الفهرس 
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Abstract
This work examines the effect of bridging phenomena, first in composite healing and the extent to which it can be considered a beneficial artifact, and second in its effect on fracture toughness at different strain rate in the quasi-static range. Extrinsic non-autonomic self-healing of composite materials is demonstrated in two cases of cracks, one of which exhibits bridging phenomena due to sample formation and the other of which exhibits normal cracking without bridging. Experiments for mode I composite fracture failure was carried out on a double cantilever beam (DCB) specimen. The test specimen, which was made of unidirectional E-glass fibre and polyester resin, was formed using an open wooden mould technique. Both cases required manual intervention, with the healing agent being manually catalysed and then injected into the delamination area. An experimental study was conducted to determine the function of fibre bridging prior to and following healing; samples with and without bridging were compared. Non-bridging specimens have an average healing efficiency of 101 percent, with a maximum healing efficiency of 113.5 percent, whereas bridging specimens have an average healing efficiency of 112.4 percent, with a maximum healing efficiency of 132.6 percent. The results indicate that crossing fibres play a significant role in bridging cases, increasing the efficiency of crack healing and demonstrating the transcendence of bridging healing. The mode I delamination behaviour of unidirectional glass/epoxy composites is investigated experimentally at strain rates of 1, 3, and 5. When comparing variation between fracture toughness GIC values at 1 mm/min and GIC at 3 mm/min, the average variation is 30% increasing. However, the average variance in GIC between 3 mm/min and 5 mm/min is 11% increasing. The fracture toughness has got an increasing effect when increasing strain rate at a quasi-static range the same comparison is made with bridging specimens for 1 and 3 mm/min strain rate, the average variation is 37 % reduction, which contradicts the non-bridging case. Fiber bridging causes the measured fracture toughness to be overestimated while concealing the strain rate effect. The specimens with a 5 mm/min strain rate, on the other hand, did not produce the expected bridging and instead operated as non-bridging specimens. The viscoelastic nature of composites can be associated to these findings.