Experimental study on mechanical properties and recoverability of FRP/shape memory alloy composites
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摘要: 利用形状记忆合金(SMA)的回复效应将预应力引入到纤维增强复合材料(FRP)中是一种新理念。本文将FRP与SMA复合,形成一种新的复合材料用于结构加固修复中,开展了FRP/SMA复合材料的力学性能和受限回复性能试验。在力学性能试验中,将SMA丝的数量和直径作为试验变量,分析它们对FRP/SMA复合材料拉伸性能的影响;在受限回复试验中,将SMA丝直径和预应变水平作为试验变量,分析其对SMA丝及FRP/SMA复合材料可回复性能的影响。在试验研究的基础上,给出了第一类FRP/SMA复合材料的材料强度、极限应变和弹性模量的预测模型和FRP/SMA复合材料回复应力-温度模型。试验结果表明,在一定掺量内,提高掺入SMA丝的数量能够提高复合材料的最大断裂应变和抗拉强度,掺入的丝数量越多,断后残余强度越大。SMA丝的直径显著影响复合材料试件的拉伸弹性模量。在受限回复性能试验中,FRP/SMA复合材料的回复应力在相变区间内随温度的升高呈明显的上升趋势,复合材料的最大回复应力将会随预应变水平的提高而增大。提出的基于Brinson模型的修正模型,预测值与试验值吻合较好,可以有效地预测SMA丝和FRP/SMA复合材料的回复应力与温度的关系。Abstract: Using the recovery effect of shape memory alloy (SMA) to introduce prestress into fiber reinforced polymer (FRP) is a new idea. In this paper, FRP and SMA are compounded to form a new composite material for structural strengthening and repair. The mechanical properties and limited recovery properties of FRP/SMA composites are tested. In the mechanical property test, the number and diameter of SMA wires are taken as test variables, and their effects on the tensile properties of FRP/SMA composites are analyzed. In the limited recovery test, the SMA wire diameter and pre-strain level were taken as test variables to analyze their effects on the recoverable properties of SMA wire and FRP/SMA composites. On the basis of experimental research, the regression equations of recovery stress temperature of SMA wire and FRP/SMA composites are given. The test results show that increasing the number of SMA wires can improve the maximum fracture strain and tensile strength of the composite. The more wires are added, the greater the residual strength after fracture. The diameter of SMA wire significantly affects the tensile elastic modulus of composite specimens. In the limited recovery performance test, the recovery stress of FRP/SMA composites shows an obvious upward trend with the increase of temperature in the phase transition range, and the maximum recovery stress of composites will increase with the increase of pre-strain level. The modified model based on Brinson’s model is proposed, and the predicted values are in good agreement with the experimental values, which can effectively predict the relationship between the recovery stress and temperature of SMA wire and FRP/SMA composites.
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表 1 材料的物理力学性能
Table 1. Physical and mechanical properties of materials
Material Diameter φ/mm Austenite transition temperature/℃ Martensite transition temperature/℃ Phase transition stress/MPa Strength/
MPaElastic modulus/
GPaElongation/
%Start
AsFinish Af Start Ms Finish Mf SMA wire 0.5 106.12 121.40 55.34 27.34 122 982 12.2 78.0 1.0 79.13 105.46 59.00 35.81 117 906 10.4 75.0 CFRP – – – – – 3000 247.7 1.2 Epoxy resin – – – – – 35 2.2 1.6 Notes: CFRP—Carbon fiber reinfored plastic; Af—Austenite finish temperature; As—Austenite start temperature; Ms—Martensite start temperature; Mf—Martensite finish temperature. 表 2 两种类型的FRP/SMA复合材料试件
Table 2. Two types of FRP/SMA composite specimens
Specimen type Specimen Number of
SMA wiresDiameter of
SMA/
mmPrestrain/
%Length of composite
section/
mmFRP/SMA-I FRP/SMA-I-0.5-5-4% 5 0.5 4 250 FRP/SMA-I-0.5-10-4% 10 0.5 4 250 FRP/SMA-I-0.5-15-4% 15 0.5 4 250 FRP/SMA-I-1-10-4% 10 1.0 4 250 FRP/SMA-II FRP/SMA-II-1.0-10-4% 10 1.0 4 2×70 FRP/SMA-II-1.0-10-6% 10 1.0 6 2×70 FRP/SMA-II-1.0-10-8% 10 1.0 8 2×70 表 3 FRP/SMA复合材料试验与分析结果
Table 3. Test and analysis results of FRP/SMA composites
Specimen No. Strength/MPa Elastic modulus/GPa Fracture strain/% Failure mode Test value Calculated value Test value/
calculated valueTest value Calculated value Test value/
calculated
valueTest value Calculated value Test value/
calculated
valueFRP/SMA-I-0.5-
5-4%1 2206 2840 0.78 158.7 234.7 0.68 1.39 1.2 1.16 Longitudinal splitting 2 2617 0.92 186.9 0.80 1.40 1.17 3 2809 0.98 205.0 0.87 1.37 1.14 FRP/SMA-I-0.5-10-4% 1 2326 2697 0.86 169.7 222.9 0.76 1.32 1.2 1.10 Longitudinal splitting 2 2566 0.95 192.9 0.87 1.33 1.11 3 2828 1.05 212.6 0.95 1.28 1.07 FRP/SMA-I-0.5-15-4% 1 2602 3000 0.87 154.9 212.4 0.73 1.68 1.41 1.19 Burst failure 2 2992 1.04 188.4 0.89 1.65 1.17 3 2999 1.00 196.0 0.92 1.65 1.17 FRP/SMA-I-1.0-10-4% 1 1968 2078 0.95 145.8 171.8 0.85 1.35 1.2 1.13 Longitudinal splitting 2 2085 1.00 156.8 0.91 1.33 1.11 3 2039 0.98 156.8 0.91 1.30 1.08 Average value 0.95 0.85 1.13 Standard deviation 0.08 0.08 0.04 Coefficient of variation 0.08 0.09 0.04 表 4 SMA回复性能试验试件设计与试验结果
Table 4. Design and test results of SMA recovery test specimen
Specimen Length
of SMA/
mmDiameter of SMA/
mmPrestrain/
%Average value of
maximum recovery
stress/
MPaSMA-0.5-4% 200 0.5 4 202 SMA-0.5-6% 200 0.5 6 273 SMA-0.5-8% 200 0.5 8 288 SMA-0.5-10% 200 0.5 10 295 SMA-1.0-4% 200 1.0 4 267 SMA-1.0-6% 200 1.0 6 312 SMA-1.0-8% 200 1.0 8 391 表 5 FRP/SMA回复性能试验试件设计与试验结果
Table 5. FRP/SMA recovery test specimen design and test results
Specimen Length of activated section/
mmDiameter of SMA/
mmPrestrain/
%Average value of
maximum
recovery stress/MPaFRP/SMA-
II-1.0-4%150 1.0 4 247 FRP/SMA-
II-1.0-6%150 1.0 6 284 FRP/SMA-
II-1.0-8%150 1.0 8 358 -
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