Macroscopic Fracture Mechanics of Advanced Composite Materials

Abstract

The application of classical fracture mechanics to laminated com posites is discussed. A convenient method is presented for predicting the static strength of a flawed specimen. Theoretical predictions are compared with experimental data for specimens containing two types of flaws.

A comparative analysis of several nonlocal fracture criteria

“…Comparisons of predicted and experimental [1][2][3] data for the strength of multi-layer composite materials are given in the Fig. 11-17.…”

“…In the case of a known direction θ 0 , where the maximum in (3) is realized, the MSFC may be written in a more simple form: Criterion of such type was used by Waddoups et al [1], Cruse [11], Caprino et al [12] and other authors. It is supposed that there exists a fictitious crack with a characteristic length d 3 originating from the considered point y of the body.…”

“…The symmetric form with two cracks used earlier [1,4] corresponds to the simultaneous fracture at two points. It seems more natural for us not to demand the fracture symmetry.…”

“…The plate strength evaluated by use of the fracture criterion σ θθ = σ c is then independent of the hole radius and is equal to one third of the strength σ c of the plate without a hole (the solid line). However appropriate fracture test data for plates with small holes (see, e.g., [1][2][3]) pointed out schematically in the figure show that the plate strength depends actually on the hole radius.…”

Finding truth in fictions: identifying non-fictions in imaginary cracks

“…These flaws stem from chaotic elements in the manufacturing process, leading to "variability of chemical composition, microstructure and mechanical properties" (Fjeldstad et al 2008(Fjeldstad et al , 1186. Practitioners have long known that these flaws, regardless of their type, can be treated as though they are microcracks, so long as they are small relative to the structure and one is interested only in modelling the structure as a whole (Waddoups et al 1971). The details of the flaws, then, are not nearly as important as knowing the tendency of the manufacturing process to produce flaws of any type.…”