3D打印点阵夹芯结构冲击损伤的近场动力学模拟

Peridynamic simulation of impact damage to 3D printed lattice sandwich structure

为了有效模拟3D打印点阵材料夹芯结构在弹丸冲击下的损伤破坏行为,在近场动力学微极模型中引入塑性键,构建了适用于点阵材料夹芯结构的模型和建模方法,在验证模型准确性的基础上,模拟分析了低速和高速弹丸冲击下点阵材料夹芯结构的损伤模式与破坏机理。结果表明:低速冲击下3D打印点阵夹芯结构的破坏模式以局部塑性变形为主;高速冲击下,破坏模式表现为溃裂、孔洞贯穿和碎片喷射,并伴随着大范围的塑性变形。低速冲击下塑性变形范围随冲击速度升高而增大,而高速冲击下则相反。高速冲击下,点阵夹芯结构的贯穿过程分为面板接触、局部屈服、芯材压溃、穿透4个阶段,弹丸经历了急-缓-急3段减速过程,并对应2个加速度高峰,第2个加速度峰值低于第1个加速度峰值的50%;低速冲击过程中,弹丸仅有1次减速过程,加速度峰值随冲击速度的升高而增大,最终弹丸反弹。

Lattice sandwich structures often exhibit discontinuous characteristics under impact,with damage behaviors involving multiple scales,from micro-scale cell fracture to macro-scale structural collapse.Traditional methods based on continuum mechanics have difficulty in accurately describing non-continuum problems such as material interfaces and fracture behavior,so usually they can only handle single-scale problems.Besides,lattice materials have complex geometric shapes,and mesh-dependent numerical methods such as finite element analysis may suffer mesh sensitivity and may even struggle to obtain an ideal mesh.In order to effectively simulate the damage behavior of 3D printed lattice sandwich structures under projectile impact,a lattice sandwich structure modeling method based on the theory of peridynamics and micro-polar model,and by considering plastic bonds,is proposed.The simulation results of uniaxial compression and large-mass low-speed impact tests are compared with experimental results to verify the accuracy of the peridynamics model for lattice sandwich structures.This model is then used to analyze the damage patterns and failure mechanisms of lattice sandwich panels under projectile impact from low to high velocities.The results show that under low-speed impact,the failure mode of 3D printed lattice sandwich structures is mainly localized plastic deformation,which causes small-scale fractures in the lattice structure near the impact location after arriving at a certain level of strain;while under high-speed impact,it usually exhibits collapse,hole piercing,and fragment ejection,accompanied by extensive plastic deformation.The plastic yield range of 3D printed lattice sandwich structures shows different patterns under high-speed and low-speed impacts,with the plastic deformation range increasing as the impact velocity increases under low-speed impact,and decreasing under high-speed impact.This is mainly influenced by the characteristics of the lattice structure and the material crack propagation during the impact process.Under high-speed impact,the process of projectile penetration will go through four stages;i.e.,panel contact,local yield,core material compression,and penetration.Because the material characteristics at each stage are different,the projectile will experience a“sharp-slow-sharp”deceleration process featured by to two acceleration peaks,with the second peak value being 50%lower than the first.Compared with high-speed impact,the projectile under low-speed impact only experiences one deceleration process,and the peak acceleration increases with increasing impact velocity.When the plastic deformation and damage process of the lattice sandwich structure cannot fully dissipate the kinetic energy of the projectile,the release of elastic strain energy in the sandwich structure will cause the projectile to bounce back.The rebound speed in this study is less than 30%of the initial velocity.The research results can provide theoretical support and new analytical methods for the design and application of lattice materials.