纤维金属层板成形极限测试的新试样设计

New specimen design for forming limit test of fibre metal laminates

在拉深成形过程中,纤维金属层板常见的失效模式主要有起皱、纤维拉伸断裂以及界面分层。受金属拉深成形测试的启发,经研究,当纤维金属层板以纤维拉伸断裂与界面分层失效为主要的失效模式时,可以将纤维应变引入到成形极限图中。但是,由于用于拉深测试的传统金属条状试样形状会干扰纤维金属层板内纤维应变的计算,因此,本研究设计了一种新型切槽形状试样。通过对比传统的条状试样和新型切槽试样的成形试验以考察玻璃纤维/聚酰胺树脂(Gf/PA)复合材料-铝合金层板的成形性能。研究结果表明:所设计的新型切槽试样可以将纤维计算的应变水平控制在6%以内,通过对不同纤维应变区间的分类,可以明显地区分出层板拉深成形的破坏形式是纤维拉伸断裂或者界面分层。研究得出,切槽试样的成形极限图包含3个区域:成形安全区-纤维拉伸断裂区-界面分层区。除此之外,切槽试样获得的成形极限曲线可以将变形演化与破坏机理结合起来,更有效地表征纤维金属层板的拉深成形性能。

In the process of deep drawing,the common failure modes of fibre metal laminates are wrinkling,fibre tensile fracture,and interface delamination.Inspired by the deep drawing test of metal,fibre strain can be introduced into the forming limit diagram when fibre tensile fracture and interface delamination failure are the main failure modes of fibre metal laminates.However,since the shape of the traditional metal strip specimen used for deep drawing test is an obstacle for the calculation of fibre strain in fibre metal laminates,a new notched specimen was designed in this study.The formability of glass fibre/polyamide resin(Gf/PA)composite-aluminum alloy laminate was investigated by comparing the forming tests of traditional strip specimens and the proposed notched specimens.Results show that the proposed notched specimen could ensure the calculated fibre strain level within 6%.Through the classification of different fibre strain intervals,it could be clearly divided that the failure form of deep drawing of laminates was fibre tensile fracture or interface delamination.It was found that the forming limit diagram of the notched specimen consisted of three regions:forming safety zone,fibre tensile fracture zone,and interface delamination zone.In addition,the forming limit curves obtained from the notched specimens could combine the deformation evolution with the failure mechanism,and more effectively characterize the deep drawing formability of fibre metal laminates.