Papers by Keyword: Quasi-Isotropic Laminate

Abstract: A fully-modeled unit cell analysis is performed to investigate the macroscopic and microscopic elastic-viscoplastic behaviors of a quasi-isotropic carbon fiber-reinforced plastic (CFRP) laminate. To this end, a quasi-isotropic CFRP laminate and its microstructure composed of carbon fibers and a matrix material are considered three-dimensionally. Then, a hexagonal prism-shaped unit cell fully modeled with fibers and a matrix including interlaminar areas is defined. For this quasi-isotropic laminate, a homogenization theory for nonlinear time-dependent composites with point-symmetric internal structures is applied, enabling us to analyze both the macroscopic and microscopic elastic-viscoplastic behaviors of the laminate. The substructure method is introduced into the theory to reduce computational costs. The present method is then applied to the elastic-viscoplastic analysis of a quasi-isotropic carbon fiber/epoxy laminate subjected to an in-plane uniaxial tensile load, to investigate the macroscopic elastic-viscoplastic behavior of the laminate and the microscopic stress and strain distributions in them.

Abstract: This paper investigates the interlaminar stress distributions of notched angle-ply thermoplastic laminate under tension numerically. The representative AS4/PEEK laminate with configuration of was studied by finite element code ANSYS. Computation results show: The interlaminar stress concentrations are evident and localized in the vicinity of the hole and the two free sides, and the maximum values always appear near the hole. Meanwhile, at interfaces of-45/+45 and +45/0, the concentration of peel stress is evident, while at interfaces of 90/-45 and 0/90, the concentration of shear stress is evident. Further analysis demonstrates interlaminar shearing stress is the dominating stress and may be the leading cause of laminate delamination.

Abstract: This paper presents a damage detection of surface crack in composite laminate. Carbon/epoxy composite AS4/PEEK was used to fabricate a quasi-isotropic laminate [0/90/±45]2s. Surface crack was created by using laser cutting machine. Modal analysis was performed to obtain the mode shapes of the laminate before and after damage. The mode shapes were then adopted to compute the strain energy, which was used to define a damage index. Consequently, the damage index successfully predicted the location of surface crack in the laminate. Differential quadrature method (DQM) was introduced to calculate the partial differential terms in strain energy formula.