Modulus Measurement for Prepreg-based Discontinuous Carbon Fiber/Epoxy Systems
Modulus Measurement for Prepreg-based Discontinuous Carbon Fiber/Epoxy Systems
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DOI：
10.1177/0021998309343028
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发表时间：
2009-09-01
影响因子：
2.9
通讯作者：
Stickler, Patrick B.
中科院分区：
文献类型：
--
作者：
Feraboli, Paolo;Peitso, Elof;Stickler, Patrick B.
用几种方法测量了用剪切单向预浸带压缩成型的不连续碳纤维/环氧复合材料的弹性模量。这种类型的材料形式的商业应用已经存在，例如heexcel HexMC (R)。虽然这种材料的平均弹性模量已被证明与连续纤维准各向同性基准的弹性模量一样高，但其非均匀性使其在使用应变计或伸长计进行测量时产生高达19%的变化。这种现象将归因于制造过程的可变性，如果不是因为强度变化要低得多，最大值为9%。为了评估观察到的变化是否是测量技术的结果，而不是材料性能的实际变化，在系统地改变应变片长度和位置时进行了一系列拉伸试验。然后将测量值相对于彼此以及沿着试样的长度和相对侧的多个延伸计读数进行比较。数字图像相关（DIC）技术用于进一步了解所观察到的现象，并且已经证明它是获得全场应变测量的基础，它比任何传统的测量技术都更具可重复性。此外，DIC表明，试样表面存在复杂的应变分布，沿试样宽度和长度变化很大，这与子结构的非均匀性有关。
The elastic modulus of discontinuous carbon fiber/epoxy laminates produced by compression molding of chopped unidirectional prepreg tape is measured by several means. Commercial applications for this type of material form already exist, such as Hexcel HexMC (R). Although the average elastic modulus of this material has been shown to be as high as that of the continuous fiber quasi-isotropic benchmark, its non-homogenous nature gives rise to variations as high as 19% in the measurement by means of strain gage or extensometer. This phenomenon would be attributed to the variability of the manufacturing process, were it not for the fact that strength variation is much lower, with a maximum of 9%. In order to assess whether the variation observed is a result of the measurement technique and not an actual variation in material properties, a series of tensile tests is conducted while systematically varying strain gage length and location. The measurements are then compared relative to each other as well as to multiple extensometer readings along the length and opposite sides of the specimen. Digital image correlation (DIC) technique is used to gain further insight on the observed phenomena, and it has shown to be fundamental to obtain a full-field strain measurement, which is more repeatable than any of the traditional measurement techniques. Furthermore, DIC shows that complex strain distributions exist on the surface of the specimen, varying greatly along the width and across the length of the specimen, and these are associated to the non-homogeneous nature of the sub-structure.