Analysis of Mechanical Properties Related to Fiber Length of Closed-Loop-Recycled Offcuts of a Thermoplastic Fiber Composites (Organo Sheets)

Increasing demand for energy-efficient means of transport has steadily intensified the trend towards lightweight components. Thermoplastic glass fiber composites (organo sheets) play a major role in the production of functional automotive components. Organo sheets are cut, shaped and functionalized by injection molding to produce hybrid components, such as those used in car door modules. The cutting process produces a considerable amount of production waste, which has thus far been thermally recycled. This study develops a closed mechanical recycling process and analyzes the different steps of the process. The offcuts were shredded using two shredding methods and implemented directly in the injection-molding process. Using tensile tests and impact bending tests, the material properties of the recycled materials were compared with the virgin material. In addition, fiber length degradation via the injection-molding process and the influence of the waterjet-cutting process on the mechanical properties are investigated. Recycled offcuts are both comparable to new material in terms of mechanical properties and usability, and are also economically and ecologically advantageous. Recycling polypropylene waste with glass fiber reinforcement in a closed loop is an effective way to reduce industrial waste in a sustainable and economical production process.     

Bond Properties of Magnesium Phosphate Cement-Based Engineered Cementitious Composite with Ordinary Concrete

A magnesium phosphate cement-based engineered cementitious composite (MPC-ECC) was developed using polyvinyl alcohol (PVA) fibers and fly ash. In this study, the bond behavior of MPC-ECC with ordinary concrete was evaluated through single and double shear bond strength tests. The effects of the water to solid mass ratio (W/S), the sand to binder mass ratio (S/B), the molar ratio of MgO to KH2PO4 (M/P), the fly ash content (F), the borax dosage (B), the volume fraction of PVA fibers (Vf), and curing age on the bond behavior of MPC-ECC with ordinary concrete were examined. The results showed that as the W/S increased, the single and double shear bond strengths were gradually reduced. As the S/B increased, the double shear bond strength increased; the single shear bond strength first decreased up to an S/B of 0.1 and then increased. With the increase of M/P, the single and double shear bond strengths increased. With the increase of F, the single shear bond strength first increased up to an F of 30% and then decreased; the double shear bond strength decreased. With the increase of B, the single and double shear bond strengths increased first and then decreased, and their strength reached its maximum at a B of 6%. The increase of Vf improved the single and double shear bond strengths. The research results can provide some technical guidance for repairing concrete structures with MPC-ECC.     

A Review on Synthetic Fibers for Polymer Matrix Composites: Performance,Failure Modes and Applications

In the last decade, synthetic fiber, as a reinforcing specialist, has been mainly used in polymer matrix composites (PMC’s) to provide lightweight materials with improved stiffness, modulus, and strength. The significant feature of PMC’s is their reinforcement. The main role of the reinforcement is to withstand the load applied to the composite. However, in order to fulfill its purpose, the reinforcements must meet some basic criteria such as: being compatible with the matrix, making chemical or adhesion bonds with the matrix, having properties superior to the matrix, presenting the optimal orientation in composite and, also, having a suitable shape. The current review reveals a detailed study of the current progress of synthetic fibers in a variety of reinforced composites. The main properties, failure modes, and applications of composites based on synthetic fibers are detailed both according to the mentioned criteria and according to their types (organic or inorganic fibers). In addition, the choice of classifications, applications, and properties of synthetic fibers is largely based on their physical and mechanical characteristics, as well as on the synthesis process. Finally, some future research directions and challenges are highlighted.     

尾部悬吊与30月龄大鼠比目鱼肌的形态学特征比较

目的 观察尾部悬吊和30月龄大鼠比目鱼肌发生萎缩过程的异同点.方法 SD雄性大鼠42只,随机分为7组,即尾部悬吊5 d、7 d、14 d组,相应的同步对照和30月鼠龄组,在各时间点制备比目鱼肌横截面冰冻切片标本,用抗MHC Ⅱ单克隆抗体进行免疫组织化学染色,计算比目鱼肌Ⅰ、Ⅱ型肌纤维横截面积并计数各型肌纤维数目.结果 与同步对照组相比,悬吊组大鼠比目鱼肌的湿重,相对湿重,Ⅰ、Ⅱ型肌纤维横截面积,经体重归一化的肌纤维横截面积均显著降低,Ⅱ型肌纤维比例显著增加,而Ⅰ型肌纤维比例减少.与14 d对照组相比,30月龄组大鼠比目鱼肌湿重和Ⅰ、Ⅱ型肌纤维横截面积均明显增大,但其相对湿重和经体重归一化的肌纤维横截面积却显著降低,与悬吊14 d组无显著差异.30月龄组大鼠比目鱼肌中Ⅰ、Ⅱ型肌纤维比例与各对照组相比亦无显著差异.结论 30月龄大鼠比目鱼肌萎缩以首先出现相对湿重与归一化肌纤维横截面积降低为特征,且发生较慢,而尾部悬吊大鼠比目鱼肌则在较短时间内发生全面萎缩.     

假肥大型肌营养不良患者骨骼肌纤维再生病理特点研究

目的研究假肥大型肌营养不良患者骨骼肌纤维再生病理特点。方法收集25例假肥大型肌营养不良患者活检骨骼肌标本,其中杜兴型肌营养不良（DMD）18例,贝克型肌营养不良（BMD）7例,冷冻连续切片,采用组织化学及免疫组织化学染色,光镜下观察再生肌纤维特点,同时应用形态计量学方法分析肌纤维再生的活跃程度。结果 HE染色下见再生肌纤维深染,胞质嗜碱性,细胞核大,同源观察NCAM染色,再生肌NCAM呈阳性表达,伴随肌纤维的成熟NCAM表达逐渐减弱,成熟肌纤维无表达。DMD患者再生肌纤维直径及横截面积明显小于BMD患者再生肌纤维,再生肌纤维数量较多。结论假肥大型肌营养不良患者骨骼肌纤维再生与年龄有相关性。     

噻奈普汀对抑郁模型大鼠学习记忆能力及海马胆碱能纤维的作用

目的观察噻奈普汀(TIA)对抑郁模型大鼠学习记忆能力以及海马胆碱能纤维的作用。方法采用慢性轻度不可预见性的应激和孤养建立大鼠抑郁模型,对模型大鼠行噻奈普汀灌胃4周,Y迷宫测试大鼠的学习记忆能力,用乙酰胆碱脂酶(AChE)的组织化学方法染色,显微镜方格目测计数对大鼠海马AchE阳性纤维的密度行定量分析。结果抑郁模型大鼠经噻奈普汀4周治疗后,学习记忆能力:应激+TIA组[(43.0±4.1)分、(7.9±0.8)分]与应激组[(69.3±8.4)分、(4.6±0.7)分]、应激+生理盐水组[(58.0±9.3)分、(5.3±1.1)分]比较学习记忆能力均有极显著差异(P<0.01);AchE阳性纤维密度为应激+TIA组[CA1:(54.65±14.29);CA3:(51.00±10.77);DG:(57.63±14.59)],应激组[CA1:(40.68±10.17);CA3:(41.27±9.33);DG:(43.90±11.37)],应激+生理盐水组[CA1:(42.47±11.83);CA3:(48.53±10.75);DG:(50.69±14.59)],应激+TIA组各区AchE阳性纤维密度极显著高于应激组(P<0.01),应激+TIA组CA1区、DG区AchE阳性纤维密度显著高于应激+生理盐水组(P<0.05)。结论噻奈普汀能有效促进抑郁模型大鼠学习记忆能力的恢复以及海马胆碱能纤维的再生。     

重硅油玻璃体替代物的应用观察

玻璃体替代物的研究发展,极大的改善了玻璃体视网膜疾病的治疗和预后,但是PVR的玻璃体视网膜手术后再手术的比例仍然很高并且最终视力很差。重硅油由于比重比水重用于治疗合并有PVR的复杂孔源性视网膜脱离时对眼底后极部及下方视网膜顶压效果较佳。所以近年来研究观察重硅油在玻璃体视网膜手术中的应用成为热点。本文就重硅油的临床应用及最新研究结果进行综述。     

Drop Weight Impact Test on Prepacked Aggregate Fibrous Concrete—An Experimental Study

In recent years, prepacked aggregate fibrous concrete (PAFC) is a new composite that has earned immense popularity and attracted researchers globally. The preparation procedure consists of two steps: the coarse aggregate is initially piled into a mold to create a natural skeleton and then filled with flowable grout. In this instance, the skeleton was completely filled with grout and bonded into an integrated body due to cement hydration, yielding a solid concrete material. In this research, experimental tests were performed to introduce five simple alterations to the ACI 544 drop weight impact test setup, intending to decrease result dispersion. The first alteration was replacing the steel ball with a steel bar to apply a line impact instead of a single point impact. The second and third introduced line and cross notched specimens at the specimen’s top surface and the load applied through a steel plate of cross knife-like or line load types. These modifications distributed impact load over a broader area and decrease dispersion of results. The fourth and fifth were bedding with sand and coarse aggregate as an alternate to the solid base plate. One-hundred-and-eight cylindrical specimens were prepared and tested in 12 groups to evaluate the suggested alteration methods. Steel and polypropylene fibers were utilized with a dosage of 2.4% to produce PAFC. The findings indicated that the line notched specimens and sand bedding significantly decreased the coefficient of variation (COV) of the test results suggesting some alterations. Using a cross-line notched specimen and line of impact with coarse bedding also effectively reduced COV for all mixtures.     

Comparison of Melting Processes for WPC and the Resulting Differences in Thermal Damage,Emissions and Mechanics

The necessity for resource-efficient manufacturing technologies requires new developments within the field of plastic processing. Lightweight design using wood fibers as sustainable reinforcement for thermoplastics might be one solution. The processing of wood fibers requires special attention to the applied thermal load. Even at low processing temperatures, the influence of the dwell time, temperature and shear force is critical to ensure the structural integrity of fibers. Therefore, this article compares different compounding rates for polypropylene with wood fibers and highlights their effects on the olfactory, visual and mechanical properties of the injection-molded part. The study compares one-step processing, using an injection-molding compounder (IMC), with two-step processing, using a twin-scew-extruder (TSE), a heating/cooling mixer (HCM) and an internal mixer (IM) with subsequent injection molding. Although the highest fiber length was achieved by using the IMC, the best mechanical properties were achieved by the HCM and IM. The measured oxidation induction time and volatile organic compound content indicate that the lowest amount of thermal damage occurred when using the HCM and IM. The advantage of one-time melting was evened out by the dwell time. The reinforcement of thermoplastics by wood fibers depends more strongly on the structural integrity of the fibers compared to their length and homogeneity.