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The fluoropolymer CYTOP was investigated in order to evaluate its suitability as a coating material for ultracold neutron (UCN) storage vessels. Using neutron reflectometry on CYTOP-coated silicon wafers, its neutron optical potential was measured to be 115.2(2) neV. UCN storage measurements were carried out in a 3.8 l CYTOP-coated aluminum bottle, in which the storage time constant was found to increase from 311(9) s at room temperature to 564(7) s slightly above 10 K. By combining experimental storage data with simulations of the UCN source, the neutron loss factor of CYTOP is estimated to decrease from 1.1(1)$$\times 10^{-4}$$ × 10 - 4 to 2.7(2)$$\times 10^{-5}$$ × 10 - 5 at these temperatures, respectively. These results are of particular importance to the next-generation superthermal UCN source SuperSUN, currently under construction at the Institut Laue-Langevin, for which CYTOP is a possible top-surface coating in the UCN production volume.

The mechanism of reinforcement is not compliant interlayer creation, but rather is a fiberstitching mechanism, as no increase in interlayer thickness occurs with the nanostitches. Unlike traditional (large-fiber/tow/pin) stitching or z-pinning techniques that damage inplane fibers and reduce laminate in-plane strengths, the nano-scale CNT-based 'stitches' improve in-plane strength, demonstrating the potential of such an architecture for aerospace structural applications. The quality of VACNT transfer to the prepreg laminates has not been optimized and therefore the noted enhancement to strength may be considered conservative. Ongoing work has been undertaken to both improve VACNT transfer and expand the data set. Nomenclature AE= Acoustic Emission CNTs = Carbon Nanotubes

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Environmental factors that affect matrix cracking in composite laminates include temperature, moisture content, and hygrothermal history. Matrix cracking in laminates exposed to aircraft environments was modelled using a fracture mechanics approach based on strain energy release rates. Residual stress relaxation due to hygrothermal history was found to alter the static mechanical strain necessary to cause matrix cracking in experiments. Depending on material type and hygrothermal history, this effect was shown to either increase or decrease the resistance to matrix cracking. Close agreement between predicted and measured strains at the onset of matrix cracking was obtained using a modification to the fracture mechanics approach. Viscoelastic stress relaxation was modelled as shifts in the stress free temperature. This approach seems feasible providing that matrix crack growth is an elastic phenomena. Matrix crack growth in laminates subjected to creep loads and severe environments may require the development of viscoelastic failure criteria.