Issue 65

V. S. Uppin et alii, Frattura ed Integrità Strutturale, 65 (2023) 17-31; DOI: 10.3221/IGF-ESIS.65.02

IM7/8552 Carbon fiber/epoxy prepregs with ply block thickness of 0.25mm and overlap length of 8mm[44]. In introducing the pseudo ductility in interfacial slip laminated composites[43-44], platelet length and its thickness play a key role.

Figure 20: The schematic of the interlayer discontinuous composite [43]. The pseudo ductile failure was successfully demonstrated using intermingled and hierarchical hybrid composites [45-46]. The maximum pseudo ductile strain of 1.1% with a tensile modulus of 110 MPa was observed in high modulus Carbon/E glass intermingled hybrid composite [45]. The pseudo ductile response of hierarchical hybrid composites is depending on the stress-strain response of intermingled hybrid composite and the volume fraction of LE fiber [46]. Improved specific strength and stiffness were noticed in micro and nano-cellulose-filled polymer composites [47]. The pseudo ductile strain of 0.04% was noticed in Glass Cellulose epoxy composite for a surface coating density of 319.08 g/m2 [48]. The uniform surface coating of micro-sized Cellulose fibers on Glass UD plies leads to gradual failure. High Performance-Discontinuous Fiber (HiPerDiF) method is a new high-speed process to produce discontinuous fiber architectures with high volume fraction. It allows the manufacture of tow or tape-type prepregs with highly aligned reinforcements directly from short fibers rather than from pre-existing tows. [45,46,49-50] The HiPerDiF method provides 67% of fibers were aligned with a deviation of േ 3 0 and performed better in terms of mechanical properties concerning continuous fiber composites [49]. The volume fraction of the recycled carbon fiber (rCF) in intermingled rCF/vCF composites and in interlaminated (sandwiching the intermingled rCF/vCF composite in between UD Glass fiber layers) hybrid composites play a major role in inducing the pseudo ductility [50]. The hybrid Carbon fiber/Self-Reinforcement Polypropylene composite has a gradual failure in tension mode and it depends on cut length, cut friction, and step length of Carbon prepreg [51]. Gradual failure associated with the pseudo ductile strain of greater than 10% was claimed in hybrid composites of Aligned Discontinuous Carbon Fiber (ADCF) and SRPP[52]. Brittle to ductile phase transition was observed for the range of 6.9% to 8.6% of total volume fraction (Vf) in randomly orientated discontinuous Carbon fiber/self-reinforced Polypropylene composites. But pseudo ductility associated with a failure strain of 10 % was achieved for the Vf of Carbon fiber lower than 7%[53]. The concept of interleaving helps to delay the catastrophic failure in UD composites as compared to interlayer composites [54].  The favorable pseudo ductile stress-strain response has been successfully demonstrated with different mechanisms by various research investigators. But, the scaling effect on pseudo ductile response is yet to explore. Hence, in the present study, a gradual failure similar to that of metals was achieved by developing hybrid laminates using thin plies.  The reorientation of fibers towards the loading direction and fiber fragmentation was successfully demonstrated by existing analytical and experimentation methods. Dispersion of orientation showed that the developed composites were free from edge delamination. But, a Bidirectional stress-strain response is yet to explore.  The HiPerDiF method helps to develop laminates by aligning the short fibers in a specific direction with a higher fiber volume fraction.  The HiPerDuCT program also showed newer techniques to develop high-performance composite laminates to overcome catastrophic failures. C ONCLUSIONS

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