Mechanical Behavior of Patched Steel Panels at Elevated Temperatures

Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of ship hull parts to optimize expenditure.This is relevant in view of the difficulty in reaching farthest corners in ballast tanks,fuel storage tanks,cofferdams etc.Prior maintenance of the deck and hull parts save a considerable amount of the owner's budget.A portable technology like patching becomes more handy and economic.Performance of both unpatched and patched samples during dynamic loading conditions being examined in the present investigation.The high strength steel panels with a dimension of 70mm×15mm×3mm were edge cracked for lengths of 4mm and 7mm,with width of 1mm for both.The edge cracked high strength steel panels are repaired with composite patches using GFRP(glass fiber reinforced plastic),CFRP(carbon fiber reinforced plastic)and AFRP(aramid fiber reinforced plastic).The patching was done by 3 and 5 layered and impact tested by Charpy impact tester at ranges of high temperatures.The amount of energy absorbed in the impact is converted to dynamic fracture toughness values and compared for evaluating the performance of FRP(fiber reinforced plastics).Finite element analysis was done for evaluating the stress intensity factors at different types of patching and testing conditions.Comparatively the AFRP patched samples showed better dynamic fracture toughness values at different temperatures.

含预埋缺陷复合材料帽形加筋壁板界面失效研究

本文对复合材料帽形加筋壁板后屈曲破坏过程中粘接面失效问题开展了研究。首先设计并完成了无缺陷、含预埋缺陷的帽形单筋板四点弯曲试验以表征加筋壁板典型区域的后屈曲失效;然后基于数值模拟方法,利用内聚力模型(CZM)对无缺陷和含预埋缺陷试件弯曲受载时的界面脱黏进行了渐进破坏分析。结果表明:采用cohesive单元和考虑厚度方向压缩影响的层间失效准则方法建立有限元模型可以很好地模拟复合材料加筋结构界面脱黏;凸缘-蒙皮预埋缺陷对帽形加筋壁板起裂载荷基本没有影响,筋条内角和填充区界面预埋缺陷会显著降低帽形加筋板的承载能力,但起始裂纹均发生在筋条内角和填充区的粘接界面。