Understanding Composite Compression 测试 Methods

复合材料的压缩性能受树脂和纤维树脂界面的影响, and often determine the overall design, 大小, and weight of a part. 复合材料压缩试验是筛选新材料和保持质量控制的关键.   

复合材料压缩试验的目标是将压缩力驱动到均匀的规范区域，而不会在试样的其他部分造成过早破坏或不适当的破坏模式. As composite materials continue to become more advanced, 获得执行压缩测试的通用标准提出了挑战.  

Composite testing 通常遵循ASTM或ISO方法，但组织有时会开发专有的测试方法. The various techniques may present differing results, 因此，仔细记录测试方法和结果对于了解材料特性至关重要. 

现有的复合材料压缩试验方法可分为三类, depending on how materials are loaded on the test frame:

• 弯曲
• 剪切
• End-loaded

ASTM Bend composite compression test 

ASTM D5467和ASTM D7249记录了复合材料压缩性能的两种最常见的弯曲试验方法. 

Bend loading utilizes a sandwich beam construct for testing, where one face is in compression, and the opposite face is in tension. 抗压面板通常采用较薄的面板，以便梁在受压时首先失效. 

When constructing the specimen, 跨越, core material, 厚度, 并选择胶粘剂，以确保达到正确的失效模式(压缩面). 压缩面上的应变片用于测量模量, Poisson’s ratio, and strain to failure.  

剪切 loaded compression testing ASTM D3410

Some methods apply a shear load to the gauge area of the specimen. One of the first methods, commonly called Celanese compression, 将样品装入由锥形夹具夹住的楔子中. The specimens are rectangular and usually tabbed. 塞拉尼斯压缩最初在ASTM D3410标准中提到，但此后已被删除. The Celanese specimens were generally limited to 0.25” in width by the ASTM Standard and 10mm by ISO 14126.  The overall length is 5.5 inches with a 0.5” unsupported length. 

Though Celanese compression is generally considered obsolete, it is sometimes requested to compare to historical data. For this method, 材料厚度是一个关键的考虑因素，必须在规定的窄范围内, which allows proper seating of the wedges with the cones. 

当前版本的ASTM D3410通常被称为IITRI方法, 这种方法是为了弥补塞拉尼斯方法的缺点而发展起来的. IITRI的夹具又大又重，在极端温度下使用会带来挑战. Specimens used for this method may be up to 1 inch wide and 5.5 inches long with 0.5 inches of unsupported length. The wedges are loading through a rectangular seat, 因此，标本的整体厚度不像塞拉尼斯方法那样重要. 然而，测量区域内的材料必须足够厚以防止欧拉屈曲. 大多数数据使用者都同意，由于材料中存在显著的无支撑长度，因此测试提供了压应力结果. 

End-loading compression testing ASTM D695

塑料传统上使用ASTM D695中描述的末端加载方法进行测试. 这种方法允许端加载的棱镜是方形或圆形的横截面. 也可以使用狗骨形状的扁平试样，并将其装入防止屈曲的侧支撑夹具中.   

The Suppliers of Advanced Composites Materials Association, SACMA, 采用并形式化了使用带有0的标签样本的im体育平台app下载实践.188-inch gauge length. 试样通常具有较高的表观抗压强度，因为测尺长度较短. 由于所有这些试件都是端载的，因此为了得到相关的结果，两端必须是平且平行的. 如果试样失效或两端出现扫把现象，则认为试验结果无效.  

Additionally, 如果施加在固定试样的螺栓上的扭矩水平过高, test results may be invalid. 由于短规长度和可变性的摩擦从侧面支持夹具, further standardization of this method has been slow.   

剪切和端载压缩试验的组合

持续的夹具开发产生了组合式加载压缩夹具. ASTM D6641 describes the appropriate fixture and test method. 
Like the earlier methods, the nominal specimen is 5.5 inches long with a 0.5 inch of unsupported length. By clamping the ends of the fixture between square ends, 试件受端载荷和剪切载荷组合作用. 

组合加载压缩夹具比IITRI夹具更小，更容易使用. 小心地将夹具螺栓扭到均匀的指定水平是必不可少的. 试样是应变测量背靠背压力表监测欧拉屈曲. 弯曲百分比与测试数据一起报告，可用于排除异常数据.

对于复合材料设计，通常需要用孔的压缩值来模拟应力隔水管. Open hole compression test ASTM D6484 is such a method for obtaining those values.

Comparison of composite compression test methods 

结论 

复合压缩测试方法因夹具设计、加载技术和试样尺寸而异. 而复合材料的抗压强度测试尚无统一的标准, 我们的专家可以帮助您选择将产生所需结果的测试方法. im体育APP孜孜不倦地工作以确保您的复合材料适合用途.

如果您需要复合材料压缩测试或对哪种方法适合您的材料有疑问, 请 contact us today.