Enhanced theory and finite element method for wrinkling analysis of composite sandwich structure
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摘要:
夹芯结构广泛应用于航空航天和航海等领域。但由于面板和芯材的力学性能和几何尺寸差异较大,夹芯结构失效行为与其他复合材料结构的失效行为不同。对于承受复杂载荷的夹芯结构,褶皱失效行为可能比其他失效模式更早发生。本文针对夹芯梁在承受面内压缩载荷时容易发生屈曲和起皱的行为,构建了考虑局部形变和横法向应变的增强型高阶模型,该模型满足面内位移和横向剪切应力层间连续条件及自由表面条件。基于构建的理论模型,构造两节点梁单元公式并分析夹芯结构屈曲和褶皱问题。为了研究屈曲行为和褶皱行为之间的差异,使用本模型和三维有限元计算得到的屈曲和起皱行为对应的位移模态绘制在 图1 中。对于屈曲行为,中平面的变形与上下表面的变形一致。对于褶皱行为,由于中平面仅受压缩变形,但是上、下表面受到弯曲变形,所以中平面的变形与上下表面的变形完全不同。通过算例验证了所构建模型的准确性。数值分析结果表明,发展的模型计算夹芯结构的屈曲和褶皱行为有较高的精度,与三维有限元方法相比,本文构造的模型具有较高计算效率。相较于使用金属面板,使用纤维方向弹性模量大于金属面板弹性模量的复合材料面板,能有效增强夹芯梁抵抗起皱的能力。使用本文提出的模型和三维有限元计算得到的屈曲和褶皱行为的位移模态 Abstract: Panels wrinkling behaviors may occur when composite soft-core sandwich structures subjected to coplanar compression loads. Once the panels wrinkling appears, the sandwich structures will lose its load-bearing capacity. Therefore, it is necessary to develop an accurate model to predict the wrinkling behaviors of soft-core sandwich structures. Sandwich structure wrinkling is a typical three-dimensional (3D) problem, and few high-order models can accurately predict such issues. Therefore, this paper proposed an enhanced higher-order model including the local deformation and the 3D effects. Based on the proposed theory, the beam element formulation was derived, and the wrinkling behaviors of sandwich structures with different boundary conditions were analyzed. By comparing with the quasi-3D elasticity solution and the 3D finite element results, accuracy of the proposed method has been verified. In order to improve the capability of sandwich structures resisting the wrinkling deformation, this work attempted to use composite face sheets instead of metal panel in the sandwich structure. Numerical results show that the developed enhanced high-order model can accurately predict the wrinkling behaviors of the composite sandwich structures, and the use of composite panels can effectively resist the wrinkling behaviors of sandwich structures.-
Key words:
- composite /
- sandwich structures /
- enhanced higher-order theory /
- wrinkling /
- beam element
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表 1 三维有限元边界条件
Table 1. Boundary condition for 3 D finite element
x=0 x=a y=0 y=1 U2=U3=UR3=0 U3=UR3=0 U2= 0 U2= 0 表 2 三层铝面板夹芯梁屈曲载荷
Table 2. Buckling load of three-layer sandwich beam with aluminum panels
tc/tf a/h 3 D-FEM
(270000 elements)BE18
(64 elements)HYF11[20] HYF21[20] HOST[21] Allen[22] 5 2 6.6111 6.7131
(1.54)6.2220
(5.89)37.551
(468.00)37.238
(463.26)6.3544
(3.88)5 14.7065 14.838
(0.89)14.320
(2.63)159.05
(981.49)159.32
(983.33)14.385
(2.19)10 41.658 41.819
(0.39)41.084
(1.38)329.63
(691.28)321.26
(671.18)41.115
(1.30)25 2 1.5342 1.5600
(1.68)1.5299
(0.28)2.3207
(51.26)2.3112
(50.64)1.5923
(3.79)5 9.0749 9.1046
(0.33)9.0314
(0.48)13.130
(44.68)13.113
(44.50)9.0971
(0.24)10 31.649 31.655
(0.02)31.096
(1.75)42.433
(34.07)42.436
(34.08)31.159
(1.55)50 2 1.4432 1.4640
(1.44)1.4419
(0.09)1.8335
(27.04)1.8301
(26.81)1.5074
(4.45)5 8.5657 8.6504
(0.99)8.5553
(0.12)10.311
(20.38)10.301
(20.26)8.6191
(0.62)10 27.585 27.522
(0.23)26.762
(2.98)30.746
(11.46)30.769
(11.54)26.849
(2.67)Notes: BE18 is the present model; HYF11 is the quasi-3 D model; HYF21 and HOST are the higher-order models; Allen represents the model proposed by Allen. 表 3 三层铝面板夹芯梁褶皱载荷
Table 3. Wrinkling loads of three-layer sandwich beam with aluminum panels
tc/tf a/h 3 D-FEM
(270000 elements)BE18
(480 elements)HYF11[20] HYF21[20] Allen[22] 50 2 0.7311 (5) 0.7632 (5) 0.7073 (6) 0.8074 1.3020 (9) 5 4.5097 (13) 4.7147 (14) 4.3583 (14) 5.0048 8.1376 (23) 10 18.091 (27) 18.883 (27) 17.433 (28) 20.019 -- 100 2 0.2610 (9) 0.2845 (9) 0.2517 (9) 0.3121 0.6638(9) 5 1.6318 (22) 1.7768 (22) 1.5736 (23) 1.9480 4.1486 (22) 10 6.5273 (44) 7.1612 (43) 6.2921 (45) 7.7921 16.594 (45) Note: Numbers in brackets represent half-wave numbers. 表 4 三层复合材料夹芯梁屈曲载荷
Table 4. Buckling load of three-layer composite sandwich beam
tc/tf a/h 3 D-FEM
(270000 elements)BE18
(240 elements)BHSDT[24] RHSDT[25] 25 2 11.301 11.457 14.951 15.525 5 64.288 64.441 85.873 89.282 10 239.10 239.20 313.65 325.22 50 2 10.016 10.135 13.442 12.360 5 61.853 61.978 80.805 73.963 10 222.56 222.51 280.98 259.83 Notes: BHSDT is the higher order model proposed by Babu et al. [24]; RHSDT is 表 5 三层复合材料夹芯梁褶皱载荷
Table 5. Wrinkling load of three-layer composite sandwich beam
tc/tf a/h SS CC 3 D-FEM
(270000 elements)BE18
(480 elements)3 D-FEM
(270000 elements)BE18
(480 elements)50 2 7.5768 (4) 8.0174 (4) 8.0246 (4) 8.5964 (4) 5 46.413 (11) 49.265 (11) 47.101 (11) 50.086 (11) 10 185.72 (22) 197.49 (22) 186.43 (21) 198.31 (21) 100 2 2.7004 (7) 2.8531 (7) 2.7806 (7) 2.9505 (7) 5 16.835 (18) 17.829 (18) 16.929 (18) 17.937 (18) 10 67.333 (36) 71.741 (36) 67.441 (36) 71.849 (36) Note: Numbers in brackets represent half-wave numbers.the higher-order model proposed by Reddy [25]. -
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