Stress Fracture Criteria for Laminated Composites Containing Stress Concentrations

Abstract

Two related criteria based on stress distribution are presented for predicting the uniaxial tensile strength of laminated composites containing through the thickness discontinuities of a general shape. The criteria result in two parameter (unnotched tensile strength and a characteristic dimension) models which are capable of predicting observed discontinuity size effects without resorting to classical concepts of linear elastic fracture mechanics. As a direct consequence of the stress criteria, however, a relationship between Mode I fracture toughness and unnotched laminate tensile strength is determined. Limited comparison of theory to experimental data for circular holes and straight cracks yields good results. The simplicity of the analytical approach coupled with its generality make it of practical value to the designer.

Effects of external patch configuration on repaired composite laminates subjected to multi-impacts

“…However, according to Pandita et al [4], the failure starts at the location of the highest stress concentration and grows perpendicular to the loading direction, what can be determinant in this study for small distances. For higher distances the stress concentration is not so determinant, because, according Whitney and Nuismer [36,37], it is assumed that failure occurs only when the stress at some distance away from the notch is equal to or greater than the unnotched laminate strength. Simultaneously to the stress concentration effect, the lower stiffness of the laminates, promoted by the hole, has also some influence on the impact parameters [38].…”

On the Line Method apparent fracture toughness evaluations: Experimental overview, validation and some consequences on fracture assessments

“…The PM establishes that fracture occurs when the stress reaches the inherent strength, σ 0, at a distance from the defect tip equal to L/2 [12,21,22]. Therefore, the failure criterion is:…”

“…The LM assumes that fracture occurs when the average stress along a certain distance, 2L, reaches the inherent strength, σ 0 [11,[22][23][24]. Therefore, the LM expression is:…”

A generalised approach to rapid finite element design of notched materials against static loading using the Theory of Critical Distances

“…In 1974, Whitney and Nuismer [11] investigated the problem of monotonic failure of fibre composite materials containing stress concentration features. With no reported knowledge of the early work, they developed identical theories to the LM and PM but gave them different names.…”