高速冲击载荷下梯度金属泡沫夹芯梁的动态响应与失效

采用泡沫弹冲击加载实验对梯度金属泡沫夹芯梁结构开展了不同冲击强度下的动态响应和失效研究，分析了由三种不同密度泡沫铝组成的等面密度的五种不同梯度的夹芯结构在夹支边界条件下的抗高速冲击性能，结合三点弯曲实验，研究梯度效应对夹芯结构抗冲击性能的影响。研究表明：密度梯度对结构的失效过程和失效模式有着明显的影响，且夹芯梁结构的初始失效模式对结构整体响应和主要的能量吸收机制起着主导作用；当冲击条件不足以使得均质芯材发生压缩时，均质及负梯度夹芯结构初始失效模式为整体弯曲变形，低强度芯层位于前两层的梯度结构随着冲击强度的变化出现不同程度的局部芯层压缩；当冲击强度较低时，梯度结构通过丰富的局部失效表现出明显优于均质结构的抗冲击变形能力；当冲击强度大于临界值时，均质结构具有更好的抗冲击变形能力。通过合理地设计密度梯度实现逐层压缩吸能，能够有效的提升防护结构的抗冲击性能。

Dynamic response and failure of sandwich beams with graded metal foam core under high-velocity impact

The dynamic response and failure of sandwich beams with gradient metal foam core subjected to high-velocity impact are studied experimentally. The impact resistance of five sandwich beams with different density gradient arrangements but the same surface density composed of three aluminum foams with different densities is analyzed. All the sandwich beams are simply-clamped. Combined with the quasi-static three-point bending tests, the impact resistance of the gradient sandwich beams is evaluated in terms of dynamic deformation and failure modes by considering the effects of core density gradient and impulsive intensity. The results show that the density gradient effect significantly influences the dynamic response and failure mode. The initial failure mode plays an important role in the structural response and the predominant energy absorption mechanism. Since the impact condition can not produce the local compression of the medium-density core, the initial failure mode of the uniform and negative gradient sandwich structures is the overall bending deformation, while the local core compression is the initial failure mode of the other structures with weak cores located in the first two layers. When the impulsive intensity is low, the gradient sandwich beam has superior impact resistance to the uniform counterpart. With increasing intensity, once a critical intensity is exceeded, the gradient sandwich beam shows low bending resistance to the uniform counterpart. Therefore, the optimal design of the core density gradient can efficiently improve the impact resistance of the sandwich beams under the high-velocity impact, which is a valuable reference for engineering applications.