OPTIMAL-DESIGN OF COMPOSITE HOOD WITH REINFORCING RIBS THROUGH STIFFNESS ANALYSIS

Fiber glass reinforced composites like sheet molding compounds (SMC) h ave recently been widely used in the fabrication of two-piece automobi le hoods for passenger cars. In the present investigation, a one-piece composite hood with reinforcing ribs was optimally designed and manuf actured by resin transfer molding in order to reduce manufacturing cos t. In order to obtain the optimal design, stiffness analyses for defle ctions due to self-weight, oil canning, and torsion test conditions we re carried out by applying the ABAQUS/Standard program. Based on these analyses, the thickness dimension of the composite hood required to m aintain a stiffness comparable to a conventional steel hood was determ ined. For optimization studies of the weight reduction of the currentl y proposed one-piece composite hood with reinforcing ribs, IDESIGN pro gram was employed. Based on a recursive quadratic programming techniqu e, the thickness dimensions of the reinforcing ribs were optimized. Th e deflection ratios between fiber glass reinforced composite and conve ntional steel hoods were minimized in the optimization studies. From t he present studies, it was found that the weight saving effect obtaine d by introducing the optimally designed one-piece composite hood was 3 7% compared to the conventional steel hood. This ranged approximately from 30 to 40% for composite hoods manufactured by resin transfer mold ing, depending on the composite materials used. Through these studies, it was confirmed that the one-piece composite hood was a preferable d esign and manufacture, compared to currently used composite hood made in two pieces, in terms of weight reductions and manufacturing cast wi thout losing the stiffness required. Copyright (C) 1997 Elsevier Scien ce Ltd.