Yasaee, MehdiBigg, LawrenceMohamed, GalalHallett, Stephen R.2017-01-042017-01-042016-11-10Yasaee M, Bigg L, Mohamed G, Hallett SR, Influence of Z-pin embedded length on the interlaminar traction response of multi-directional composite laminates, Materials & Design, Volume 115, 5 February 2017, Pages 26–360264-1275http://dx.doi.org/10.1016/j.matdes.2016.11.025https://dspace.lib.cranfield.ac.uk/handle/1826/11203The work in this paper investigated the performance of composites through-thickness reinforcing Z-pins as a function of their embedded length in pre-preg laminates. Single Z-pins were inserted into multidirectional carbon fibre laminates with increasing thicknesses, corresponding to embedded lengths from 1 mm to 10 mm and tested through a range of mixed mode displacement ratios to investigate their interlaminar bridging traction response. Detailed analysis of the tests revealed a non-linear tangential friction response and its strong dependence on the embedded length of the Z-pin. Using a new power law empirical relationship for the tangential friction force per unit length, a modified Z-pin bridging traction analytical model was proposed, giving good predictions of the full mixed mode bridging mechanics of a CFRP Z-pin in a multidirectional composite laminate of varying thickness. Several characteristics of the model are discussed and their influence on predicting the Z-pin bridging energy response have been analysed.enAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/Structural compositesZ-pinsDelaminationFracture toughnessAnalytical modelArticle15930383