Theoretical Failure Envelopes of Open Hole Composite Laminates with A- and B-Basis Allowables Estimated from Smooth Specimen Properties

Published

July 29, 2013

Author(s)

Jeffrey Fong, Carlos A. Cimini, Jose D. Melo, N. Alan Heckert, James J. Filliben

Abstract

Composite material property databases are important information to guide designers. Aeronautical companies spend a great deal of effort in terms of money and labor to build such databases, which are considered confidential. The development of a single fiber-resin system design allowables database can take years and cost in the order of tens of million dollars. Based on this information, theoretical failure theories can generate failure envelopes which will define the reliability of composites components. However, most handbook-based composite material property databases contain incomplete information. Usually only the test average values of material properties are given. Failure envelopes generated from these databases are thus deterministic. It would then be desirable to include uncertainties in order to increase the reliability of the design. A-basis (99% coverage; 95% confidence) and B-basis (90% coverage; 95% confidence) design allowables are a standard way to introduce uncertainties in the experimental data. In this paper, it is presented a case study where average design allowable failure envelope of open hole specimens was obtained numerically for a quasi-isotropic carbon fiber-epoxy laminate from smooth specimens material property database. Using the method of statistical design of experiments, it is then showed how the average design allowable can be supplemented with uncertainty estimates. In addition, A-basis and B-basis design allowables failure envelopes are presented using DATAPLOT, a public-domain statistical analysis software package available online. Application of this methodology to predicting reliability of composite structures is discussed.

Proceedings Title

Proceedings of the 19th International Conference of Composite Materials

Conference Dates

July 29-August 1, 2013

Conference Location

Montreal, CA

Pub Type

Conferences

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Keywords

A-bass, B-basis, carbon fiber-epoxy laminate, composite materials, design allowables, design of experiments, factorial orthogonal design, failure envelopes, failure theories, open-hole strength, reliability, tolerance limits theory, uncertainty quantification.

Citation

Fong, J. , Cimini, C. , Melo, J. , Heckert, N. and Filliben, J. (2013), Theoretical Failure Envelopes of Open Hole Composite Laminates with A- and B-Basis Allowables Estimated from Smooth Specimen Properties, Proceedings of the 19th International Conference of Composite Materials, Montreal, CA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=912347 (Accessed October 27, 2025)