In consequence of the linear displacement approximation the strains are independent of the coordinates ( xand y) and thus constant within the element. Ε x = u 2 x 2 ε y = v 3 y 3 γ x y = x 2 u 3 − x 3 u 2 x 2 y 3 E12 Figure 2 shows a micro section of a carbon fibre sensor in longitudinal and transverse direction. The embedding process of the sensor fibre depends on the used patch type and patch material. Depending on the application of the CFS (surface application or structural integration) the ends of the sensor fibre can be provided with soldered pins. An applied current of 40 mA for 30 seconds leads to an excellent nickel coating. In order to attain a homogeneous nickel coating of the filaments the resin must be removed at the fibre endingsįor example, the epoxy resin EP 310 S can be burned off or removed using acid. ![]() Spring elements provided a constant tension force along the roving during the curing process at 180☌ for 1.5 hours.įor preparation of electrical connections a galvanic process is applied based on a nickel electrolyte. Good results for the impregnation of the carbon fibre roving T300B 1K were obtained by using the epoxy resin EP301 S (HBM) and a twist of 20 turns per meter. For this purpose the twisted carbon fibre roving is impregnated by a resin with low viscosity and cured by using a special tooling. The pre-curing process is used to stabilize the carbon fibre roving and to align the filaments of the roving. The manufacturing process of a CFS includes three basic steps: Pre-curing of the carbon fibre, preparation of the electrical connection and embedding of the sensor fibre into the sensor carrier. Figure 1 shows a CFS with a single layer GFRP patch (UD prepreg EG/913).Ĭarbon fibre sensor with an ex-Pan sensor fibre and a GFRP patch ![]() In the ex-PAN fibre T300B was identified as one suitable carbon fibre for CFSs because of the excellent linear piezoresistive behaviour, the high specific resistivity and a high breaking elongation of the fibre. CFSs with a GFRP patch exhibits an improved linearity of the signal due to the supportive effect of the glass fibres to the carbon sensor fibre especially in the case of compression loading. In terms of the mechanical properties GFRP is a particularly suitable patch material. glass fibre reinforced plastic (GFRP), polyester film, neat epoxy resin) are used. Depending on the requirements of the application different patch types (e.g. carbon fibre sensor (CFS) consists of a single carbon fibre roving with electrical connected endings embedded in a sensor carrier (patch) for electrical insulation. Piezoresitivity describes the change in electrical resistance of a conductor due to an applied strain.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |