Recent development and challenges of multifunctional structural supercapacitors for automotive industries

In the last decades, fuel scarcity and increasing pollution level pave the way for an extensive interest in alternatives to petroleum‐based fuels such as biodiesel, solar cells, lithium ion batteries, and supercapacitors. Among them, structural supercapacitors have been considered as promising candidates for automotive industries in present time. Herein, the use of carbon fiber‐based supercapacitors in automotive applications is reviewed. Carbon fiber is an excellent candidate for vehicle body applications, and its composites could be widely used in the development of supercapacitors that could provide both structural and energy storage functions. Different surface modification processes of the carbon fiber electrode to enhance the electrochemical as well as mechanical performances are discussed. The advantages of the glass fiber separator and its comparison with other types of dielectric media have been incorporated. The synthesis procedures of the multifunctional solid polymer electrolyte and its significance have been also elaborated. The fabrication process, component selection, limitations, and future challenges of these supercapacitors are briefly assimilated in this review. Copyright © 2017 John Wiley & Sons, Ltd.     

Influences of diffusion coefficient of 1-allyl-3-methylimidazolium chloride on structure and properties of regenerated cellulose fiber obtained via dry-jet-wet spinning

The diffusion dynamics of the cellulose/1-allyl-3-methylimidazolium chloride ([Amim]Cl) solution during coagulation of regenerated cellulose fiber in a nonsolvent bath was investigated in detail. According to Fick's second law of diffusion, the experimental data were fitted to obtain the diffusion coefficients of [Amim]Cl (D). The cellulose concentration, bath type, and temperature were varied to analyze their influence on the diffusion coefficient of [Amim]Cl. Furthermore, the dependence of the structure and properties of the regenerated fiber obtained via dry-jet-wet spinning on the diffusion coefficients were analyzed. Many defects were formed in the surface and cross sections of the regenerated fibers prepared with high diffusion coefficients. The crystallization and mechanical properties deteriorated with the increase in the diffusion rate of [Amim]Cl. Therefore, the diffusion coefficients of [Amim]Cl should be kept relatively low to enable the preparation of uniform-structured regenerated cellulose fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47609.     

The effect of atmospheric plasma treatment of recycled carbon fiber at different plasma powers on recycled carbon fiber and its polypropylene composites

To increase the mechanical properties of recycled carbon fiber-reinforced polypropylene (PP) composites, recycled carbon fibers (RCF) were subjected to atmospheric plasma treatment at different plasma powers (100, 200, and 300 W). The changes on surface topography and roughness of RCF were examined by atomic force microscopy. Plasma treatment of RCF increased the roughness value of RCF. The variation of surface elemental compositions and tensile strength of RCF were determined by using X-ray photoelectron spectroscopy and tensile test, respectively. Plasma-treated RCF-reinforced PP composites were fabricated using high speed thermo-kinetic mixer. Plasma treatment of RCF at 100 W increased the tensile and flexural strength values of RCF-reinforced PP composites considerably by 17 and 11%, respectively. However, plasma treatment of RCF at higher plasma powers (200 W and 300 W) decreased tensile and flexural strength values of composites because of the etching of RCF. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47131.     

Fatigue behavior and failure mechanism of basalt FRP composites under long-term cyclic loads

This paper studies the fatigue behavior of basalt fiber reinforced epoxy polymer (BFRP) composites and reveals the degradation mechanism of BFRP under different stress levels of cyclic loadings. The BFRP composites were tested under tension–tension fatigue load with different stress levels by an advanced fatigue loading equipment combined with in-situ scanning electron microscopy (SEM). The specimens were under long-term cyclic loads up to 1 × 10⁷ cycles. The stiffness degradation, S–N curves and the residual strength of run-out specimens were recorded during the test. The fatigue strength was predicted with the testing results using reliability methods. Meanwhile, the damage propagation and fracture surface of all specimens were observed and tracked during fatigue loading by an in-situ SEM, based on which damage mechanism under different stress levels was studied. The results show the prediction of fatigue strength by fitting S–N data up to 2 × 10⁶ cycles is lower than that of the data by 1 × 10⁷ cycles. It reveals the fatigue strength perdition is highly associated with the long-term run-out cycles and traditional two million run-out cycles cannot accurately predict fatigue behavior. The SEM images reveal that under high level of stress, the critical fiber breaking failure is the dominant damage, while the matrix cracking and interfacial debonding are main damage patterns at the low and middle fatigue stress level for BFRP. Based on the above fatigue behavior and damage pattern, a three stage fracture mechanism model under fatigue loading is developed.     

含醚间位芳香族聚酰胺共聚物的制备与表征

通过在芳香族聚酰胺化合物中引入4,4'-二氨基二苯醚制备含醚间位芳香族聚酰胺(PMIA)共聚物,并对其相关性能进行了检测。试验结果表明:通过反应成功将4,4'-二氨基二苯醚引入了共聚物,含醚PMIA共聚物溶液的表观黏度随剪切速率的升高而降低;制备的含醚PMIA共聚物起始分解温度低于PMIA;随着4,4'-二氨基二苯醚加入量的增加,含醚PMIA共聚物成纤能力降低;纤维断裂强度以及弹性模量降低,断裂伸长率升高,耐热持久性下降。     

不同软硬段含量的聚醚酯纤维结构与性能的关系

为了说明聚醚酯纤维的形态结构与性能的对应关系,选择不同软硬段含量的聚醚酯切片进行熔融纺丝试验。结果发现:随着硬段含量的增加,纤维的断裂强度增大,但回弹性降低;当硬段质量分数为65%时,纤维的断裂强度为1.12 cN/dtex,而回弹性降至50%左右。通过广角X射线散射、小角X射线散射以及双折射、声速取向等试验进一步分析了不同软硬段含量的聚醚酯纤维的形态结构变化,发现在硬段含量高的聚醚酯纤维内部有利于形成较高的取向结构,有助于纤维强度的提升;然而,此时纤维内形成较小尺寸的结晶结构分散于无定形区内,相分离程度低,致使其回弹性降低。     

Mechanical behavior of hybrid steel-fiber self-consolidating concrete: Materials and structural aspects

This work presents the preliminary results of an experimental investigation on the mechanical behavior of self-consolidating concrete reinforced with hybrid steel fibers in the material and structural scale. Straight and hooked end steel fibers with different lengths and diameters were used as reinforcement in fiber volume fractions of 1.0 and 1.5%. In the fresh state the concrete was characterized using the slump flow, L-box and V-funnel tests. To determine the effect of the hybrid reinforcement on the plastic viscosity and shear yield stress a parallel plate rheometer was used. Following, the mechanical response was measured under tension and bending tests. In the flexural test, the movement of the neutral axis was experimentally determined by strain-gages attached to compression and tensile surfaces. Furthermore, the mechanical response of the material under bi-axial bending was addressed using the round panel test. During the test the crack opening was measured using three linear variable differential transformers (LVDT’s). The cracking mechanisms were discussed and compared to that obtained under four point bending and direct tension. The obtained results indicated that the fiber hybridization improved the behavior of the composites for low strain and displacement levels increasing the serviceability limit state of the same through the control of the crack width. For large displacement levels the use of the longer fibers led to a higher toughness but with an expressive crack opening. Due to its structural redundancy the round panel test allowed the formation of a multiple cracking pattern which was not observed in the four point beam tests. Finally, the obtained material’s properties were used in a nonlinear finite element model to simulate the round panel test. The simulation reasonably agreed with the experimental test data.     

Deep‐black‐coloring effect of fabrics made of noncircular cross‐section polyester filaments

The effects of noncircular cross‐section (NCCS) poly ethylene terephthalate (PET) filaments and its shape factor on deep‐black‐coloring of dyed fabrics were investigated by comparing to that of the circular cross‐section PET ones. Indexes such as K/S, L* and Integ values were used for characterizing the deep‐black‐coloring effect on fabrics. The results indicated that fabrics made with NCCS PET filaments exhibited good deep‐black‐coloring effects. The calculated shape factor of the NCCS PET fiber had a significant correlation with the degree of deep‐black‐coloring exhibited by the fabric made from the fibers. A qualitative optical analysis of the NCCS PET fibers was carried out to explain the causes of the deep‐coloring of the NCCS fibers. This analysis implies that the contours of the NCCS fiber composed of surfaces with varied curvature increase the scattering of light by lowering specular reflection and increasing interior reflected and refracted light. This, in turn, strengthens the deep‐coloring effect. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 511–518, 2014