FEATURE / THERMOPLASTIC COMPOSITE BRACKET Figure 17. CT Scan section of design iteration 1. Pull Test Design Iteration 2 The same test procedure as described was used to evaluate the second iteration of the bracket design, results of the initial DOE are shown in Figure 21. Bracket 15 is the process condition that is used for our 50 bracket production manufacture simulation trial. The load capability increased to 16.7 kN (3750 lb), a 36% improvement over iteration 1. Most importantly the fractures have moved to the injection molded base, the fractures were not occurring at the overmold interface. Pull test results of design iteration 2 demonstrated the following: 36% improved load capacity over iteration 1 * Lower mass vs initial concept (over 50% less than current aluminum bracket) * Minimized porosity over iteration 1 * Minimized insert deformation * Improved bond at interface Figure 18. CT scan section of design iteration 2. CONCLUSIONS The study concludes the presented hybrid low melt PEAK continuous composite / injection overmold PEEK bracket can replace a machined aluminum bracket. The hybrid bracket offers a mass reduction and cost benefit. The design meets load requirements. Some process parameters and design features can still be further refined. In summary: * The hybrid bracket offers an ~ 50% mass reduction * Initial estimates show a reduction in part cost of ~ 19% * There are potential process and design improvements to further optimize performance * An aerospace supplier is comfortable with initiating a limited production run for qualification and flight test Figure 19. Pull test fixture. RESULTS To evaluate parts at the mold trial a fixture was built for testing in a tensile pull (most critical load case). The fixture is shown in Figure 19. * Higher injection melt temperatures provide better interface bond * Insert deformation can be controlled with design and process condition optimization Pull Test Initial Design The initial pull tests are shown in Figure 20. A maximum load of ~ 11.1 kN (2500 lb) was achieved, the thinner inserts resulted in an increase of capacity to ~12.0 kN (2700 lb). The fractures were occurring at the bond interface. 24 | SAMPE JOURNAL | M A R C H /A P R I L 2 0 2 0 w w w. s a m p e . o r ghttp://www.sampe.org