Effect of specimen width on strength in off-axis compression tests
Paper in proceeding, 2016

Compression tests have been performed according to ASTM D6641 to check whether 12 mm is a sufficient width for off-axis tests of a unidirectional Non Crimp Fabric (NCF) reinforced carbon-fibre composite. Various off-axis angles are tested in a larger context and it is important to establish a representative material volume. The test matrix consists of two different widths for two off-axis cases, 15° and 20° with a total sample size of 24. A two-sample T-test is performed for each off-axis angle to check if there is a statistically significant difference of the compressive strength between specimens with different widths. The null hypothesis, that there is no difference between the mean values is tested with a double-tailed test on a 5 % significance level. Neither of the cases may be rejected, i.e. there is no statistically significant difference on the 5 % level. The 15° off-axis case returns a p-value of 7.4 % and the 20° off-axis case gives a p-value of 21.3 %. It can be concluded that the effect is small and not statistically significant. It means that remaining off-axis testing in the larger context can proceed with the nominal width of 12 mm.


Dennis Wilhelmsson

Chalmers, Applied Mechanics, Material and Computational Mechanics

Leif Asp

Chalmers, Applied Mechanics, Material and Computational Mechanics

Renaud Gutkin


Fredrik Edgren

GKN Aerospace Services

Proceedings of 17th European Conference on Composite Materials, ECCM17

978-300053387-7 (ISBN)

Areas of Advance


Materials Science

Subject Categories

Aerospace Engineering

Composite Science and Engineering



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