Name: magnet assisted composite manufacturing: a flexible new technique for achieving high consolidation pressure in vacuum bag/lay-up processes
Uploaded: 2018-05-17T13:00:00.000+00:00
Duration: 9 min 41 s
Description: Watch this Scientific Journal Video about Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes at JoVE.com

作者感谢俄克拉荷马大学的机器店, 帮助制造模具和制造设备, 以及复合材料制造研究实验室的成员素福 k. 哈米迪, m. Akif Yalcinkaya, 和雅各布安德森为帮助讨论。

警告: 使用前请查阅所有相关的材料安全数据表 (MSDS)。使用个人防护设备 (安全眼镜、手套、实验室大衣、全长长裤和闭合脚趾鞋)。
1. 材料
<ol><li>切割6层20.3 厘米х15.2 厘米, 平纹编织玻璃织物与旋转织物切割机。 注: 平纹织物可由其它织物类型代替, 包括无纺布、随机垫。碳纤维也可用于这种方法。</li>
	<li>先称量环氧树脂, inf (40 克), tared 平衡, 然后加入硬化剂, inf (10.96 克), 用100到27.4 的重量比来制备树脂系统。搅拌树脂/硬化剂混合物 (在 37 rad 的-1), 直到达到完全分散 (5 分钟)。 注: (1) 树脂类型可替代任何适合湿式真空袋加工的树脂。(2) 环氧树脂-固化剂比的选择取决于树脂和固化剂的组合。(3) 树脂/固化剂混合物重量的选择取决于所需的成品纤维体积分数和预期的废料量, 如树脂的出血量, 刷上的剩余树脂等。考虑到6层织物的重量约为34克, 选择了树脂纤维比为60到40的重量。</li>
	<li>在树脂陷阱中加了树脂 (约15分钟), 以除去在环氧树脂和固化剂混合过程中形成的所有被困空气。</li>
</ol>2. 在湿式真空袋工艺中使用磁性压力的复合制造
注意:图 1显示了复合放置和应用磁性压力的简化示意图, 这在 2.1-2.15 节中描述。
<ol><li>准备实验所需的所有材料:<ol>
<li>在4.76 毫米厚的钢顶板上, 将二十五 N52 钕铁硼 (钕金属硼) 永磁 (2.54 厘米长, 2.54 厘米宽, 1.27 厘米厚), 通过其厚度磁化。将磁体排列在 5 x 5 平方配置中交替极性。在固定磁铁的排列和放置过程中, 必须小心, 因为有伤害的危险。</li>
		<li>将0.3 毫米厚的铝科尔板 (20.3 х15.2 厘米2) 预涂上聚四氟乙烯脱模剂, 正好在穿孔释放膜的中间 (26.7 х21.6 厘米2)。</li>
		<li>使用12.7 毫米宽聚酯胶带将科尔板的周长贴到释放膜上。</li>
	</ol>
</li>
	<li>在6.35 毫米厚、61.0 x 61.0 厘米2、钢底工具板表面的 43.2 x 27.9 厘米2区域的外围放置一个12.7 毫米宽粘性胶带。</li>
	<li>在铺设织物之前, 在工具板上涂上树脂, 涂上一层型无孔聚四氟乙烯涂层的玻璃纤维释放膜 (76 µm 厚)。只用足够的树脂饱和第一层织物。</li>
	<li>放置第一层织物, 然后, 用滚筒, 按下挤出多余的树脂。</li>
	<li>将少量的附加树脂浇注到织物上, 然后均匀地在整个区域刮刀, 从而使纤维床完全饱和。</li>
	<li>对所有的层 (在这种情况下, 6 层) 重复步骤2.4 和2.5。确保所有的层层都完全饱和树脂和大约相同数量的树脂 (8.5 克) 用于每层。</li>
	<li>将科尔板, 附着在穿孔释放膜上, 在纤维预制件的顶部, 后跟一层0.5 英寸宽的聚酯胶带环绕在释放膜的外围。</li>
	<li>将两片呼吸/出血布插入纤维预制件上, 将扭锁真空阀的底部放在呼吸布的顶部。确保阀距饱和预制件足够远, 防止阀门与多余树脂接触。</li>
	<li>卸下粘胶带的背纸, 并将真空袋放在工具板上, 并将其牢牢压在胶带上密封。</li>
	<li>将真空软管的一端连接到真空阀的顶部, 另一侧的压力调节器, 连接到真空泵。</li>
	<li>把一个小缝放在袋子里的底部的阀门是, 插入顶部的真空阀进入孔, 然后轻轻拧它关闭, 使袋下方不皱。</li>
	<li>启动真空泵, 直到达到93帕 (13.5 psi) 的恒定真空压力, 以除去固化和过量树脂中产生的任何挥发物。确保真空系统无泄漏。</li>
	<li>将底部工具板的四边缘夹紧到支撑底座上。底部的工具板必须固定在放置磁铁之前的运动, 因为磁吸引力可能移动和转移板块向上。</li>
	<li>允许层压板在室温下固化45分钟, 然后将该套磁铁 (准备在2.1.1 部分) 放在真空袋上, 然后将刀具板的温度提高到60摄氏度, 其坡道速度为5摄氏度/分钟。 注: (1) 固化周期取决于所选树脂。(2) 硅橡胶热板置于工具板下加热。</li>
	<li>固化后8小时在60摄氏度, 取出真空袋, 脱模复合材料层压板。 注: 为了评估在施加磁性压力的情况下层压板质量的提高, 我们用传统的湿式真空袋工艺制造了一系列层合板, 不施加外部压力。将这些层合板的质量与磁压力下的材料进行了比较。为了用传统的湿式真空袋制造层压板, 2.1.2 了2.15 步, 除了磁铁的位置。为了评估每个制造过程的重复性, 在相同的条件下制作了第二层层压板。</li>
</ol>3. 磁力压实压力的测量
<ol><li>在机械测试仪器上将顶部板连接到负载单元的末端。</li>
	<li>将一 N52 钕铁硼永磁体放在底部移动板上, 定位在足够的距离 (至少25毫米) 远离顶部固定板在测试的开始。 注: 对于磁力的测量, 顶部和底板都应由磁性材料如钢制成。</li>
	<li>将底板向上移动1-2 毫米/分钟到顶板的低速, 并记录产生的磁力, 同时测量从线性变差变压器 (LVDT) 的相应位移, 采样速率为6赫兹。 注: (1) 这个测试的速度是至关重要的, 因为磁铁产生的力取决于指数之间的空气间隙。(2) 所有磁性测量均在室温下进行。</li>
	<li>继续监视磁力压实力, 直到磁铁的顶面触及顶板。</li>
	<li>用磁铁的横截面积除以磁力, 计算磁力压实压力。</li>
</ol>4. 树脂燃烧和热重分析 (TGA)
<ol><li>树脂烧掉<ol>
<li>根据 ASTM D2584-11 规范41, 从每个层压板中剪切三个试样, 以进行树脂燃烧试验。</li>
		<li>把每个标本放在一个单独的瓷坩埚中, 注意试样的重量以及坩埚。</li>
		<li>将含有样品的坩埚放入炉内, 打开炉子, 将炉温提高到600摄氏度, 并允许树脂烧掉约4小时。</li>
		<li>关掉炉子, 小心地打开炉子门, 在拆卸坩埚之前, 让它冷却到室温。</li>
		<li>冷却后, 从炉内取出坩埚并称量回收的玻璃纤维。 注: 在树脂燃烧过程中, 纤维可能会减肥。纤维在高温下的重量损失量可以通过热重分析 (TGA) 来确定。</li>
	</ol>
</li>
	<li>热重分析 (TGA)<ol>
<li>测量纤维的重量损失, 以提高大气压力下的空气温度, 使用 TGA。放置大约30毫克纤维在白金平底锅并且装载它入 TGA 设备。</li>
		<li>斜坡温度从25°c 到600°c 的速率15°c/分钟, 保持温度为4小时, 并计算重量减少百分比。在纤维体积分数和空隙率计算过程中, 纤维的重量损失百分比被核算。 注: 根据600摄氏度的热重测试结果, 本研究所用的平织和随机垫坯的重量损失分别为0.2% 和5.46%。</li>
	</ol>
</li>
</ol>5. 空隙率和纤维体积分数计算
<ol><li>确定复合试样、基体和纤维的密度:<ol>
<li>使用悬浮方法42确定散装复合试样的密度。 注: 对于此方法, 使用具有2.49 克/厘米3密度的透明重液, 使复合试样在浸入重液体时最初漂浮。<ol>
<li>在 105 rad 的-1中加入3毫升水, 用磁力搅拌器混合溶液, 以5分钟的速度降低重液体的密度. 重复此步骤, 直到复合试样开始缓慢悬浮在重液/水混合物中。</li>
			<li>一旦溶液密度调整, 使试样保持悬浮在重的液体和水混合物, 测量溶液密度使用一个特定的重力杯。</li>
		</ol>
</li>
		<li>用步骤2.14 和2.15 中给出的相同的固化周期制备无空隙树脂试样, 然后使用与5.1.1.1 和5.1.1.2 相同的方法确定固化树脂试样的密度。 注: 固化的 INF 和 EPON 标本的密度分别为 1.152 0.003 克/厘米3和1.171 英寸0.003 克/厘米3。</li>
		<li>使用带有10厘米3杯的氮气焦真43来获得纤维的密度。 注: 纯织和随机垫织物的密度分别为 2.600 0.003 克/厘米3和2.470 英寸0.004 克/厘米3。</li>
	</ol>
</li>
	<li>根据 ASTM D2584-1141计算纤维和树脂的重量分数。</li>
	<li>计算在 ASTM D3171-15 过程后的空隙率和纤维体积分数44 <img alt="Equation 1" src="/files/ftp_upload/57254/57254eq1.jpg">(1) <img alt="Equation 2" src="/files/ftp_upload/57254/57254eq2.jpg">(2) <img alt="Equation 3" src="/files/ftp_upload/57254/57254eq3.jpg">(3) 其中, 是树脂体积分数, 是光纤体积分数, 是 void 体积分数, 是复合密度, 是树脂的密度, 是光纤的密度, 是<img alt="Equation 4" src="/files/ftp_upload/57254/57254eq4.jpg"> <img alt="Equation 5" src="/files/ftp_upload/57254/57254eq5.jpg"> <img alt="Equation 6" src="/files/ftp_upload/57254/57254eq6.jpg"> <img alt="Equation 7" src="/files/ftp_upload/57254/57254eq7.jpg"> <img alt="Equation 8" src="/files/ftp_upload/57254/57254eq8.jpg"> <img alt="Equation 9" src="/files/ftp_upload/57254/57254eq9.jpg"> <img alt="Equation 10" src="/files/ftp_upload/57254/57254eq10.jpg">示例粗细, 是纤维粗细. <img alt="Equation 11" src="/files/ftp_upload/57254/57254eq11.jpg"> 注意: void 卷内容的不确定性计算为±0.21%45。这一水平的准确性是足够的复合材料层压板, 即使在层压材料的低空隙率小于1%。</li>
</ol>6. 扫描电镜 (SEM) 成像
<ol><li>从每层板上剪下两个25.4 毫米 x 6.4 毫米的试样, 然后将它们嵌入快速固化的丙烯酸中进行 SEM 成像。 注: 试样是嵌入的, 这样, 沿25.4 毫米样品长度的层压板的侧面表面 (通过厚度表面) 被暴露用于成像。</li>
	<li>使用抛光机打磨表面的嵌入复合试样的砂砾大小不等, 从30到0.04 µm。</li>
	<li>溅射涂层大约5毫微米金子或钯到准备的样品提供导电层数。</li>
	<li>把标本装到样品架上, 放到 SEM 的房间里。</li>
	<li>将 SEM 成像参数 (如加速度电压为20伏) 和工作距离设置为25.5 毫米。</li>
	<li>以35X 或更高的放大倍数在不同位置捕捉多层层压图像。 注: 所选的放大倍数允许对大断面区域的空隙进行评估, 并可对层压厚度进行可视化比较。使用这些图像可以精确测量层压厚度。</li>
</ol>7. 弯曲性能的表征
<ol><li>根据 ASTM D790-1546使用金刚石砂锯, 从每个复合层压板中切割出一套七12.7 毫米宽的试样, 用于三点弯折弯曲试验。</li>
	<li>用卡尺测量每个试样的宽度和厚度。</li>
	<li>使用跨度厚度比为 24:1, 并调整三点弯曲试验夹具的支撑跨度。将试样放在装配在机械测试仪器上的三点弯曲试验夹具上。</li>
	<li>以2毫米/分钟的十字头速度进行弯曲试验, 记录试样的荷载偏转行为。</li>
	<li>对所有标本重复上述步骤以确认并确保结果的重复性。</li>
	<li>实验完成后, 计算试样的弯曲强度及弯曲模量39,40。</li>
</ol>

作者没有任何披露。

高固结压力在复合层压板固化过程中的应用对于制造高质量的复合部件47尤为重要。如果外部压力不应用, 层压板仅在真空下固化, 则最终部分一般会含有高空隙率, 可能超过5% 的体积, 以及不良树脂富区48。高空隙率、低纤维体积分数和树脂富区是影响复合材料层合板力学性能的因素。在这项工作中, 在湿敷真空袋工艺中应用高固结压力的实验性协议, 介绍了在固化过程中使用的一个试验方案29。在该技术中, 首先根据传统的湿式真空袋工艺, 在磁底工具板上制备了复合布置。然后, 一组固定在磁顶钢板上的永磁磁铁放在真空袋上。在这项研究中, 磁铁的应用, 同时增加了放置温度到60°c, 其中树脂黏度显著下降。在不同的时间 (如胶凝点) 施加压力, 可能会产生不同属性的层压板13,40,49。施加的磁压力的水平取决于磁铁和磁性底板之间的间隙。因此, 我们提出一个程序, 以测量磁铁产生的磁压力作为一个功能的差距 (即,铺设厚度)。
为确定 MACM 的有效性, 采用六种无磁压压的方案, 制作了不同材料成分的湿式真空袋层压板。然后, 对复合材料层合板的孔隙和纤维体积分数、显微组织和弯曲性能的表征作了详细的说明。为评价复合成分的体积分数, 采用了树脂烧断和悬浮方法,42。结果表明, 利用磁力压实压力显著提高了纤维体积分数, 降低了零件的空隙率。此外, 对于复合材料的显微结构分析, 采用扫描电子显微镜 (SEM) 成像技术, 并对空洞15的位置和几何特征进行了深入的探讨。例如,图 3显示, 在固化过程中使用磁性压力也有利于减小空隙的大小和数量, 从而减少过早失败的可能性20,24。因此, 这些因素大大提高了层压板的弯曲性能。然而, MACM 的有效性取决于复合成分 (纤维和树脂) 的类型。
虽然用这种方法制作层压板很简单, 但在安排和放置永磁磁铁时必须注意, 因为它们产生非常高的压力 (即最大压力为0.64 兆帕)。这种方法的局限性是, 底部的工具板需要磁性, 如400系列不锈钢, 它必须是固定的反对运动之前, 放置磁铁, 因为磁吸引力可能移动和转移板块向上。此外, 磁铁施加的压力取决于层压的厚度。例如, 钕铁硼, N52-2 54 x 2.54 x 1.27 厘米3永磁不能产生高固结压力 (> 0.1 兆帕) 时, 复合铺设厚度超过6.5 毫米。在这种情况下, 需要使用更强的磁铁来达到高的固结水平。
所提出的方法使用方便, 优于高压釜, 不需要昂贵的设备和工装。虽然这里没有阐明, 这种方法不仅广泛适用于湿式真空袋, 而且对其他复合材料的制造工艺, 如聚酯胶片和真空辅助树脂转移成型 (辅助) 的蒸压固化。此外, 如果在磁铁和真空袋之间使用合适的润滑剂, 则可以相对容易地在真空袋上滑动磁铁来制造大型复合材料部件。此外, 根据我们的知识, 这是唯一的方法, 允许应用局部和非均匀压力的复合铺设。这个方法的未来方向是制造几何复杂的复合零件, 但不是把磁铁放在平板上, 而是放在一个匹配的上模上。

纤维增强聚合物复合材料已广泛应用于汽车1,2, 航空航天3,4, 海洋5,6, 建筑7,8工业由于其独特的性能, 如高比强度和模数, 良好的疲劳行为, 和耐腐蚀性。目前, 高品质复合材料层压板主要是用预浸渍织物 (预浸料) 在高温高压下固化, 高固结压力为 0.27-0. 69 兆帕 (40-100 psi)9。一些较低质量的复合材料层压板是由湿铺设过程产生的, 在那里不应用更高的固结压力。这一过程是劳动密集型的, 不需要昂贵的设备, 并通过放置一层干织物在模具上, 随后应用树脂进行。在大多数应用中, 手持滚筒被用来强迫树脂进入纤维增强, 挤出多余的树脂。此序列重复, 直到获得所需的厚度。在固化过程中, 采用真空 (称为湿式真空袋工艺) 和额外的固结压力, 可大大提高湿式铺层板的质量。在固化过程中应用高固结压力有利于树脂的流动, 导致纤维体积分数增加, 并去除空隙10,11 , 从而提高机械性能。亚伯拉罕et 等。12表明, 在 1.2 MPa 的固结压力下, 采用湿式真空袋制作高纤维体积分数约64% 和低空隙体积分数为1.6% 的高质量纯织电子玻璃复合材料层压板。适用于高压釜。
孔隙是复合材料层合板制造过程中最常见的缺陷之一。从几微米到数个微米的空隙主要是由于在放置时被包裹的空气, 树脂中溶解的水分, 以及在固化过程中被排出的挥发物13,14,15形成的。此外, 纤维增强的浸渍动力学被发现对空洞的诱捕有显著的影响16,17。人们普遍认为, 在复合层压板中存在空隙会导致强度的大幅度降低13,18,19, 模数20,21, 断开韧性22和疲劳寿命23,24的层压板。例如, 贾德和赖特25发现, 每1% 增加的空隙率 (最多 4%), 导致短光束剪切性质约7% 下降。此外, Ghiorse26发现, 在碳/环氧树脂复合材料中, 每增加1% 的空隙率, 就可以看到10% 的层间剪切和弯曲强度降低, 弯曲模量减少5%。此外, 空隙对裂纹萌生和传播以及吸湿27、28都有不利影响。众所周知, 含孔隙率较高的层合板的吸湿速率较大, 吸收的水分可能导致纤维基质界面的退化和下长期机械性能下降29, 30,31,32。因此, 为了保证机械性能的一致性, 达到复合材料产品的最高质量, 应尽量减少空隙率。
虽然在高压釜中固化复合层压板可生产出可靠、高质量的零件, 但由于最初的资本投资和过度的能源使用, 产品成本将会很高。除高压釜治疗外, 还开发了多种技术, 如真空辅助树脂转移成型 (真空成型) 和快步工艺, 用于在高压釜中制造复合层压板32,33,34,35,36. 然而, 由于缺乏统一、高压, 这些方法所产生的层压板通常比在高压釜37中制造的机械性能低。近年来, 采用一种新的技术称为磁铁辅助复合材料制造 (MACM), 通过应用一套大功率永久性的固结压力, 提高湿式真空袋复合材料层合板的质量。磁铁38,39。该技术的应用, 然后扩展到生产高品质, 结构复合材料层压板使用高温永磁体40。
本文提出了一种利用 MACM 技术制造湿式真空袋复合材料层合板的协议。在 MACM 中, 钕铁硼永磁在固化过程中采用了足够高的固结压力, 从而提高了层合板的质量。首先, 介绍了在底部钢板上制备6层、纯织 E 玻璃/环氧树脂复合物的方法。然后, 证明了在顶钢板上交替极性上的永磁磁体的布置, 以及它在真空袋上的位置, 对复合材料的铺设施加固结压力。最后, 概述了磁性压实压力的测量步骤, 以及复合材料层合板的孔隙率、纤维体积分数、显微组织和力学性能的表征方法。通过在磁压力下制作湿式真空袋层压板, 并将其性能与传统的湿式真空袋 (无磁铁) 制成的材料进行比较, 研究了 MACM 过程的有效性。所得结果证明了 MACM 法提高整体层压板质量的能力。该方法是一种低成本、简单的制造高质量层压板的方法, 可应用于相对容易地制作大型、几何复杂的复合材料构件。

<table><tbody><tr><td>Plain weave glass fiber</td><td>Hexcel</td><td>HexForce 3733</td><td>The type of fibers can be substituted with any type of fabrics</td></tr><tr><td>Randomly oriented chopped strand glass fiber</td><td>Fiberglast</td><td>248</td><td></td></tr><tr><td>TenCate EX-1522/IM7</td><td>Tencate</td><td></td><td>it is a plain weave carbon/epoxy prepreg</td></tr><tr><td>PRO-SET INF-114 Infusion Epoxy</td><td>Composite Envisions</td><td>1758</td><td>The type of resin can be substituted with any type of resin suitable for wet lay-up vacuum bag process</td></tr><tr><td>PRO-SET INF-211 Medium Infusion Hardener</td><td>Composite Envisions</td><td>1760</td><td></td></tr><tr><td>EPON 862</td><td>Hexion Inc.</td><td></td><td></td></tr><tr><td>EPIKURE Curing Agent 3300</td><td>Hexion Inc.</td><td></td><td></td></tr><tr><td>NdFeB, N52-2.54 &amp;times; 2.54 &amp;times; 1.27 cm3</td><td>K&amp;amp;J Magnetics, Inc.</td><td>BX0X08-N52</td><td>Magnets can be substitued with any type depending on the required pressure and application</td></tr><tr><td>OLFA rotary cutter</td><td>Fibre Glast</td><td>1706-A</td><td></td></tr><tr><td>Tacky tape</td><td>De-Comp Composites</td><td>D413Y</td><td></td></tr><tr><td>Polyester tape</td><td>De-Comp Composites</td><td>D574A</td><td></td></tr><tr><td>Squeegees</td><td>Fibre Glast</td><td>62-A</td><td>Any type of squeegees can be used</td></tr><tr><td>Roller</td><td>De-Comp Composites</td><td>D205</td><td>Any type of rollers can be used</td></tr><tr><td>PTFE-Coated&amp;nbsp;fiberglass fabric sheets</td><td>McMaster-Carr Supply Company</td><td>8577K81</td><td></td></tr><tr><td>PTFE release agent dry lubricant</td><td>Miller-Stephenson</td><td>MS122AD</td><td></td></tr><tr><td>Perforated release film</td><td>Fibre Glast</td><td>1787-C</td><td></td></tr><tr><td>Breather cloth</td><td>De-Comp Composites</td><td></td><td></td></tr><tr><td>Vacuum&amp;nbsp;bag&amp;nbsp;film</td><td>Rock West Composite</td><td>WRIGHTLON 7400</td><td></td></tr><tr><td>Aluminum twist lock vacuum valve</td><td>De-Comp Composites</td><td>D401</td><td></td></tr><tr><td>Vacuum pump</td><td>Best Value Vacs</td><td>BVVRS1</td><td></td></tr><tr><td>Flexible silicone-rubber heat sheets, adhesive backing</td><td>McMaster-Carr Supply Company</td><td>35765K429</td><td></td></tr><tr><td>400-series steel plate, 6.35 mm-thick</td><td></td><td></td><td>The lay-up is prepared on this plate</td></tr><tr><td>steel plate, 4.76 mm-thick</td><td></td><td></td><td>The magnets are attached to this plate</td></tr><tr><td>Aluminum sheet, 0.3-mm thick</td><td></td><td></td><td></td></tr><tr><td>Lab stirrer mixer</td><td>Caframo</td><td></td><td></td></tr><tr><td>Laboratory weigh scale</td><td></td><td></td><td></td></tr><tr><td>AccuPyc II 1340 automatic gas pycnometer</td><td>Micromeritics Instrument Corporation</td><td>134/00000/00</td><td></td></tr><tr><td>Specific gravity cup, 83.2 mL</td><td>Gardco</td><td>EW-38000-12</td><td></td></tr><tr><td>Acrylic cold mounting resin</td><td>Struers</td><td>LevoCit</td><td></td></tr><tr><td>Grinder/polisher</td><td>Struers</td><td>LaboSystem</td><td></td></tr><tr><td>Porcelain crucibles, 30 mL</td><td>United Scientific Supplies</td><td>JCT030</td><td></td></tr><tr><td>Plastic Cups, 12 Oz, clear</td><td></td><td></td><td>It is used as epoxy mixing cups</td></tr></tbody></table>

magnet assisted composite manufacturing: a flexible new technique for achieving high consolidation pressure in vacuum bag/lay-up processes

这项工作表明了一个协议, 以提高复合材料层合板的质量, 由湿躺在真空袋工艺, 利用最近开发的磁铁辅助复合材料制造 (MACM) 技术。在这种技术中, 利用永磁磁铁在固化阶段应用足够高的固结压力。为了提高磁场强度, 从而提高磁压压, 磁铁被放在磁顶板上。首先, 介绍了用传统的湿式真空袋工艺制备磁性底钢板复合材料的全过程。其次, 对真空袋上的一组钕铁硼永磁磁体进行了布置, 并将其置于交流极性中。其次, 给出了测量复合成分的磁压和体积分数的实验程序。最后, 详细讨论了复合材料层合板的显微组织和力学性能表征方法。结果证明了 MACM 法在提高湿式真空袋层压板质量中的有效性。此方法不需要对工具或设备进行大量的资本投资, 也可以通过将磁体放置在真空袋上的匹配顶模上来整合几何复杂的复合材料部件。

为了研究 MACM 对层压板质量的影响, 考虑了几种不同的织物类型和树脂体系的应用情况。表 1报告了在六种不同的制造方案下制造的6层、E 玻璃/环氧树脂复合材料层压板的制造工艺和复合成分。在基线方案中 (w-inf、w rm inf 和 w rm-EPON), 层压板是由湿式真空袋制成的, 没有外部压力。另外三种方案 (wm--inf、wm rm inf 和 wm rm) 用于在磁力压实压力下制造湿糊式真空袋层压板。然后将这些层压板的质量与基线方案所做的比较。在第一和第二种情况下, 制作了纯织电子玻璃/inf 层压板。在第三和第四种情况下, W rm inf 和 WM rm-inf, 纯织织物被随机垫取代, 使用相同的树脂系统 (即, INF)。在第五和第六方案中, W rm-epon 和 WM-epon, 该织物是随机垫 E 玻璃, 而树脂系统取代了 EPON, 它具有适度较高的粘度为766.9 兆帕比 296 mpa s 的 INF 树脂。对最近四种情况的更详细的分析可以在 Pishvar et 2017 和 Amirkhosravi et . 201738,39中找到。
图 2a显示由钕铁硼生成的磁性压力, N52-2 54 x 2.54 x 1.27 厘米3磁铁作为磁铁和钢板之间距离的函数。这一距离将对应于复合材料层合板制造过程中的铺设厚度, 从而可用于确定磁体施加的压实压力的变化。图 2a中的嵌入显示了用于测量磁压力的变化作为距离函数的实验设置的照片。如《议定书》3节所述, 该设置由两个平行钢板 (12.5 厘米 x 12.5 厘米 x 1.8 厘米) 组成。顶板连接到 4.45 kN (1000 磅) 的负载单元。底板安装在机械测试仪器的十字头上。通过使用此设置, 在底板上放置的永磁磁铁的吸引力被测量为间隙的函数 (即,磁铁和顶钢板之间的距离)。图 2a中的虚线表示由机械测试仪器测量的磁压力 (磁体区域的力), 而实线表示由磁体供应商提供的数据确定的压力。在测量的压力和从供应商提供的技术数据表中获得的值之间通常有很好的一致。可见, 磁压力的增加取决于间隙的减少。因此, 随着层压板在固化过程中的巩固, 其厚度逐渐减小, 从而使磁体施加的压力增大。图 2b显示了图 2a中提供的相同实验数据, 但空白 (即放置厚度) 范围为 1-4. 5 毫米。此外, 在图 2b中, 所采用的初始和最终的磁压力在固化的层压材料中 (即,平纹编织和随机垫) 和树脂系统 (即INF 和 EPON) 中显示。在固结过程中, 由于树脂流出和固化, 平织/inf 层压板 (WM-inf) 的铺设厚度从1.5 毫米减少到1.4 毫米。因此, 磁压力略有增加, 从0.38 至 0.39 MPa。随机垫子/inf 层压板 (WM-RM) 的铺设厚度从2.8 毫米变到1.7 毫米, 因此, 磁性压力从0.27 到0.36 兆帕显著增加。由随机垫/epon (WM-epon) 制成的层压板的铺设厚度从3.7 毫米减少到2.5 毫米, 由此产生的压力从0.22 到0.29 兆帕中适度上升。
表 2列出了与无磁性固结压力一起制造的层压板的平均厚度、纤维体积分数和空隙率。如表 2所示, 利用磁压压极大地降低了层压板的平均厚度12-47%。正如预期的那样, 层压厚度的降低与层压板纤维体积分数的增加有很大的关系, 在那里, 由于磁压力, 层压板的纤维体积分数显著提高了13-98%。在所有的情况下, 施加磁压力对随机垫/INF 层压板的影响更明显 (即, 98% 纤维体积分数增加), 因为两个因素: (1) 显著降低初始纤维体积分数的欠压实随机垫层板与纯织层压板相比, (2) 使用低粘度为296兆帕的树脂, 从而使多余树脂更容易去除。同样值得注意的是, 施加磁压力在减少层合板的空隙率从 3.4-5.8% 到 1.5-2.7% 有额外的优势。因此, 磁性压力不仅驱动多余的树脂, 而且还会使层压板的空隙。
图 3显示了在6种不同场景下制造的电子玻璃/环氧树脂层压板的 SEM 图像, 其放大倍数为35X。为了便于直观的比较, 在左侧显示了不带外部压力的层压板的图像, 并在该右侧进行了磁压缩下的层压板。从这些图像, 很明显, 利用磁力压实压力的结果, 大大改善了层间的整合, 从而导致大幅度减少树脂丰富的领域。结果表明, 层合厚度明显降低, 纤维体积分数增加, 特别是由随机垫布和 inf 树脂 (WM-RM) 制成的层压板。这些图像还表明, 在与没有外部压力的层压板中, 空隙的形貌是完全不同的。施加磁压可以减少空隙数, 使空隙变小, 从而导致层合板中的空隙率降低。最后, 压缩位于层间的空隙会导致更长的空隙。
表 3显示了所有层压材料的弯曲强度和模量, 以及在磁固结压力下的层压板的弯曲性能的百分比增加。结果表明, 利用磁压力能显著提高层压板的抗弯强度和模量。在随机垫/inf 层压板 (WM-RM) 的纤维体积分数中增加 98%, 而最小空隙率为 1.46%, 则分别导致板的弯曲强度和模量增加62% 和67%。正如预期的那样, 最初表现为纤维体积分数最低提高13% 的纯织/INF 层压板 (WM), 在弯曲强度和模量上分别呈最低的增加, 7% 和22%。因此, 在磁固结压力下, 各种复合材料层合板的弯曲性能的提高, 证明了 MACM 提高整体层压质量的能力。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td>制造 场景</td>
			<td>面料类型</td>
			<td>树脂系统</td>
			<td>制造工艺</td>
		</tr>
<tr>
<td>W-密码-INF</td>
			<td>纯织电子玻璃</td>
			<td>Inf</td>
			<td>常规湿式真空袋不使用外压</td>
		</tr>
<tr>
<td>WM-密码-INF</td>
			<td>纯织电子玻璃</td>
			<td>Inf</td>
			<td>用磁固结压湿式真空袋</td>
		</tr>
<tr>
<td>W-RM-INF</td>
			<td>随机垫 E 玻璃</td>
			<td>Inf</td>
			<td>常规湿式真空袋不使用外压</td>
		</tr>
<tr>
<td>WM-RM-INF</td>
			<td>随机垫 E 玻璃</td>
			<td>Inf</td>
			<td>用磁固结压湿式真空袋</td>
		</tr>
<tr>
<td>W-EPON</td>
			<td>随机垫 E 玻璃</td>
			<td>Epon</td>
			<td>常规湿式真空袋不使用外压</td>
		</tr>
<tr>
<td>WM-RM-EPON</td>
			<td>随机垫 E 玻璃</td>
			<td>Epon</td>
			<td>用磁固结压湿式真空袋</td>
		</tr>
</tbody></table>表 1: 6 层复合材料层压板制造中使用的成分和六种制造方案的详细情况。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td>制作方案</td>
			<td>平均厚度 (毫米)</td>
			<td>纤维体积分数 (%)</td>
			<td>纤维体积分数增加 (%)</td>
			<td>空隙体积分数 (%)</td>
			<td>减少空隙体积分数 (%)</td>
		</tr>
<tr>
<td>W-密码-INF</td>
			<td>0.98 @ 0.01</td>
			<td>45.65 @ 0.82</td>
			<td>―</td>
			<td>3.44 @ 0.46</td>
			<td>―</td>
		</tr>
<tr>
<td>WM-密码-INF</td>
			<td>0.86 @ 0.01</td>
			<td>51.63 @ 0.87</td>
			<td>13</td>
			<td>1.74 @ 0.39</td>
			<td>49</td>
		</tr>
<tr>
<td>W-RM-INF29
</td>
			<td>2.28 @ 0.04</td>
			<td>24.84 @ 1.14</td>
			<td>―</td>
			<td>5.09 @ 0.69</td>
			<td>―</td>
		</tr>
<tr>
<td>WM-RM-INF29
</td>
			<td>1.21 @ 0.01</td>
			<td>49.10 @ 0.87</td>
			<td>98</td>
			<td>1.46 @ 0.24</td>
			<td>71</td>
		</tr>
<tr>
<td>W RM-EPON30
</td>
			<td>3.18 @ 0.01</td>
			<td>17.34 @ 0.84</td>
			<td>―</td>
			<td>5.81 @ 1.24</td>
			<td>―</td>
		</tr>
<tr>
<td>WM-RM-EPON30
</td>
			<td>1.99 @ 0.03</td>
			<td>26.88 @ 1.99</td>
			<td>55</td>
			<td>2.71 @ 0.36</td>
			<td>53</td>
		</tr>
</tbody></table>表 2: 在六种不同情况下制造的6层层压板的平均厚度、纤维体积分数和空隙率.由于磁性压实 (纤维体积分数和空隙体积分数和 n = 35 的平均层压厚度, 纤维体积分数和孔隙体积分数减少百分比的增加百分比; 对所有数据的95% 置信区间) 是也给了。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td>制作方案</td>
			<td>弯曲强度 (MPa)</td>
			<td>弯曲强度增加 (%)</td>
			<td>弯曲模量 (GPa)</td>
			<td>弯曲模量增加 (%)</td>
		</tr>
<tr>
<td>W-密码-INF</td>
			<td>638.9 @ 27。0</td>
			<td>―</td>
			<td>24.1 @ 0。5</td>
			<td>―</td>
		</tr>
<tr>
<td>WM-密码-INF</td>
			<td>681.1 @ 35。5</td>
			<td>7</td>
			<td>29.5 @ 0。9</td>
			<td>22</td>
		</tr>
<tr>
<td>W-RM-INF29
</td>
			<td>218.9 @ 11。4</td>
			<td>―</td>
			<td>8.4 @ 0。3</td>
			<td>―</td>
		</tr>
<tr>
<td>WM-RM-INF29
</td>
			<td>354.6 ±15。5</td>
			<td>62</td>
			<td>14.0 @ 0。8</td>
			<td>67</td>
		</tr>
<tr>
<td>W RM-EPON30
</td>
			<td>158.1 @ 8。9</td>
			<td>―</td>
			<td>6.8 @ 0。1</td>
			<td>―</td>
		</tr>
<tr>
<td>WM-RM-EPON30
</td>
			<td>253.5 @ 20。1</td>
			<td>60</td>
			<td>9.9 @ 0。6</td>
			<td>46</td>
		</tr>
</tbody></table>表 3: 复合材料层合板的弯曲强度和模量, 以及由于磁压缩而引起的弯曲性能的百分比增加 (由 EPON 和 n = 14 为其余的层压板制作的层压材料的比例为 7; 所有数据的置信区间为 95%)。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57254/57254fig1.jpg"> 图 1: 如 "协议" 部分所述, 简化了制备复合放置和应用磁压力的示意图.为此, 二十五钕铁硼, N52-2 54 x 2.54 x 1.27 厘米3永磁体用于对复合材料的铺设施加固结压力。<a href="/files/ftp_upload/57254/57254fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57254/57254fig2.jpg"> 图 2: (a)钕铁硼产生的磁性压力的变化, N52-2. 54 x 2.54 x 1.27 cm3磁铁作为空白的作用 (即,放置厚度)。该插图显示了用于测量磁压力的实验设置的照片。(b)在固化纯织/inf (wm-inf)、随机垫/inf (wm-rm) 和随机垫/epon (wm) 层压板时应用的初始和最终磁压力。<a href="/files/ftp_upload/57254/57254fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57254/57254fig3.jpg"> 图 3: 6 层电子玻璃/环氧树脂复合材料层压板的 SEM 图像, 采用湿式真空袋工艺, 无磁压力。(a) W 密码-inf (不带外部压力的纯织/inf 层压板), (b) WM--inf (具有磁性压力的纯织/inf 层压板)、 (c) W RM inf (随机垫/INF 层压板, 无外部压力), (d) WM-RM inf (随机垫/INF 层压, 带有磁性压力), (e) W RM-epon (随机垫/epon 层压, 没有外部压力), 和(f) WM-RM-epon (随机垫/epon 层压, 具有磁性压力)。<a href="/files/ftp_upload/57254/57254fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes at JoVE.com

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

介绍了一种将固结压力应用于制造复合材料层合板的真空袋铺设的新技术。本协议的目标是开发一种简单、经济高效的技术, 以提高湿式真空袋法制备的层压板的质量。

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 ...

magnet-assisted-composite-manufacturing-flexible-new-technique-for

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

13.4K 次观看.  University of Oklahoma. 介绍了一种将固结压力应用于制造复合材料层合板的真空袋铺设的新技术。本协议的目标是开发一种简单、经济高效的技术, 以提高湿式真空袋法制备的层压板的质量。

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

Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite in&#64257;ltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink.&#160;Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built using this method. The resulting tubular micro&#64258;uidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g.&#160;single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e.&#160;materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Three-dimensional (3D) microstructured composite beams are fabricated through the directed and localized infiltration of nanocomposites into 3D porous microfluidic networks. The flexibility of this manufacturing method enables the utilization of different thermosetting materials and nanofillers in order to achieve a variety of functional 3D reinforced nanocomposite macroscopic products.

通过微流体渗透制备三维微结构纳米复合材料的制造

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite ...

科研

化学

Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting

One of the typical methods to manufacture 3D lattice metals is the direct-metal additive manufacturing (AM) process such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In spite of its potential processing capability, the direct AM method has several disadvantages such as high cost, poor surface finish of final products, limitation in material selection, high thermal stress, and anisotropic properties of parts. We propose a cost-effective method to manufacture 3D lattice metals. The objective of this study is to provide a detailed protocol on fabrication of 3D lattice metals having a complex shape and a thin wall thickness; e.g., octet truss made of Al and Cu alloys having a unit cell length of 5 mm and a cell wall thickness of 0.5 mm. An overall experimental procedure is divided into eight sections: (a) 3D printing of sacrificial patterns (b) melt-out of support materials (c) removal of residue of support materials (d) pattern assembly (e) investment (f) burn-out of sacrificial patterns (g) centrifugal casting (h) post-processing for final products. The suggested indirect AM technique provides the potential to manufacture ultra-lightweight lattice metals; e.g., lattice structures with Al alloys. It appears that the process parameters should be properly controlled depending on materials and lattice geometry, observing the final products of octet truss metals by the indirect AM technique.

An indirect additive manufacturing method combining a 3D printing of polymers with a centrifugal casting is outlined for manufacturing 3D octet truss metals (Al and Cu alloys) having a unit cell length of 5 mm with a wall thickness of 0.5 mm.

与超薄切片格金属制造间接使用离心铸造

One of the typical methods to manufacture 3D lattice metals is the direct-metal additive manufacturing (AM) process such as Selective Laser Melting (SLM) ...

工程学

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 ...

Manufacturing Of Robust Natural Fiber Preforms Utilizing Bacterial Cellulose as Binder

A novel method of manufacturing rigid and robust natural fiber preforms is presented here. This method is based on a papermaking process, whereby loose and short sisal fibers are dispersed into a water suspension containing bacterial cellulose. The fiber and nanocellulose suspension is then filtered (using vacuum or gravity) and the wet filter cake pressed to squeeze out any excess water, followed by a drying step. This will result in the hornification of the bacterial cellulose network, holding the loose natural fibers together.
Our method is specially suited for the manufacturing of rigid and robust preforms of hydrophilic fibers. The porous and hydrophilic nature of such fibers results in significant water uptake, drawing in the bacterial cellulose dispersed in the suspension. The bacterial cellulose will then be filtered against the surface of these fibers, forming a bacterial cellulose coating. When the loose fiber-bacterial cellulose suspension is filtered and dried, the adjacent bacterial cellulose forms a network and hornified to hold the otherwise loose fibers together.
The introduction of bacterial cellulose into the preform resulted in a significant increase of the mechanical properties of the fiber preforms. This can be attributed to the high stiffness and strength of the bacterial cellulose network. With this preform, renewable high performance hierarchical composites can also be manufactured by using conventional composite production methods, such as resin film infusion (RFI) or resin transfer molding (RTM). Here, we also describe the manufacturing of renewable hierarchical composites using double bag vacuum assisted resin infusion.

We present a novel method of manufacturing rigid and robust short natural fiber preforms using a papermaking process. Bacterial cellulose acts simultaneously as the binder for the loose fibers and provides rigidity to the fiber preforms. These preforms can be infused with a resin to produce truly green hierarchical composites.

制造业的鲁棒天然纤维预制体的利用细菌纤维素为粘结剂

A novel method of manufacturing rigid and robust natural fiber preforms is presented here. This method is based on a papermaking process, whereby loose ...

生物工程

Fabrication of Magnetic Nanostructures on Silicon Nitride Membranes for Magnetic Vortex Studies Using Transmission Microscopy Techniques

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared on transparent membranes which are very fragile and difficult to manipulate. We present processes for the fabrication of samples with magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for Lorentz transmission electron microscopy and magnetic transmission x-ray microscopy studies. The samples are prepared on silicon nitride membranes and the fabrication consists of a spin coating, UV and electron-beam lithography, the chemical development of the resist, and the evaporation of the magnetic material followed by a lift-off process forming the final magnetic structures. The samples for the Lorentz transmission electron microscopy consist of magnetic nanodiscs prepared in a single lithography step. The samples for the magnetic x-ray transmission microscopy are used for time-resolved magnetization dynamic experiments, and magnetic nanodiscs are placed on a waveguide which is used for the generation of repeatable magnetic field pulses by passing an electric current through the waveguide. The waveguide is created in an extra lithography step.

A protocol for the fabrication of magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for transmission electron microscopy (TEM) and magnetic transmission x-ray microscopy (MTXM) studies is presented.

用透射显微技术制备氮化硅薄膜磁性纳米结构的研究

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared ...

Negative Additive Manufacturing of Complex Shaped Boron Carbides

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for high wear, high hardness, and lightweight material applications such as armors. To overcome this challenge, negative additive manufacturing (AM) is employed to produce complex geometries of boron carbides at various length scales. Negative AM first involves gelcasting a suspension into a 3D-printed plastic mold. The mold is then dissolved away, leaving behind a green body as a negative copy. Resorcinol-formaldehyde (RF) is used as a novel gelling agent because unlike traditional hydrogels, there is little to no shrinkage, which allows for extremely complex molds to be used. Furthermore, this gelling agent can be pyrolyzed to leave behind ~50 wt% carbon, which is a highly effective sintering aid for B4C. Due to this highly homogenous distribution of in situ carbon within the B4C matrix, less than 2% porosity can be achieved after sintering. This protocol highlights in detail the methodology for creating near fully dense boron carbide parts with highly complex geometries.

A method called negative additive manufacturing is used to produce near fully dense complex shaped boron carbide parts of various length scales. This technique is possible via the formulation of a novel suspension involving resorcinol-formaldehyde as a unique gelling agent that leaves behind a homogenous carbon sintering aid after pyrolysis.

复合型碳化硼的负添加剂制造

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for ...

Operation of the Collaborative Composite Manufacturing (CCM) System

The automated tape placement and the automated fiber placement (AFP) machines provide a safer working environment and reduce the labor intensity of workers than the traditional manual fiber placement does. Thus, the production accuracy, repeatability and efficiency of composite manufacturing are significantly improved. However, the current AFP systems can only produce the composite components with large open surface or simple revolution parts, which cannot meet the growing interest in small complex or closed structures from industry.
In this research, by employing a 1-degree of freedom (DoF) rotational stage, a 6-RSS parallel robot, and a 6-DoF serial robot, the dexterity of the AFP system can be significantly improved for manufacturing complex composite parts. The rotational stage mounted on the parallel robot is utilized to hold the mandrel and the serial robot carries the placement head to mimic two human hands that have enough dexterity to lay the fiber to the mandrel with complex contour.
Although the CCM system increases the flexibility of composite manufacturing, it is quite time-consuming or even impossible to generate the feasible off-line path, which ensures uniform lay-up of subsequent fibers considering the constraints like singularities, collisions between the fiber placement head and mandrel, smooth fiber direction change and keeping the fiber placement head along the norm of the part&#39;s surface, etc. Moreover, due to the existing positioning error of the robots, the on-line path correction is needed. Therefore, the on-line pose correction algorithm is proposed to correct the paths of both parallel and serial robots, and to keep the relative path between the two robots unchanged through the visual feedback when the constraint or singularity problems in the off-line path planning occur. The experimental results demonstrate the designed CCM system can fulfill the movement needed for manufacturing a composite structure with Y-shape.

Operation of the Collaborative Composite Manufacturing CCM System

A collaborative composite manufacturing system is developed for robotic lay-up of composite laminates using the prepreg tape. The proposed system allows the production of composite laminates with high levels of geometrical complexity. The issues in the path planning, coordination of the robots and control are addressed in the proposed method.

协同复合制造 （CCM） 系统的操作

The automated tape placement and the automated fiber placement (AFP) machines provide a safer working environment and reduce the labor intensity of ...

Fabrication and Design of Wood-Based High-Performance Composites

Delignified densified wood is a new promising and sustainable material that possesses the potential to replace synthetic materials, such as glass fiber reinforced composites, due to its excellent mechanical properties. Delignified wood, however, is rather fragile in a wet state, which makes handling and shaping challenging. Here we present two fabrication processes, closed-mold densification and vacuum densification, to produce high-performance cellulose composites based on delignified wood, including an assessment of their advantages and limitations. Further, we suggest strategies for how the composites can be re-used or decomposed at the end-of-life cycle. Closed-mold densification has the advantage that no elaborate lab equipment is needed. Simple screw clamps or a press can be used for densification. We recommend this method for small parts with simple geometries and large radii of curvature. Vacuum densification in an open-mold process is suitable for larger objects and complex geometries, including small radii of curvature. Compared to the closed-mold process, the open-mold vacuum approach only needs the manufacture of a single mold cavity.

Delignified densified wood represents a new promising lightweight, high-performance and bio-based material with great potential to partially substitute natural fiber reinforced- or glass fiber reinforced composites in the future. We here present two versatile fabrication routes and demonstrate the possibility to create complex composite parts.

基于木材的高性能复合材料的制造与设计

Delignified densified wood is a new promising and sustainable material that possesses the potential to replace synthetic materials, such as glass fiber ...

纤维复合材料层压板的制造和机械性能评估

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

The traditional wet hand lay-up process (WL) has been widely applied in the manufacturing of fiber composite laminates. However, due insufficiency in the forming pressure, the mass fraction of fiber is reduced and lots of air bubbles are trapped inside, resulting in low-quality laminates (low stiffness and strength). The wet hand lay-up/vacuum bag (WLVB) process for the fabrication of composite laminates is based on the traditional wet hand lay-up process, using a vacuum bag to remove air bubbles and provide pressure, and then carrying out the heating and curing process. 
Compared with the traditional hand lay-up process, laminates manufactured by the WLVB process show superior mechanical properties, including better strength and stiffness, higher fiber volume fraction, and lower void volume fraction, which are all benefits for composite laminates. This process is completely manual, and it is greatly influenced by the skills of the preparation personnel. Therefore, the products are prone to defects such as voids and uneven thickness, leading to unstable qualities and mechanical properties of the laminate. Hence, it is necessary to finely describe the WLVB process, finely control steps, and quantify material ratios, in order to ensure the mechanical properties of laminates. 
This paper describes the meticulous process of the WLVB process for preparing woven plain patterned glass fiber reinforcement composite laminates (GFRPs). The fiber volume content of laminates was calculated using the formula method, and the calculated results showed that the fiber volume content of WL laminates was 42.04%, while that of WLVB laminates was 57.82%, increasing by 15.78%. The mechanical properties of the laminates were characterized using tensile and impact tests. The experimental results revealed that with the WLVB process, the strength and modulus of the laminates were enhanced by 17.4% and 16.35%, respectively, and the specific absorbed energy was increased by 19.48%.

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 

This paper describes a fabrication process for fiber-reinforced polymer matrix composite laminates obtained using the wet hand lay-up/vacuum bag method.

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 ...

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

摘要

探索更多视频

此视频中的章节

通过微流体渗透制备三维微结构纳米复合材料的制造

与超薄切片格金属制造间接使用离心铸造

基于多尺度复合材料的增强与石墨烯纳米片应变传感

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

制造业的鲁棒天然纤维预制体的利用细菌纤维素为粘结剂

用透射显微技术制备氮化硅薄膜磁性纳米结构的研究

复合型碳化硼的负添加剂制造

协同复合制造（CCM）系统的操作

基于木材的高性能复合材料的制造与设计

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

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

摘要

探索更多视频

此视频中的章节

通过微流体渗透制备三维微结构纳米复合材料的制造

与超薄切片格金属制造间接使用离心铸造

基于多尺度复合材料的增强与石墨烯纳米片应变传感

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

制造业的鲁棒天然纤维预制体的利用细菌纤维素为粘结剂

用透射显微技术制备氮化硅薄膜磁性纳米结构的研究

复合型碳化硼的负添加剂制造

协同复合制造 （CCM） 系统的操作

基于木材的高性能复合材料的制造与设计

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

协同复合制造（CCM）系统的操作