Thermally-induced responses of triaxially woven fabric composites.

The article examines the thermal responses of one-ply triaxially woven fabric composites (TWFCs). A temperature change experimental observation is first conducted on plate and slender strip specimens of TWFCs. Computational simulations are then performed with analytical and simple, geometrically-similar model configurations to capture thereby offering insights into the anisotropic thermal effects of the experimentally observed deformation. It is revealed that the leading cause of the observed thermal responses is the advancement of a locally formed twisting deformation mode. Therefore, a newly defined thermal deformation description called the coefficient of thermal twist is then characterized for TWFCs for different loading cases.

Experimental and numerical evaluations of composite concrete-to-concrete interfacial shear strength under horizontal and normal stresses.

Effects of different surface textures on the interface shear strength, interface slip, and failure modes of the concrete-to-concrete bond are examined through finite element numerical model and experimental methods in the presence of the horizontal load with 'push-off' technique under different normal stresses. Three different surface textures are considered; smooth, indented, and transversely roughened to finish the top surfaces of the concrete bases. In the three-dimensional modeling via the ABAQUS solver, the Cohesive Zone Model (CZM) is used to simulate the interface shear failure. It is observed that the interface shear strength increases with the applied normal stress. The transversely roughened surface achieves the highest interface shear strength compared with those finished with the indented and smooth approaches. The smooth and indented surfaces are controlled by the adhesive failure mode while the transversely roughened surface is dominated by the cohesive failure mode. Also, it is observed that the CZM approach can accurately model the interface shear failure with 3-29% differences between the modeled and the experimental test findings.

Failure behavior of sandwich honeycomb composite beam containing crack at the skin.

Skin crack defects can develop in sandwich honeycomb composite structures during service life due to static and impact loads. In this study, the fracture behavior of sandwich honeycomb composite (SHC) beams containing crack at the skin was investigated experimentally and numerically under four-point loading. Three different arrangements of unidirectional (UD) carbon fiber composite and the triaxially woven (TW) fabric were considered for the skins. The presence of a 10 mm crack at mid-span of the top skin, mid-span of the bottom skin, and mid-way between load and support of the top skin, respectively, were considered. Failure load equations of the load initiating the skin crack extension were analytically derived and then numerically developed using the J-integral approach. The crack extension failure mode dominated all cracked specimens except those with low-stiffness skin which were controlled by the compressive skin debonding and core shear failures.