螺杆类型对玻纤增强阻燃聚己二酰丁二胺二次料力学和热学性能的影响

通过研究挤出过程中螺杆类型的变化对玻纤增强阻燃聚己二酰丁二胺二次料(RGFFRPA46)的玻纤长度、力学、热学性能的影响。结果说明,采用长径比为4.3∶1的单螺杆挤出后,RGFFRPA46的玻纤平均长度和力学性能下降幅度分别为4.4%和3.6%,热性能下降不明显。随着单螺杆长径比增加为40∶1,RGFFRPA46在挤出过程的停留时间加长,受到剪切作用增加,导致RGFFRPA46挤出后的玻纤平均长度、力学和热学性能下降幅度增加。当RGFFRPA46采用螺杆长径比30∶1、直径为30mm的双螺杆挤出后,其玻纤平均长度和力学性能下降幅度分别达到了33.2%和23%,并且热学性能降低幅度最大。     

碳纤维增强alpha-TCP/TTCP骨水泥的研究

制备了经过氧化处理的碳纤维增强磷酸钙骨水泥(a-tricalcium phosphate cement/tetracalcium phosphate, a-CP/TTCP), 初步探讨了碳纤维长径比、含量对硬化体抗压、抗折强度的影响.实验结果表明长径比为375, 添加量为0.3wt%时, 增强效果最为理想, 抗压强度提高了55%(最大为63.46MPa), 抗折强度提高近100%(最大为11.95MPa), 而掺入量太大及长径比太高, 碳纤维因不能均匀分散将限制其性能的发挥.生物学评价实验结果表明碳纤维增强的骨水泥具有良好的生物相容性.     

螺杆类型对玻纤增强液晶聚合物二次料流变及力学热学性能的影响

研究了挤出过程中螺杆类型的变化对玻纤增强液晶聚合物二次料(RLCP-6130)流变、力学、热学性能的影响。结果表明,采用长径比为30∶1、直径为30mm的单螺杆挤出,RLCP-6130的流变和热性能下降幅度最低,玻纤平均长度和力学性能下降幅度分别低于8.4%和7.6%。随着单螺杆长径比和直径的增加,复合材料在挤出过程的停留时间加长,受到的剪切作用也增加,材料的玻纤平均长度、力学和热学性能下降幅度增加。RLCP-6130采用双螺杆(L/D=30,Φ=30mm)挤出时,玻纤平均长度和力学性能下降幅度分别超过50%和21%,剪切黏度和热学性能也出现最大幅度的降低。     

4种改性聚苯硫醚贮存寿命热老化试验研究

对不同颜色(黑色和本色),长玻纤和碳纤增强、增韧增强改性聚苯硫醚进行了热空气老化试验研究,通过选择拉伸性能下降超过30%作为贮存寿命判据,预测40%长碳纤增强聚苯硫醚(黑色)、40%长玻纤增强聚苯硫醚(本色)、40%长玻纤增韧增强聚苯硫醚(黑色),40%长玻纤PA66增强聚苯硫醚(黑色)贮存寿命分别为32.4、55.5、23.8和60.3年,适宜在武器装备上推广使用     

连续玻纤/PE增强复合带弹性参数计算方法

为研究连续玻纤/PE增强复合带的弹性性能,建立了连续玻纤/PE增强复合带模型,并对其材料及结构提出了基本假设,在此基础上采用理论公式法求解了复合带的弹性参数.建立了复合带在单向拉伸状态下的有限元模型,对玻纤与PE进行了位移耦合处理,求得了复合带沿玻纤长度方向的弹性模量,该结果与理论结果吻合很好.通过拉伸实验获得了复合带玻纤长度方向与带宽方向的弹性模量,带宽方向的弹性模量与理论结果吻合;而在玻纤长度方向上,由于加工工艺、材料状态等与假设条件之间的偏差,以及实验测试过程中存在的误差,其弹性模量与理论解、数值解相比偏低.     

磨碎玻纤增强环氧树脂应变片基底材料的研究

以表面改性的磨碎玻纤为增强材料制备了环氧树脂薄膜作为传感器应变片的基底材料。考察了玻纤表面改性及添加量对材料性能的影响。结果表明,随着偶联剂用量、玻纤填充量的增加材料的拉伸强度和拉伸模量均先增大后减小。薄膜微结构表明,填充20wt%的改性玻纤增强材料中纤维能够更好的分散在树脂中,玻纤在材料内部比较集中的区域能够互相交叠。随着改性玻纤含量的增加材料的玻璃化温度和抗蠕变性能明显改善。结果证实,填充20wt%的1wt%KH-550偶联剂改性的磨碎玻纤的增强环氧树脂材料具有最佳的力学强度、耐热性和抗蠕变性能。     

温湿度和紫外老化对纸浆模塑材料性能的影响

目的 研究温度、湿度和紫外老化对脱木素和未脱木素纸浆模塑材料性能的影响,定量地对比不同因素作用下2种材料的力学性能差异。方法 以废纸浆为原料,经打浆、脱木素、湿成型、热压等工艺制得脱木素和未脱木素等2种纸浆模塑材料;模拟不同的温湿度和紫外老化环境,测试2种纸浆模塑材料物理力学性能的变化。结果 在同等条件下,脱木素材料的拉伸强度与弯曲强度均高于未脱木素材料;2种材料的拉伸强度、弹性模量和弯曲强度随着含水率升高而大幅降低;当温度为20 ℃、含水率为0~40%时,脱木素材料的拉伸强度下降了45 MPa,未脱木素材料的拉伸强度下降了35 MPa。当温度为0 ℃、含水率为0~40%时,脱木素材料的弯曲强度下降了70 MPa,未脱木素材料的弯曲强度降低了62 MPa;当含水率低于20%时,脱木素材料的拉伸性能和弯曲性能更易受到温度影响;虽然2种材料的拉伸性能和弯曲性能均随着紫外老化时间的延长而不断降低,但其影响程度远小于温湿度。结论 湿度对材料的力学性能影响最大,其次是温度和紫外老化;脱去木素有利于提高纸浆模塑材料的力学性能和抗紫外老化性能。     

复合树脂/空心微珠耐高温浮力材料的制备及性能

本工作针对环氧树脂基固体浮力材料热稳定性差的问题,提出选用耐温性能优良的酚醛树脂和甲基硅树脂与环氧树脂形成耐高温复合基体,从而提高整体浮力材料的耐温特性.通过密度测试和准静态单轴压缩实验,研究了不同温度下树脂含量对固体浮力材料压缩强度、体积密度、弹性模量、比强度的影响,并测试了浮力材料的吸水性能和耐高温性能.研究结果表明:酚醛树脂的加入可以提升浮力材料的耐高温性能.环氧树脂中环氧基通过开环反应与硅树脂中硅氧烷发生共聚反应,形成复合树脂基体,从而增强基体的耐高温性能.硅树脂含量为40％的试样性能最好,200℃热处理后压缩强度、体积密度、弹性模量、比强度分别为39 MPa、0.652 g/cm3、4.02 GPa、59.82 MPa/(g/cm3).300℃热处理后浮力材料抗压强度仍能维持在30 MPa以上.不同温度热处理后浮力材料的吸水率不超过0.5％.     

芳纶Ⅲ纤维拉伸性能的实验研究

测试了芳纶Ⅲ纤维的拉伸性能等,并与F-12和Kevlar-49纤维进行了对比.对由芳纶Ⅲ纤维与环氧树脂基体复合成型的单向纤维增强环形试样,测试了其拉伸强度、弹性模量和层间剪切强度,结果表明:芳纶Ⅲ纤维单向纤维复合材料的拉伸强度和弹性模量与F-12纤维相当,分别比Kevlar-49纤维要高出约25.7%和24.7%;但早期的芳纶Ⅲ纤维与环氧树脂基体的界面结合性较差,层间剪切强度仅为32.0～35.2MPa.     

建筑用聚酯玻纤复合材料的制备与性能分析

选择不饱和聚酯树脂为基体材料，以玻璃纤维为增强相，采用模压成型工艺制备了不同玻璃纤维掺杂量(0,5%,10%,15%和20%(质量分数))的聚酯玻纤复合材料，分析了玻璃纤维含量对复合材料的微观形貌、热稳定性、拉伸性能和弯曲性能的影响。结果表明，聚酯玻纤复合材料中玻璃纤维和不饱和聚酯主要以物理作用为主，适量的玻璃纤维掺杂后能与聚酯基材紧密结合，分布具有方向性。随着玻璃纤维掺杂量的增大，聚酯玻纤复合材料的分解温度先增大后减小，且耐热性能提高，当玻璃纤维的掺杂量为15%(质量分数)时，复合材料的T_50%达到最大值368.47℃。力学性能测试表明，随玻璃纤维掺杂量的增大，复合材料的拉伸强度和冲击强度先增大后减小，断裂延伸率和弯曲强度持续降低，当玻璃纤维的掺杂量为15%(质量分数)时，复合材料的力学性能最优，拉伸强度最大为26.1 MPa,断裂延伸率为2.6%,冲击强度达到最大值8.1 MPa,弯曲强度为30.5 MPa。     

粗骨料与钢纤维对超高性能混凝土单轴拉伸性能的影响

为了提高含粗骨料超高性能混凝土(Ultra-high performance concrete,UHPC)的单轴拉伸性能,采用单轴拉伸试验和图像分析技术分别研究了粗骨料掺量、颗粒粒径对含粗骨料UHPC单轴拉伸性能和钢纤维在UHPC体系中分散性能的影响规律。结果表明,随着粗骨料掺量及颗粒粒径的增大,钢纤维在UHPC体系中的分散系数和取向系数显著降低,含粗骨料UHPC的单轴拉伸初裂强度、裂后强度和耗能也随之减小。根据粗骨料颗粒最大粒径与钢纤维体积分数、直径间的匹配关系式(Dmax=3df/(Vf)0.5),采用纤维混杂可以充分发挥多尺度纤维与具有不同粒径分布的骨料间的分级匹配关系;粗骨料体积分数和颗粒最大粒径分别为10%和10mm时,采用平直钢纤维(直径0.12mm、长度10mm、体积掺量1.2%)和端钩钢纤维(直径0.35 mm、长度20mm、体积掺量1.8%)混杂实现了含粗骨料UHPC的单轴拉伸性能的提升,其裂后强度和耗能分别为8.69 MPa和11.10J。     

碱处理提取竹黄纤维的响应曲面优化

采用响应曲面设计（Box-Behnken设计）优化竹纤维的提取工艺。以碱和脂肪醇聚氧乙烯醚（JFC）渗透剂对竹片进行沸煮,并结合机械碾压提取竹黄纤维,以碱浓度为0.5%~0.7%、JFC浓度为0.1%~0.3%、沸煮时间为1.5~2.5 h为考察因素,采用响应曲面法,以竹纤维断裂强度、提取率、直径和摩擦系数为响应值,建立数学模型,获得综合性能最佳工艺。并采用扫描电镜观察不同工艺处理的竹纤维的纵向结构。结果表明：最优提取工艺为碱浓度为0.7%、JFC浓度为0.3%、沸煮时间为2.5 h,此时纤维的综合性能最佳,拉伸断裂强度为386.25 MPa,直径为191.79 μm,摩擦系数为0.206,与响应曲面预测值（断裂强度为405.08 MPa,直径为175.59 μm,摩擦系数为0.191）接近。响应曲面法优化得到的竹纤维性能较好,并能很好地预测试验结果,断裂强度与预测值偏差4.6%,摩擦系数与预测值偏差7.8%,直径与预测值偏差9.2%。SEM表明：碱处理、JFC处理和沸煮时间对纤维表面的胶质有影响,碱浓度为0.5%、JFC浓度为0.3%、沸煮时间为2.5 h时有利于竹纤维表面胶质的去除。     

低模量聚酯纤维/水泥基复合材料抗冲击性能及损伤机制

研究聚酯纤维长径比、掺量对混凝土抗压强度、抗折强度、劈裂抗拉强度、断裂韧性及冲击荷载等力学性能的影响;运用复合材料理论和纤维间距理论对聚酯纤维/混凝土增韧阻裂机制进行研究,结合SEM观察微观形貌分析纤维长径比与掺量对增韧阻裂机制的影响;采用正交试验设计方法及激光扫描共聚焦显微镜(LSCM)研究冲击高度、试件厚度、长径比及掺量对纤维/混凝土抗冲击性能的影响。结果表明,长径比为300与600的聚酯纤维会降低混凝土抗压强度,低掺量长径比为150的聚酯纤维通过提高混凝土致密程度使混凝土抗压强度有所提升;在抗拉强度方面长径比为150的聚酯纤维主要以缺陷形式存在,长径比为300的聚酯纤维对改善混凝土内部拉结作用最显著,3%(与胶凝材料体积比)掺量聚酯纤维对提高混凝土抗折强度最显著;对于混凝土断裂韧性,长径比为300与600的聚酯纤维/混凝土断裂韧性提高明显,通过SEM微观形貌发现纤维拉结作用产生的微裂纹会提高混凝土耗能能力,从而提高混凝土极限荷载与破坏时中心挠度,长径比为300的聚酯纤维/混凝土抗拉强度变化规律与复合材料理论和纤维间距理论分析结果较吻合;冲击高度为影响冲击荷载大小的主要因素,纤维长径比较纤维掺量影响较大,通过LSCM三维损伤形貌分析得出长径比为150的聚酯纤维对混凝土材料损伤改善效果较显著,同等掺量下长径比为150的聚酯纤维间距较小导致混凝土局部力学性能提高,从而提高混凝土抗冲击性能。      

Mechanism and behavior of bitumen strength reinforcement using fibers

This paper investigates the reinforcement mechanism of bitumen mixed with fibers. Fibers including cellulose, rock wool and polyester types were added to bitumen. The viscosity, toughness and tenacity, microscopy and rheological tests were conducted to characterize the engineering properties of bitumen-fiber mastics. Test results indicate that the reinforcing effect increases with increasing fibers up to a critical fraction. With higher mixing temperatures, there is a higher viscosity ratio of mastic to bitumen. The tensile strength of bitumen-fiber mastics also increases with increasing fiber concentrations because the fibers carry parts of tensile loads. With the increasing tensile strength, it is implied that there is a good adhesion between bitumen and fibers. Scanning electron micrographs show that fibers reinforce bitumen through a three dimensional structure. However, there is a critical fiber fraction when fibers start to interact with each other, resulting in lower toughness. The optimum fiber content is dependent on fiber type, length and diameter.     

Effects of short-fiber shape on tensile properties of reinforced rubber

The tensile properties under various conditions were investigated to ascertain the optimum conditions to yield the best tensile properties. Fiber aspect ratio (AR: length of fiber/diameter of fiber), diameter ratio (DR: sphere diameter of dumbbell/diameter of fiber), interphase condition and fiber content were all considered as variables which impact the tensile strength, tensile moduli, pull-out force. In general, under good interphase conditions the tensile strength increased when the fiber aspect ratio was more than 20. The short-fiber reinforced SBR with a big end (DR = 3) did not show the dilution effect under interphase conditions when the fiber aspect ratio was more than 20. In case of short-fiber reinforced NR, when the specimen had DR = 3 and AR≥20, the dilution effect only showed up in the no-coated one. The tensile moduli were significantly improved due to the fiber aspect ratio, fiber content and good interphase at the same diameter ratio. The pull-out force increased with the diameter ratio, and keeping the diameter ratio the same, better interphase conditions also resulted in a higher pull-out force. Overall, it was found that the fiber aspect ratio, fiber diameter ratio, and interphase condition all have an important effect on tensile properties.     

聚酰亚胺表面处理玻璃纤维/环氧树脂复合材料力学性能

采用浇铸成型工艺制备含0.5wt%、长度分别为1 mm、3 mm、5 mm的短切玻璃纤维/环氧树脂（GF/EP）复合材料,研究含活性酚羟基和不含酚羟基的两种聚酰亚胺（PI）处理GF表面对纤维束拉伸强度及GF/EP复合材料力学性能的影响,并进一步研究PI处理GF对复合材料热性能的影响。研究结果表明,经过PI处理的GF,集束性和拉伸强度得到提高。含活性酚羟基聚酰亚胺（PI1）处理的GF拉伸强度由原丝束的517 MPa提高到1 032 MPa,不含酚羟基聚酰亚胺（PI2）处理的GF提高到986 MPa。当PI1处理的GF长度为3 mm时,GF/EP复合材料的力学性能最好,拉伸强度比未处理的提高23.62%,拉伸模量提高34.03%,弯曲强度提高28.74%,断裂韧性提高13.04%;PI2处理的GF,GF/EP复合材料拉伸强度提高15.87%,拉伸模量提高23.70%,弯曲强度提高14.11%,断裂韧性提高4.05%。此外,PI处理GF对GF/EP复合材料热性能也有一定程度的提高。     

溶胶配比对碳纤维增强炭气凝胶隔热复合材料力学性能的影响

以异丙醇(I)为溶剂、 六次甲基四胺(H)为催化剂, 配制间苯二酚(R)-糠醛(F)的醇溶胶, 经浸渍纤维预制件、凝胶老化、超临界干燥和炭化制得碳纤维增强炭气凝胶隔热复合材料。研究了溶胶配比对碳纤维增强炭气凝胶隔热复合材料密度、微观结构和力学性能的影响规律。结果表明:随着异丙醇与间苯二酚物质的量之比增大, 碳纤维增强炭气凝胶隔热复合材料的密度逐渐降低, 基体炭气凝胶内及与碳纤维形成的界面内孔径增大, 大孔数量增多, 碳纤维增强炭气凝胶隔热复合材料的强度降低。当异丙醇与间苯二酚物质的量之比由18增加到28时, 压缩强度由2.498 MPa(应变10%)降至0.716 MPa(应变10%), 拉伸强度由2.019 MPa降至1.001 MPa, 弯曲强度由3.984 MPa降至1.818 MPa。随着六次甲基四胺与间苯二酚物质的量之比增大, 碳纤维增强炭气凝胶隔热复合材料的密度先增大后减小, 基体炭气凝胶内及与碳纤维形成的界面内孔径先减小后增大, 大孔数量先减少后增加, 碳纤维增强炭气凝胶隔热复合材料的强度先增大后减小。当六次甲基四胺与间苯二酚物质的量之比为0.008 5时, 碳纤维增强炭气凝胶隔热复合材料的密度最大, 强度最大, 其压缩强度为1.066 MPa(应变10%), 拉伸强度为1.256 MPa, 弯曲强度为3.556 MPa。      

Optimal fiber distribution for tensile properties of injection molded composite

The survival rate of a composite is the residual fiber length divided by the initial fiber length, and it decreases with the initial fiber length and fiber volume content (V_f) during injection molding processes. The degree of damage is higher for carbon fiber than for glass fiber, and the survival rate increases with a hyperbolic tangent relationship as the nozzle diameter increases. Higher survival rate corresponds to a stronger material. Five different lengths of fiber with 29 different size fibers were selected based on the distribution and shape of residual fiber in experimental works. These were examined to study the effects of fiber distribution on the tensile properties of a short-fiber reinforced composite (SFRC). Compared with the experimental results, the modulus predicted using the Halpin-Tsai relation shows reasonable agreement with the prediction obtained using the residual fiber length instead of the initial fiber length. It was found that the tensile modulus and strength generally differ by a factor of up to 3.2, depending on the fiber distribution patterns with V_f = 30%, and the trend is more significant as the fiber aspect ratio increases. The interactions between the fiber and matrix and the staggered-type distribution are the most important factors in the reinforcement of the SFRC. With the same combination of short fiber length, an optimized fiber distribution pattern is suggested.     

Bond strength of reinforcing steel embedded in fly ash-based geopolymer concrete

Geopolymer concrete (GPC) is an emerging construction material that uses a by-product material such as fly ash as a complete substitute for cement. This paper evaluates the bond strength of fly ash based geopolymer concrete with reinforcing steel. Pull-out test in accordance with the ASTM A944 Standard was carried out on 24 geopolymer concrete and 24 ordinary Portland cement (OPC) concrete beam-end specimens, and the bond strengths of the two types of concrete were compared. The compressive strength of geopolymer concrete varied from 25 to 39 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 20 mm and 24 mm diameter 500 MPa steel deformed bars. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. Failure occurred with the splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This is because of the higher splitting tensile strength of geopolymer concrete than of OPC concrete of the same compressive strength. A comparison between the splitting tensile strengths of OPC and geopolymer concrete of compressive strengths ranging from 25 to 89 MPa shows that geopolymer concrete has higher splitting tensile strength than OPC concrete. This suggests that the existing analytical expressions for bond strength of OPC concrete can be conservatively used for calculation of bond strength of geopolymer concrete with reinforcing steel.     

An amorphous ceramic Al32.4Er7.6O60 fiber with large viscous flow deformation and a high-strength nanocrystallized ceramic fiber

An amorphous ceramic Al_32.4Er_7.6O₆₀ continuous fiber with a diameter of about 20 m could be made successfully by using the melt extraction method. This fiber shows large viscous flow deformation at the supercooled liquid state (about 1273 K). The fiber's tensile strength is about 900 MPa and this strength is maintained up to around 1100 K. A high-strength continuous ceramic fiber with a uniform Er₃Al₅O₁₂ nanocrystalline phase in an amorphous matrix can also be obtained with suitable crystallization from the amorphous state by heat treatment. The heat resistance, Young's modulus, and other properties are therefore improved. The nanocrystallized fiber which was heat-treated at 1373 K for 2 hours in an air atmosphere has a maximum room temperature tensile strength of 1.9 GPa, around twice that of an as-extracted amorphous fiber. The amorphous continuous ceramic fiber is promising as a ceramic that can be easily shaped at relatively low temperatures (about 1273 K), and as a reinforcing fiber for composites that can undergo secondary processing. Furthermore, this fiber can be considered as more superior to glass fibers because of its greater high-temperature strength and its high Young's modulus.