作者希望对西卡的支持表示感谢, 特别是他们为锚杆和增援部队提供的材料。Betazul 是特别承认他们的帮助与定制钻头和视频的准备。

1. 锚杆安装方法
注: 该方法包括孔边钻孔、清洗和平滑, 以及锚杆的浸渍和插入。
<ol><li>钻孔到所需的嵌入长度和指定直径。
	<ol>
<li>使用合适的钻孔工具 (也就是说, 电锤或金刚石芯)。对于混凝土结构, 钻削工具的选择标准与胶粘剂锚点相同, 可以在以前发布的工作10、11中找到。对于电锤, 最大速度为 800 rpm 的钻头。<ol>
<li>提供一个孔间隙 (即, 钻头与接头的直径之间的差额) 不少于4毫米。此外, 建议这种差异是8-10 毫米。这样可以简化孔的平滑, 并允许在钻头内弯曲锚杆。 注: 应注意的是, 商用纤维绳索的公称直径 (当浸渍) 范围从10到12毫米不等。在拍摄的协议中显示的锚是由纤维绳索, 公称直径为12毫米。</li>
		</ol>
</li>
	</ol></li>
	<li>控制埋入长度, 使孔光滑。长度控制是非常重要的, 因为锚固性能是非常长敏感的。被推荐的埋置长度从75到150毫米不等。
	<ol>
<li>要执行长度控制, 请在钻孔中插入刚性条, 并在插入测量带时比较条形的总长度和保持在孔外的长度。</li>
		<li>使用吹出的手泵, 一旦钻井完成, 执行第一除尘。按照泵制造商的指示进行操作。吹出不少于两次, 第一次除尘。</li>
		<li>用旋转的非撞击工具使孔光滑。有关自定义钻头的详细信息, 请参阅图 2 。一个钻头, 如建议可以很容易地适应大多数电动锤。工作时, 用清水将承印物连续冷藏。平滑是完整的, 当没有尖锐的边缘出现, 和上部的钻头接触混凝土表面。</li>
	</ol></li>
	<li>用吹刷循环的组合清洁孔, 因为它是达到最高粘结强度的关键。该清洗过程类似于玻璃钢尖峰和胶粘剂锚。建议至少执行两个清洗周期。有关清洗过程的其他建议, 请参阅现有准则10 , 并始终按照制造商的建议使用其他清洁工具。
	<ol>
<li>刷牙前后总是吹。因此, 每一个周期的机械刷牙涉及两个 blowings 和一个刷牙。</li>
		<li>从内部吹向孔的开口, 以清除钻孔内的松散颗粒。有两种方式吹。如果锚杆安装在干混凝土上, 可以用吹出的手泵进行吹气。如果安装在湿混凝土上, 必须用加压空气 (最大压力为10巴) 进行吹气。 注: 该协议已开发为干式支承, 虽然它可以适应潮湿的条件。值得注意的是, 平滑技术涉及保湿的基质。因此, 由此产生的湿度将取决于环境条件以及在孔的平滑和连接器插入之间的时间流逝。干式支承条件为相对湿度为5% 以下, 通常对应于几天的正常干燥条件。在现有混凝土结构的情况下, 当 24 h 在孔边缘的平滑和锚杆的插入之间经过时, 孔可以被认为是干的。潮湿条件是指近100% 相对湿度, 通常对应于海洋结构。</li>
		<li>用钢丝刷径向刷孔。画笔的直径必须等于或大于钻直径的20毫米。选择画笔的直径尽可能接近孔的大小, 以允许在孔截面周围产生相等的摩擦力。</li>
		<li>清洗后立即安装锚点。如果这是不可能的 (如果没有插入锚在1小时内从清洁), 执行一个额外的清洁周期, 然后插入锚。最后的清洗周期对于水平锚和基板上表面的孔尤其重要。</li>
	</ol></li>
	<li>准备并安装锚杆。这涉及三个不同的过程。
	<ol>
<li>将纤维束或绳子剪成所需长度。锚杆的长度必须等于嵌入长度 (或桩长) 加上锚杆风扇的长度。</li>
		<li>用软刷子将低粘度环氧底漆浸渍锚杆。根据制造商的情况, 始终尊重树脂的花盆寿命。每锚需要大约150克的树脂。浸渍需要部分扇出纤维束, 以最大限度地渗透树脂。<ol>
<li>总是向连接器的末端注入, 以避免弯曲纤维。按住折弯区域, 防止某些纤维从束丛中滑出, 并防止在这个步骤中自由端被扇出。</li>
		</ol>
</li>
		<li>浸渍后立即用电缆栓固定浸渍端。然后, 插入锚钉。协助插入电线, 推动电缆领带, 以确保纤维实际达到所需的嵌入长度。</li>
	</ol></li>
	<li>将钢筋连接到锚点, 以确保连接器的传输机制正确。这项议定书已经制定, 并进一步解释了多用外部粘结 FRP 加固的最终锚固。有关进程的图形说明, 请参见图 3 。
	<ol>
<li>在插入锚点前 (但始终在孔的准备和清理之后) 应用钢筋的第一层, 如图 3所示。或者, 使用比粘附在锚风扇上的第一层短, 以允许在应用第一层钢筋之前插入锚杆。</li>
		<li>当预期出现端板脱粘 (或分层) 时, 提供末端锚固。对于外部钢筋的湿式应用, 总是根据当前的标准或准则 (12,13) 准备基板的表面。 注: 锚杆风机应完全粘结在钢筋上, 因为这种粘结将累积应力传递机制。在 FRP 加固的情况下, 由多层和端锚固, 建议在两层之间的锚机安装。这样就无需用锚杆刺穿层压板, 避免损坏钢筋。迄今为止, 文献中没有确定最小风扇长度。作者建议使用不少于50毫米的风扇长度。</li>
		<li>将环氧树脂应用于外玻璃钢加固和锚杆风机。该树脂可应用于滚筒或刷子。用相同的树脂将外部 FRP 加固物与基体和锚杆风扇粘结在外部钢筋上。根据制造商的情况, 始终考虑树脂的花盆寿命。<ol>
<li>通过使用气泡辊, 防止在钢筋层间出现空隙 (包括锚杆风扇), 使其在浸渍后能释放空气。 注: 为发展协议, 使用了一个树脂以90分钟在20°c。</li>
		</ol>
</li>
	</ol></li>
</ol>2. 带钉锚的设计
注: 设计方法在这里解释为风扇锚, 但相似的规程可以跟随为不同的锚固设备。该方法包括锚杆承载力、粘结强度和锚杆对加筋构件整体强度的评价。
<ol><li>
评估锚杆的容量。这主要取决于锚杆是否受拉力或剪切力的影响。在最常见的桩角小于 180° (剪切应用) 的情况下, 定位角将限制连接器由于应力集中在弯曲区域的效能。按照上面介绍的安装方法控制弯曲强度。
	<ol>
<li>将锚杆的承载力表示为其抗拉强度的一小部分。锚杆的设计能力将是以下的最低限度: 混凝土锥强度, 粘结强度 (计算为在任何后安装的锚在混凝土的10), 弯曲强度和抗拉强度, 具有安全系数。这将导致锚点 () 的设计能力。在维拉纽瓦 Llauradó et 。14, 讨论了钉锚预期的所有失效模式的表达式。</li>
		<li>用一个表达式 (如 Kim 和 Smith15中的一个表示) 估计混凝土锥强度, 以防止混凝土锥断裂。混凝土锥强度只对极浅的锚杆非常重要, 一般情况下, 可忽略嵌段长度大于75毫米的锚杆。</li>
		<li>计算锚固桩的粘结强度。这可以使用从代码和设计指南安装后的锚点的一般表达式执行。根据这些表达式, 粘结强度取决于以下内容: 混凝土的抗拉强度、钻孔直径和嵌入长度15、16。在使用环氧树脂时, 采用从8到 15 MPa 不等的混凝土到树脂界面的平均剪切强度值。</li>
		<li>估计因弯曲而降低的强度。这主要取决于内部弯曲半径, 根据 JSCE8提供的表达式, 它已被广泛地应用于内 FRP 筋。然而, 建议对孤立锚杆进行互补测试, 以评估给定几何构型中连接器的实际强度。这项测试应进行剪切试验, 并与安装的锚, 按照本文提出的程序。</li>
		<li>计算了锚杆的抗拉强度和纤维在连接件截面上的纤维含量和拉伸强度。对于纤维绳索, 制造商一般指定浸渍连接器的抗拉强度, 这可以采用一个足够的还原系数 (从1.25 到 1.5) 的设计。对于手工制作的锚杆纤维束, 应按照 ASTM 标准17进行平票测试。</li>
	</ol>
</li>
	<li>从国际代码或分析模型 (如引用18、19) 中提供的任何表达式计算立式增强剂的粘结强度。另外, 还可以对粘结的立式试样进行单次或双剪试验。必须在进一步计算中使用键强度 (Pdb、d) 的设计值。</li>
	<li>估计整体强度的结果, 结合强度的加固加锚的能力, 为增援与一个锚。根据现有数据, 当锚扇完全覆盖 FRP 的宽度时, 可以接受这个假说, 这与作者比较粘结和无粘结锚固试样的性能的结果相一致20, 21。用以下方程式计算锚杆锚固 FRP 的设计强度: 
	   Pd = pdb, d + p非国大, d (1)</li>
	<li>对于多个锚点, 确定锚杆的效率和贡献作为锚的安排的功能 (层数和行, 锚间距)。请测试所需的安排, 以评估由于多个锚点而降低效率, 并表示锚定接头 (Pd) 的设计强度, 如下所示: 
	  Pd = pdb, d + y ' · n · P非国大, d (2) 根据项目的每个特定安排, 从测试中获取系数y ' , 给定钉锚的数目, 如引用20、23中所述。作为测试的替代方法, 请考虑在相同发布20、23中从这些测试中报告的方法中所建议的效率y ' 。</li>
</ol>

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作者没有什么可透露的。

提出了一种用于 FRP 钉锚杆安装与设计的分步协议。据作者所知, 在安装参数和工艺对锚固能力的影响方面, 没有制定关于钉锚的详细协议。
所提出的平滑钻头对钉锚杆的性能有很有利的作用, 通过降低应力集中度, 证明了其在减小孤立锚杆试验散射方面的有效性。这与安装质量控制的提高有关。此外, 在建议的安装协议之后执行的锚点的低分散允许降低标准偏差, 从而有助于可...

FRP 锚提供了一种有希望的方式来增强外部粘合 FRPs 应用于现有结构的性能, 因为它们可以延迟甚至防止剥离失败1,2。然而, 对于设计者来说, 一个主要的问题是由于弯曲区域的应力集中导致了在剪切中锚杆的过早失效。安装质量和间隙孔的准备对于限制这种过早失效的应力集中至关重要。
本文论述了一种安装方法, 旨在减少应力集中的影响, 为钻孔的制备和锚杆的安装提供适当的质量控制。该方法涉及四部分: 钻孔和清洗孔, 平滑的孔边缘与定制钻头, 以避免不规则的应力分布在弯曲区域内, 安装锚本身, 包括浸渍锚栓和它的插入, 并且锚的黏附力到加强。
从以前发布的研究3,4,5,6,7, 它可以得出结论, 钉锚与弯曲的区域 (也就是说, 在自由端之间的某一角度和嵌入区域), 受应力集中, 容易引发过早失败。由于原始成员的几何形状, 因此不能始终避免这种情况。在许多情况下, 90°的销角是广泛使用的, 虽然它普遍认为, 135°的桩角允许减少应力集中, 并导致更好的性能的钉锚。使用90°定位角的主要原因是, 它们在任何方向上的执行和控制都更简单, 并降低了满足内部增援的可能性。
图 1显示了一个典型的钉锚, 其中最常见的定位角。与90°定位角安装的钉锚, 不过, 可以显示一个相对良好的性能, 如果适当控制的应力集中。极限应力集中通常涉及设计具有较大内弯曲半径的锚杆, 因为内部弯曲半径已被发现在光纤扭结8,9中发挥主要作用。在这个意义上, 作者如奥登等人3建议使用锚直径四倍的弯曲半径。这项建议导致不实际的弯曲半径, 即使对小的锚直径, 因为增加弯曲半径涉及减少实际嵌入长度的给定孔深度。
作者认为, 大弯曲半径的建议与控制实际内弯曲半径的难度有关, 从几何角度看, 当用手进行平滑处理时。因此设计了自定义钻头, 使安装易于质量控制, 并确保在设计中考虑弯曲半径。
本文考虑了两个不同的过程。第一个是与连接器 (锚, 特别是在扇出自由端之前) 的安装程序有关, 而第二个则包括建议的钉锚设计方法和验证需求。

<table border="0" cellpadding="0" cellspacing="0" style="width:957px;" width="957">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Concrete</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">The concrete for support has a dosage made by the authors, and a strength class no lower than C40</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">SikaWrap anchor C</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">This material has been used for the FRP spike anchors. SikaWrap Anchor C is a unidirectional, carbon fiber rope, sheathed in an elastic gauze. The gauze can be cut onsite to create a fan end that anchors CFRP fabrics and plates used in the structural strengthening of masonry and concrete.&#160;</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Sikadur 330</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Impregnating resin, apt for manual saturation methods. The product was used for impregnating the anchor dowel before insertion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sikadur 30</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Thixotropic, two part epoxy resin applied by spatula and therefore suitable for virtually any application, including overhead</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Drill bit</td>
			<td style="width:96px;">Betazul</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Drill bit employed to smooth the holes that was designed by the authors and developed by Betazul SA</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hammer drill</td>
			<td style="width:96px;">Hilti</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Tool for the execution of anchor holes on masonry and concrete, for different drilling ranges</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Wire brush</td>
			<td style="width:96px;">Hilti</td>
			<td style="width:119px;">Hit series</td>
			<td style="width:527px;">For the proper brushing of drilled holes of varying diameters and embedment depths</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Blow-out pump</td>
			<td style="width:96px;">Hilti</td>
			<td style="width:119px;">Hit series</td>
			<td>Manual blow-out pump&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SikaWrap-230 C</td>
			<td style="width:96px;">SIKA</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Unidirectional woven carbon fiber fabric for dry application process</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Aluminium Bubble Roller</td>
			<td style="width:96px;">Fibre glast</td>
			<td style="width:119px;"></td>
			<td style="width:527px;">For laminations where increased pressure is necessary to release air bubbles. They are straight across the width of the head and provide excellent air relief for nearly all applications.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Brush</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td>For impregnation of FRP bundle and sheet</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">600 kN testing machine</td>
			<td style="width:96px;">Proeti</td>
			<td style="width:119px;">DI-CP/S</td>
			<td style="width:527px;">This is used for the shear test of anchors, in order to evaluate the efficacy of the proposed insertion method</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Cable ties</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">Cable ties are needed to fasten the end of the anchor dowel in order to prevent fanning out of the fibers during insertion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Measuring tape</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">The measuring tape is necessary to control the embedment length as well as the diameter of the drill bit and hole clearance</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Steel wire</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td>Required to assist insertion</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Rigid (steel) bar</td>
			<td style="width:96px;"></td>
			<td style="width:119px;"></td>
			<td style="width:527px;">A rigid bar of any material (in this case, it was made with a steel bar) is needed to control the embedment length</td>
		</tr>
	</tbody>
</table>

installation method to enhance quality control for fiber reinforced polymer spike anchors

纤维增强聚合物 (FRP) 锚杆是提高外部粘结 FRPs 在现有结构中的性能的一种有希望的方法, 因为它们可以延缓甚至防止脱粘失效。然而, 设计者所面临的一个主要问题是由于应力集中导致锚杆过早失效。安装质量差和间隙孔的准备会导致应力集中, 从而引发过早的故障。本文论述了一种安装方法, 旨在减少应力集中的影响, 为钻孔的制备提供适当的质量控制。该方法涉及三部分: 钻孔和清洗的孔, 平滑的孔边缘与定制钻头, 并安装锚本身, 包括浸渍的锚钉和其插入。锚杆风扇 (峰值的自由长度) 然后粘结到外部 FRP 加固。对于末端锚固, 并且在多层层增援的情况下, 建议将锚杆风扇插入两层之间以协助应力传递机制。
根据广泛的数据库, 所提出的程序辅以一种用于钉锚的设计方法。提出了设计中应遵循的几个步骤, 即: 选择锚径和后续抗拉强度的连接器 (即在扇出自由端前的锚杆), 评价降低抗拉强度的原因弯曲, 提供足够的嵌入, 以防止滑移失败, 并考虑到锚的数量和间距的一个给定的加固。在这个意义上, 应该指出, 需要进一步的研究, 以获得一个普遍的表达, 为钉锚的贡献, 整体粘结强度的 FRP 加固。

对孤立连接器进行了测试, 以评估平滑方法的有效性。此外, 还比较了两种浸渍和插入连接器的方法。湿法涉及在插入前立即浸渍锚栓, 如提交的协议。硬化 (或预浸渍) 方法包括预先浸渍的锚的嵌入区域, 至少24小时前插入。
在所提出的方法下进行的试验中, 与相同埋入长度和孔径的非光滑试样相比, 平均增加了27兆帕。值得注意...

Watch this Scientific Journal Video about Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors at JoVE.com

Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

本文介绍了一种控制钢钉锚杆安装质量的方法, 旨在延缓外部粘结纤维增强聚合物的脱层。该协议包括钻孔的准备和插入过程。讨论了影响锚杆效率的最重要参数。

提高纤维增强聚合物穗锚质量控制的安装方法

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they ...

installation-method-to-enhance-quality-control-for-fiber-reinforced

Research

Education

JoVE Core

JoVE Journal

Civil Engineering

Engineering

Unit 1

Fresh Concrete

SCIENTISTS IN ACTION

7.0K 次观看.  Technical University of Madrid. 本文介绍了一种控制钢钉锚杆安装质量的方法, 旨在延缓外部粘结纤维增强聚合物的脱层。该协议包括钻孔的准备和插入过程。讨论了影响锚杆效率的最重要参数。

视频: Installation Method to Enhance Quality Control for Fiber Reinforced Polymer Spike Anchors

Fabricating Metamaterials Using the Fiber Drawing Method

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 &deg;C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.

Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 &mu;m diameter indium wires separated by ~100 &mu;m, which exhibit a terahertz plasmonic response.

制造超材料使用光纤拉丝法

Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe ...

科研

工程学

Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents and hence higher efficiencies. Photon up-conversion by way of triplet-triplet annihilation (TTA-UC) is an attractive technique for using these otherwise wasted low energy photons to produce photocurrent, while not interfering with the photoanodic performance in a deleterious manner. Further to this, TTA-UC has a number of features, distinct from other reported photon up-conversion technologies, which renders it particularly suitable for coupling with DSC technology. In this work, a proven high performance TTA-UC system, comprising a palladium porphyrin sensitizer and rubrene emitter, is combined with a high performance DSC (utilizing the organic dye D149) in an integrated device. The device shows an enhanced response to sub-bandgap light over the absorption range of the TTA-UC sub-unit resulting in the highest figure of merit for up-conversion assisted DSC performance to date.

An integrated device, incorporating a dye-sensitized solar cell and triplet-triplet annihilation up-conversion unit was produced, affording enhanced light harvesting, from a wider section of the solar spectrum. Under modest irradiation levels a significantly enhanced response to low energy photons was demonstrated, yielding a record figure of merit for dye-sensitized solar cells.

集成的三重态 - 三重态湮灭上转换系统，提高染料敏化太阳能电池的响应子带隙光

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents ...

Preparation and Friction Force Microscopy Measurements of Immiscible, Opposing Polymer Brushes

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low friction at the interface. Nevertheless, these systems can be sensitive to wear due to interdigitation of the opposing brushes. In a recent publication, we have shown via molecular dynamics simulations and atomic force microscopy experiments, that using an immiscible polymer brush system terminating the substrate and the slider surfaces, respectively, can eliminate such interdigitation. As a consequence, wear in the contacts is reduced. Moreover, the friction force is two orders of magnitude lower compared to traditional miscible polymer brush systems. This newly proposed system therefore holds great potential for application in industry. Here, the methodology to construct an immiscible polymer brush system of two different brushes each solvated by their own preferred solvent is presented. The procedure how to graft poly(N-isopropylacrylamide) (PNIPAM) from a flat surface and poly(methyl methacrylate) (PMMA) from an atomic force microscopy (AFM) colloidal probe is described. PNIPAM is solvated in water and PMMA in acetophenone. Via friction force AFM measurements, it is shown that the friction for this system is indeed reduced by two orders of magnitude compared to the miscible system of PMMA on PMMA solvated in acetophenone.

The methodology to perform friction force microscopy experiments for contacting brushes is presented: Two polymer brushes that are grafted from (a) substrates and (b) colloidal probes are slid to show that, by using two contacting immiscible brush systems, friction in sliding contacts is reduced compared to miscible brush systems.

互溶的测量准备和摩擦力显微镜，反对聚合物刷

Solvated polymer brushes are well known to lubricate high-pressure contacts, because they can sustain a positive normal load while maintaining low ...

A Testing Platform for Durability Studies of Polymers and Fiber-reinforced Polymer Composites under Concurrent Hygrothermo-mechanical Stimuli

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs and condition-based maintenance. These materials are adopted in a wide range of engineering applications, from aircraft and ship structures, to bridges, wind turbine blades, biomaterials and biomedical implants. Polymers are viscoelastic materials, and their response may be highly nonlinear and thus make it challenging to predict and monitor their in-service performance. The laboratory-scale testing platform presented herein assists the investigation of the influence of concurrent mechanical loadings and environmental conditions on these materials. The platform was designed to be low-cost and user-friendly. Its chemically resistant materials make the platform adaptable to studies of chemical degradation due to in-service exposure to fluids. An example of experiment was conducted at RT on closed-cell polyurethane foam samples loaded with a weight corresponding to ~50% of their ultimate static and dry load. Results show that the testing apparatus is appropriate for these studies. Results also highlight the larger vulnerability of the polymer under concurrent loading, based on the higher mid-point displacements and lower residual failure loads. Recommendations are made for additional improvements to the testing apparatus.

The durability of polymers and fiber-reinforced polymer composites in service is a critical aspect for their designs and condition-based maintenance. We present a novel low-cost laboratory testing platform for the investigation of the influence of concurrent mechanical and environmental loadings, and may help design more efficient yet safer composite structures.

一个测试平台为聚合物的耐久性研究，并在同期Hygrothermo机械刺激纤维增强聚合物复合材料

The durability of polymers and fiber-reinforced polymer composites under service condition is a critical aspect to be addressed for their robust designs ...

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

Morphology Control for Fully Printable Organic&amp;#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

基于一个钛醇盐和半导体聚合物为全可印刷有机 - 无机批量异质结太阳能电池形貌控制

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

用于光学谐振器和激光应用的聚合物微球的制造

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Experimental Protocol to Determine the Chloride Threshold Value for Corrosion in Samples Taken from Reinforced Concrete Structures

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these structures. Corrosion of the embedded reinforcing steel is the most frequent cause for degradation. While it is well known that the ability of a structure to withstand corrosion depends strongly on factors such as the materials used or the age, it is common practice to rely on threshold values stipulated in standards or textbooks. These threshold values for corrosion initiation (Ccrit) are independent of the actual properties of a certain structure, which clearly limits the accuracy of condition assessments and service life predictions. The practice of using tabulated values can be traced to the lack of reliable methods to determine Ccrit on-site and in the laboratory.
Here, an experimental protocol to determine Ccrit for individual engineering structures or structural members is presented. A number of reinforced concrete samples are taken from structures and laboratory corrosion testing is performed. The main advantage of this method is that it ensures real conditions concerning parameters that are well known to greatly influence Ccrit, such as the steel-concrete interface, which cannot be representatively mimicked in laboratory-produced samples. At the same time, the accelerated corrosion test in the laboratory permits the reliable determination of Ccrit prior to corrosion initiation on the tested structure; this is a major advantage over all common condition assessment methods that only permit estimating the conditions for corrosion after initiation, i.e., when the structure is already damaged.
The protocol yields the statistical distribution of Ccrit for the tested structure. This serves as a basis for probabilistic prediction models for the remaining time to corrosion, which is needed for maintenance planning. This method can potentially be used in material testing of civil infrastructures, similar to established methods used for mechanical testing.

We propose a method to measure a parameter that is highly relevant for corrosion assessments or predictions of reinforced concrete structures, with the main advantage of permitting testing of samples from engineering structures. This ensures real conditions at the steel-concrete interface, which are crucial to avoid artifacts of laboratory-made samples.

测定钢筋混凝土结构试样腐蚀的氯化物阈值的试验规程

The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these ...

Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the Earth&#39;s magnetic field, for manufacturing a cementitious composite reinforced with aligned steel fibers. Aligned steel fiber reinforced cementitious composites (ASFRC) were prepared by applying a uniform electromagnetic field to fresh mortar containing short steel fibers, whereby the short steel fibers were driven to rotate in alignment with the magnetic field. The degree of alignment of steel fibers in hardened ASFRC was assessed both by counting steel fibers in fractured cross-sections and by X-ray computed tomography analysis. The results from the two methods show that the steel fibers in ASFRC were highly aligned while the steel fibers in non-magnetically treated composites were randomly distributed. The aligned steel fibers had a much higher reinforcing efficiency, and the composites, therefore, exhibited significantly enhanced flexural strength and toughness. The ASFRC is thus superior to SFRC in that it can withstand greater tensile stress and more effectively resist cracking.

This protocol describes an approach for manufacturing aligned steel fiber reinforced cementitious composite by applying a uniform electromagnetic field. Aligned steel fiber reinforced cementitious composite exhibits superior mechanical properties to ordinary fiber reinforced concrete.

定向钢纤维增强水泥基复合材料的制备及其弯曲性能研究

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the ...

用于电容式压力传感的基于微流体通道的软电极

Microfluidic Channel-Based Soft Electrodes and Their Application in Capacitive Pressure Sensing

Flexible and stretchable electrodes are essential components in soft artificial sensory systems. Despite recent advances in flexible electronics, most electrodes are either restricted by the patterning resolution or the capability of inkjet printing with high-viscosity super-elastic materials. In this paper, we present a simple strategy to fabricate microchannel-based stretchable composite electrodes, which can be achieved by scraping elastic conductive polymer composites (ECPCs) into lithographically embossed microfluidic channels. The ECPCs were prepared by a volatile solvent evaporation method, which achieves a uniform dispersion of carbon nanotubes (CNTs) in a polydimethylsiloxane (PDMS) matrix. Compared to conventional fabrication methods, the proposed technique can facilitate the rapid fabrication of well-defined stretchable electrodes with high-viscosity slurry. Since the electrodes in this work were made up of all-elastomeric materials, strong interlinks can be formed between the ECPCs-based electrodes and the PDMS-based substrate at the interfaces of the microchannel walls, which allows the electrodes to exhibit mechanical robustness under high tensile strains. In addition, the mechanical-electric response of the electrodes was also systematically studied. Finally, a soft pressure sensor was developed by combining a dielectric silicone foam and an interdigitated electrodes (IDE) layer, and this demonstrated great potential for pressure sensors in soft robotic tactile sensing applications.

作者聚焦：基于微流体通道的软电极及其在电容式压力传感中的应用  

Flexible electrodes have a wide range of applications in soft robotics and wearable electronics. The present protocol demonstrates a new strategy to fabricate highly stretchable electrodes with high resolution via lithographically defined microfluidic channels, which paves the way for future high-performance soft pressure sensors.

基于微流控通道的软电极及其在电容式压力传感中的应用

Flexible and stretchable electrodes are essential components in soft artificial sensory systems. Despite recent advances in flexible electronics, most ...