https://pubs.kist.re.kr/handle/123456789/75354 Tue, 14 Apr 2026 01:04:59 GMT 2026-04-14T01:04:59Z https://pubs.kist.re.kr/handle/201004/141726 Title: Three-dimensional fiber reinforcement shapes obtainable from flat, bidirectional fabrics without wrinkling or cutting. Part 1. A single four-sided pyramid Authors: Robertson, RE; Chu, TJ; Gerard, RJ; Kim, JH; Park, M; Kim, HG; Peterson, RC Abstract: Criteria are derived for the adoption by bidirectional fabrics, without wrinkling or having to be cut, of the shapes of regular and truncated four-sided pyramids. Pyramids have topological kinship with general convex shapes. Also, their covering by fabrics is fairly simple, and the Rat surfaces result in distinct deformation zones that can be compared with experiment. Only the major mode of fabric deformation, trellis shear, was considered. A fishing net analysis was applied to fabrics in specific orientations. The criterion for a fabric, to cover a pyramid having four faces rising to a peak, is that the sum of angles of the fabric quadrants arrayed around the peal; must equal the sum of angles of the four faces of the pyramid. Short truncated pyramids can often be covered without wrinkling even when a taller pyramid having sides of similar steepness cannot. The criterion is again a match of angle sums. For taller truncated pyramids, the condition required for covering the corresponding non-truncated pyramid also applies. (C) 2000 Elsevier Science Ltd. All rights reserved. Sat, 01 Jan 2000 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/141726 2000-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/141725 Title: Three-dimensional fiber reinforcement shapes obtainable from flat, bidirectional fabrics without wrinkling or cutting. Part 2: a single n-sided pyramid, cone, or round box Authors: Robertson, RE; Chu, TJ; Gerard, RJ; Kim, JH; Park, M; Kim, HG; Peterson, RC Abstract: Criteria are derived for the adoption, without wrinkling or having to be cut, of the shapes of regular and truncated n-sided pyramids, cones, and round boxes by bidirectional fabrics. The flat surfaces of pyramids result in distinct deformation zones that can be compared with experiment and allow simple geometrical visualization and explanations. Only trellis shear, the major mode of fabric deformation, was considered. As with four-sided pyramids, the criterion for a fabric to cover a non-truncated n-sided pyramid is a match in angles between the fabric and the pyramid. Needing to be matched are the sum of angles of the n faces and the sum of angles of the four quadrants of the fabric that are determined by the two fibers crossing at the apex. The fabric is least deformed everywhere when the fabric is given the same deformation over the entire surface of the pyramid. The covering of a cone is analogous with n --> infinity. For truncated pyramids and prisms, the fabric deformation is never uniform. With deformation increasing away from the top surface, short truncated pyramids can be covered without wrinkling even when a taller pyramid having sides of similar steepness cannot. The rules for covering a truncated pyramid or prism and the first appearance on the side of specific degrees of fabric deformation are derived. (C) 2000 Elsevier Science Ltd. All rights reserved. Sat, 01 Jan 2000 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/141725 2000-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/141724 Title: Diffraction pattern functions of a wedge composed of metal and lossless dielectric illuminated by an E-polarized plane wave Authors: Ha, HT; Ra, JW; Kim, SY Abstract: Diffraction pattern functions of an E-polarized scattering by a wedge composed of perfectly conducting metal and lossless dielectric with arbitrary permittivity are analyzed by applying an improved physical optics approximation and its correction. The correction terms are expressed into a complete expansion of the Neumann's series, of which coefficients are calculated numerically to satisfy the null-field condition in the complementary region. Sat, 01 Jan 2000 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/141724 2000-01-01T00:00:00Z https://pubs.kist.re.kr/handle/201004/141723 Title: Blending of poly(L-lactic acid) with poly(cis-1,4-isoprene) Authors: Jin, HJ; Chin, IJ; Kim, MN; Kim, SH; Yoon, JS Abstract: Poly(L-lactic acid) (PLLA), a brittle biodegradable thermoplastic polymer, was blended with rubbery poly(cis-1,4-isoprene) (PIP). The PLLA/PIP blend, however, was incompatible as indicated by two T-g's, each stemming from PLLA and PIP domains, respectively. Since PLLA was known to be compatible with poly(vinyl acetate) (PVAc), PIP was grafted with vinyl acetate monomer to form PIP-g-PVAc, which was then blended with PLLA. The blend of PLLA and PIP-g-PVAc had two T-g's. The lower T-g, which was due to PIP phase, did not vary with the blend composition, while the higher T-g, which was due to PLLA rich phase, decreased with an increase in the graft copolymer content. The PVAc moiety of the graft copolymer seems to have been mixed in with PLLA. The tensile properties of the PLLA/PIP-g-PVAc blend were much superior to those of the PLLA/PIP blend. (C) 1999 Elsevier Science Ltd. All rights reserved. Sat, 01 Jan 2000 00:00:00 GMT https://pubs.kist.re.kr/handle/201004/141723 2000-01-01T00:00:00Z