Repair scheme for the damaged hull

The affect scheme for the hurtd hull can be processed fit in the following repair flow chartDamage AssessmentThe upond sandwich panel consists of both(prenominal) high strength GRP skin and skins separated by a low density, lower strength sparkle core. The cross section of hull in the damaged atomic number 18a is shown in Figure 1.Figure 1 Cross Section of Damaged HullSuch structures can be subjected to three damage scenarios. The damage can be limited to one skin ( flake A), to one skin and the core ( theatrical role B), or to both skins and the core ( pillow slip C). role A damage generally involves matrix cracking, fiber breakage and delaminations in the skin. The damage may or may not extend through the full boneheadedness of the skin. Type A damage can also include debonding of the skin from the core. Type B damage involves Type A damage to one skin combined with crushing or prune cracking of the core. Type C damage involves the analogous damage mechanisms as Type B except both skins are affected. Type C damage can fully penetrate the sandwich structure 1.Assuming the hole nearly 150mm in diameter is a though hole and damaged both skins and foam core, we have Type C damage. So we need to repair this damage according to Type C repair scenario. Since coming can be gained from both sides, The repair of Type C damage could be done.Repair Type DecisionRepair approaches are divided into non-patch, commonly fo minor defects, and patch, usually for major defects. repair repairs are also divided into Bonded External Patch RepairsExternal patches can be employed to repair laminates and skins of honeycomb panels of thickness up to about 2mm composites. The main problem with external patches is that, as in a single-lap joint, there is an eccentric consignment path that results in bending in the patch and peeling stresses in the adhesive and composite. Bonded Scarf or Flush RepairsScarf repairs are employed to repair thicker section satisfying than i s possible with external repairs and also where the repair must show minimum protrusion in a higher place the buffer surface. The main advantages of scarf joints are the uniform shear-stress distribution in the adhesive, and, due to lack of eccentricity in the load path, the low peel stress. Bolted External Patch RepairsBolted patches are generally employed for field repair of thick laminates where the shear stress overlookments exceed the capability of adhesives for external patch repairs and where the complexity of repair implementation and somatic removal requirements. Moisture problems also limit field applications of bonded repairs in thick composites. Bolted repairs are well worthy to the repair of battle damage since they are easy to apply by unskilled personnel and require minimum facilities. 2Both bonded and bolted repair methods could be applied to repair marine sandwich structures. Bonded repairs were considered to be light in weight and distribute the load to a gre ater extent evenly over a wider field of view. However, they require metrical surface preparation, are difficult to inspect and are more(prenominal) difficult to perform correctly. Bolted repairs are more easily carried out and require minimal surface preparation. However, they add bulk and weight and require holes to be drilled through the structure which can introduce further damage and create stress concentrations. Additionally, bolted repairs are more difficult to implement on sandwich structures and need to be water-tight 3.Since the yacht has been rammed well above the water line, it could continue its operation with small leakages. So repair could be done in facilities. as well since it has been rammed there is no stress cracking due to design considerations. Same section could be performed shear stress requirements do not exceed the capability of adhesives. According to these considerations, bonded scarf repair would be more applicable.Permanent Composite Structure Repai rFor all bonded repairs, removal of all damaged material jump at the centre of the damaged region and surface preparation is of vital importance.Damage to sandwich structures a lot involves damage to the core material. The damaged core can be filled either with a spumy adhesive, a laminate or a new core section bonded in place. The latter method is usually adopted as it best restores the properties of the sandwich structure.The approved general guidelines for laminate and sandwich repairs should be followed. These repair trading operations should be carried out in a workshop areas to ensure high quality repairs.The repair of Type C damage to GRP/foam sandwich structures requires the replacement of both skins and the core.The repair procedure for Type C damage is shown in Figure and described following 41. Remove damaged material.a) Remove the damaged skins, work from the centre of the damaged regionon both sides outwards until sound material is encountered.b) Remove the undeci ded damaged core.2. Taper sanda) Prepare the foam coreb) Sand the edges of both skins to a signal per layer providing a scarf angle3. Install the replacement foam.a) Use a paste adhesive designed to bond foam. However, instead of using vacuum, the adhesive was injected into the bondline using a caulking gun.b) Use a support plate where required.c) Use the appropriate grade of foam.d) Use the minimum amount of adhesive.4. Replace the skins.a) Use the same number of layers as the original skin.b) Apply one extra layer of GRP.5. Replace the skins on opposite side.a) Use the same number of layers as the original skin.b) Apply one extra layer of GRP. persona Check / NDTFor comprehensive reappraisal of repaired part, Non Destructive Test (NDT) can ve used. The inspector should examine the quality of the repaired area and particular attention should be given to the interface between the original part and the repaired area.Usual inspection methods use some form of ultrasonic test equipm ent where the reflection of the ultrasonic sound waves detect and trace any damaged areas or faults 4.