超越混合规则的脱木素木塑互穿复合材料,ACS Applied Materials & Interfaces

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超越混合规则的脱木素木塑互穿复合材料
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2019-09-10 , DOI: 10.1021/acsami.9b11105
M. Frey ₁ , L. Schneider ₁ , K. Masania , T. Keplinger ₁ , I. Burgert ₁

Affiliation

木材由于其层次结构，包括定向的增强纤维素相以及碳捕获和可再生性，越来越多地被认为是可持续结构材料的开发。自上而下的制造技术可以直接使用这种分层的纤维素支架，用于新的功能材料。对于高性能承重木基材料，需要将增强相的体积含量增加到更高的纤维体积含量（FVC）。这是通过保留结构的脱木质素并随后进行致密化来实现的。所获得的不含基质的材料由于保持了分层的纤维排列而具有高的拉伸刚度。然而，它们在弯曲时表现出较低的机械性能，并且由于其易于吸水的特性而不能在潮湿的条件下使用。为了解决这两个挑战，开发了一种互穿木材聚合物相复合材料，其中使用脱木素的木质支架作为连续的增强相，而环氧树脂作为互连的基质相。我们在木质支架中开放连续孔隙的情况下，利用脱木素木材中的连续流道进行真空辅助基质渗透。在基质固化之前，将材料进行致密化处理，以增加FVC，降低孔隙率并减少木质支架中的密度变化。由于脱木质纤维素纤维的可压缩性，可以生产出FVC高达80％的互穿相复合材料（IPC），导致极高的拉伸刚度和强度，最高可达70 GPa和600 MPa。由于通过机械互锁的纤维-纤维界面增强了应力传递，并且结合了提供基体相的刚度，从而进一步帮助了相邻木单元之间通过凹坑之间的应力传递，所获得的刚度值远远超过了混合规则的上限。这种新方法为高效生产高性能可持续材料铺平了道路，该材料可替代玻璃纤维增强复合材料或天然纤维复合材料。由于通过机械互锁的纤维-纤维界面增强了应力传递，加上刚度提供了基体相，从而进一步帮助了相邻木单元之间通过凹坑之间的应力传递，所获得的刚度值远远超过了混合规则的上限。这种新方法为高效生产高性能可持续材料铺平了道路，该材料可替代玻璃纤维增强复合材料或天然纤维复合材料。由于通过机械互锁的纤维-纤维界面增强了应力传递，并且结合了提供基体相的刚度，从而进一步帮助了相邻木单元之间通过凹坑之间的应力传递，所获得的刚度值远远超过了混合规则的上限。这种新方法为高效生产高性能可持续材料铺平了道路，该材料可替代玻璃纤维增强复合材料或天然纤维复合材料。

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Delignified Wood–Polymer Interpenetrating Composites Exceeding the Rule of Mixtures

Wood is increasingly considered in sustainable structural materials development due to its hierarchical structure, including an oriented reinforcing cellulose phase combined with carbon capturing and renewability. Top-down manufacturing techniques can provide direct access to this hierarchical cellulose scaffold for use in new functional materials. For high-performance load-bearing wood-based materials, the volume content of the reinforcing phase needs to be increased to much higher fiber volume contents (FVCs). This has been achieved by structure-retaining delignification followed by densification. The obtained matrix-free materials possess high tensile stiffness due to preservation of hierarchical fiber alignment; however, they demonstrate low mechanical properties in bending and cannot be used in moist conditions due to their propensity for water absorption. In order to address these two challenges, an interpenetrating wood polymer phase composite is developed using a delignified wood scaffold as a continuous reinforcing phase and epoxy resin as the interconnected matrix phase. We utilize the continuous flow channels in delignified wood for vacuum-assisted matrix infiltration in a condition of open continuous porosity in the wood scaffold. Prior to matrix curing, the material is densified in order to increase the FVC, decrease porosity, and reduce density variations in the wood scaffold. Due to the compressibility of delignified cellulose fibers, interpenetrating phase composites (IPCs) with very high FVCs of up to 80% could be produced, leading to exceptionally high tensile stiffness and strength of up to 70 GPa and 600 MPa. The obtained stiffness values far exceed the upper limit of the rule of mixtures due to an enhanced stress transfer through mechanically interlocked fiber–fiber interfaces combined with the stiffness providing matrix phase that further aids stress transfer between neighboring wood cells via their pits. This new approach paves the way for an efficient production of high-performance sustainable materials that can be used as alternative for glass fiber reinforced composites or natural fiber composites.

更新日期：2019-09-11

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