Inter laminar crack initiation and propagation is amajor failure mode in structural compositeapplications. Manufacturing induced fiberdiscontinuities within a laminate composite act asstress concentrations and initiation sites of suchdelamination cracks. A local inter laminarreinforcement method is proposed to mitigate theeffects of manufacturing induced stress concentrationsand increase the local fracture toughness of thecomposite. A through thickness laser fusion joiningprocess is developed for the out of plane reinforcementof glass fiber pre-forms used in the vacuum infusionfabrication of thick composite structures. Laser joiningis achieved through a thermal fusion process whichjoins fibers within a single bundle and fiber bundlesbetween successive woven fabric layers. Coupled twophase heat transfer and viscous flow modeling iscarried out to simulate the temperature andmorphology of the joining process underexperimentally observed conditions. Mode I fracturetoughness of through thickness reinforced compositelaminates is measured experimentally and compared toun-reinforced plane weave glass composites. Laserfusion joint effects on mode I crack propagation andfracture dynamics are observed through high resolutionimaging during the crack propagation process and postmortem imaging of the fracture surface. Increaseddelamination resistance of laser joined composites isfound to be a function of the joint thickness.
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