Comparison of Different Joining Techniques as a Benchmark for Integrally Joined Thermoformed Components Based on Tailored rCF Organosheets

<div class="section abstract"><div class="htmlview paragraph">Climate-neutral aviation requires resource-efficient composite manufacturing technologies and solutions for the reuse of carbon fibers (CF). In this context, thermoplastic composites (TPC) can make a strong contribution. Thermoforming of TPC is an efficient and established process for aerospace components. Its efficiency could be further increased by integration of joining processes, which would otherwise be separate processes requiring additional time and equipment. In this work, an integrative two-step thermoforming process for hollow box structures is presented. The starting point are two organosheets, i.e. fiber-reinforced thermoplastic sheets. First, one of the organosheets, intended for the bottom skin of the uplift structure, is thermoformed. After cooling, the press opens, the organosheet remains in the press and an infrared heater is pivoted in, to locally heat up just the joining area. Meanwhile, a second organosheet, intended for the top skin, is heated and thermoformed and simultaneously joined to the lower skin, thereby forming the box structure. The process can be referred to as co-consolidation with localized heating of the joining areas. The target of this study was to initially built up a test setup allowing to process single lap shear samples with this concept, test the shear strength (tensile test based on DIN 1465) and compare it with similar tests on samples joined via co-consolidation and resistance welding. The tests were based on organosheets processed from nonwovens made of polyamide 6 fibers and recycled carbon fiber. Resistance welding and co-consolidation gave similar shear strength of about 9 MPa, but the co-consolidation with localized heating reached only around 56 % of the shear strength (around 5.4 MPa). Optical observation shows adhesive failure, indicating that the contact time above temperatures allowing for healing was insufficient and requires further improvement.</div></div>