Buckling and postbuckling behaviour of a delaminated plate subjected to shear loading has been studied by means of the finite element analysis. The plate was assumed to contain either one or two circular delamintions of various diameteers and of various out-of-plane and in-plane positions. The size of the plate corresponded to the size of laminate panels used in aircraft structures. It was therefore possible to assess the practical applicability of numerous studies which focused on the buckling behaviour of substantially smaller plates. and Obsahuje seznam literatury
Polymer materials exhibit a high ductility. Determination of the yield strain as well as the break (ultimate) strain is usually done on the basis of tensile tests performed on standard samples and evaluated for normalizhed measured length, supposing the homogeneous material deformation along the sample axis. This experimental approach does not take into account the plastic strain concentration ii small neck area during the final deformation phase before the sample rupture, what is typical for the plastics behavior. Application of so defined material characteristic in the case of Finite element metod (FEM) analyses of real constructions made of TSCP plastics (typical semi-crystal polymer) led to significantly conservative (smaller) values of ultimate loads compared to the measured ones. A special experimental method making use of high-speed camera has been developed to determine the strain in defined small area of local strain concentration being also in correlation with the FEM element size. Application of the more realistic (higher local) break strain value in the case of FEM analyses of real TSCP constructions led to much better agreement between the calculated and measured stiffness and ultimate load values.
Buckling behaviour of a small delaminated plate subjected to compression loading has been studied by means of the finite element analysis. The study shows several trends in the effect of number, orientation and through-the-thickness position of delaminations upon the buckling response. These findings could be used for evaluation of reliability of laminate structures which might be subjected to impact loading, such as aircraft structures. and Obsahuje seznam literatury
The influence of the steel strip cracking at the wound part of the high pressure compound vessel on the stress, strain and vessel safety has been investigated. An equivalent orthotropic material model with the zero tangential elasticity modulus Et has been utilised to describe this phenomenon. The stress and strain analysis was carried out by means of the problem oriented finite element method (F EM) code PROKOP [2]. The damaged strip packet of thickness 10 mm at any radial position influences negatively the vessel safety. The steel strip cracking near the inner winding radius is more dangerous than the cracking near the outer radius. and Obsahuje seznam literatury