TAILIEUCHUNG - Mechanics Analysis Composite Materials Episode 12

Tham khảo tài liệu 'mechanics analysis composite materials episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapters. Optimal composite structures 371 As a rule helical plies are combined with circumferential plies as in Fig. . For this case k 3 1 12 íộ 2 ự -ự 2 ộ hì h90 90 and Eq. gives 3cos2ự 1 . h Because the thickness cannot be negative this equation is valid for 0 í ộ í ộ0. For Ộ 90 the helical layer should be combined with the axial one . we should put k 3 ỉ 12 tộ 2 01 2 Ộ and 13 10 03 0 . Then - 3cos2ự . n l 2 Dependencies corresponding to Eqs. and are presented in Fig. . As an example consider a filament wound pressure vessel whose parameters are listed in Table . Cylindrical part of the vessel shown in Figs. and consists of a 36 angle-ply helical layer and a circumferential layer whose thickness h hộ and 12 190 are presented in Table . The ratio h9ị hộ for two experimental vessels is and while Eq. gives for this case h99 hộ which shows that both vessels are close to optimal structures. Laminates reinforced with uniformly stressed fibers can exist under some restrictions imposed on the acting forces Nx Ny and Ạvv. Such restrictions follow from Eqs. and under the conditions that hi 0 0 sin2 cos2 I and have the form Fig. . Optimal thickness ratios for a cylindrical pressure vessel consisting of helical plies combined with circumferential 90 or axial 0 plies. 372 Mechanics and analysis of composite materials 0 z SỈ 1 -1 sỉ ẢnXy 5 . Particularly Eqs. and do not describe the case of pure shear for which only shear stress resultant Nxv is not zero. This is quite natural because strength condition ffj 1 ỡ under which Eqs. - were derived is not valid for shear inducing tension and compression in angle-ply layers. To study in-plane shear of the laminate we should use both solutions of Eq. and assume that for some layers . with i 1 2 3 . n - 1 Ỡ while for the other layers i n n l n 2 . k ơ ì ỡ . Then Eqs. can be reduced to the following forms Nx Ny Ỡ 1 h

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