In recent years the use of thermoplastics has become popular in aerospace applications, with a primary focus on fiber-reinforced composites. Displaying greatly improved mechanical properties, new components using these materials still need to be characterized and their suitability for aviation applications demonstrated. A common restriction to the implementation of fiber-reinforced thermoplastic parts is the almost default autoclave manufacturing, which is both time consuming and expensive. Aiming for a more economical final product, this study utilizes a one-step in-situ Automated Fiber Placement (AFP) process to produce samples for mechanical and thermal characterization. The recently developed and highly popular material CF/LM-PAEK was used within this study, with the four major AFP processing parameters varied to assess material sensitivity. Test samples were manufactured using Design of Experiment (DoE). Subsequently, single lap shear (SLS) and differential scanning calorimetry (DSC) tests were performed to assess consolidation quality. With rising tooling temperature, both SLS strength and crystallinity increase up to 31 MPa and 25%, respectively. A post-manufacturing tempering process improved crystallinity of the tested CF/LM-PAEK specimens up to 29% and SLS strength up to 38 MPa. Within the tested parameter range, CF/LM-PAEK appeared to be unaffected by increasing layup speed, which is a promising aspect with regard to faster industrial production.

No abstract

No abstract

In order to develop inductive electric propulsion as a flexible, throttleable technology for future space operations, a greater understanding of discharge transitions within the inductive plasma generator discharge chamber is required. This paper presents a non-intrusive method to determine the conditions under which transitions between the capacitive, low inductive, and high inductive regimes occur with greater accuracy, as well as determining the proportion of a single discharge cycle the plasma spends in either capacitive or inductive regime. Such a method allows a more robust method of classification of inductive discharges than previously available and can be applied to numerous gases. This approach presents an advantage over previous methods which relied on strongly radiating or thermally reactive gases to exhibit certain behaviour (due to the restriction of classical diagnostics on such high power sources) before a transition could be confirmed. This paper presents results from the proposed method applied to a pure oxygen plasma as well as two combinations of argon and oxygen (at 1:1 and 3:2 Ar:O 2 volumetric ratios) in order to assess the tunability of electromagnetic regime transitions through modifications of gas composition rather than mechanical alterations. Transitions to the higher inductive mode were observed for much lower input powers for the argon-oxygen blends, as was expected, allowing final discharge conditions to occupy the inductive regime for 94% and 85% of a single discharge cycle for the 3:2 and 1:1 Ar:O 2 mixtures, respectively. Pure oxygen achieved a maximum inductive proportion of 71% by comparison.

No abstract