这项工作得到了联合大豆委员会拨款1940-352-0701-C和美国农业部\林务局的支持。我们感谢AES的Phil Humphrey的支持和详细信息。

1. 基材的制备
<ol><li>使用适合应用的基材表面。对于木材，请使用可靠生产商提供的约 0.6 至 0.8 毫米厚的切片单板，因为这些单板用于胶合板和层压单板木材 （LVL） 制造。这些是从单板供应商处获得的，厚度为 0.6 至 0.8 毫米，侧面切成 305 毫米。一致的基材是硬枫（Acer saccharum）面单板，因为它的表面光滑度和一致的厚度，它是一种弥漫多孔和高模量硬木。枫木面贴面通常用于橱柜结构，通常没有缺陷。</li>
	<li>使用前，将木材在21°C和50%相对湿度（RH）下调理至少一天。避免使用过度波浪形、表面不平整且包含变色等缺陷的贴面。 注意:其他木材种类可用于了解粘合剂与这些树种的粘合性能。然而，建议使用弥漫多孔硬木和具有渐变早木到晚木过渡的软木，因为它们的均匀性。要小心，因为木材可以是酸性的或碱性的，或者表面上有提取物，可以改变粘合剂固化过程。此外，树木从切割到单板生产的加工可以改变粘合强度12，13。由于ABES使用少量木材，因此受其他测试（例如木材水分含量和单板检查深度）发生的木材变化的影响较小。</li>
	<li>确保单板的侧面沿边缘没有任何松散的纤维，并且粘合产品没有任何明显的粘合剂挤出，因为这些会高估粘合强度，因为样品没有粘合后改性。</li>
</ol>2. 标本的制备
<ol><li>将木材试样在21°C和50%RH下调节至少一天。切割试样时，检查单板是否有任何裂缝、变色或颗粒不规则。</li>
	<li>确保气动驱动的试样切割装置可操作。</li>
	<li>使用特殊的模切机，将所需的试样尺寸从 0.6 至 0.8 毫米厚的枫木单板切割 20 mm x 117 mm（图 1， 材料表）。<ol><li>在切割刀片下方放置一块至少 150 mm x 300 mm 的单板，使单板纹理与长方向平行，然后按下气压按钮以切割每块 20 mm x 117 mm 的木材。</li>
		<li>将切割刀片下方的单板移动到未切割的区域，然后再次按下按钮以切割另一块木头。继续直到单板完全切成碎片。 注意:如果试样的长方向与纹理方向不平行，则在测试期间，远离粘合部分的木材可能会发生早期断裂。</li>
	</ol></li>
	<li>对于木材以外的材料，请使用适当的技术切割试样。如果无法用试样切割器切割材料，请使用任何可以切割的材料将其切割成所需的尺寸。由于粘合面积小，切割必须准确，试样边缘和粘合表面没有碎屑，这一点很重要。</li>
</ol>3. 设备的可操作性
<ol><li>对于粘合过程，请确保ABES设备按照标准操作程序11正常运行。ABES装置正面用于粘接和破碎样品的设置为:LP压力机0.2 MPa，HP压力机0.2 MPa，拉力0.65 MPa和冷空气0.2 MPa。</li>
	<li>使用至少 0.62 MPa （90 psig） 的供气压力，因为压力过低会导致夹具和压盘在样品上关闭得太慢或不均匀，从而导致粘合强度不正确（图 2，顶部）。</li>
	<li>清洁从先前样品中挤出的任何粘合剂的压盘。将压盘的温度调节到所需温度，并在粘合样品之前进行平衡。</li>
	<li>要粘合木材，请在21°C和50%RH的房间内操作设备。如果无法做到这一点，请将经过处理的试样放在塑料袋中，直到粘合，因为试样的尺寸很小，木材水分会迅速变化。</li>
	<li>为了获得动力学固化数据，请按照ASTM D7998-1911中所述，设计使机械和电子速度足以准确收集数据的方法。</li>
</ol>4. 试样与粘合剂的粘合
注意:粘合剂的应用对于木材粘合剂来说是一个关键问题，因为从胶合板中的层压粘合剂到粘合剂应用的可喷涂粘合剂，粘度和固体百分比的变化很大。木材粘合剂通常是水性的，因此蒸发只是一个小问题。然而，水浸入多孔木材中很重要。
<ol><li>将5mg正在研究的粘合剂涂抹在0.5cm的末端，足以覆盖粘合区域并转移到另一个样品上，但不要过度挤出。为了获得相对恒定的粘合剂铺展速率，请在天平上对木材试样进行去皮，并在粘合剂应用后重新称重。</li>
	<li>在分配粘合剂、重叠试样并确保两个试样对齐时要格外小心，因为使用小的粘合区域，强度确定为粘合区域的拉力（图 2 底部）。可以使用不同的粘合区域，但由于搭接剪切试验力学的变化，强度不一定具有可比性。 注意:文献推荐了几种将粘合剂涂在木材上的方法，具体取决于粘合剂的稠度。最初推荐的粘合剂应用方法使用专门设计的微喷涂装置10，但发现这很杂乱，速度慢，并且非常依赖于粘合剂的流变性。尽管这种方法将粘合剂作为离散点应用于刨花板和定向刨花板的粘合剂应用，但印刷方法似乎更可靠14。该微量移液器施用方法可以提供可重复体积的粘合剂10，但是要均匀分布有些困难。刮刀法对于使粘合剂在粘合区域均匀分布效果最好，建议使用微量天平来获得测量量11。</li>
	<li>最终强度数据<ol><li>将试样在120°C下粘合2分钟，并在21°C和50%RH下调节过夜，因为粘合过程中的热压会使木材变干。要粘合木材，请关闭ABES测试仪上的夹具，确保样品与测试仪对齐，将样品锁定到位。然后按下机器上的启动按钮，让120°C压盘压在重叠部分2分钟，然后缩回压盘并松开夹具，以便取出样品。 注意:固化的时间和温度由应用和粘合剂化学决定。应优化粘接温度和时间，通过使用不同的粘合温度和时间来确定最大强度的条件，使强度达到最高平台。对于木粘结，测试干剪切强度很有价值，但湿测试通常对于确定粘合剂耐久性更为关键，并且需要将样品浸泡在水中4小时室温。</li>
		<li>对于测试，通过关闭ABES测试仪上的夹具来锁定样品，确保样品与测试仪对齐。然后，通过按下启动按钮，仪器通过伺服驱动器拉动一端，而样品的另一端拉动连接到夹具的称重传感器。这种拉动一直持续到键断裂。计算机记录样品可以承受的最大力，记录为粘合强度。<ol><li>对干燥和水浸泡的样品使用相同的程序。在测量断裂力时，请注意确保握把紧握住木材，因为如果粘合剂非常牢固，木材可能会打滑。如果样品在粘合区域之外破裂，请丢弃该值，因为这是在测量木材强度，而不是粘合剂。</li>
		</ol></li>
	</ol></li>
	<li>动能强度开发<ol><li>确定粘合剂的强度发展速度，以估计大规模产品所需的压制时间。遵循与步骤 4.3 中相同的步骤，但改变温度和时间。在100°C压板温度下开始强度测试，使用10，30，60，90，120，150，180和210秒的粘合时间。随后，将温度升高10°C，并重复粘合时间，直到在低粘合时间下不再有任何强度与时间的线性部分。</li>
		<li>粘合后，缩回压盘并使用ABES的风冷功能将样品冷却到接近室温，然后测量样品强度。通过从低压榨时间开始，首先增加后续样品的时间，收集强度与时间的数据，直到增加时间导致强度增加很少或没有增加。然后在较高温度下执行相同的序列将产生强度随时间的关系图和固化速率作为斜率的结果（图 3）。 注意: 图3a10 中的酚醛粘合剂数据显示了不同时间温度对强度发展的影响。 图3b 显示了回归的等温强度发展速率与温度的关系。为了获得等温强度的发展，在测试前冷却样品。一些粘合剂，如脲醛15，在开始降解之前具有最佳的粘合时间和温度。此方法可以检测此问题并确定最佳条件。</li>
	</ol></li>
	<li>耐热性<ol><li>如果产品需要满足一定的耐温性，请将粘合的样品夹入ABES单元中。将压盘加热到该温度后，例如220°C，高于该温度，木材开始降解，将它们关闭在预粘合样品上2分钟，然后打开以测量粘合强度，如4.3.2所示，以确定粘合剂与120°C的粘合温度相比的任何热软化。</li>
		<li>重复此测试，除了将压板关闭在样品上30分钟，然后测试强度以确定粘合剂是否热降解的强度。压盘的释放和测试强度将决定样品的耐热性与加热前的值相比。这种类型的程序用于测试木材粘合剂16。由于ABES使用快速加热，并且可以在热时测量强度，而无需将样品移动到另一台机器，因此可用于区分两种故障模式（即热软化或降解）。热软化在加热后立即产生强度损失，并且通常是可以恢复的。在高温下，化学降解会随着时间的推移逐渐发生，并且在冷却时不会恢复机械强度。 注意:粘合剂制造商需要区分强度损失是由热软化还是化学降解引起的，因为这些问题需要不同的解决方案。有许多方法可以测量软化转变，包括其他热分析，但它们不能区分机械性能和化学结构的变化。</li>
	</ol></li>
</ol>5. 失效粘接面的图像分析
<ol><li>由于主要目的是确定粘合强度或内聚强度发展速率，因此请确保故障发生在粘合剂内部，而不是粘附在基材上（图4）或基材失效。如果发生基材故障，则粘合剂具有足够的强度。或者，本体粘合剂中的内聚失效表明粘合剂薄弱。然而，在粘附和粘合剂相间失效之间做出选择可能很困难17.已经开发了多种木材分析方法18.</li>
</ol>

<ol>
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作者没有什么可透露的。

程序中的关键步骤如下:基材的选择、样品的制备、设备的可操作性和样品的粘合。
基材必须坚固，缺陷最小（光滑，平整，无裂纹和变色）。未打磨，旋转切割的橱柜面单板为漫反射多孔硬木，首选糖枫（Acer saccharum）。打磨会产生不那么平坦和更破碎的表面7.在21°C和50%RH下调节单板至少一天后，切割20毫米乘117毫米的条带。通常将 5 毫克粘合剂均匀...

木材粘接是最大的单一粘合剂市场，并导致森林资源的有效利用。几个世纪以来，除家具结构外，实木被用于大多数应用，除了产品使用耐久性外，没有测试标准。然而，粘合木制品变得更加普遍，从胶合板和胶合木梁开始，使用生物基粘合剂1，2。虽然这些产品在当时令人满意，但用含有甲醛的合成粘合剂代替大豆、酪蛋白和血胶，改善了性能。这些新型粘合剂的更高性能导致了明确的测试标准，与大多数生物基粘合剂相比，具有更高的性能期望。合成粘合剂还可以粘合颗粒，包括形成刨花板的锯末、形成不同密度纤维板的纤维、提供定向刨花板和平行刨花材的木片、生产胶合板和层压单板木材的单板，以及指接木材、胶合木、交叉层压木材和木工字托梁3。这些产品中的每一个都有自己的测试标准4.因此，开发新型粘合剂可能需要大量的配方工作和广泛的测试，以确定是否有潜力开发足够的强度。这种耗时的测试以及木材性能和木材粘合的复杂性5限制了新型粘合剂的开发。此外，木材粘合剂在木材表面之间固化时的机械性能可能与整齐6不同。与木材接触固化允许粘合剂中的水和低分子量组分逸出，此外粘合剂与木材的复杂界面和化学相互作用3，7。
自动粘接评估系统（ABES）的开发对于了解木材粘合剂的强度发展非常有帮助，因为它快速且易于使用8，9，10。该系统是一个整体单元，用于粘合搭接剪切样品，然后测量断裂粘合所需的张力。它的实用性导致了使用该系统的ASTM方法D7998-19的开发11。虽然该系统最初设计用于测量粘合剂强度随温度和时间的变化，但它也可以测量固化粘合剂的耐热性，以及常规的粘合强度评估。尽管ABES测试是一种非常有用的初步筛选工具，但与任何测试一样，它有其局限性，并不能取代所有特定的产品强度和耐久性测试。
虽然有许多方法可以测量粘合剂的固化特性，从凝胶时间流变仪到差示扫描量热法、动态力学分析和多种类型的光谱法，但只有ABES方法测量机械强度的发展。这需要一台严格控制的仪器，用于加热、冷却和原位拉伸测试11。

<table><tbody><tr><td>Adhesive</td><td>Supplied by user</td><td></td><td></td></tr><tr><td>Balance</td><td>Normal supply house</td><td></td><td></td></tr><tr><td>Mark II Automated Bonding Evaluation System (ABES-II)</td><td>Adhesive Evaluation Systems Inc</td><td></td><td></td></tr><tr><td>Pneumatically driven sample cutting device</td><td>Adhesive Evaluation Systems Inc</td><td></td><td></td></tr><tr><td>Regular spatula</td><td>Normal supply house</td><td></td><td></td></tr><tr><td>Wood supply &amp;ndash; Hard maple</td><td>Besse Forest Products Group</td><td></td><td></td></tr></tbody></table>

standard test method astm d 7998-19 for the cohesive strength development of wood adhesives

固化木材胶粘剂的性能由于水分和其他组分对木材的损失，木材对胶粘剂固化的影响以及粘合剂渗透对木材界面的影响而难以研究;因此，对纯胶膜进行正常测试通常没有用。大多数木材粘合剂粘合强度的测试都是缓慢的，费力的，可能受到木材的强烈影响，并且不能提供有关固化动力学的信息。然而，测试方法ASTM D 7998-19可用于快速评估木材粘结强度。使用光滑、均匀和坚固的木材表面（如枫木面饰面）和足够的粘合压力可降低粘附力和木材强度对粘合强度的影响。此方法有三个主要应用。首先是提供一致的粘结强度发展数据。第二种是测量粘结搭接剪切样品的干湿强度。第三是通过快速评估热灵敏度并区分热软化和热降解来更好地了解粘合剂的耐热性。

该程序已广泛用于林产品实验室的蛋白质粘合剂研究。已经发现，低于2 MPa的湿粘合强度不足以保证进一步的木材粘合剂测试，而大于3 MPa是进一步测试的有希望的结果19。它已被证明可用于证明木材加工条件的敏感性12，13。更多的例子可以在弗里哈特的出版物中找到 7.该方法的精密度和偏差已经确定（研究报告RR:D14-...

Watch this Scientific Journal Video about Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives at JoVE.com

Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives

我们提出了一种程序，ASTM D7998-19，用于快速，更一致地评估木材上粘合剂的干强度和湿强度。该方法还可用于提供强度发展信息，作为温度和时间的函数或高达250°C的强度保持。

用于木材粘合剂内聚强度发展的标准测试方法 ASTM D 7998-19

The properties of cured wood adhesives are difficult to study because of the loss of water and other components to the wood, the influence of wood on the ...

standard-test-method-astm-d-7998-19-for-cohesive-strength-development

Research

JoVE Journal

Bioengineering

2.8K 次观看.  USDA, Forest Service. 我们提出了一种程序，ASTM D7998-19，用于快速，更一致地评估木材上粘合剂的干强度和湿强度。该方法还可用于提供强度发展信息，作为温度和时间的函数或高达250°C的强度保持。

视频: Standard Test Method ASTM D 7998-19 for the Cohesive Strength Development of Wood Adhesives

Preparation and Testing of Plant Seed Meal-based Wood Adhesives

Recently, the interest in plant seed meal-based products as wood adhesives has steadily increased, as these plant raw materials are considered renewable and environment-friendly. These natural products may serve as alternatives to petroleum-based adhesives to ease environmental and sustainability concerns. This work demonstrates the preparation and testing of the plant seed-based wood adhesives using cottonseed and soy meal as raw materials. In addition to untreated meals, water washed meals and protein isolates are prepared and tested. Adhesive slurries are prepared by mixing a freeze-dried meal product with deionized water (3:25 w/w) for 2 hr. Each adhesive preparation is applied to one end of 2 wood veneer strips using a brush. The tacky adhesive coated areas of the wood veneer strips are lapped and glued by hot-pressing. Adhesive strength is reported as the shear strength of the bonded wood specimen at break. Water resistance of the adhesives is measured by the change in shear strength of the bonded wood specimens at break after water soaking. This protocol allows one to assess plant seed-based agricultural products as suitable candidates for substitution of synthetic-based wood adhesives. Adjustments to the adhesive formulation with or without additives and bonding conditions could optimize their adhesive properties for various practical applications.

To facilitate the effort in seeking more economic and environment-friendly formulations of natural product-based wood adhesives, this work demonstrates the preparation and testing of plant seed-based wood adhesives. This protocol allows one to assess plant seed-based agricultural products as suitable candidates for the substitution of synthetic-based wood adhesives.

准备和植物种子膳食为基础的木材胶粘剂的测试

Recently, the interest in plant seed meal-based products as wood adhesives has steadily increased, as these plant raw materials are considered renewable ...

科研

环境科学

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 ...

工程学

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

Fiber reinforced polymer (FRP) anchors are a promising way to enhance the performance of externally-bonded FRPs applied to existing structures, as they can delay or even prevent debonding failure. However, a major concern faced by designers is the premature failure of the anchors due to stress concentration. Poor installation quality and preparation of the clearance holes can result in stress concentration that provokes this premature failure. This paper deals with an installation method that aims to reduce the impact of the stress concentration and to provide a proper quality control of the preparation of the drill hole. The method involves three parts: the drilling and cleaning of the holes, the smoothing of the hole edges with a customized drill bit, and the installation of the anchor itself, including the impregnation of the anchor dowel and its insertion. Anchor fans (the free length of the spikes) are then bonded to the external FRP reinforcement. For the end anchorage, and in the case of reinforcements with multiple plies, it is recommended that the anchor fan be inserted between two plies to assist the stress-transfer mechanism. 
The proposed procedure is complemented with a design approach for spike anchors, based on an extensive database. It is proposed that the design follow a number of steps, namely: selection of the anchor diameter and subsequent tensile strength of the connector (that is to say, the anchor before fanning out the free end), evaluation of the reduction in the tensile strength due to bending, provision of enough embedment to prevent slippage failure, and consideration of the number and spacing of anchors for a given reinforcement. In this sense, it should be noted that further research is needed in order to obtain a general expression for the contribution of spike anchors to overall bond strength of FRP reinforcements.

This manuscript presents a method for controlling the quality of installation for spike anchors designed to delay delamination of externally bonded fiber reinforced polymers. The protocol includes the preparation of the drill hole and the insertion process. The most influential parameters on the efficiency of the anchors are discussed.

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 ...

The Effect of Construction and Demolition Waste Plastic Fractions on Wood-Polymer Composite Properties

Construction and demolition waste (CDW), including valuable materials such as plastics, have a remarkable influence on the waste sector. In order for plastic materials to be re-utilized, they must be identified and separated according to their polymer composition. In this study, the identification of these materials was performed using near-infrared spectroscopy (NIR), which identified material based on their physical-chemical properties. Advantages of the NIR method are a low environmental impact and rapid measurement (within a few seconds) in the spectral range of 1600-2400 nm without special sample preparation. Limitations include its inability to analyze dark materials. The identified polymers were utilized as a component for wood-polymer composite (WPC) that consists of a polymer matrix, low cost fillers, and additives. The components were first compounded with an agglomeration apparatus, followed by production by extrusion. In the agglomeration process, the aim was to compound all materials to produce uniformly distributed and granulated materials as pellets. During the agglomeration process, the polymer (matrix) was melted and fillers and other additives were then mixed into the melted polymer, being ready for the extrusion process. In the extrusion method, heat and shear forces were applied to a material within the barrel of a conical counter-rotating twin-screw type extruder, which reduces the risk of burning the materials and lower shear mixing. The heated and sheared mixture was then conveyed through a die to give the product the desired shape. The above-described protocol proved the potential for re-utilization of CDW materials. Functional properties must be verified according to the standardized tests, such as flexural, tensile, and impact strength tests for the material.

Secondary material streams have been shown to include potential raw materials for production. Presented here is a protocol in which CDW-plastic waste as a raw material is identified, followed by various processing steps (agglomeration, extrusion). As a result, a composite material was produced, and mechanical properties were analyzed.

建筑与拆迁废塑料馏分对木聚合物复合性能的影响

Construction and demolition waste (CDW), including valuable materials such as plastics, have a remarkable influence on the waste sector. In order for ...

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, ...

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 ...

Evaluation of the Curing of Adhesive Systems by Rheological and Thermal Testing

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose the best option for any specific application. The proposed methodology for the curing characterization, based on thermal analysis and rheology, is described through the comparison of three commercial adhesives. The experimental techniques used here are Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Rheology. TGA provides information about the thermal stability and filler content, DSC allows the evaluation of some thermal events associated to the cure reaction and to thermal changes of the cured material when subjected to temperature changes. Rheology complements the information of the thermal transformations from a mechanical point of view. Thus, the curing reaction can be tracked through the elastic modulus (mainly the storage modulus), the phase angle and the gap. In addition, it is also shown that although DSC is of no use to study the curing of moisture curable adhesives, it is a very convenient method to evaluate the low temperature glass transition of amorphous systems.

An experimental methodology based on thermal and rheological measurements is proposed to characterize the curing process of adhesives with to obtain useful information for industrial adhesive selection.

流变和热测试对粘合系统固化的评价

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose ...

Twin-Screw Extrusion Process to Produce Renewable Fiberboards

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as source of mechanical reinforcement in fully bio-based fiberboards was developed. Various lignocellulosic crop by-products have already been successfully pre-treated through this process, e.g., cereal straws (especially rice), coriander straw, shives from oleaginous flax straw, and bark of both amaranth and sunflower stems.
The extrusion process results in a marked increase in the average fiber aspect ratio, leading to improved mechanical properties of fiberboards. The twin-screw extruder can also be fitted with a filtration module at the end of the barrel. The continuous extraction of various chemicals (e.g., free sugars, hemicelluloses, volatiles from essential oil fractions, etc.) from the lignocellulosic substrate, and the fiber refining can, therefore, be performed simultaneously.
The extruder can also be used for its mixing ability: a natural binder (e.g., Organosolv lignins, protein-based oilcakes, starch, etc.) can be added to the refined fibers at the end of the screw profile. The obtained premix is ready to be molded through hot pressing, with the natural binder contributing to fiberboard cohesion. Such a combined process in a single extruder pass improves the production time, production cost, and may lead to reduction in plant production size. Because all the operations are performed in a single step, fiber morphology is better preserved, thanks to a reduced residence time of the material inside the extruder, resulting in enhanced material performances. Such one-step extrusion operation may be at the origin of a valuable industrial process intensification.
Compared to commercial wood-based materials, these fully bio-based fiberboards do not emit any formaldehyde, and they could find various applications, e.g., intermediate containers, furniture, domestic flooring, shelving, general construction, etc.

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pretreatment on lignocellulosic biomass was developed, which leads to an increased average fiber aspect ratio. A natural binder can also be added continuously after fiber refining, leading to bio-based fiberboards with improved mechanical properties after hot pressing of the obtained extruded material.

双螺丝挤压工艺，以生产可再生纤维板

A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as ...

Determination of the Mechanical Properties of Flexible Connectors for Use in Insulated Concrete Wall Panels

This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete sandwich wall panels (ICSWPs). Such a standardized test does not exist, but several iterations of this and similar tests have been performed in the literature to varying degrees of success. Further, the tests in the literature are rarely-if ever-described in detail or discussed at length with respect to the testing, data analysis, or safety procedures. A test specimen configuration is recommended herein, and variations are discussed. Important mechanical properties are identified from the load versus displacement data, and their extraction is detailed. The use of test data for design, such as for determining the stiffness of the connectors, is briefly demonstrated to show how ICSWP deflection and cracking behavior may be calculated. The strength behavior of panels may be determined using the full load versus displacement curve or only the maximum connector strength. Shortcomings and unknowns are acknowledged, and significant future work is delineated.

We propose a testing protocol that can be combined with widely available analytical methods to assess the mechanical properties of shear connectors for use in the design of insulated concrete wall panels to predict full-scale insulated panel behavior.

用于隔热混凝土墙板的柔性连接器的机械性能测定

This document contains recommendations for performing a non-standard, double-shear test suitable for both continuous and discrete insulated concrete ...