Design, Construction and Validation of a Digitally Controlled Variable Bending Test Station for Thermoplastic CFRP-Specimens (Masterarbeit)

Kurzfassung

Replacing structural components in an aircraft with a lighter and more efficient material, like carbon fibre reinforced plastic, is becoming increasingly important in the aerospace industry. Especially thermoplastic matrices are more and more popular due to their possibility to be reheated and reshaped. One of these redesigned parts, with a thermoplastic matrix, are aircraft mounting brackets. Their production process is nowadays simplified by heating the brackets entirely and reshaping them into the desired form. Before using thermoplastics, these brackets were produced with a thermoset matrix which production methods were complex, required a huge variety of different shaping tools and were therefore in conjunction with high manufacturing costs. This master thesis will deal with an attempt to not entirely but locally heat and reshape thermoplastic mounting bracket blanks to avoid any complex press tool. Therefore, a variable and digitally controlled three and four-point-bending test machine is, at first designed, then constructed and finally validated. The experimental validation of the tests show that all different tests are working apart from a slight problem with the load cell. Temperature influence is creating a significant fluctuation in the load cells values and final deformation forces have to be examined with care. The objective is to locally heat a mounting bracket blank, where a certain angle is desired, to then form it into shape with the given three-point-bending fixture. The following four-point-bending test serves as a validation of the reshaped bracket quality, to track any loss of mechanical properties in the created aircraft mounting bracket.