作者感谢国家重点研发计划（编号：2022YFB3706503）和深圳市自然科学基金稳定支持计划计划（编号：20220815133826001）的资助。

1、材料准备
<ol><li>用剪刀剪下八块 300 毫米 x 300 毫米的玻璃纤维编织布。先用胶带粘住切口，以防止纤维丝脱落。 注意： 在切割织物时，请戴上口罩和手套，以防止手指刺伤和吸入细丝。不仅有玻璃纤维编织物，还有单向织物和其他类型的纤维，如碳纤维和芳纶纤维。</li>
	<li>按10：3的质量比称出环氧树脂260g和硬化剂78g。 注：纤维织物与树脂体系的比例建议为每平方米单层纤维织物360克环氧树脂体系。</li>
</ol>2.制造过程
注： 图 1 显示了用于手糊工艺的复合层压板的制造示意图，如第 2 节所示。
<ol><li>WLVB型<ol>
<li>将织物放入60°C的烘箱中8小时。</li>
		<li>在亚克力板上粘贴隔离膜，防止树脂粘结。</li>
		<li>将模具放在铺设区域。</li>
		<li>将树脂和硬化剂缓慢混合5min，然后放入真空室中，抽出里面的气泡。</li>
		<li>将无孔离型膜铺在模具上，并用胶带固定。</li>
		<li>在无孔离型膜上铺设一层剥离层。</li>
		<li>倒入环氧树脂，用刮刀将树脂均匀地分布在整个薄膜上。</li>
		<li>铺上第一层纤维织物，用裸辊卷起，确保树脂充分渗入织物，气泡被挤出，然后倒入树脂，用刮刀将树脂刮均匀。</li>
		<li>重复步骤 2.1.7 和 2.1.8，直到用完所有结构。</li>
		<li>在织物上铺上一层剥离层，然后手动挤出气泡。</li>
		<li>依次铺设一层穿孔离型膜和一块透气织物。</li>
		<li>将吸道和透气垫放在一侧。</li>
		<li>在模具外贴上一圈带有亚克力板的耐热胶带，然后用胶带将真空袋贴在周围，形成一个封闭的空间。</li>
		<li>打开真空泵，在室温下按压1巴压力10小时。然后，关闭真空泵并保持静止14小时。</li>
		<li>将层压板放入80°C的烘箱中16小时以完全固化。</li>
		<li>使用公式 （1-3）38,39 测量纤维体积分数。 <img alt="Equation 1" src="/files/ftp_upload/65376/65376eq01.jpg" style="margin: auto;">（一） <img alt="Equation 2" src="/files/ftp_upload/65376/65376eq02.jpg" style="margin: auto;">（二） <img alt="Equation 3" src="/files/ftp_upload/65376/65376eq03.jpg" style="margin: auto;">（三） n是层压板的层数，ρ纤维是制造商提供的纤维织物的面密度，A纤维是层压板的面积，m纤维是 纤维织物的质量，m总计是层压板的质量，ρ环氧树脂是环氧树脂的密度，v环氧树脂和v 总和v分别是环氧树脂和层压板的体积，是纤维体积分数。</li>
	</ol>
</li>
	<li>西城<ol>
<li>将织物放入60°C的烘箱中8小时。</li>
		<li>将树脂和固化剂缓慢混合5分钟，然后将其放入真空室中以抽出内部的气泡。</li>
		<li>将无孔离型膜铺在模具上，并用胶带固定。</li>
		<li>在无孔离型膜上铺设一层剥离层。</li>
		<li>倒入环氧树脂，用刮刀将树脂均匀地分布在整个薄膜上。</li>
		<li>铺上第一层纤维织物，用裸辊卷起，确保树脂充分渗入织物，气泡被挤出，然后倒入树脂，用刮刀将树脂刮均匀。</li>
		<li>重复步骤 2.2.5 和 2.2.6，直到所有结构都用完。</li>
		<li>在织物上铺上一层剥离层，然后手动挤出气泡。</li>
		<li>依次铺设一层穿孔离型膜、一层透气织物和一层无孔离型膜。</li>
		<li>将一块与纤维织物大小相同的铝板放在上面。</li>
		<li>在室温下保持静止14小时。</li>
		<li>将层压板放入80°C的烘箱中16小时以完全固化。</li>
	</ol>
</li>
</ol>3. 冲击特性的表征
注：复合材料层压板的冲击试验方法有很多种。在低速冲击条件下，常用的方法是落锤冲击试验，而在高速或超高速冲击条件下，常用的方法是子弹冲击法。在这项研究中，应用了落锤冲击试验。设备如图 2所示。
<ol><li>根据 ASTM D7136 标准，使用高精度切割机从 GFRP 切割一组 150 mm x 100 mm 样品进行冲击测试。</li>
	<li>测量每个样品的重量和大小。</li>
	<li>在每次测试中撞击器可以接触的样品中心使用定位钉固定样品的位置。</li>
	<li>用四个橡胶尖端将样品固定在冲击支撑夹具上。</li>
	<li>使用 10 J 能量水平的落锤冲击塔进行冲击测试。打开落锤试验机，点击连接，将控制器与下拉菜单 连接 ，然后点击 首页|好测试前。将冲击能量设置为 10 J，将附加质量设置为 2 kg。输入测量厚度，WLVB 样品为 2.1 mm，WL 样品为 2.5 mm，以确定撞击器的高度，然后单击“开始” 开始 实验。</li>
	<li>记录冲击响应数据，包括力、挠度和能量历史。</li>
	<li>取出样品。记录撞击后样品的形态。</li>
	<li>重复冲击试验五次，以确保结果的可重复性。</li>
	<li>计算和比较样本数据。</li>
</ol>4. 拉伸性能的表征
<ol><li>根据 ASTM D3039 标准，使用带有金刚石切割机的高精度切割机从层压板上切割一组 250 mm x 25 mm 的样品进行拉伸测试。</li>
	<li>用游标卡尺测量每个样品的大小。</li>
	<li>使用环氧树脂粘合剂在样品两端粘接四个 50 mm x 25 mm x 2 mm 的铝片，以避免应力集中。</li>
	<li>在样品正面喷上一层薄薄的白色油漆，然后喷上黑色斑点。</li>
	<li>将试样放在拉力试验机夹具的中心，设置图像采集系统， 如图3所示。</li>
	<li>为确保应变数据的准确性，请改变样品的位置，使其位于相机拍摄区域的中间和垂直位置。此外，调整相机焦距和曝光率，以确保清晰记录样品上的斑点。</li>
	<li>进行拉伸试验。单击 CONFIGURE TEST。将测试速度设置为 0.5 mm/min。单击“标本数据”。输入样品的测量宽度和厚度。单击“开始”，然后单击“接受当前位置”。记录加载时间数据。</li>
	<li>取出样品。记录拉伸试验后试样的形貌。</li>
	<li>重复拉伸试验五次，以确保结果的重复性。</li>
	<li>在拉伸试验过程中，使用数字图像相关（DIC）软件测量样品的标称应变。</li>
	<li>单击 “长度缩放 图像”以校准像素的长度，单击“参考图像”，然后选择第一个图像作为 参考图像。单击“变形图像”，然后选择剩余图像作为 变形图像 。单击 “绘图工具”|”选择矩形以选择 测量区域。单击引伸计并将引 伸计 的长度设置为 100 mm，然后单击 “处理”|”启动关联。</li>
	<li>将荷载除以横截面积得到公称应力。</li>
	<li>将DIC测量的标称应变和拉伸试验机的标称应力结合起来。</li>
	<li>选择应变-应力曲线线性段的斜率作为弹性模量。选择拉力-时间曲线的峰值作为强度。</li>
	<li>比较样品的弹性模量和强度。</li>
</ol>

纤维复合材料层压板的制造和机械性能评估

作者没有任何利益冲突。

本文重点介绍了两种不同的低成本手糊法制造工艺。因此，本文选择了两种制造工艺进行仔细描述，它们更简单、更容易掌握、投资成本较低，并且适合在实验室和小规模工厂进行材料改性生产。在层压板的固化过程中，高固结压力在制造高质量的层压板中起着重要作用。在没有足够外部压力的情况下采用传统的WL工艺会导致树脂体积分数过高。树脂体积大是降低层压板机械性能的主要因素之一?...

纤维增强聚合物复合材料（FRP）是一种由纤维增强材料和聚合物基体混合而成的高强度材料1,2,3。由于其密度低、比刚度和强度高、疲劳性能好、耐腐蚀性好等特点，被广泛应用于航空航天4、5、6、建筑7、8、汽车9、船舶101等行业。常见的合成纤维包括碳纤维、玻璃纤维和芳纶纤维12。本文选择玻璃纤维进行研究。与传统钢相比，玻璃纤维增强复合层压板（GFRPs）更轻，密度不到三分之一，但可以达到比钢更高的比强度。
FRP的制备工艺包括真空辅助树脂传递模塑（VARTM）13、纤维缠绕（FW）14和预浸料成型，以及许多其他先进的制造工艺15,16,17,18。与其他制备工艺相比，湿手糊/真空袋（WLVB）工艺具有设备要求简单、工艺技术不复杂等优点，产品不受尺寸和形状的限制。该工艺具有高度的自由度，可以与金属、木材、塑料或泡沫集成。
WLVB工艺的原理是通过真空袋施加更大的成型压力，以增强制备的层压板的机械性能;该工艺的生产工艺易于掌握，是一种经济、简单的复合材料制备工艺。这个过程完全是手工的，受准备人员技能的影响很大。因此，产品容易出现空隙和厚度不均匀等缺陷，导致层压板的质量和机械性能不稳定。因此，有必要详细描述WLVB工艺，精细控制步骤，量化材料比例，以获得高稳定性的层压板机械性能。
大多数研究人员研究了复合材料的准静态19,20,21,22,23和动态行为24,25,26,27,28，以及性能改性29,30。纤维与基体的体积分数比对玻璃钢层压板的力学性能起着至关重要的作用。在适当的范围内，较高的纤维体积分数可以提高玻璃钢层压板的强度和刚度。Andrew等[31]研究了纤维体积分数对熔融沉积成型（FDM）增材制造工艺制备的试样力学性能的影响。结果表明，当纤维体积分数为22.5%时，拉伸强度效率达到最大，当纤维体积分数达到33%时，强度略有提高。Khalid等[32]研究了具有不同纤维体积分数的连续碳纤维（CF）增强3D打印复合材料的力学性能，结果表明，拉伸强度和刚度均随着纤维含量的增加而提高。Uzay等[33]研究了手糊、压缩成型和真空袋3种制备方法对碳纤维增强聚合物（CFRP）力学性能的影响。测量层压板的纤维体积分数和空隙，进行拉伸和弯曲试验。实验表明，纤维体积分数越高，力学性能越好。
空隙是玻璃钢层压板中最常见的缺陷之一。空隙会降低复合材料的机械性能，例如强度、刚度和抗疲劳性34.空隙周围产生的应力集中促进了微裂纹的扩展，降低了钢筋与基体之间的界面强度。内部空隙还会加速FRP层压板的吸湿性，导致界面脱粘和性能下降。因此，内部空隙的存在影响了复合材料的可靠性，限制了复合材料的广泛应用。Zhu等[35 ]研究了空隙率对CFRP复合材料层合板静态层间剪切强度性能的影响，发现空隙率在0.4%-4.6%之间增加1%会导致层间剪切强度下降2.4%。Scott等[36 ]利用计算机断层扫描（CT）研究了静水载荷作用下CFRP复合材料层合板空隙对损伤机理的影响，发现空隙数量是随机分布裂纹数量的2.6-5倍。
使用高压釜可以制造高质量和可靠的FRP层压板。Abraham 等人 37 通过将 WLVB 组件放置在压力为 1.2 MPa 的高压釜中进行固化来制造低孔隙率、高纤维含量的层压板。然而，高压灭菌器是一种大型且昂贵的设备，导致相当大的制造成本。真空辅助树脂转移工艺（VARTM）虽然已经使用了很长时间，但在时间成本、制备工艺更复杂、导流管、导流介质等一次性耗材较多等方面存在局限性。与WL工艺相比，WLVB工艺通过低成本的真空袋补偿成型压力不足，从系统中吸收多余的树脂，以增加纤维体积分数并降低内部孔隙含量，从而大大提高层压板的机械性能。
本文探讨了WL工艺与WLVB工艺的区别，并详细介绍了WLVB工艺的细致工艺。采用公式法计算层合板的纤维体积含量，结果表明，WL层合板的纤维体积含量为42.04%，而WLVB层合板的纤维体积含量为57.82%，提高了15.78%。层压板的机械性能通过拉伸和冲击试验进行表征。实验结果表明，采用WLVB工艺，层合板的强度和模量分别提高了17.4%和16.35%，比吸收能提高了19.48%。

<table><tbody><tr><td>breather fabric</td><td>Easy composites</td><td>BR180</td><td></td></tr><tr><td>drop-weight impact testing machine</td><td>Instron</td><td>9340</td><td></td></tr><tr><td>Epoxy matrix</td><td>Axson Technologies</td><td>5015/5015</td><td></td></tr><tr><td>glass fiber</td><td>Weihai Guangwei Composites</td><td>W-9311</td><td></td></tr><tr><td>non-porous release film</td><td>Easy composites</td><td>R240</td><td></td></tr><tr><td>Peel ply&amp;nbsp;</td><td>Sino Composite</td><td>CVP200</td><td></td></tr><tr><td>perforated released film</td><td>Easy composites</td><td>R120-P3</td><td></td></tr><tr><td>test machine</td><td>ZwickRoell</td><td>250kN</td><td></td></tr><tr><td>vacuum film</td><td>Easy composites</td><td>GVB200</td><td></td></tr></tbody></table>

measuring the mechanical properties of glass fiber reinforcement polymer composite laminates obtained by different fabrication processes

传统的湿手糊工艺（WL）已广泛应用于纤维复合材料层压板的制造。然而，由于成型压力不足，纤维的质量分数降低，内部滞留大量气泡，导致层压板质量低下（刚度和强度低）。用于制造复合层压板的湿手糊/真空袋（WLVB）工艺是在传统湿手糊工艺的基础上，使用真空袋去除气泡并提供压力，然后进行加热和固化过程。 
与传统的手糊工艺相比，WLVB工艺制造的层压板表现出优异的机械性能，包括更好的强度和刚度、更高的纤维体积分数和更低的空隙体积分数，这些都是复合材料层压板的优势。这个过程完全是手工的，受准备人员技能的影响很大。因此，产品容易出现空隙和厚度不均匀等缺陷，导致层压板的质量和机械性能不稳定。因此，有必要详细描述WLVB工艺，精细控制步骤，量化材料比例，以确保层压板的机械性能。 
本文介绍了WLVB工艺制备编织平纹玻璃纤维增强复合材料层合板（GFRPs）的细致工艺。采用公式法计算层合板的纤维体积含量，计算结果显示，WL层合板的纤维体积含量为42.04%，而WLVB层合板的纤维体积含量为57.82%，提高了15.78%。使用拉伸和冲击测试表征层压板的机械性能。实验结果表明，采用WLVB工艺，层合板的强度和模量分别提高了17.4%和16.35%，比吸收能提高了19.48%。

表 1 显示了样品的纤维体积分数、平均厚度和制造工艺。G8-WLVB 和 G8-WL 分别代表了由 8 层玻璃织物组成的层压板，这些层压板分别采用和不采用真空袋工艺，采用湿手糊法制造。显然，在真空袋的辅助下，层压板的纤维体积分数增加了15.78%，平均厚度减少了16.27%。
WLVB和WL试样拉伸试验得到的应变-应力曲线如图 4所示。纵轴显示由力除以横截...

Watch this Scientific Journal Video about Enhancing Fiber Composite Laminate Quality with the Wet Hand Lay-Up/Vacuum Bag Process at JoVE.com

作者聚焦：使用湿法手糊/真空袋工艺提高纤维复合材料层压板质量 

本文介绍了使用湿手糊/真空袋法获得的纤维增强聚合物基复合材料层合板的制造工艺。

测量通过不同制造工艺获得的玻璃纤维增强聚合物复合层压板的机械性能

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the ...

我们的研究重点是提高纤维复合材料的界面韧性和受损电阻。我们正试图通过加入纳米颗粒来提高纤维复合材料的抵抗力。纤维复合材料制造中最常见的挑战之一是缺乏可重复性。通过精确控制制造深度和量化材料比例，我们可以获得具有非常稳定的机械性能的层压板。这种方法确保了不同批次的测试结果具有高度可重复性。用于制造复合材料层压板的 eWLB 工艺使用真空袋去除气泡。与其他工艺相比，该工艺具有很多优点。它需要简单的设备，涉及的工艺技术并不复杂，产品也不受尺寸或形状的限制。

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Measuring the Mechanical Properties of Glass Fiber Reinforcement Polymer Composite Laminates Obtained by Different Fabrication Processes

Strength of Concrete

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1.8K 次观看.  Southern University of Science and Technology. 我们的研究重点是提高纤维复合材料的界面韧性和受损电阻。我们正试图通过加入纳米颗粒来提高纤维复合材料的抵抗力。纤维复合材料制造中最常见的挑战之一是缺乏可重复性。通过精确控制制造深度和量化材料比例，我们可以获得具有非常稳定的机械性能的层压板。这种方法确保了不同批次的测试结果具有高度可重复性。用于制造复合材料层压板的 eWLB 工艺使用真?...

视频: 作者聚焦：使用湿法手糊/真空袋工艺提高纤维复合材料层压板质量 

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 ...

科研

工程学

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

A protocol is presented for the synthesis and preparation of nanoparticles consisting of electroactive polymers.

电活性聚合物纳米粒子参展光热特性

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step ...

Strain Sensing Based on Multiscale Composite Materials Reinforced with Graphene Nanoplatelets

The electrical response of NH2-functionalized graphene nanoplatelets composite materials under strain was studied. Two different manufacturing methods are proposed to create the electrical network in this work: (a) the incorporation of the nanoplatelets into the epoxy matrix and (b) the coating of the glass fabric with a sizing filled with the same nanoplatelets. Both types of multiscale composite materials, with an in-plane electrical conductivity of ~10-3 S/m, showed an exponential growth of the electrical resistance as the strain increases due to distancing between adjacent functionalized graphene nanoplatelets and contact loss between overlying ones. The sensitivity of the materials analyzed during this research, using the described procedures, has been shown to be higher than commercially available strain gauges. The proposed procedures for self-sensing of the structural composite material would facilitate the structural health monitoring of components in difficult to access emplacements such as offshore wind power farms. Although the sensitivity of the multiscale composite materials was considerably higher than the sensitivity of metallic foils used as strain gauges, the value reached with NH2 functionalized graphene nanoplatelets coated fabrics was nearly an order of magnitude superior. This result elucidated their potential to be used as smart fabrics to monitor human movements such as bending of fingers or knees. By using the proposed method, the smart fabric could immediately detect the bending and recover instantly. This fact permits precise monitoring of the time of bending as well as the degree of bending.

The integration of conductive nanoparticles, such as graphene nanoplatelets, into glass fiber composite materials creates an intrinsic electrical network susceptible to strain. Here, different methods to obtain strain sensors based on the addition of graphene nanoplatelets into the epoxy matrix or as a coating on glass fabrics are proposed.

基于多尺度复合材料的增强与石墨烯纳米片应变传感

The electrical response of NH2-functionalized graphene nanoplatelets composite materials under strain was studied. Two different manufacturing methods are ...

Experimental Implementation of a New Composite Fabrication Method: Exposing Bare Fibers on the Composite Surface by the Soft Layer Method

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional component that should have high electrical conductivity, high mechanical properties, and high productivity.
In this regard, a carbon fiber/epoxy resin composite can be an ideal material to replace the conventional graphite bipolar plate, which often leads to the catastrophic failure of the entire system because of its inherent brittleness. Though the carbon/epoxy composite has high mechanical properties and is easy to manufacture, the electrical conductivity in the through-thickness direction is poor because of the resin-rich layer that forms on its surface. Therefore, an expanded graphite coating was adopted to solve the electrical conductivity issue. However, the expanded graphite coating not only increases the manufacturing costs but also has poor mechanical properties.
In this study, a method to expose fibers on the composite surface is demonstrated. There are currently many methods that can expose fibers by surface treatment after the fabrication of the composite. This new method, however, does not require surface treatment because the fibers are exposed during the manufacture of the composite. By exposing bare carbon fibers on the surface, the electrical conductivity and mechanical strength of the composite are increased drastically.

A protocol to expose bare fibers on the composite surface by eliminating resin rich area is presented. The fibers are exposed during fabrication of the composites, not by the post surface treatment. The exposed carbon composites exhibit high electrical conductivity in the through-thickness direction and high mechanical property.

一种新的复合制备方法的实验实现: 用软层法对复合材料表面裸露纤维进行曝光

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional ...

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, ...

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 ...

Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed magnet assisted composite manufacturing (MACM) technique. In this technique, permanent magnets are utilized to apply a sufficiently high consolidation pressure during the curing stage. To enhance the intensity of the magnetic field, and thus, to increase the magnetic compaction pressure, the magnets are placed on a magnetic top plate. First, the entire procedure of preparing the composite lay-up on a magnetic bottom steel plate using the conventional wet lay-up vacuum bag process is described. Second, placement of a set of Neodymium-Iron-Boron permanent magnets, arranged in alternating polarity, on the vacuum bag is illustrated. Next, the experimental procedures to measure the magnetic compaction pressure and volume fractions of the composite constituents are presented. Finally, methods used to characterize microstructure and mechanical properties of composite laminates are discussed in detail. The results prove the effectiveness of the MACM method in improving the quality of wet lay-up vacuum bag laminates. This method does not require large capital investment for tooling or equipment and can also be used to consolidate geometrically complex composite parts by placing the magnets on a matching top mold positioned on the vacuum bag.

A new technique for applying consolidation pressure on the vacuum bag lay-up to fabricate composite laminates is described. The goal of this protocol is to develop a simple, cost-effective technique to improve the quality of laminates fabricated by the wet lay-up vacuum bag method.

磁铁辅助复合制造: 真空袋/糊化过程中实现高固结压力的一种柔性新技术

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed ...

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

解析高强共聚物芳纶纤维使其力学性能的测定

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

化学

Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (&#60;0.05 mm) layers of high-performance yarns, where the yarns in each layer are oriented parallel to each other and held in place using binder resins and thin polymer films. The armor is constructed by stacking the unidirectional layers in different orientations. To date, only very preliminary work has been performed to characterize the ageing of the binder resins used in unidirectional laminates and the effects on their performance. For example, during the development of the conditioning protocol used in the National Institute of Justice Standard-0101.06, UD laminates showed visual signs of delamination and reductions in V50, which is the velocity at which half of the projectiles are expected to perforate the armor, after ageing. A better understanding of the material property changes in UD laminates is necessary to comprehend the long-term performance of armors constructed from these materials. There are no current standards recommended for mechanically interrogating unidirectional (UD) laminate materials. This study explores methods and best practices for accurately testing the mechanical properties of these materials and proposes a new test methodology for these materials. Best practices for ageing these materials are also described.

The goal of the study was to develop protocols to prepare consistent specimens for accurate mechanical testing of high-strength aramid or ultra-high-molar-mass polyethylene-based flexible unidirectional composite laminate materials and to describe protocols for performing artificial ageing on these materials.

柔性单向复合层压板的切割程序、拉伸测试和老化

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (&#60;0.05 mm) layers of high-performance yarns, ...

Tension Test of Fiber-Reinforced Polymeric Materials

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Fiber-reinforced polymeric materials (FRP) are composite materials that are formed by longitudinal fibers embedded in a polymeric resin, thereby creating a polymer matrix with aligned fibers along one or more directions. In its simplest form, the fibers in FRP materials are aligned in an orderly, parallel fashion, thus imparting orthotropic material characteristics, meaning that the material will behave differently in the two directions. Parallel to the fibers, the material will be very strong and/or stiff, whereas perpendicular to the fibers will be very weak, as the strength can only be attributed to the resin instead of the whole matrix.
An example of this unidirectional configuration is the commercially available FRP reinforcing bars, which mimic the conventional steel bars used in reinforced concrete construction. FRP materials are used both as stand-alone structures such as pedestrian bridges and staircases, and also as materials to strengthen and repair existing structures. The thin, long plates are often epoxied to existing concrete structures to add strength. In this case, the FRP bars act as external reinforcement. The FRP bars and plates are lighter and more corrosion resistant, so they are finding applications in bridge decks and parking garages, where de-icing slats lead to rapid deterioration of conventional bars.
In this laboratory exercise, the tensile behavior of a unidirectional specimen will be studied, with emphasis on its ultimate strength and deformation capacity. The behavior of the specimen is expected to be elastic until failure, which is expected to occur in a sudden and explosive manner. This behavior should be contrasted with those of ductile steels, which exhibit extensive deformation capacity and strain hardening before failure.

Uniaxial Tension Test of Fiber-Reinforced Polymeric Materials

纤维增强高分子材料的拉伸试验

Source:&#160;Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA
Fiber-reinforced polymeric materials (FRP) are ...