Energy absorption behavior of foam-filled sandwich composite materials reinforced by lattice webs under quasi-static compression
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摘要: 复合材料夹芯结构具有较高的比强度和比刚度、优异的耐腐蚀性能、良好的抗疲劳性能、简单的成型工艺等特点。以聚氨酯(Polyurethane,PU)泡沫作为芯材,玻璃纤维增强树脂复合材料(Glass fiber reinforced polymer,GFRP)作为面层和腹板,制备了空间格构腹板增强泡沫夹芯复合材料试件。保持试件的几何尺寸不变,改变竖直格构腹板的空间位置,将竖直格构腹板优化设计为双层正交格构腹板、双层错位格构腹板和三层错位格构腹板。对试件开展准静态压缩试验,对比研究其破坏形式与吸能特性。发现三层错位格构腹板试件具有较理想的荷载-位移曲线。改变格构腹板的空间位置后,试件的弹性行程延长,同时,试件的承载能力也有所提升。与竖直格构腹板相比,三层错位格构腹板试件的能量吸收值提升91.9%。运用等效十字模型计算了双层正交格构腹板试件的面内等效弹性压缩刚度,可知双层正交格构腹板试件的弹性刚度受格构压缩模量影响较大。利用ANSYS/LS-DYNA对试件进行数值模拟,对比试验研究得到的材料特性和破坏模式,验证了数值模拟的准确性,进而运用数值模拟对各试件的GFRP腹板和泡沫芯材吸收能量的情况进行对比和分析。Abstract: Composite sandwich structure has higher specific strength, specific stiffness, excellent corrosion resistance, good fatigue resistance and simple molding process, etc. Composite sandwich specimens were produced with face sheets and lattice webs which were made from glass fiber reinforced polymer (GFRP) and core made from polyurethane (PU) foam. The vertical lattice webs were transformed into double-layered orthogonal lattice webs, double-layered dislocation lattice webs and triple-layered dislocation lattice webs. Quasi-static compression experiment was performed on specimens to compare their failure modes and performance of energy absorption. The results show that the triple-layered dislocation lattice webs have ideal load-displacement curves. After changing the spatial position of the lattice webs, the elastic decline is extended, and the bearing capacity of the specimen is improved. Compared with the vertical lattice webs, the energy absorption value of the triple-layered dislocation lattice webs increases by 91.9%. The equivalent cross model was assumed to calculate the equivalent elastic compression stiffness of the double-layered orthogonal lattice webs, and the elastic stiffness of the double-layered orthogonal lattice webs is greatly affected by the lattice compression modulus. Numerical simulations using ANSYS/LS-DYNA were conducted on composite panels. By comparing the material properties and failure modes obtained from the experimental investigations, the accuracy of the numerical simulation could be well predicted, and the energy absorption of the GFRP webs and foam was compared and analyzed by numerical simulation.
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图 1 空间格构和竖直格构腹板增强泡沫夹芯复合材料试件荷载-位移曲线对比
Figure 1. Comparison of load-displacement curves between the specimens with foam-filled sandwich composite materials reinforced by vertical lattice webs and spatial lattice webs
Pu—Peak load; Pb—Yield load; ∆y—Yield displacement; ∆st—Stroke length; A—Elastic abrupt point; B—Front-yield point; C—Post-yield point; D—Reinforcement point
图 16 双层正交格构腹板增强泡沫夹芯复合材料试件十字等效模型
Figure 16. Equivalent cross model of the specimens with foam-filled sandwich composite materials reinforced by double-layered orthogonal lattice webs
t—Thickness of the lattice webs; a—Length of the horizontally lattice webs; b—Length of the vertical lattice webs; Fb—Force along the vertical lattice webs; Fp—Force along the vertical foam core; σ—Pressure stress on foam core; m-m—m-m section
表 1 格构腹板增强泡沫夹芯复合材料试件的尺寸参数
Table 1. Dimension parameters of foam-filled sandwich composite materials reinforced by lattice webs specimens
Specimen Length/mm Width/mm Height/mm Face-sheet thickness/mm Lattice-web thickness/mm V 300 300 150 2.4 2.4 DO 300 300 150 2.4 2.4 DD 300 300 150 2.4 2.4 TD 300 300 150 2.4 2.4 Notes: V—Vertical lattice webs; DO—Double-layered orthogonal lattice webs; DD—Double-layered dislocation lattice webs; TD—Triple-layered dislocation lattice webs. 表 2 玻璃纤维增强树脂复合材料(GFRP)片材拉伸试验结果
Table 2. Results of tensile experiment on glass fiber reinforced polymer (GFRP) sheet
Specimen Tensile strength ft Elastic modulus E Experiment/MPa Average/MPa Coefficient/% Experiment/GPa Average/GPa Coefficient/% 1 196.7 208.1 5.48 12.4 12.9 3.88 2 200.3 3.75 12.8 0.78 3 217.5 4.52 12.5 3.10 4 213.4 2.55 13.2 2.33 5 212.6 2.16 13.6 5.43 表 3 聚氨酯(PU)泡沫压缩试验结果
Table 3. Results of compression experiment on polyurethane (PU) foam
Specimen Compressive strength fc Elastic modulus E Experiment/MPa Average/MPa Coefficient/% Experiment/GPa Average/GPa Coefficient/% 1 0.101 0.139 27.34 1.76 2.27 22.47 2 0.141 1.44 2.24 1.32 3 0.130 6.47 2.02 11.01 4 0.163 17.27 2.63 15.86 5 0.161 15.83 2.71 19.38 表 4 不同格构腹板增强泡沫夹芯复合材料试件试验结果
Table 4. Results of the specimens with foam-filled sandwich composite materials reinforced by different lattice webs
Specimen Pu
/kN∆1
/mmK/(kN·mm−1) $ {\bar{{P}}}_{\text{u}} $/kN $ {\bar{\varDelta }}_{\text{1}} $/mm $ {\bar{K }} $/(kN·mm−1) V-1 116.1 5.4 21.5 114.2 5.2 22.0 V-2 112.3 5.0 22.5 DO-1 106.1 4.2 25.3 110.6 4.7 23.9 DO-2 115.0 5.1 22.5 DD-1 50.1 8.7 5.8 54.5 9.8 5.6 DD-2 58.9 10.9 5.4 TD-1 36.7 12.8 2.9 37.4 12.7 3.0 TD-2 38.0 12.5 3.0 Notes: Pu—Elastic ultimate bearing capacity; ∆1—Elastic stroke; K—Average initial stiffness; $ {\bar{{P}}}_{\text{u}} $—Average elastic ultimate bearing capacity; $ {\bar{\varDelta }}_{\text{1}} $—Average elastic stroke; $ {\bar{K }} $—Average initial stiffness. 表 5 空间格构腹板增强泡沫夹芯复合材料试件能量吸收值(J)
Table 5. Energy absorption of the specimens with foam-filled sandwich composite materials reinforced by spatial lattice webs (J)
Specimen Load level 0.1 0.2 0.3 0.4 0.5 0.6 0.7 V-1 710 1073 1444 1927 2295 2623 3060 V-2 616 891 1241 1711 2057 2395 2760 DO-1 914 1490 1936 2343 2813 3491 4349 DO-2 959 1504 1931 2349 2932 3811 4683 DD-1 552 1253 1851 2540 3232 3904 4778 DD-2 653 1300 1879 2466 2901 3397 4170 TD-1 365 1019 1733 2499 3300 4426 5873 TD-2 391 1060 1791 2602 3467 4795 6325 表 6 空间格构腹板增强泡沫夹芯复合材料试件比吸能值
Table 6. Specific energy absorption of the specimens with foam-filled sandwich composite materials reinforced by spatial lattice webs
Specimen Ea/J m/kg Es/(J·kg−1) $ {\bar{{E}}}_{\text{s}}/ $(J·kg−1) V-1 3060 2.35 1302.1 1226.1 V-2 2760 2.40 1150.0 DO-1 4349 2.85 1526.0 1584.6 DO-2 4683 2.85 1643.2 DD-1 4778 2.90 1647.6 1555.4 DD-2 4170 2.85 1463.2 TD-1 5872 3.60 1631.1 1694.0 TD-2 6325 3.60 1756.9 Notes: Ea—Total energy absorption; m—Mass of specimens; Es—Specific energy absorption; $ {\bar{{E}}}_{\text{s}} $—Average specific energy absorption. 表 7 空间格构腹板增强泡沫夹芯复合材料试件平均压溃力
Table 7. Mean crushing load of the specimens with foam-filled sandwich composite materials reinforced by spatial lattice webs
Specimen Ea/J s/mm Fm/kN $ {\bar{{F}}}_{\text{m}} $/kN V-1 3060 105 29.1 27.7 V-2 2760 105 26.3 DO-1 4349 105 41.4 43.0 DO-2 4683 105 44.6 DD-1 4778 105 45.5 42.6 DD-2 4170 105 39.7 TD-1 5872 105 55.9 58.1 TD-2 6325 105 60.2 Notes: s—Total compression; Fm—Mean crushing load; $ {\bar{{F}}}_{\text{m}} $—Average mean crushing load. 表 8 GFRP模型材料参数
Table 8. Material parameters of the GFRP model
ρ/(g·cm−3) Efx/GPa Efy/GPa Efz/GPa 1.8 12.9 12.9 4.30 Gxy/GPa Gxz/GPa Gyz/GPa νxy 2.5 1.25 1.25 0.15 νxz νyz Sc/MPa Xt/MPa 0.1 0.1 55.0 322.9 Yt/MPa Yc/MPa α 322.9 168.2 0.3 Notes: ρ—Density of specimen; Ef—Young’s modulus; G—Shear modulus; ν—Poission’s ratio; Sc—Shear strength; Xt—Longitudinal tensile strength; Yt—Transverse tensile strength; Yc—Transverse compressive strength; α—Nonlinear shear coefficient (Subscripts x, y, z indicate the directions of the axes). 表 9 PU泡沫和刚体模型材料参数
Table 9. Material parameters of the PU foam and the rigid model
ρ/(g·cm−3) E/MPa ν PU foam 0.04 2.48 0.3 Rigid model 7.8 2.0×105 0.27 表 10 空间格构腹板增强泡沫夹芯复合材料试件力学性能试验值与有限元值对比
Table 10. Comparison between experimental and numerical values of mechanical properties of the specimens with foam-filled sandwich composite materials reinforced by spatial lattice webs
Specimen Pu/kN Δ1/mm K/(kN·mm−1) Exp. Num. Deviation/% Exp. Num. Deviation/% Exp. Num. Deviation/% V 114.2 90.4 −20.8 5.2 3.6 −30.7 22.0 25.1 14.1 DO 110.6 98.5 −10.9 4.7 3.8 −19.1 23.9 25.9 8.4 DD 54.5 46.2 −15.2 9.8 6.7 −31.6 5.6 6.9 23.2 TD 37.4 45.6 21.9 12.7 17.6 38.6 3.0 2.6 −13.3 表 11 空间格构腹板增强泡沫夹芯复合材料试件能量吸收试验值与有限元值对比(J)
Table 11. Comparison between experimental and numerical values of energy absorption of the specimens with foam-filled sandwich composite materials reinforced by spatial lattice webs (J)
Specimen Load level 0.1 0.3 0.5 Exp. Num. Deviation/% Exp. Num. Deviation/% Exp. Num. Deviation/% V 736.6 594.9 −19.2 1474.7 1416.6 −3.9 2314.2 2206.1 −4.7 DO 958.4 677.4 −29.3 1961.1 1610.8 −17.9 2851.3 2506.5 −12.1 DD 601.2 467.0 −22.3 1891.2 1487.6 −21.3 2531.9 3272.0 29.2 TD 404.2 504.7 24.9 1777.8 1807.2 1.7 3364.2 2939.4 −12.6 表 12 空间格构腹板增强泡沫夹芯复合材料试件GFRP腹板和PU泡沫的吸能对比(MJ)
Table 12. Comparison of energy absorption between the GFRP webs and the PU foam of specimens with foam-filled sandwich composite materials reinforced by spatial lattice webs (MJ)
Part V DO DD TD GFRP webs 0.13 0.17 0.19 0.23 PU foam 0.92 0.77 0.73 0.63 -
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