Excellent bistability was demonstrated in a ferroelectric liquid crystal electrooptic device prepared using polyimide Langmuir-Blodgett films for the orientation of the liquid crystals without performing rubbing.
The degree of work done on polyimide films in the rubbing process with a nylon fabric was detected and evaluated in terms of induced birefringence. Strong and weak rubbing (effecting two extremes) gave rise to the optical retardation of 1 degree and 0.1 degree, respectively, with a resolution of 0.1 degree. Generation of a pretilt angle of up to 10 degrees (even up to 30 degrees) for nematic liquid crystals was achieved by performing weak rubbing in a specially synthesized polyimide which was successfully used to fabricate supertwisted nematic liquid crystal displays. Fairly good bistability in a ferroelectric liquid crystal device was obtained by weak rubbing.
This paper investigates the effect of the fiber discontinuity, caused by the prepreg cut in fabricating laminated structures, on the mechanical properties in CFRP laminates. Stress-strain relations under tensile loadings are obtained for unidirectional laminates that contain the fiber discontinuity, and damages in the laminates have also been observed. Nonlinear stress-strain relations at the center of the laminates have been found to be due to the interfacial debonding at discontinuous edge. In addition, it has been revealed that strains at distant from the fiber discontinuity increase sharply because the interlaminar shear stress is released by the interlaminar delamination that grows from the discontinuity. Finite element (FE) analysis model has been developed in order to calculate the stress distribution in the plates. The FE results have shown that stress concentrates in the fiber discontinuous edge with thicker discontinuous layer. Furthermore, shear-lag analysis model has also been proposed, and it has been shown that obtained stress distributions agree well qualitatively with the FE results.
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