Effect of specimen width on strength in off-axis compression tests

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 representativematerial volume. The test matrix consists of two different widths for two off-axis cases, 15\ub0 and 20\ub0 witha total sample size of 24. A two-sample T-test is performed for each off-axis angle to check if there is astatistically 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 teston a 5 % significance level. Neither of the cases may be rejected, i.e. there is no statistically significantdifference on the 5 % level. The 15\ub0 off-axis case returns a p-value of 7.4 % and the 20\ub0 off-axis casegives a p-value of 21.3 %. It can be concluded that the effect is small and not statistically significant. Itmeans that remaining off-axis testing in the larger context can proceed with the nominal width of 12 mm