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The aim of this research is to manufacture intermingled hybrid composites using aligned discontinuous fibres to achieve pseudo-ductility. Hybrid composites, made with different types of fibres that provide a balanced suite of modulus, strength and ductility, allow avoiding catastrophic failure that is a key limitation of composites. Two different material combinations of high strength carbon/E-glass and high modulus carbon/E-glass were selected. Several highly aligned and well dispersed short fibre hybrid composites with different carbon/glass ratios were manufactured and tested in tension in order to investigate the carbon ratio effect on the stress-strain curve. Good pseudo-ductile responses were obtained from the high modulus carbon/E-glass composites due to the fragmentation of the carbon fibres. The experimental results were also compared with an analytical solution. The intermingled hybrid composite with 0.25 relative carbon ratio gave the maximum pseudo-ductile strain, 1.1%, with a 110 GPa tensile modulus. Moreover, the initial modulus of the intermingled hybrids with 0.4 relative carbon ratio is 134 GPa, 3.5 times higher than that of E-glass/epoxy composites. The stress-strain curve shows a clear "yield point" at 441 MPa and a well dispersed and gradual damage process

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This paper proposes a new FE-based approach for modelling all of the possible damage modes in glass/carbon UD hybrid laminates in tensile loading. The damage development is modelled by two sets of cohesive elements, (i) periodically embedded in the carbon layer for modelling carbon fibre failure and (ii) at the glass/carbon interface to capture delamination. The analysis is stopped when the glass layer failure is predicted by integrating the stress distribution over the glass layer to calculate an equivalent stress for unit volume of the glass. The proposed method is validated against the experimental results and then used to simulate the progressive damage process of other hybrid configurations and finally produce a damage-mode map for this material set. The method can easily be applied to other hybrids to assess their performance by producing damage-mode maps.

A variety of thin-ply pseudo-ductile unidirectional interlayer hybrid composite materials comprising high modulus and high strength thin carbon fibre/epoxy prepregs was investigated. The central high modulus carbon plies fragmented and delaminated stably from the outer high strength carbon layers under uniaxial tensile loading in the hybrid materials. These pseudo-ductility mechanisms resulted in favourable, metal-like stress-strain responses featuring pseudo-yielding, a stress plateau and further rise in stress before final failure. The high initial elastic modulus of up to 240 GPa, the early warning and the wide safety margin between damage initiation and final failure make the new hybrids advantageous for safety-critical applications where ultimate performance and low density are key design drivers. A hybrid effect with an increase in the failure strain of the high modulus carbon material was highlighted for very thin plies

This study focuses on the clustering of the indentation-induced interlaminar and intralaminar damages in carbon/epoxy laminated composites using Acoustic Emission (AE) technique. Two quasi-isotropic specimens with layups of [60/0/-60] 4S (is named dispersed specimen) and [60 4 /0 4 /-60 4 ] S (is named blocked specimen) were fabricated and subjected to a quasi-static indentation loading. The mechanical data, digital camera and ultrasonic C-scan images of the damaged specimens showed different damage evolution behaviors for the blocked and dispersed specimens. Then, the AE signals of the specimens were clustered for tracking the evolution behavior of different damage mechanisms. In order to select a reliable clustering method, the performance of six different clustering methods consisting of k-Means, Genetic k-Means, Fuzzy C-Means, Self-Organizing Map (SOM), Gaussian Mixture Model (GMM), and hierarchical model were compared. The results illustrated that hierarchical model has the best performance in clustering of AE signals. Finally, the evolution behavior of each damage mechanism was investigated by the clustered AE signals with hierarchical model. The results of this study show that using AE technique with an appropriate clustering method such as hierarchical model could be an applicable tool for structural health monitoring of composite structures.