Open Access

ARTICLE

Facts and Effects to be Considered when Validating 2D and 3D UD Composite Failure Conditions - experiences from participation in the World-Wide-Failure-Exercise

R. G. Cuntze¹

1 Prof. Dr.-Ing. habil. Ralf G. Cuntze, formerly MAN Technologie AG, Augsburg, Germany; D85229 Markt Indersdorf, Tel. & Fax: 0049 8136 7754, E-mail: Ralf_Cuntze@t-online.de

Structural Durability & Health Monitoring 2010, 6(3&4), 123-160. https://doi.org/10.3970/sdhm.2010.006.123

Abstract

The paper deals with the validation of 2D and 3D failure conditions of unidirectional (UD) composites composed of endless fibres and thermoset matrices. The generation of these failure conditions is shortly described and then applied to test cases of the World-Wide-Failure-Exercises WWFE-I and II, organized by Qinetic in the past 20 years. The derivation of the conditions for the brittle fracture failure experiencing UD lamina material was based on the author's so-called Failure Mode Concept (FMC) which basically builds up on the hypotheses of Beltrami and Mohr-Coulomb. The generally applicable FMC is applied here to UD material. Essential topics of the paper are specific facts and effects to be considered when validating. This includes 'global fitting' versus 'failure mode fitting' and some test specifica.
As conclusions can be drawn from the investigations: 1. The FMC is an efficient concept because it very strictly utilizes a 'thinking in failure modes' as well as the consideration of material symmetry aspects. It has proven to be a helpful tool in simply fitting the course of multi-axial UD strength test data, and it can capture several failure modes in one final `global' effort equation; 2. The validation was partly successful, sometimes first after re-evaluation of test data provided by Qinetic. A full 2D and 3D validation can be not yet achieved due to some still missing test data and some shortfalls in the experiments.

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