Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

In order to explore the effect of artificial accelerated aging temperature on the performance of carbon fiber/epoxy resin composites,we used artificial seawater as the aging medium,designed the aging environment of seawater at different temperatures under normal pressure,and studied the aging behavior of carbon fiber/epoxy composites.The infrared spectroscopy results show that,with the increase of aging temperature,the degree of hydrolysis of the composite is greater.At the same time,after 250 days of aging of artificial seawater at regular temperature,40 and 60 ℃,the moisture absorption rates of composite materials were 0.45%,0.63%,and 1.05%,and the retention rates of interlaminar shear strength were 91%,78%,and 62%,respectively.It is shown that the temperature of the aging environment has a significant impact on the hygroscopic behavior and mechanical properties of the composite,that is,the higher the temperature,the faster the moisture absorption of the composite,and the faster the decay of the mechanical properties of the composite.

Influence of Annealing Time on the Microstructure and Properties of Pb(Zr_(0.53)Ti_(0.47))O_3 Thin Films

The PZT thin films were prepared on （111）- Pt/Ti/SiO2/Si substrates by sol-gel method, and lead acetate [Pb（CH3COO）2], zirconium nitrate [Zr（NO3）4] were used as raw materials. The X-ray diffractometer （XRD） and scanning electron microscopy （SEM） were used to characterize the phase structure and surface morphology of the films annealed at 650 ~C but with different holding time. Ferroelectric and dielectric properties of the films were measured by the ferroelectric tester and the precision impedance analyzer, respectively. The PZT thin films were constructed with epoxy resin as a composite structure, and the damping properties of the composite were tested by dynamic mechanical analyzer （DMA）. The results show that the films annealed for 90 minutes present a dense and compact crystal arrangement on the surface; moreover, the films also achieve their best electric quality. At the same time, the largest damping loss factor of the composite constructed with the 90 mins-annealed film shows peak value of 0.9, hi^her than the pure epoxy resin.

TiB_2增强酚醛泡沫的制备及性能

为提高酚醛泡沫材料的耐高温性能和高温裂解前后的力学性能,通过物理共混法在发泡酚醛树脂中添加二硼化钛(TiB_2)无机填料制备了酚醛/TiB_2泡沫复合材料。研究了泡沫复合材料的固化过程和在1 000℃下裂解前后的微观结构,以及不同的TiB_2颗粒含量对泡沫复合材料的热物理性能、裂解前后力学性能的影响。结果表明,添加的TiB_2颗粒并不能被引入到酚醛树脂的分子链中,但是能够与酚醛树脂裂解释放出的含氧气体发生氧化还原反应,将裂解气体中的C和O元素吸收并转化为无定形碳和TiO_2等固相产物,从而提高了酚醛泡沫的残炭率和裂解后的力学性能。随着TiB_2含量的增加,泡沫复合材料的残炭率以及裂解前后的表观密度、比压缩强度和比弯曲强度均呈上升趋势,其中裂解后的强度上升更为明显。当TiB_2用量为30份时,酚醛泡沫复合材料在1 000℃下裂解产物的残炭率、比压缩强度和比弯曲强度分别比纯酚醛泡沫材料提高了39.2%,76.5%和43.9%。

纤维缠绕成型碳纤维/环氧复合材料人工海水老化行为研究

碳纤维/环氧树脂复合材料具有轻质高强、耐化学介质等特点,加之纤维缠绕成型工艺可设计性强、可充分发挥碳纤维高比强和高比模的特性,碳纤维/环氧树脂复合材料广泛应用于海洋工程领域,如无人水下潜航器、耐压壳体等典型产品。本文使用人工海水作为老化介质,研究了碳纤维/环氧树脂复合材料在25℃、2~6MPa压力环境下的老化行为。结果表明,试验条件下,不同压力的复合材料吸湿行为基本符合Fick第二定律。压力对碳纤维/环氧树脂复合材料力学性能影响较小,试样拉伸强度、压缩强度、弯曲强度和层间剪切强度最低保留率依次为90%、88%、88%和92%,表明所制备的复合材料能够满足深海环境下的承载要求。傅里叶变化红外光谱(FT-IR)结果表明,试验条件下环氧树脂主链结构相对稳定,没有发生明显的降解。动态热机械分析(DMA)结果表明,试样的玻璃化转变温度(Tg)和损耗因子峰值(tanδ_(max))随着老化时间的延长而降低。

耐高温可陶瓷化聚氨酯泡沫复合材料燃烧性能

采用复合阻燃体系和陶瓷粉改性聚氨酯制备了可陶瓷化聚氨酯泡沫复合材料,讨论了复合材料的耐燃性、高温线性变化、燃烧性能和显微结构等。结果表明,可陶瓷化聚氨酯泡沫复合材料持续燃烧20 min后仍保持初始状态时的结构外形和尺寸;平均离火自熄时间约为21 s,持续火焰燃烧条件下有发烟现象,但在持续燃烧20 min内无熔滴,质量保留率大于50%,且结构保持完好;新的含碳无机陶瓷多孔结构通过高温原位结构重建而保持结构自支撑特性;耐高温可陶瓷化聚氨酯泡沫复合材料具有良好的耐燃性。

Ceramification of Composites of MgO-Al_(2)O_(3)-SiO_(2)/Boron Phenolic Resin with Different Calcine Time

The ceramifiable polymer composite of MgO-Al_(2)O_(3)-SiO_(2)/boron phenolic resin(MAS/BPF)with 40wt%of inorganic fillers was calcined at 1200℃for different time to promote ceramification of ceramifiable composite and improve heat resistance.The effects of different calcine time on the macroscopical morphology,mass loss,phase evolution,microstructure and chemical bond evolution of MAS/BPF composites were characterized by XRD,XPS,and SEM analyses.The experimental results reveal that the increase of calcine time result in the fewer holes,relatively denser and smoother top layer of MAS/BPF composites and protect the interior from deeper decomposition.The final residues of composites are amorphous carbon and C-O-Si-Al-Mg ceramic.And MAS/BPF composites show excellent mass stability,low shrinkage and self-supporting features after 2 h holding compared with BPF composites without 40wt%of inorganic fillers.

Enhancement of the Mechanical Performance of SiCf/Phenolic Composites after High-temperature Pyrolysis Using ZrC/B_(4)C Particles

The composites were prepared by modifying silicon carbide fiber with particles of zirconium carbide(ZrC)and boron carbide(B_(4)C)and incorporating them into a phenolic resin matrix.The influence of ZrC and B_(4)C on the mechanical performance of SiCf/phenolic composites after high-temperature pyrolysis was studied through flexural performance test.The results show that the composite material has good thermal stability and high-temperature mechanical properties.After static ablation at 1400℃ for 15 minutes,the flexural strength of the composite material reaches 286 MPa,which is still 7.3%higher than at room temperature,indicating that the composite material still has good mechanical properties even after heat treatment at 1400℃.