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This work presents a novel experimental method to characterize the through-thickness shear response for fiber-reinforced polymer composite materials. A sandwich short-beam shear specimen with a thin 0° laminated face sheet bonded with a thick 90° laminated core is proposed. A combination of a finite element model-based stress calculation and a full-field surface strain measurement in a custom sandwich specimen under bending is used in the method. An entire interlaminar shear response in the 2–3 principal material plane has been generated using a regression of FEM-calculated shear stress and DIC-measured shear strain. The measured 23-plane interlaminar shear stress–strain response was very close to the 23-plane Iosipescu test and the plate-twist shear test, but a higher ultimate shear strain was achieved. Transverse tensile failure with a 45° fracture angle originated from the transverse shear stress on the neutral surface. A full set of the three-dimensional stress–strain constitutive relations has been assessed using one short-beam-shear test method, and identical nonlinear shear stress–strain responses with distinct ultimate shear strengths have been observed in the three principal material planes for the generic FRP tape material in this work for the first time. [Display omitted] • A sandwich short-beam-shear test method is proposed to obtain the shear behavior. • The entire shear responses of composites were measured in the 2-3 plane. • The shear stress-strain behaviors obtained from three test methods were compared. • The full set of 3D constitutive relations is evaluated using a single test method. [ABSTRACT FROM AUTHOR]

Thick-section fiber-reinforced polymer matrix composites (TSCs) have been increasingly used in primary and secondary load-bearing structures. Due to complex deformation mechanisms, accurate out-of-plane constitutive relations, including nonlinear shear stress–strain response, are required for structural analysis and failure prediction of TSC structures. A plate torsion test is proposed to assess the nonlinear out-of-plane shear stress–strain response using an artificial neural network (ANN) and digital image correlation (DIC). The ANN model was developed using three-dimensional finite element numerical simulations, and the out-of-plane shear stress was obtained with good accuracy. The efficiency of the shear stress calculation has been improved. The usability of the test method has been refined substantially. A comparison of the shear stress with the FEM-calculated result showed that the average error of the ANN-predicted shear stress was less than 0.5%. Accordingly, the constitutive parameters of a 15-ply thick S6C10/AC318 glass/epoxy unidirectional tape panel have been extracted from the minimization of the normalized error between ANN-calculated shear stress and DIC-measured shear strain iteratively. The efficiency of stress updating for the plate-torsion specimen has been improved by 10 5 times to extract the material constitutive parameters. Not limited to plate-torsion specimens, the proposed ANN-DIC method can be extended further for rapid assessment of material constitutive parameters for other anisotropic polymer-based composite materials using complex, statically indeterminate tests. • The out-of-plane shear stress-strain response was extracted using the ANN-DIC method. • Identification efficiency for the shear response has been increased by 1 0 5 times. • The effect of the interaction between the image number and strain noise on identification is studied. • The in-plane shear response is essential for extracting the out-of-plane shear behavior. [ABSTRACT FROM AUTHOR]