Influence Of Finite Width Research Articles

Open holes in composite laminates with finite dimensions: structural assessment by analytical methods

Open circular holes are an important design feature, for instance in bolted joint connections. However, stress concentrations arise whose magnitude depends on the material anisotropy and on the defect size relative to the outer finite plate dimensions. To design both safe and light-weight optimal structures, precise means for the assessment are crucial. These can be based on analytical methods providing efficient computation. For this purpose, the focus of the present paper is to provide a comprehensive stress and failure analysis framework based on analytical methods, which is also suitable for use in industry contexts. The stress field for the orthotropic finite-width open-hole problem under uniform tension is derived using the complex potential method. The results are eventually validated against Finite-Element analyses revealing excellent agreement. Then, a failure analysis to predict brittle crack initiation is conducted by means of the Theory of Critical Distances and Finite Fracture Mechanics. These failure concepts of different modelling complexity are compared to each other and validated against experimental data. The size effect is captured, and in this context, the influence of finite width on the effective failure load reduction is investigated.

Influence of finite width on notched laminate strength predictions

Notched strength of composite laminates is commonly predicted by first determining the stress distribution within the laminate and subsequent application of a stress fracture criterion. Common test specimen geometries typically require finite width stress distributions for correct data reduction and strength predictions. Numerical difficulties are encountered with this approach, however, because closed-form expressions for the stress distribution in orthotropic materials exist only for infinite width-to-hole diameter (w/D) geometries. In this paper, finite element stress analysis is presented for isotropic and orthotropic plates containing circular notches. Results are correlated with available analytical solutions. For geometries where w/D < 4 there is a substantial change in the normal stress distribution and related strength predictions. An approximate finite width stress distribution for orthotropic plates with circular notches is proposed and the influence of finite width on notched strength predictions is discussed.