This paper studies the compressive failure behavior of pw-GFRP (plain-woven glass fiber reinforced polymer) sandwich composite L-joints for ships. Six L-joint specimens were subjected to ultimate compressive tests, which show that damage and stiffness degradation started much earlier than any visible signs. A modified fiber kinking criterion is developed for the compressive failure of pw-GFRP layup structure. Moreover, a hybrid stiffness degradation model is applied to simulate the damage progression. The criterion and the degradation model are implemented in simulation through Abaqus user coding. The simulation results are compared with other existing theories, and the proposed criterion is validated by the similar damage initiation time. The combination of the proposed criterion and hybrid degradation model demonstrates a clear advantage over conventional methods in predicting the compressive damage evolution and ultimate failure behavior of the L-joint structure.

Fiber bundles are an important component of woven composite materials, and predicting the mechanical properties of fiber bundles can provide a basis for the study of the mechanical properties of woven composite materials. This paper establishes the micro representative volume element (RVE) model of composite materials, and obtains the equivalent elastic constant of yarn through the model homogenization theory and periodic boundary conditions. Strength prediction is performed through the VUMAT user subroutine of ABAQUS. This paper uses the maximum stress standards and Von Mises standards to predict the damage initiation of TC33 carbon fiber and epoxy resin matrix, respectively. Combined with the constant degradation method, the simulation of the damage behaviors of the micro model is achieved, and the equivalent strength of the fiber bundle is obtained. The effectiveness and correctness of this method are verified by comparing the numerical model results with the Chamis theoretical model results. The accurate prediction of mechanical properties and damage process of fiber bundles provides theoretical support for the analysis of mechanical properties of composites, and has guiding significance for the performance design of composite materials.

For the shear problem of the bolt connection structure of Sandwich Composite Plate, shear test is carried out on two kinds of Bolt Connection Structure of Sandwich Composite Plate, namely, Pre-embedded countersunk bolt and Assembled countersunk bolt, and the shear strength and stress distribution of the two kinds of bolt connection structure are investigated by using ABAQUS, and the finite element simulation results coincided with the test phenomenon well. Using this model, the stress distribution under shear damage of the Bolt Connection Structure of Sandwich Composite Plate is analysed, and the influence of bolt preload is also analysed, and the results showed that: the stress of the Sandwich Composite Plate is mainly concentrated in the Skin on the bottom side, and gradually decreased to the top surface; the influence of bolt preload could be disregarded in the analysis of the shear strength and stress peak of the Sandwich Composite Plate.

This paper analyzes how the deformation pattern of the superstructure's side wall alters when the material parameters of the laminate face sheet are tempered while the Foam-Core Sandwich Superstructure is under vertical and horizontal forces separately. The results revealed that, under each separate load of vertical forces and horizontal forces, the general pattern of longitudinal stress distribution is not affected by altering the elastic modulus of the face sheet; whereas its variation rate gradually increase as elastic modulus climbs. Comparatively, longitudinal stress distribution suffers from larger effect when the shear modulus is altered, and it presented different patterns with different loads: Under vertical forces, the variation rate of longitudinal stress grows, while it drops when under horizontal forces.