含有泡沫铝芯的复合板弯曲断裂行为的原位研究

IN-SITU STUDY ON BENDING FRACTURE OF SANDWICH AND MULTILAYER BEAMS CONTAINING ALUMINUM FOAM CORE

对由泡沫金属铝芯和金属面板组成的三层和多层复合板四点弯曲条件下的变形和断裂行为进行原位观察。研究结果表明:在弯曲条件下,复合板有两种基本的破坏方式,一种是复合板表面凹陷(Indentation,ID),它是表面局部集中塑性变形的结果;另一种是泡沫铝内芯切断(Core shear,CS),它是内芯在最大切应力作用下的破坏。对一个给定的三层复合板,当凹陷破坏的载荷极限FID大于内芯切断的载荷极限FCS时发生内芯切断式破坏,反之发生表面凹陷式破坏。对于多层复合板,破坏方式受金属面板制约,不能直接应用三层板的破坏判据。若三层板发生凹陷型破坏,具有与三层板相同金属面板厚度的多层复合板发生凹陷加内芯切断的混合型破坏。当三层板只发生内芯切断型破坏时,具有与三层板相同金属面板厚度的多层复合板完全发生内芯切断型破坏。

Deformation and damage mechanisms of sandwich and multilayer beams composed of aluminum foam core and metallic face sheets under four-point bending condition are investigated by in-situ surface displacement analysis software （SDA）. Plastic collapse oft.he sandwich beams within the foam core is by. two basic modes： One is indentation （ID）, which is resulted from concentrated deformation on the beam beneath the loading rollers; The other is core shear （CS） that is controlled by maximum shear stress on the center of beam. Beams tend to fail in ID mode when FID, the loading limit of the indentation, is less than Fcs, the loading limit of the core shear. Conversely, CS mode takes places. This criterion, however, can not be used directly to judge failure mode of the rnultilayer beams. Mixed failure ID ＋ CS mode takes place when face sheets of multilayer beams displayed similar ID characteristic in sandwich beams. Face sheets that do not display ID characteristic in sandwich lead to failure in multilayer beams in pure CS mode.