On the calculation of energy release rates for cracked laminates

Abstract

A general method is given for calculating the energy release rate G from the local values of bending moments and loads in a cracked laminate. This total value is then partitioned into mode I and II components. Examples are given of the analysis of several test geometries including both variable and constant ratio mixed mode tests. Solutions for compression failures with buckling are also given. Finally there is some discussion of specimen compliances and stability criteria for fixed load and fixed displacement.

On the calculation of energy release rates for cracked laminates with residual stresses

“…Shear forces may be included (as discussed in Ref. [3]), but are not included here because prior results on laminate residual stress effects suggest that shear corrections are not needed to analyze residual stress energy …”

“…[2] and [3] for total energy release rate. For heterogeneous beams, this result reduces to the results in Ref.…”

“…Although Ref. [3] considered only homogeneous beams, it was noted that it is trivial to extend it to include any heterogeneous elastic arrangement of the layers. When heterogeneity is present including differential thermal expansion properties and the structure is subjected to a change in temperature, however, there will be residual stresses that are not included in prior analyses and may contribute to energy release rate.…”

“…Second, the partitioning in Ref. [3] is not unique. There are an infinite number of ways to partition applied moments into M I and M II such that G partitions into decoupled G I and G II .…”

“…They also were omitted in Ref. [3] because that analysis was limited to homogeneous beams where the coupling terms are zero.…”