3D Printing of Liquid Crystal Elastomer Foams for Enhanced Energy Dissipation Under Mechanical Insult
3D Printing of Liquid Crystal Elastomer Foams for Enhanced Energy Dissipation Under Mechanical Insult
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DOI：
10.1021/acsami.0c17538
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发表时间：
2021-03-24
影响因子：
9.5
通讯作者：
Yu, Kai
中科院分区：
文献类型：
--
作者：
Luo, Chaoqian;Chung, Christopher;Yu, Kai
聚合物泡沫是一种重要的轻质材料，用于保护资产免受机械损伤，如冲击和振动。两个特征对于增强其能量吸收特性是重要的：泡沫结构和基质相机械行为。本研究探讨了新的方法来控制这两个功能，以提高能量吸收能力的柔性晶格泡沫。首先，我们考虑通过数字光处理（DLP）进行3D打印，作为控制一系列周期性晶胞中泡沫介观结构的方法。其次，我们通过3D打印具有多域液晶弹性体（LCE）的晶格泡沫在固体基质相材料中引入了额外的能量耗散机制，该晶格泡沫在大应变下经历机械诱导的相变。这种相变与LC液晶基元旋转和排列相关，并且除了聚合物网络的粘弹性松弛之外，还提供了用于机械能耗散的第二机制。我们将3D打印的LCE晶格与传统的热机械接近等效的弹性体晶格泡沫进行对比，以量化LCE基质相提供的能量吸收增强。在循环准静态单轴压缩条件下，LCE晶格显示出显着增强的单轴压缩的能量耗散相比，非LCE等效的泡沫印刷与市售的可光固化弹性体树脂。晶格的几何形状也起着重要的作用，在确定之间的能量耗散比的LCE和非LCE泡沫。我们发现，当增加晶格连接，泡沫变形从弯曲为主的拉伸为主的变形，这产生更高的轴向应变的支柱和更高的能量耗散的晶格泡沫，拉伸允许更大的介晶旋转比弯曲。与非LCE等效泡沫相比，LCE泡沫在跌落测试期间的重复动态加载期间表现出上级能量吸收，证明了LCE增强物理保护系统抵抗机械冲击的潜力。
Polymer foams are an essential class of lightweight materials used to protect assets against mechanical insults, such as shock and vibration. Two features are important to enhance their energy absorption characteristics: the foam structure and the matrix phase mechanical behavior. This study investigates novel approaches to control both of these features to enhance the energy absorption capability of flexible lattice foams. First, we consider 3D printing via digital light processing (DLP) as a method to control the foam mesostructure across a suite of periodic unit cells. Second, we introduce an additional energy dissipation mechanism in the solid matrix phase material by 3D printing the lattice foams with polydomain liquid crystal elastomer (LCE), which undergo a mechanically induced phase transition under large strains. This phase transition is associated with LC mesogen rotation and alignment and provides a second mechanism for mechanical energy dissipation in addition to the viscoelastic relaxation of the polymer network. We contrast the 3D printed LCE lattices with conventional, thermomechanically near-equivalent elastomer lattice foams to quantify the energy-absorbing enhancement the LCE matrix phase provides. Under cyclic quasi-static uniaxial compression conditions, the LCE lattices show dramatically enhanced energy dissipation in uniaxial compression compared to the non-LCE equivalent foams printed with a commercially available photocurable elastomer resin. The lattice geometry also plays a prominent role in determining the energy dissipation ratio between the LCE and non-LCE foams. We show that when increasing the lattice connectivity, the foam deformation transitions from bending-dominated to stretching-dominated deformations, which generates higher axial strains in the struts and higher energy dissipation in the lattice foam, as stretching allows greater mesogen rotation than bending. The LCE foams demonstrate superior energy absorption during the repeated dynamic loading during drop testing compared with the non-LCE equivalent foams, demonstrating the potential of LCEs to enhance physical protection systems against mechanical impact.