The goal of the thesis was to see how moisture and temperature correlates to the Young’s modulus and what parameters had the greatest influence on its magnitude. Roxtec provided us with PA66GF25, 25% glass fiber reinforced polyamide 6.6 (also called nylon 6.6) frames which they use around their cable fittings. These frames were subsequently cut using a circular saw so that the parts that were desirable for tensile testing could be isolated.
After being separated from the frame, these pieces were sanded down so as not to have rough surfaces from the framework structure used to provide the frame with stability and strength. After getting a finer surface, these samples were then surface and contour milled using the smaller CNC mill, available in the wood workshop using molds/frames which had been created prior to consistently getting the same shape. These CNC frames were created using CAD (Computer Aided Design) followed by CAM (Computer Aided Manufacturing) software. Similarly the tensile test pieces contour was defined as to be within this frame and the CAM software programmed to work within the frame. After having the tensile tests surface and contour milled, the edges were sanded to be as smooth as possible and prevent loose material from falling off as the weight of some of the test pieces would be needed for the conditioning process.
Lastly these tensile test pieces were conditioned and tempered to the desired moisture content and temperature followed by tensile tests, from which force-displacement data was acquired. This force-displacement curve was then converted to stress-strain and lastly the Young’s modulus could be calculated based on these results. Normally climate chambers would encapsulate the sample during tensile tests according to the ISO standards, however, due to this not being a possibility heat retention had to be tackled separately. In order to maintain a good heat retention, steel cuboids were manufactured in order to close off the samples from the ambient environment. These cuboids were created by milling the sample contour in the surface of a steel cube as well as a slot and channel where a temperature sensor could be mounted and its wire moved out of the way.
Joel Sandberg & Samuel Sjölin.