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Examination of a small radius of curvature composite notch with a novel chevron feature to improve damage tolerance

Harman, A.B., Rapking, D., Mollenhauer, D., Iarve, E.
Composites 2019 v.118 pp. 235-249
composite materials, finite element analysis, models, prediction
Discrete damage modelling (DDM) has been used successfully for open-hole composite tensile failure prediction with the aid of Critical Failure Volume (CFV) statistical criteria. The current study considered the chevron feature, a more complex notched geometry that due to its taper has the potential to be used in aerospace design to accommodate small radius notches without a significant strength knockdown. The current study used DDM in combination with detailed experimental characterization of failure to (a) examine sub-critical damage conditions of the chevron specimen (using the open-hole specimen for comparison). Then (b), provide new understanding of the Critical Failure Volume (CFV) failure prediction method in so far as what additional verification steps are needed when predicting the strength of chevron notch composites using finite elements. The predicted development of sub-critical damage and failure predictions of the chevron notch (and open-hole) coupons matched reasonably closely with experimental observations. This study presents a new notch feature that can accommodate small radius discontinuities in aerospace composite laminates without a significant strength knockdown and proposes DDM with CFV as a reasonable method for accurately predicting its failure.