GFRP-轻木夹芯梁弯曲蠕变试验及预测

李晓龙; 方海; 吴鹏

GFRP-轻木夹芯梁弯曲蠕变试验及预测

李晓龙^1, ,,
方海²,
吴鹏²

1.
江苏开放大学　建筑工程学院, 南京 210036
2.
南京工业大学　土木工程学院, 南京 211800

基金项目: 国家自然科学青年基金(52108215)

详细信息

通讯作者:
李晓龙，工学博士，讲师，研究方向为复合材料结构　E-mail: lixl@jsou.edu.cn

中图分类号: TB332
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- 文章访问数: 171
- HTML全文浏览量: 128
- PDF下载量: 4
- 被引次数: 0
出版历程
- 收稿日期: 2023-09-27
- 修回日期: 2023-10-22
- 录用日期: 2023-11-02
- 网络出版日期: 2023-11-18
- 刊出日期: 2024-07-15

Flexural creep test and prediction of GFRP-balsa sandwich beams

LI Xiaolong^{1
, ,},
FANG Hai²,
WU Peng²

1.
School of Architecture and Civil Engineering, Jiangsu Open University, Nanjing 210036, China
2.
College of Civil Engineering, Nanjing Tech University, Nanjing 211800, China

Funds: National Natural Science Foundation of China (52108215)

摘要

摘要: 以玻璃纤维增强复合材料(GFRP)为面层，轻木(balsa)为芯材的GFRP-balsa夹芯结构在基础设施领域的应用范围不断扩大，但GFRP-balsa夹芯结构具有粘弹性，易于发生蠕变变形。为此，在温度为(25±1)°C，相对湿度为55%±5%的环境下，利用自主设计的弯曲蠕变加载装置对GFRP-balsa夹芯梁在20%、25%和30%荷载等级下的三点弯曲蠕变性能进行了3000~8760 h的测试，并利用多种模型对GFRP-balsa夹芯梁的蠕变响应进行了模拟和预测。结果表明：在试验荷载等级下，GFRP-balsa夹芯梁表现出线性粘弹性；弯曲蠕变对GFRP-balsa夹芯梁的跨中挠度具有重要影响，所有试件在3000 h的蠕变系数均不小于0.35；Findley模型适用于单一荷载等级下GFRP-balsa夹芯梁时变总挠度的拟合，在3000 h的拟合值与试验值之间的最大相对误差仅为0.7%；Bailey-Norton模型和通用幂次律模型分别适用于荷载等级不超过30%的GFRP-balsa夹芯梁蠕变挠度和时变总挠度的预测，在一年时，Bailey-Norton模型和通用幂次律模型预测值与试验值之间的最大相对误差分别为8.3%和5.9%。
- 玻璃纤维增强复合材料 /
- 轻木 /
- 夹芯梁 /
- 弯曲蠕变 /
- 预测模型
Abstract: The application scope of the glass fiber reinforced plastic (GFRP)-balsa sandwich structure composed of GFRP facings and a balsa wood core is constantly expanding in the field of infrastructure. However, GFRP-balsa sandwich structures are susceptible to creep deformation due to their viscoelasticity. Under the controlled temperature of (25±1)°C and relative humidity of 55%±5%, the three-point flexural creep performance of the GFRP-balsa sandwich beams at 20%, 25% and 30% load levels were tested for a period of 3000~8760 h using the self-designed flexural creep loading devices. Various models were used to simulate and predict the creep response of the GFRP-balsa sandwich beams. The results show that the GFRP-balsa sandwich beams exhibit linear viscoelasticity at the test load levels. Flexural creep has an important impact on the mid-span deflection of the GFRP-balsa sandwich beams, and the creep coefficients at 3000 h of all the specimens are not less than 0.35. The Findley model is applicable for fitting the time-dependent total deflection of the GFRP-balsa sandwich beams at a single load level, and the maximum relative error between the fitting value and the test value at 3000 h is only 0.7%. The Bailey-Norton model and the general power law model are applicable for predicting the creep deflection and the time-dependent total deflection of the GFRP-balsa sandwich beams when the load level does not exceed 30%, respectively. At one year, the maximum relative error between the predicted value of the Bailey-Norton model and the test value is 8.3%, and the maximum relative error between the predicted value of the general power law model and the test value is 5.9%.
- glass fiber reinforced plastic /
- balsa /
- sandwich beam /
- flexural creep /
- prediction model

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图 1 GFRP-balsa夹芯梁示意图

Figure 1. Schematic diagram of the GFRP-balsa sandwich beam

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图 2 弯曲蠕变加载装置

Figure 2. The flexural creep loading devices

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图 3 GFRP-balsa夹芯梁在不同荷载等级下的蠕变挠度平均值曲线

Figure 3. Mean creep deflection curves of the GFRP-balsa sandwich beams at the different load levels

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图 4 GFRP-balsa夹芯梁在不同荷载等级下的蠕变挠度平均值/恒定外力-时间(D_ca/F-t)曲线

Figure 4. Mean creep deflection/Force-time (D_ca/F-t) curves of the GFRP-balsa sandwich beams at the different load levels

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图 5 GFRP-balsa夹芯梁蠕变挠度平均值的对数标尺图

Figure 5. Log scale plot of the mean creep deflections for the GFRP-balsa sandwich beams

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图 6 GFRP-balsa夹芯梁蠕变挠度平均值的Bailey-Norton模型拟合结果

Figure 6. Fitting results of the Bailey-Norton model of the mean creep deflections for the GFRP-balsa sandwich beams

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图 7 GFRP-balsa夹芯梁总挠度平均值的Findley模型拟合结果

Figure 7. Fitting results of the Findley model of the mean total deflections for the GFRP-balsa sandwich beams

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图 8 GFRP-balsa夹芯梁总挠度平均值的通用幂次律模型预测结果

Figure 8. Prediction results of the general power law model of the mean total deflections for the GFRP-balsa sandwich beams

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图 9 GFRP-balsa夹芯梁蠕变挠度试验结果和Bailey-Norton模型拟合外推结果对比

Figure 9. Comparison of the creep deflection test results and the Bailey-Norton model extrapolated results for the GFRP-balsa sandwich beams

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图 10 GFRP-balsa夹芯梁总挠度试验结果和通用幂次律模型预测结果对比

Figure 10. Comparison of the total deflection test results and the general power law model prediction results for the GFRP-balsa sandwich beams

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表 1 蠕变测试试件尺寸及加载情况汇总

Table 1. Summary of the dimensions and the loading conditions of the creep test specimens

Specimen	Length /mm	Width /mm	Depth /mm	F/N
20%-1	380.3	69.82	28.80	1196
20%-2	379.8	69.88	28.76
20%-3	380.5	70.02	28.74
25%-1	380.0	69.90	28.82	1495
25%-2	380.2	69.96	28.78
25%-3	379.4	69.96	28.70
30%-1	380.0	69.78	28.74	1794
30%-2	380.2	69.98	28.72
30%-3	380.1	70.00	28.78
Notes: "20%", "25%" and "30%" refer to the load level; "−1", "−2" and "−3" refer to the serial number in a repeated test; F—Required force to be applied at the loading point.

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表 2 GFRP-balsa夹芯梁三点弯曲蠕变测试结果汇总

Table 2. Summary of the three-point flexural creep test results of the GFRP-balsa sandwich beams

Specimen	d/mm	d_a/mm	D/mm	D_a/mm	D_c/mm	D_ca/mm	$\phi $
20%-1	1.11	1.03 ± 0.075	1.52	1.43 ± 0.085	0.41	0.40 ± 0.012	0.37
20%-2	0.96		1.35		0.39		0.41
20%-3	1.03		1.42		0.39		0.38
25%-1	1.30	1.32 ± 0.082	1.80	1.81 ± 0.091	0.50	0.49 ± 0.012	0.38
25%-2	1.25		1.73		0.48		0.38
25%-3	1.41		1.91		0.50		0.35
30%-1	1.55	1.60 ± 0.050	2.15	2.19 ± 0.040	0.60	0.59 ± 0.021	0.39
30%-2	1.65		2.23		0.57		0.35
30%-3	1.60		2.20		0.61		0.38
Notes: d—Initial static deflection; d_a—Mean initial static deflection; D—Total deflection at 3000 h; D_a—Mean total deflection at 3000 h; D_c—Creep deflection at 3000 h; D_ca—Mean creep deflection at 3000 h; $\phi $—Creep coefficient at 3000 h.

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表 3 不同荷载等级下GFRP-balsa夹芯梁测试跨中挠度与容许挠度的对比

Table 3. Comparison of the test mid-span deflections and the allowable deflections of the GFRP-balsa sandwich beams at the different load levels

Load level	Deflection type	Comparison
Load level	Deflection type	[l/150]	[l/200]	[l/250]
20%	d_a	<	<	<
20%	D_a	<	<	>
25%	d_a	<	<	>
25%	D_a	<	>	>
30%	d_a	<	>	>
30%	D_a	>	>	>
Notes: d_a—The mean initial static deflection; D_a—The mean total deflection at 3000 h; l—The span length.

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表 4 Findley模型中各参数拟合结果汇总

Table 4. Summary of the fitting results of various parameters in the Findley model

Load level	d	a	N	R²
20%	0.9798	0.1481	0.1410	0.9953
25%	1.2752	0.1767	0.1410	0.9978
30%	1.5454	0.2299	0.1320	0.9971
Notes: d—Initial static deflection; a—Amplitude of creep; N—Time exponent; R²—Determination coefficients.

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表 5 GFRP-balsa夹芯梁一年时的蠕变测试值与模型预测值对比

Table 5. Comparison of the creep test values and the model prediction values at one year for the GFRP-balsa sandwich beams

Load level	D_ce /mm	D_cB /mm	δ₁ /%	D_e /mm	D_G /mm	δ₂ /%
20%	0.44	0.47	6.4	1.47	1.48	0.7
25%	0.55	0.60	8.3	1.85	1.91	3.1
30%	0.67	0.73	8.2	2.22	2.36	5.9
Notes: D_ce—The creep deflection test value at one year; D_cB—The Bailey-Norton model extrapolated value at one year; δ₁—The relative error between D_ce and D_cB; D_e—The total deflection test value at one year; D_G—The general power law model prediction value at one year; δ₂—The relative error between D_e and D_G.

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