Mid infrared integrating sphere

The mechanical stability of the composite materials was characterized by using a MARK-10 ESM303 Tension/Compression Test Stand, in conjunction with a Perkin Elmer FTIR Spectrometer outfitted with a Pike Technologies Mid-Infrared Integrating Sphere. First, the samples’ total infrared reflectance and transmittance were measured at uniaxial strains of 0%, 30%, and 50%, as described above. Next, the samples were cycled 1000 times between applied strains of 0% and 50%. In turn, the samples’ total infrared reflectance and transmittance were again measured at uniaxial strains of 0%, 30%, and 50%, as described above. The experiments were performed for at least four different samples, with similar results obtained in each instance.

The infrared properties of the composite materials were characterized according to standard protocols.^25,26,42 (link) The total infrared reflectance and transmittance spectra were obtained by using a Frontier Fourier transform infrared (FTIR) spectrometer (PerkinElmer) outfitted with a mid-infrared integrating sphere (Pike Technologies) and were analyzed with the Spectrum (PerkinElmer) and Origin 8.5 (OriginLab) software packages. The measurements were referenced to a National Institute of Standards and Technology (NIST)-verified Pike Technologies Diffuse Gold Standard. The composite materials were mounted on home-built size-adjustable stages, which allowed for the application of strains between 0% and 100%. The total reflectance spectra were collected at an illumination angle of 12°, and the total transmittance spectra were collected at a normal illumination angle. The spectra were collected in an indoor environment at room temperature, i.e., typically ∼20 °C. The average reflectance and transmittance value changes were calculated for the composites over the wavelength range of 4.5–16.5 μm by subtracting the average values at strains of 0% from the average values at strains of >0%. The experiments were performed on at least eight different composite materials of each type, with similar results obtained in each instance.

The functional stabilities of the composite materials were characterized with a combination of infrared spectroscopy and mechanical cycling according to standard protocols.^25,26 (link) First, the composites' total reflectance and transmittance spectra were measured at uniaxial strains of 0% and 50% with a Frontier FTIR spectrometer (PerkinElmer) outfitted with a Pike Technologies Mid-Infrared Integrating Sphere, as described above. Next, the composites were cycled 1000 times between applied uniaxial strains of 0% and 50% at a frequency of 1 Hz using an ESM303 tension/compression test stand (MARK-10). In turn, the composites' total reflectance and transmittance spectra were measured again at uniaxial strains of 0% and 50%. Last, the spectra were comparatively analyzed with the Spectrum (PerkinElmer) and Origin 8.5 (OriginLab) software packages. The stability testing measurements were performed on at least three composite materials of each type, with similar results obtained in each instance.