Bond Strength of Composite CFRP Reinforcing Bars in Timber

The use of near-surface mounted (NSM) fibre-reinforced polymer (FRP) bars is an interesting method for increasing the shear and flexural strength of existing timber members. This article examines the behaviour of carbon FRP (CFRP) bars in timber under direct pull-out conditions. The objective of this experimental program is to investigate the bond strength between composite bars and timber: bars were epoxied into small notches made into chestnut and fir wood members using a commercially-available epoxy system. Bonded lengths varied from 150 to 300 mm. Failure modes, stress and strain distributions and the bond strength of CFRP bars have been evaluated and discussed. The pull-out capacity in NSM CFRP bars at the onset of debonding increased with bonded length up to a length of 250 mm. While CFRP bar’s pull-out was achieved only for specimens with bonded lengths of 150 and 200 mm, bar tensile failure was mainly recorded for bonded lengths of 250 and 300 mm.     

Optical Fiber Embedded in Epoxy Glass Unidirectional Fiber Composite System

We aimed to embed silica optical fibers in composites (epoxy vinyl ester matrix reinforced with E-glass unidirectional fibers in mass fraction of 60%) in order to further monitor the robustness of civil engineering structures (such as bridges). A simple system was implemented using two different silica optical fibers (F1—double coating of 172 μm diameter and F2—single coating of 101.8 μm diameter respectively). The optical fibers were dynamically tensile tested and Weibull plots were traced. Interfacial adhesion stress was determined using pull-out test and stress values were correlated to fracture mechanisms based on SEM observations. In the case of the optical fiber (OF) (F1)/resin system and OF (F1)/composite system, poor adhesion was reported that may be correlated to interface fracture at silica core level. Relevant applicable results were determined for OF (F2)/composite system.     

Feasibility of Using Multilayer Platelets as Toughening Agents

It is known that the toughness of brittle ceramics can be improved significantly with the addition of hard platelets. In the present study, platelet-shape multilayer ceramic laminates are utilized as a toughening agent for alumina ceramics. They are prepared by laminating the BaTiO₃-based ceramic tapes. Although the elastic modulus of the BaTiO₃-based platelets is lower than that of the alumina matrix, and the platelets are also reactive to alumina at elevated temperatures, the weak platelets are found to exhibit the ability to deflect major matrix cracks by forming a large number of microcrack branches within the platelets, thus achieving the desired toughening effect.     

Consistency in the amount of linear polymerization shrinkage in syringe-type composites

OBJECTIVES: The purpose of this study was to investigate whether the composite resin in a syringe showed a consistent shrinkage through its content. Additionally, the amount of linear shrinkage was compared between materials. METHODS: Five brands of syringe-type and one brand of carpule-type composite resins were used in this study. To each brand, two to three syringes were assigned. In the carpule-type composite, 15 carpules were used. The linear polymerization shrinkage was measured using a custom-made linometer. In this linometer, the amount of displacement of an aluminum disk, which was caused by the linear shrinkage of composite resin, was recorded by a computer every second for 90 s. RESULTS: The syringe-type composites showed similar consistencies in the amount of linear shrinkage except one. The linear shrinkage of the carpule-type Tetric Ceram showed more consistency compared with syringe-type composites. The amount of linear polymerization shrinkage varied between materials. SIGNIFICANCE: This investigation demonstrates that the use of carpule-type composites is recommended instead of syringe-types, because of the consistency in its linear shrinkage. The custom-made linometer provides an effective way to study polymerization shrinkage.     

Ceramic (Feldspathic & IPS Empress II) vs. laboratory composite (Gradia) veneers; a comparison between their shear bond strength to enamel; an in vitro study

Summary Patient demand for aesthetic dentistry is steadily growing. Laminates and free metal restorations have evolved in an attempt to overcome the invasiveness nature of full veneer restorations. Although many different materials have been used for making these restorations, there is no single material that fits best for all purposes. Two groups of ceramic material (Feldspathic and IPS Empress II) and one group of laboratory composite (Gradia) discs (10 discs in each group; 4 mm in diameter and 2 mm in thickness) were prepared according to the manufacturer’s instruction. The surface of ceramic discs were etched and silanized. In Gradia group, liquid primer was applied on composite surfaces. Thirty freshly extracted sound human molars and premolars were randomly divided into three groups. The enamel surface of each tooth was slightly flattened (0·3 mm) on the buccal or lingual side and then primed and cemented to the prepared discs with the aid of a dental surveyor. The finishing specimens were thermocycled between 5 °C and 55 °C for 2500 cycles and then prepared for shear bond strength testing. The resulting data were analyzed by one‐way anova and Tukey HSD test. The fractured surfaces of each specimen were inspected by means of stereomicroscope and SEM. There is significant difference between the bond strength of materials tested. The mean bond strengths obtained with Feldspathic ceramic, IPS Empress II and Gradia were 33·10 ± 4·31 MPa, 26·04 ± 7·61 MPa and 14·42 ± 5·82 MPa, respectively. The fracture pattern was mainly mixed for ceramic groups. More scientific evidence needed for standardization of bonding protocols.     

Indicators of Adolescent Alcohol Use: A Composite Risk Factor Approach

A self-reported alcohol inventory measured prevalence and frequency of lifetime, recent, and current alcohol use by an opportunity sample of 3226 young people aged 11–18 in Welsh secondary schools in 2005 comparing findings to extant U.K. and European levels. A risk factor-based questionnaire enabled comprehensive, sensitive sample profiling by gender and age, combining factor analysis with logistic regression to identify composite risk factors influential upon alcohol use by young people in Wales and salient to policy makers and practitioners, notably the endogenous factors: anti-social behaviour/attitudes, inadequate relationships/activities in school, negative experiences in school, lack of commitment to school, and impulsivity. Overlap with composite risk factors for youth offending was identified, but not with drug use, suggesting that the commonly cited “gateway” relationship between elements of “substance use” requires further examination. The study's limitations and implications are discussed.     

Two-Way Bending Properties of Shape Memory Composite with SMA and SMP

A shape memory composite (SMC) was fabricated with a shape memory alloy (SMA) and a shape memory polymer (SMP), and its two-way bending deformation and recovery force were investigated. The results obtained can be summarized as follows: (1) two kinds of SMA tapes which show the shape memory effect (SME) and superelasticity (SE) were heat-treated to memorize the round shape. The shape-memorized round SMA tapes were arranged facing in the opposite directions and were sandwiched between the SMP sheets. The SMC belt can be fabricated by using the appropriate factors: the number of SMP sheets, the pressing force, the heating temperature and the hold time. (2) The two-way bending deformation with an angle of 56 degrees in the fabricated SMC belt is observed based on the SME and SE of the SMA tapes during heating and cooling. (3) If the SMC belt is heated and cooled by keeping the bent form, the recovery force increases during heating and degreases during cooling based on the two-way properties of the SMC. (4) The development and application of high-functional SMCs are expected by the combination of the SMA and the SMP with various kinds of phase transformation temperatures, volume fractions, configurations and heating-cooling rates.     

联合筋膜鞘+提上睑肌复合瓣悬吊矫治先天性重度上睑下垂

目的:探讨联合筋膜鞘+提上睑肌复合瓣悬吊治疗先天性重度上睑下垂的临床效果。方法:选取2017年9月至2019年3月于河北省眼科医院住院的先天性重度上睑下垂患者205例248眼,随机分为三组,分别应用联合筋膜鞘+提上睑肌复合瓣悬吊术(CFS+L复合瓣悬吊组)、联合筋膜鞘悬吊术(单纯CFS悬吊组)、额肌瓣悬吊术(额肌瓣悬吊组)加以矫正;随访6个月,比较三组患者正矫率、上睑回退率、上睑活动范围及眼睑闭合不全情况、并发症发生率和患者满意度。结果:CFS+L复合瓣悬吊组较其他两组有更高的正矫率,CFS+L复合瓣悬吊组及单纯CFS悬吊组术后较额肌瓣悬吊组有更好的上睑活动度、眼睑闭合不全状态较轻、并发症发生率较低,患者满意度较高;CFS+L复合瓣悬吊组较单纯CFS悬吊组术后上睑回退率低、具有更好的稳定性;差异均有统计学意义(P<0.05)。结论:联合筋膜鞘+提上睑肌复合瓣悬吊术矫正先天性重度上睑下垂具有治愈率高、效果更加稳定的特点,是一种符合眼睑活动生理学特点的动态术式。     

口腔陶瓷及类陶瓷修复材料在嵌体和高嵌体修复中的应用

近年来,口腔陶瓷及类陶瓷材料以其优异的物理、机械性能和美学性能越来越多地应用于牙体缺损的嵌体和高嵌体修复中,修复成功与否与修复材料的性能密切相关。目前,应用于嵌体和高嵌体修复的主要修复材料有长石质陶瓷、白榴石增强玻璃陶瓷、二硅酸锂玻璃陶瓷、氧化锆增强硅酸锂玻璃陶瓷和树脂基陶瓷复合材料。本文对此类材料的性能及临床应用进行综述,为临床选择修复材料提供参考。