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This article gives details of the input data provided for use in the Second World-Wide Failure Exercise (WWFE-II) for benchmarking triaxial failure criteria. It includes (a) three-dimensional elastic constants, ultimate strains and strengths and the nonlinear stress-strain curves for five unidirectional laminae and their constituents and (b) a description of 12 challenging test cases of 5 composite laminates, the lay-ups, layer thicknesses, stacking sequences and the loading conditions. The originators of 3D failure theories were requested to use the exact data provided here in their blind predictions of the test cases. The instructions issued to the contributors are also presented at the end of this article.

This article draws to a conclusion the results from the co-ordinated study known as the Second World-Wide Failure Exercise (WWFE-II). It contains an objective assessment of the performance of 12 leading failure criteria for predicting the response of fibre-reinforced polymer composites when subjected to 3D states of stress. Twelve challenging test problems (Test Cases) were defined by the organisers of WWFE-II, encompassing a range of materials (polymer, glass/epoxy, carbon/epoxy), lay-ups (unidirectional, angle ply, cross ply and quasi-isotropic laminates) and various 3D stress states (various triaxial strength envelopes, through-thickness and shear loading, and stress–strain curves). A systematic comparison has then been conducted between ‘blind’ predictions (i.e. without access to the experimental results beforehand) made for each Test Case by the originators of each theory and previously obtained experimental results for each Test Case. In-depth quantitative and qualitative ranking procedures have been employed to identify the strengths and weaknesses of each theory, and the overall effectiveness of each theory as a potential design tool. The theories are grouped according to their degree of maturity and ability to predict accurately the 3D behaviour of composites. The results from this study provide unique information to the community, the intent being that it will form a guide for the selection of the most appropriate failure theory for use in a given design situation.

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