An Experimental Characterisation on Rectangular Z-Pinned Parameters in the Dynamic Modal Responses of Reinforced Composites

A great deal of research has been carried out and demonstrates that through-thickness reinforcement in the form of z-pins can greatly improve the mechanical properties of carbon fiber composite laminates. The modal responses of composite laminates reinforced through the thickness with rectangular z-pin sizes and area density insertion design variables generated from the Design of Experiments (DOE) are studied with free and forced vibration tests being carried out. Although many studies have reported the use of experimental, statistical, numerical, and computational tools applied to composite structures, to date, very few have focused on the application of analysis of variance (ANOVA) to analyze the experimental data and artificial neural networks (ANN) as a technique to predict the modal responses of z-pinned composites. The experimental results indicated that, in most cases, there was an increase in the natural frequency, which highlighted the reduction, from approximately 60% to 70%, in the amplitude of vibration for all specimens with z-pin reinforcement in comparison to the unpinned. Furthermore, the experimental data compared with the statistical results pointed out that z-pins had a positive influence on increasing and decreasing natural frequency and forced vibration amplitude, respectively, of z-pinned composites compared to reinforced and trained ANNs, and the experimental data presented very good agreement with the experimental tests carried out in this investigation for predicting modal response.