A study on the compressive strength of thick carbon fibre-epoxy laminates
A study on the compressive strength of thick carbon fibre-epoxy laminates
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DOI：
10.1016/j.compscitech.2006.12.001
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发表时间：
2007-08-01
影响因子：
9.1
通讯作者：
Soutis, C.
中科院分区：
文献类型：
--
作者：
Lee, J.;Soutis, C.
本文介绍了一种实验研究，检查试样尺寸的IM 7/8552碳纤维/环氧树脂单向层合板（UD）的轴向压缩强度的影响。层压板标距长度、宽度和厚度从10 mm x 10 mm x 2 mm的基线样本尺寸增加2和4的比例因子。在所有情况下，强度随着样本尺寸的增加而降低，最大降低45%，轴向模量未观察到显著变化。光学显微照片表明，破坏机制是纤维微屈曲伴随基体开裂和劈裂。大多数试样，尤其是较厚试样的失效位置是翼片终止和量规部分开始的位置，这表明由于几何不连续性而产生的高局部应力导致过早失效，从而降低了抗压强度。还在压缩中测试了两种通用的准各向同性多方向（MD）铺层，一种具有阻挡层[45（n）/90（n）/-45（n）/0（n）]（s），另一种具有分布层[45/90/-45/0]（ns），其中n = 2、4和8。使用的材料和试验夹具与具有三种不同规格截面（30 mm x 30 mm、60 mm x 60 mm和120 mm x 120 mm）的单向样本相同，以确定任何尺寸效应。强度结果表明，没有证据表明的尺寸效应时，试样按比例放大使用分布层，并与2毫米厚的试样。除了8 mm样本外，所有阻塞样本的抗压强度与子层压样本相似，由于样本切割过程中引入的大量基质开裂，8 mm样本的抗压强度降低了30%。约1710 MPa的计算的单向失效应力（多方向层压件内的0度层片的）略高于2 mm厚的基线单向试样的1570 MPa的平均测量值，这表明对于较厚的试样观察到的降低的单向强度是测试假象。似乎发现较厚试样（> 2 mm）的单向压缩强度受到端部翼片处产生的应力集中和制造引起的缺陷（如纤维未对准、层板波纹和空隙）的限制。(c)2006爱思唯尔有限公司保留所有权利。
This paper describes an experimental study that examines the effect of specimen size on the axial compressive strength of IM7/8552 carbon fibre/epoxy unidirectional laminates (UD). Laminate gauge length, width and thickness were increased by a scaling factor of 2 and 4 from the baseline specimen size of 10 mm x 10 mm x 2 mm. In all cases, strength decreased as specimen size increased, with a maximum reduction of 45% no significant changes were observed for the axial modulus. Optical micrographs show that the failure mechanism is fibre microbuckling accompanied by matrix cracking and splitting. The location of failure in most specimens, and especially the thicker ones, is where the tabs terminate and the gauge section begins suggesting that the high local stresses developed due to geometric discontinuity contribute to premature failure and, hence, reduced compressive strength. Two generic quasi-isotropic multi-directional (MD) lay-ups were also tested in compression, one with blocked plies [45(n)/90(n)/-45(n)/0(n)](s) and the other with distributed plies [45/90/-45/0](ns) with n = 2, 4 and 8. The material used and test fixture was identical to that of the unidirectional specimens with three different gauge sections (30 rum x 30 mm, 60 mm x 60 mm and 120 mm x 120 mm) to establish any size effects. Strength results showed no evidence of a size effect when the specimens are scaled up using distributed plies and compared to the 2 mm thick specimens. All blocked specimens had similar compressive strengths to the sublaminate ones apart of the 8 mm specimens that showed a 30% reduction due to extensive matrix cracking introduced during the specimen's cutting process. The calculated unidirectional failure stress (of the 0 degrees ply within the multidirectional laminate) of about 1710 MPa is slightly higher than the average measured value of 1570 MPa of the 2 mm thick baseline unidirectional specimen, suggesting that the reduced unidirectional strength observed for the thicker specimens is a testing artefact. It appears that the unidirectional compressive strength in thicker specimens (> 2 mm) is found to be limited by the stress concentration developed at the end-tabs and manufacturing induced defects such as fibre misalignment, ply waviness and voids. (c) 2006 Elsevier Ltd. All rights reserved.