## 2 Materials and Methods
### SLA Material Properties  
A major design challenge associated with the PerFORM lies in the mechanical properties and the thermal expansion coefficient. Due to the nature of the cross-linked polymers in the SLA building process, AM materials using this process of construction exhibit a glass transition temperature. They do not have a melting point in the traditional sense and will transform into a rubbery state above the glass transition temperature [10]. Independent material testing on the PerFORM was completed to provide insight and judge feasibil  
Figure 4: AM insert cross-section pointing out key features associated with the static pressure taps. Figure 3: Workflow diagram from a new flowpath design for implementing and testing the aerodynamic performance effects. ity in the demanding application of a diffuser for an aero-engine centrifugal compressor. Details on the tests and material properties can be found in [PERSON]'s thesis on the subject [10]. Stress-strain curves are reproduced in Figure 5 using the acquired tensile test data. SLA materials have anisotropic properties due to the influences of the build direction. Multiple sets of tensile tests representing the different build directions and temperatures were performed and recorded. The curves in Figure 5 represent the weakest of the three build directions to account for this in the mechanical analysis. Mechanical behavior changes significantly between 73 \({}^{\circ}\)F (23 \({}^{\circ}\)C, room temperature) and 200 \({}^{\circ}\)F (93 \({}^{\circ}\)C). At room temperature, the ultimate tensile strength is around 21 ksi (145 MPa) and reaches an ultimate strain of 2% at failure. The curve is mostly linear, indicating there is little or no plastic deformation before the ultimate strength is exceeded. At 200 \({}^{\circ}\)F, the ultimate strength is around 9 ksi (62 MPa), or about half of the room temperature mechanical strength. Additionally, the material sample reached an ultimate strain of 5% before failure. The curve at 200 \({}^{\circ}\)F exhibits more plastic deformation compared to the room temperature curve. The highest-temperature curve shown, 300 \({}^{\circ}\)F (149 \({}^{\circ}\)C), presents the most significant reduction in strength, producing an ultimate strength of around 2.5 ksi (17 MPa). The glass transition temperature for PerFORM is close to 200 \({}^{\circ}\)F, which helps to explain some of the behavior. At temperatures close to this value, the stiffness is reduced, but as the temperature exceeds it by a significant margin, the material becomes much weaker and more brittle [10]. Fortunately, temperatures in the fan flowpath are rarely expected to exceed 200 \({}^{\circ}\)F, which makes this an excellent application for this material. The data obtained at this temperature were imposed as the structural limit for the purposes of the analysis. The linear thermal expansion coefficient for the PerFORM presents a second significant design challenge. Compared to the surrounding aluminum components, the PerFORM has a much higher thermal expansion coefficient, and the difference increases to a greater degree at elevated temperatures. Figure 6 shows the coefficients for the PerFORM and 6061 aluminum. Values for the PerFORM were determined from the material testing and values for the aluminum were obtained from the ANSYS 2022/R1 material database. At room temperature, the PerFORM will expand about twice as much as the aluminum, and at 200 \({}^{\circ}\)F, the thermal expansion will be greater by a factor of five. Figure 5: PerFORM stress–strain curves at multiple temperatures. Due to the mismatch of thermal expansion coefficients, thermal stresses will build up as both components heat up during fan operation. Herein lies the critical aspect of the mechanical analysis. The PerFORM must withstand the expected thermal stress due to the constraining aluminum parts. However, at elevated temperatures where the stress is highest, the mechanical strength decreases, creating a conflicting design goal.