| Considering the combination of the hybridization and 3D weaving technique, the objectives of this research are manufacturing hybrid 3D woven composites and investigating the effects of hybrid pattern on the properties of hybrid composites including mechanical properties and dielectric properties.An effective 3D weaving technique was used to manufacture the performs and the essence of this technique is that two or more filling (or weft) yarns are simultaneously inserted from one or both sides, thus building an increment of 3D fabric length with every revolution of the machine. Vacuum resin transfer molding was used to fabricate the final composites. All of composites were reinforced with 3D woven fabric. Five kinds of composites with were fabricated for investigating the effect of constituent fiber content on the properties of composites. Two of them are pure araimed fabric reinforced composite (PAC) and pure glass fabric reinforced composite (PGC). Three of them reinforced with 3D woven fabric composed of middle glass fiber layers and equivalent aramid fiber layers in both side including: 6 aramid fiber layers plus 2 glass fiber layers reinforce composite (6A2GC), 4 aramid fiber layers plus 4 glass fib layers reinforced composite (4A4GC) and 2 layers aramid fiber layers plus 6 glass fiber layers reinforced composite (2A6GC). In addition, another composites with the preform in which 4 aramid fiber layers and 4 glass fiber layers were alternatively assembled are also fabricated for investigating the effect of constituent fiber arrangement sequence on the properties of composites. For investigating the mechanical properties, tensile, 3 point bending and low velocity impact test were performed on all of composite types.The results observed for tensile test showed that the tensile strength and Young's modulus didn't show single change tendency with the variation of constituent fiber content. When the constituent fiber volume fraction was the closest, composite showed the lowest failure stress and Young's modulus. With the equivalent constituent fiber content, A4A4GC showed higher failure stress than 4A4GC, which was caused by the difference of assemblies of constituent fiber layer between them.The results for bending test indicate that the composites with lower glass fiber content were easy to soft under bending load, but composites with higher aramid fiber content were easy to experience significant multi-stage failure behavior. Composites with higher glass fiber content showed higher flexural strength. In addition, with equivalent constituent fiber content, A4A4GC showed a significant higher bending strength than 4A4GC.The results for impact test showed that with the increment of glass fiber content, the impact peak force decreased firstly, until the constituent fiber is the closest, corresponding to 4A4GC, and then experienced a decrease. Being opposite to peak force, with the increment of glass fiber content, total impact energy experienced a increase firstly, to the maximum value at 4A4GC, and then experienced a decrease. In addition, 4A4GC showed the almost the equivalent specific impact total energy with PAC which has the largest specific total energy. Compared with A4A4GC, composite 4A4GC showed higher normalized peak force but lower total impact energy. In addition, comparison for ductility index showed than 4A4GC and A4A4GC were more ductile than other composite types.For investigating the dielectric properties, all composite types are tested by impendence method at low frequency range (lMHz~-1000MHz) and transmissionline principle at high frequency range (lGHz~2.5GHz). It was found that 4A4GC have the lowest dielectric permittivity and the third lowest loss tangent, which indicated that permittivity didn't show a unique change tendency with constituent materials. In addition, compared with 4A4GC , A4A4GC showed both higher permittivity and loss tangent, which indicated that the fiber arrangement sequence play an important role in determining dielectric properties of hybrid composites.
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