Fracture and Tribological Evaluation of Dental Composite Resins Containing Pre-polymerized Particle Fillers

The fracture and tribological evaluation of dental composite resin containing pre-polymerized particle fillers were investigated. Composite resins, e.g. metafil, silux plus, heliomolar and palfique estelite were selected as specimens in order to evaluate the effects of pre-polymerized particle filler on the fracture and wear characteristics of composite resins. In the wear tests, a ball-on-flat wear test method was used. The friction coefficient of metafil was quite high.The wear resistance of silux plus and palfique estelite was better than that of metafil and heliomolar under the same experimental condition. The main wear mechanism of composite resins containing pre-polymerized particle fillers was an abrasive wear by brittle fracture of pre-polymerized particles and by debonding of fillers and matrix.     

Martensitic Transformation of TiNi Shape Memory Alloy Fiber Reinforced Ni Matrix Composites

In this paper, a TiNi shape memory alloy fiber Ni matrix composite was fabricated by an electroplating method using TiNi alloy as the cathode and Ni as the anode. The constrained martensitic transformation behaviors of the TiNi alloy were studied by differential scanning calorimeter (DSC), and the results showed that two endothermic peaks appear on the DSC heating curves and the reverse transformation temperatures increase with increasing prestrain levels. Moreover, comparing to the free transformation, the temperature window of the constrained reverse transformation is widely expanded due to the influence of recovery stress.     

Cyclic Flexure Tests of Masonry Walls Reinforced with Glass Fiber Reinforced Polymer Sheets

The research work reported here investigates the out-of-plane flexural behavior of masonry walls reinforced externally with glass fiber reinforced polymer (GFRP) sheets and subjected to cyclic loading. A full-scale test program consisting of eight wall specimens was conducted. Nine tests were performed, in which three parameters were studied. These included the level of compressive axial load, amount of internal steel reinforcement, and amount of externally bonded GFRP sheet reinforcement. Of the three parameters studied, varying the amount of GFRP sheets was the only parameter that significantly affected the behavior of the walls. The GFRP sheet reinforcement governed the linear response of the bending moment versus centerline deflection hysteresis. Increasing or decreasing the amount of GFRP sheet reinforcement either increased or decreased both the wall stiffness and the ultimate strength, respectively. Except for visible cracks, the walls maintained their structural integrity throughout the out-of-plane cyclic loading. The unloading/reloading paths for successive loading cycles were similar, indicating little degradation. Thus, the general behavior of the walls was very predictable. The system, therefore, could be used to advantageously rehabilitate older masonry structures that are inadequately reinforced to withstand seismic events. A simple model of the behavior is also presented to allow for the evaluation of the strength and deformation characteristics of these elements.     

Electrodeposition of Ni-Co/Al2O3 composite coating by pulse reverse method under ultrasonic condition

Ni-Co/Al₂O₃ composite coating was deposited by pulse reverse current (PRC) method under ultrasonic condition. The influence of ultrasonic power on morphology, microstructure, composition, micro-hardness and residual macrostress of composite coating was investigated by means of SEM, TEM, XRF and XRD. The results indicate the composite coating deposited under ultrasonic power becomes uniform, compact and the grains become fine; the composite content of Al₂O₃ is decreased; the micro-hardness of composite coating is improved firstly, then decreased; while the residual macrostress is increased.     

液晶运动图像投影仪

由产生图像的液晶显示元件，投影图像的光学机构和显示屏即构成液晶运动图像投影仪。液晶材料可将图像信息暂时储存，称为储存效应。连续图像投影方法是，在液晶材料中产生图像并暂时储存起来，将投影光源对准液晶材料，然后作为液晶透射或散射光函数的图像投影到投影屏上，可连续地产生投影图像。     

复合材料板簧与传动轴的研制

介绍汽车用聚合物基复合材料板簧和传动轴的原材料、成型工艺及性能研究。研制的复合材料板簧的重量是多片钢板簧的1/5,而疲劳寿命远高于多式钢制板簧。研制的混杂复合材料传动轴经强度和疲劳试验证明是合理可行的。     

Anisotropy of hygrothermal damage in fiber/polymer composites: Effective elasticity measures and estimates

Measured elasticity moduli of a highly (68%) glass-fiber reinforced epoxy matrix for different amounts of fiber/matrix interface weakening and debonding, due to different hygrothermal ageing stages, are compared to estimated ones. Ultrasonic measurements provide seven of the nine elasticity moduli of the orthotropic material samples, including all the moduli significantly affected by damage. Theoretical estimates combine homogenization modeling techniques and Finite Element (FE) calculations, the latter when the effect of observed partial debonding on effective moduli is to be specified. These estimates are performed under different assumptions for the composite structure, with special attention to the existence of a fiber–matrix interphase. Analytical comparisons for the undamaged composite establish that matching US measurements with estimates cannot be obtained, regardless of the chosen model, without the assumption of an interphase layer of modified resin coating the fibers. This coating resin, when in relevant concentration with regard to literature data about fiber coating thickness, typically conserves the epoxy moduli transversally to the fiber orientation, while, in the fiber direction its moduli approach those of the fibers. The comparison of the US measurements on damaged samples to FE calculations assuming progressive one-directional debonding shows that most of the composite stiffness loss can preferentially be due to an initial interphase weakening, while the fiber/matrix debonding seems more likely delayed to long H-ageing times. This is consistent with physical interpretation of damage by water pooling through silane bridges bonding epoxy to glass. The calculations also provide the effective stiffness, at different damage stages, of the “Undamaged Equivalent Inhomogeneity” for this damaged inclusion type.     

高强度高耐水强化木地板安装用胶粘剂的研制

摘 要 利用有机硅具有耐水性、耐候性、耐低温性，采用半连续乳液聚合法制备有机硅、丙烯酸酯、醋酸乙烯酯等不饱和单体共聚乳液。通过实验系统地考察了固含量、单体、乳化剂、聚合方式、加料速度等对乳液聚合的影响。采用该工艺制备出了一种稳定性好、粘接力强、耐水性好的木材用高固含量胶粘剂。     

Inside Front Cover: Trilayered Ceramic–Metal–Polymer Microcantilevers with Dramatically Enhanced Thermal Sensitivity (Adv. Mater. 9/2006)

A novel trilayered (ceramic–metal–polymer) design for highly sensitive, thermally responsive microcantilever arrays is reported on p. 1157 by Tsukruk and co‐workers. In this design, the topmost nanocomposite layer, reinforced with carbon nanotubes and silver nanoparticles, acts as a strong thermal‐stress‐driven actuator to enhance conventional biomaterial performance. These polymer–metal–ceramic microcantilevers with enhanced (fourfold) thermal sensitivity may serve as a basis for the next generation of uncooled thermal microsensor arrays because of outstanding thermal and spatial resolution.