Lascano Diego, Guillen-Pineda Rene, Quiles-Carrillo Luis, Ivorra-Martínez Juan, Balart Rafael, Montanes Nestor, Boronat Teodomiro
Technological Institute of Materials (ITM), Universitat Politècnica de València (UPV), Plaza Ferrándiz y Carbonell 1, 03801 Alcoy, Spain.
Polymers (Basel). 2021 Jan 21;13(3):342. doi: 10.3390/polym13030342.
This work focuses on the manufacturing and characterization of highly environmentally friendly lightweight sandwich structures based on polylactide (PLA) honeycomb cores and PLA-flax fabric laminate skins or facings. PLA honeycombs were manufactured using PLA sheets with different thicknesses ranging from 50 to 500 μm. The PLA sheets were shaped into semi-hexagonal profiles by hot-compression molding. After this stage, the different semi-hexagonal sheets were bonded together to give hexagonal panels. The skins were manufactured by hot-compression molding by stacking two Biotex flax/PLA fabrics with 40 wt% PLA fibers. The combined use of temperature (200 °C), pressure, and time (2 min) allowed PLA fibers to melt, flow, and fully embed the flax fabrics, thus leading to thin composite laminates to be used as skins. Sandwich structures were finally obtained by bonding the PLA honeycomb core with the PLA-flax skins using an epoxy adhesive. A thin PLA nonwoven was previously attached to the external hexagonal PLA core, to promote mechanical interlock between the core and the skins. The influence of the honeycomb core thickness on the final flexural and compression properties was analyzed. The obtained results indicate that the core thickness has a great influence on the flexural properties, which increases with core thickness; nevertheless, as expected, the bonding between the PLA honeycomb core and the skins is critical. Excellent results have been obtained with 10 and 20 mm thickness honeycombs with a core shear of about 0.60 and facing bending stresses of 31-33 MPa, which can be considered as candidates for technical applications. The ultimate load to the sample weight ratio reached values of 141.5 N·g for composites with 20 mm thick PLA honeycombs, which is comparable to other technical composite sandwich structures. The bonding between the core and the skins is critical as poor adhesion does not allow load transfer and, while the procedure showed in this research gives interesting results, new developments are necessary to obtain standard properties on sandwich structures.
这项工作聚焦于基于聚乳酸（PLA）蜂窝芯以及PLA-亚麻织物层压蒙皮或面板的高度环保轻质夹层结构的制造与表征。PLA蜂窝采用厚度从50至500μm不等的PLA片材制造。通过热压成型将PLA片材加工成半六边形型材。在此阶段之后，将不同的半六边形片材粘结在一起形成六边形面板。蒙皮通过热压成型制造，将两块含40 wt% PLA纤维的Biotex亚麻/PLA织物堆叠在一起。温度（200℃）、压力和时间（2分钟）的共同作用使PLA纤维熔化、流动并完全嵌入亚麻织物中，从而得到用作蒙皮的薄复合层压板。最后，使用环氧胶粘剂将PLA蜂窝芯与PLA-亚麻蒙皮粘结在一起，得到夹层结构。预先在外部六边形PLA芯上附着一层薄的PLA无纺布，以促进芯与蒙皮之间的机械互锁。分析了蜂窝芯厚度对最终弯曲和压缩性能的影响。所得结果表明，芯厚度对弯曲性能有很大影响，弯曲性能随芯厚度增加而提高；然而，正如预期的那样，PLA蜂窝芯与蒙皮之间的粘结至关重要。对于厚度为10和20mm的蜂窝，芯剪切力约为0.60，蒙皮弯曲应力为31 - 33MPa，取得了优异的结果，可被视为技术应用的候选材料。对于具有20mm厚PLA蜂窝的复合材料，样品重量比的极限载荷达到141.5 N·g，这与其他技术复合夹层结构相当。芯与蒙皮之间的粘结至关重要，因为粘结不良会导致载荷无法传递，虽然本研究中展示的工艺给出了有趣的结果，但要获得夹层结构的标准性能仍需新的进展。
