In order to study the effects of impact damage on the compressive strength and failure modes of woven carbon fiber reinforced thick composite laminates, in-plane compression tests are carried out.

The modified Hashin failure criterion and material degradation model are realized with user-defined subroutines to simulate the failure behaviors of laminates using the ABAQUS/Explicit modelling package. The effectiveness of the numerical model is validated through comparison with experiments aimed at the compressive strength and failure modes.

The results show that the impact damage reduces the compressive strength of the impacted laminates. The compressive failure mode of the non-destructive specimen is concentrated at the ends of the impacted laminates, while truncated failure occurs across the middle region. The compressive strength decreases with the increase in impact energy, but there is no linear relationship between the compressive strength and impact energy. The evolution of the damage behavior of laminated plates is closely related to the history of compression load. The damage failure of laminates hardly develops when the compression load is below the threshold of the failure load. Otherwise, the damage expands rapidly in the width direction, and compression damage eventually occurs across the whole width direction of the laminate.

The results of this study can provide references for evaluating the impact resistance of woven carbon fiber reinforced thick composite laminates.

In order to explore the effects of different stiffening configurations on the bearing capacity and anti-blast performance of double stiffened cylindrical shells, a numerical study is made of the responses of four kinds of double stiffened cylindrical shells under hydrostatic pressure and underwater explosion load.

First, finite element models of stiffened cylindrical shells with different structural forms are established. Next, finite element software ANSYS is used to calculate and analyze the influence of each structural form on the strength, stability and ultimate bearing capacity of the cylindrical shell. Finally, finite element software Abaqus/Explicit is used to calculate and analyze the influence of each structural form on the deformation deflection and plastic strain of the cylindrical shell under explosion load.

Compared with a traditional single stiffened cylindrical shell with the same mass, the I-shaped double stiffened cylindrical shell has a great advantage in carrying capacity. When the explosion load level is low, the anti-blast performance of a double cylindrical shell with small rib spacing is similar, but decreases when the explosion load level is high.

The reasonable design of double stiffened cylindrical shells can yield better design schemes for bearing capacity and anti-blast performance.

The optimization of midship sections is characterized by the large amount of design variables and the complex constraints. Most relevant research applied the intelligent optimization algorithm embedded with the rule-based calculation program (e.g., Mars2000) from classification society to deal with this issue, which has a large computation cost. Therefore, a general fast optimization method based on sensitivity ranking is proposed for the optimization of midship sections.

Firstly, the sensitivity of each constraint about each design variable was evaluated. According to the result of sensitivity, the order of design variables to be modified can be obtained when each constraint is violated. Whether the constraint is only related to local variables or not can be determined as well. During optimization iteration, based on the constraint violation of the current scheme, variable adjustment can be made with the above sensitivity information, and the sensitivity result was updated periodically. Finally, minor adjustment of optimized schemes based on coordinate alternation was employed to further improve the optimization effect.

The optimization result of an oil tanker midship section shows that the proposed method can achieve a 5.195% reduction of weight.

Compared with the intelligent optimization algorithm nesting Mars2000 directly, the optimization effect of the proposed method is satisfactory, and the time cost is only 5.58% of the former. The advantage of the proposed method in time cost is quite obvious.

This paper aims to evaluate the impact resistance of Ti80 alloy under low-velocity impact loads using a numerical study of the dynamic response.

First, the finite element software Abaqus/Explicit is used to establish a finite element model of a Ti80 alloy plate under low-velocity impact load. Second, the rationality of the material parameters and reliability of the finite element model are verified through a comparison with the experimental results. Finally, the effects of the impactor shape, yield strength and fracture energy on the dynamic response of the Ti80 alloy plate under low-velocity impact load are discussed on the basis of the finite element model.

The numerical results agree well with the experimental results in their dynamic response and deformation/failure modes. Under low-velocity impact load, damage initializes on the backside of the Ti80 alloy plate due to excessive tensile deformation. The hole expansion effect of the conical impactor causes serious plugging damage to the Ti80 alloy plate. The peak impact force, peak displacement of the impactor and energy absorbtion exhibit an approximately linear relationship to the yield strength. The fracture energy has a significant effect on the deformation/failure mode of the Ti80 alloy plate. Compared to the yield strength, the energy absorbtion is less sensitive to the fracture energy.

The results can provide references for the impact resistance design of Ti80 alloy structures.

The effects of the thickness of the face plate, angle of the wall plate and height of the core layer on the anti-explosion performance of carbon fiber reinforced composite trapezoidal corrugated sandwich structures were investigated.

First, based on the 3D Hashin failure criterion, a subroutine module of the damage evolution of fiber reinforced composites is developed using the VUMAT user subroutine interface in ABAQUS. Second, through comparison with experiments in the public literature, the effectiveness of the dynamic response simulation method of carbon fiber reinforced composites based on a development subroutine under explosion impact loading is verified. Finally, a parametric study on the explosion resistance of carbon fiber reinforced composite trapezoidal corrugated plates is carried out based on the numerical method.

The results show that, compared with increasing the thickness of the blast face panel, increasing the thickness of the back blast face panel can improve the explosion resistance of the sandwich plate more obviously; when the folding angle of the core wall plate decreases from 45° to 30°, the explosion resistance increases by 1.3%; when it decreases from 60° to 45°, the explosion resistance increases by 6.3%; and when the core height increases from 8 mm to 20 mm, the explosion resistance increases by 27.7%.

The results of this study can provide references for the explosion-proof design of carbon fiber reinforced composite sandwich structures.