Inter-laminar fracture toughness is an important parameter to characterize the delamination propagation performance of composite laminates. Compared with the mode I fracture, the results of mode II fracture behavior are limited. In this study, the effect of varying ply angle on the mode II delamination behavior of carbon/polymer was studied. T800 carbon fiber/EH104 epoxy resin laminates with different ply interfaces were prepared and tested according to ASTM D7905 standard. Four kinds of straight ply interfaces (0°//−0°, 15°//−15°, 30°//−30°, and 45°//−45°) and two kinds of curved ply interfaces with the curvature radius of 300 mm and 500 mm were considered. The fracture toughness G_IIC of different ply interfaces was obtained by compliance method. The experimental results revealed that the mode II toughness of the variable angle ply interface is significantly larger than that of the straight ply interface. The mode II delamination behavior was characterized by finite element model with a bilinear traction separation law and was validated by the experimental data.

The aim of this work was to study the buckling behavior and failure mode of the double-sided laser-welded Al–Li alloy panel structure under the effect of axial compression via experimental and numerical simulation methods. In the test, multi-frequency fringe projection profilometry was used to monitor the out-of-plane displacement of the laser-welded panel structure during the axial compression load. In addition, the in-plane deformation was precisely monitored via strain gauge and strain rosette. The basic principles of fringe projection profilometry were introduced, and how to use fringe projection profilometry to obtain out-of-plane displacement was also presented. Numerical simulations were performed using the finite element method (FEM) to predict the failure load and buckling modes of the laser-welded panel structure under axial compression, and the obtained results were compared with those of the experiment. It was found that the fringe projection profilometry method for monitoring the buckling deformation of the laser-welded structure was verified to be effective in terms of a measurement accuracy of sub-millimeter level. The structural failure was caused by local buckling of the skin. The observed failure modes such as local buckling of the skin, bending deformation of the stringers, continuous fracture of several welds, and failure of local strength and stiffness were attributed to the deformed laser-welded panel structure under the axial compression. The predicted failure load in the numerical simulation was slightly smaller than that of the experimental test, and the error of the simulation result relative to the test result was −2.7%. The difference between them might be due to the fact that the boundary and loading conditions used in the FEM model could not be completely consistent with those used in the actual experiment.

Energy storage is a common challenge for spacecraft and vehicles, whose operating range and operational availability are limited to a considerable extent by the storage capacity; mass and volume are the main issues. Composite structural batteries (CSBs) are emerging as a new solution to reduce the size of electric systems that can bear loads and store energy. Carbon-fiber-reinforced polymers (CFRP) offer significant advantages over metallic structures. This paper reviews the recent design of multifunctional composites by combining batteries with CFRP to obtain structural lightweight and excellent mechanical properties. The assembly methods for different CSBs based on the type of electrolyte used are discussed. A comparative analysis is performed on the energy density, rate performance, cycle performance, and mechanical performance with a particular focus on the multifunctional efficiency of various CSBs. Furthermore, the opportunities and challenges in CSBs are discussed, and research ideas are proposed for this emerging field.