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SUMMARYA method of numerical plate testing (NPT) for composite plates with in-plane periodic heterogeneity is proposed. In the two-scale boundary value problem, a thick plate model is employed at macroscale, while three-dimensional solids are assumed at microscale. The NPT, which is nothing more or less than the homogenization analysis, is in fact a series of microscopic analyses on a unit cell that evaluates the macroscopic plate stiffnesses. The specific functional forms of microscopic displacements are originally presented so that the relationship between the macroscopic resultant stresses/moments and strains/curvatures to be consistent with the microscopic equilibrated state. In order to perform NPT by using general-purpose FEM programs, we introduce control nodes to facilitate the multiple-point constraints for in-plane periodicity. Numerical examples are presented to verify that the proposed method of NPT reproduces the plate stiffnesses in classical plate and laminate theories. We also perform a series of homogenization, macroscopic, and localization analyses for an in-plane heterogeneous composite plate to demonstrate the performance of the proposed method.

It is well known that the strength of glass fibers increases with increasing strain rate. Consequently, impact strength of glass fiber is competitive with that of carbon fiber. This strengthening phenomenon is well recognized for bulk glass. Strain-rate dependence of the strength for bulk glass was described by considering slow crack growth in glass. The analytical model that considered the slow crack growth of glass is proposed to predict the strength of glass fibers. The proposed model considered the stress corrosion limit and a constant crack velocity region. Calculations showed almost same results with the previous model, however, some differences were confirmed. To discuss the validity of the analysis, tensile tests of E-glass fiber bundles were conducted at various strain rates. It was observed that the fracture behaviors differ with the strain rates. Experimental results showed that the strength of E-glass fibers increased with increasing strain rate. Furthermore, we confirmed that the analytical results were in good agreement with the experimental results. The strain-rate dependence of the strength of glass fibers was successfully predicted by considering the slow crack growth in glass.