In this work, a tertiary epoxy composite reinforced with polypyrrole (PPy) coated cotton fabric layers exhibiting electrical voltage induced thermally tunable stiffness is reported. The thin coating of PPy over cotton fabric is accomplished via oxidative vapor phase polymerization that allows creation of an active thin layer over the fibers without affecting their mechanical properties. Six such functional layers are stacked within an epoxy matrix to prepare the composite that shows in‐plane electrical insulator behavior (volume resistivity > 10⁹ Ω cm) but considerably reduced resistivity by an order of 10³ across the cross‐sections. The presence of conductive layers enables the composite to heat via Joule's effect when an electrical voltage is applied across two ends. This causes softening of matrix near the matrix‐reinforcement interface and thereby changing composite's stiffness. On application of variable voltage, a non‐linear decrease of 91% in composite stiffness is observed (6371.2 N m⁻¹ at 0 V to 566.4 N m⁻¹ at 63 V). A stable and tunable mechanical performance of the composite is further demonstrated by cyclic changes in stiffness due to voltage change with recovery up to 95% of original stiffness after 14 continuous cycles.

中文翻译：

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具有电可调性的环氧-聚吡咯-棉三元复合材料

在这项工作中，报道了用聚吡咯（PPy）涂覆的棉织物层增强的三元环氧复合材料，表现出电压感应的热可调刚度。PPy在棉织物上的薄涂层是通过氧化气相聚合完成的，该聚合可以在纤维上形成活性薄层而不影响其机械性能。六个这种功能层被堆叠在环氧基体中以制备复合材料，其示出了平面内的电绝缘体行为（体积电阻率> 10 ⁹  Ω厘米），但显着地降低电阻率以10的顺序³横切面。当两端两端施加电压时，导电层的存在使复合材料能够通过焦耳效应加热。这会导致基体-钢筋界面附近的基体软化，从而改变复合材料的刚度。可变电压的应用中，复合材料刚度的91％的非线性减小，观察到（6371.2 N×M个^-1在0V至566.4 N×M个^-1在63 V）。复合材料具有稳定且可调节的机械性能，这是由于电压变化引起的刚度循环变化，连续14次循环后恢复到原始刚度的95％，从而进一步证明了复合材料的稳定性。