孔隙对碳纤维/环氧树脂复合材料剪切性能和破坏模式的影响

史俊伟; 杨柳; 王文贵; 荀国立; 信泽坤

doi:10.13801/j.cnki.fhclxb.20240722.004

孔隙对碳纤维/环氧树脂复合材料剪切性能和破坏模式的影响

doi: 10.13801/j.cnki.fhclxb.20240722.004

中国航空制造技术研究院　复合材料检测与评估技术室，北京 101300

详细信息

通讯作者:
史俊伟，硕士，高级工程师，研究方向为复合材料无损检测与评估技术　E-mail: aaron_sjw@163.com

中图分类号: TB332
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- 被引次数: 0
出版历程
- 收稿日期: 2024-04-28
- 修回日期: 2024-06-06
- 录用日期: 2024-07-09
- 网络出版日期: 2024-07-22
- 刊出日期: 2024-09-15

Effects of voids on shear properties and failure mode of carbon fiber/epoxy resin composites

Laboratory of Composite Nondestructive Testing and Evaluation Technology, AVIC Manufacturing Technology Institute, Beijing 101300, China

摘要

摘要: 孔隙对碳纤维/环氧树脂复合材料剪切性能的影响十分显著。本文采用吸湿饱和和固化压力阶梯下降的方法在复合材料层压板中模拟制备出不同含量的孔隙缺陷，通过短梁剪切强度测试试验，建立不同孔隙率对短梁剪切强度的影响曲线，结合金相观察和超声成像分析了不同孔隙率下损伤分布与破坏模式。研究结果表明：当孔隙率小于1.0%时，短梁剪切强度保留率约为88.4%~90.8%；当孔隙率增加至1.0%~1.5%时，短梁剪切强度保留率约为74.9%~80.6%；当孔隙率增加至1.5%~2.0%时，短梁剪切强度保留率约为66.3%~71.9%；当孔隙率增加至2.0%~3.0%时，短梁剪切强度急剧下降，短梁剪切强度保留率降至50%以下。短梁剪切破坏模式对孔隙缺陷十分敏感，层剪破坏主要发生在孔隙及其周边应力集中的区域，孔隙对裂纹的萌生和扩展具有明显的促进作用。
- 复合材料 /
- 孔隙率 /
- 破坏模式 /
- 短梁剪切强度
Abstract: Voids have significant influence on the shear properties of carbon fiber/epoxy resin composites. In this paper, carbon fiber/epoxy resin composite laminates with varies porosity were produced by hygroscopic saturation and stepping down the autoclave pressures. Short beam shear (SBS) tests were performed to establish the influence curve of different porosity on SBS strength. The evolution of shear damage induced by voids and the degradation mechanism of SBS strength were both studied by ultrasonic imaging and metallographic observation. The result shows that when the porosity is less than 1.0%, the SBS strength retention rate is about 88.4%-90.8%; When the porosity increases to 1.0%-1.5%, the SBS strength retention rate is about 74.9%-80.6%; When the porosity increases to 1.5%-2.0%, the SBS strength retention rate is about 66.3%-71.9%; When the porosity increases to 2.0%-3.0%, the SBS strength decreases sharply, and the SBS strength retention rate drops below 50%. The SBS shear failure mode is very sensitive to voids. Shear failure mainly occurs close to void and the surrounding stress concentration. The higher the porosity, the more obvious the promotion effect of voids on crack initiation and propagation, yielding the higher crack density, the earlier crack occurrence time, and the faster propagation speed.
- composites /
- porosity /
- failure mode /
- short beam shear (SBS) strength

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图 1 GW800G/BA9918E碳纤维增强环氧树脂单向带预浸料的标准固化曲线

Figure 1. Typical curing curves for GW800G/BA9918E CF/EP unidirectional prepreg

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图 2 短梁剪切试样取样示意图

Figure 2. Diagrams of ILSS specimen preparations

SBS—Short beam shear

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图 3 短梁剪切(SBS)测试装置及层压板加载示意图

Figure 3. SBS test device and laminate load diagram

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图 4 金相显微镜对孔隙、裂纹和损伤分析的示意图

Figure 4. Elaboration of microscopy for voids, cracks, and damage analysis

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图 5 CUS-21 J水浸式超声检测系统

Figure 5. CUS-21 J immersion ultrasonic detection system

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图 6 换能器聚焦声束截面

Figure 6. Focused transducer beam cross-section

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图 7 超声反射法B-Scan成像检测示意图

Figure 7. Ultrasonic reflection B-Scan imaging detection diagram

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图 8 不同孔隙率(P_v) CF/EP复合材料层压板中孔隙的微观形貌和分布

Figure 8. Morphology and distributions of voids in CF/EP composite laminates with different porosities (P_v)

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图 9 孔隙率对SBS强度的影响：(a) 短梁剪切强度；(b) 归一化短梁剪切强度

Figure 9. Effects of porosity on SBS strength: (a) SBS strength; (b) Normalized SBS strength

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图 10 SBS载荷作用下0°和90° SBS试件的应力状态图：(a) 拉压应力；(b) 剪应力

Figure 10. Stress state diagrams of the 0° and 90° SBS specimens under SBS loading: (a) Tension-compression stress; (b) Shear stress

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图 11 不同孔隙率SBS试样断口处的金相观察图：(a) P_v=0.02%，0°取样方向；(b) P_v=0.02%，90°取样方向；(c) P_v=1.01%，0°取样方向；(d) P_v=1.32%，0°取样方向；(e) P_v=1.69%，0°取样方向；(f) P_v=2.89%，0°取样方向

Figure 11. Metallographic observations at the fractures of SBS specimen with different porosities: (a) P_v=0.02%, 0° sampling direction; (b) P_v=0.02%, 90° sampling direction; (c) P_v=1.01%, 0° sampling direction; (d) P_v=1.32%, 0° sampling direction; (e) P_v=1.69%, 0° sampling direction; (f) P_v=2.89%, 0° sampling direction

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图 12 不同孔隙率SBS试样破坏后的超声三维成像结果(0°取样方向)

Figure 12. 3D ultrasonic imaging results of SBS specimens with different porosities after failure (0° sampling direction)

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图 13 不同孔隙率SBS试样破坏后的超声三维成像结果(90°取样方向)

Figure 13. 3D ultrasonic imaging results of SBS specimens with different porosities after failure (90° sampling direction)

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表 1 碳纤维增强环氧树脂(CF/EP)单向带预浸料的力学性能

Table 1. Mechanical properties of carbon fiber/epoxy resin (CF/EP) unidirectional prepreg

Mechanical property	Strength/ MPa	Modulus/ GPa
0°-Tension	2867	171
0°-Compression	1470	158
90°-Tension	76	8.9
90°-Compression	235	9.33
In-plane shear	143	—
In-plane shear (5% strain)	88.1	4.67
Interlaminar shear	101	—
Note: The properties are characterized at room temperature dry (RTD) environmental condition.

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表 2 CF/EP复合材料层压板的孔隙率

Table 2. Porosity of CF/EP composite laminates

Sample No.	Autoclave pressure/kPa	Porosity/%
1	600	0.02
2	300	0.32
3	250	0.82
4	220	1.01
5	200	1.08
6	150	1.52
7	130	1.69
8	110	2.35
9	100	2.89

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表 3 不同孔隙率下CF/EP复合材料层压板的SBS强度

Table 3. SBS strength of CF/EP composite laminates at different porosities

Sampling direction	P_v/%	SBS strength of samples τ/MPa						Mean strength $ \stackrel{-}{\tau } $/MPa	Standard deviation S_n-1/MPa	Coefficient of variation (CV)/%
Sampling direction	P_v/%	1#	2#	3#	4#	5#	6#	Mean strength $ \stackrel{-}{\tau } $/MPa	Standard deviation S_n-1/MPa	Coefficient of variation (CV)/%
0°	0.02	85.05	86.37	88.51	77.39	87.71	86.12	85.19	4.011	4.71
	0.32	74.47	76.40	78.21	73.90	75.26	76.94	75.86	1.620	2.14
	0.82	76.15	71.95	77.38	75.64	76.21	74.48	75.30	1.892	2.51
	1.01	68.08	63.68	61.20	60.69	62.82	63.96	63.40	2.638	4.16
	1.08	64.57	62.96	64.18	62.05	66.00	63.27	63.84	1.387	2.17
	1.52	55.61	58.88	59.74	56.60	55.20	53.79	56.64	2.275	4.02
	1.69	57.44	52.63	59.00	57.94	58.01	53.82	56.47	2.592	4.59
	2.35	39.62	38.50	39.61	37.89	37.79	35.12	38.09	1.515	4.00
	2.89	14.35	10.44	11.41	9.410	12.89	12.27	11.79	1.767	14.98
90°	0.02	74.70	76.80	74.99	76.01	78.94	76.57	76.33	1.526	2.00
	0.32	68.87	70.17	69.28	69.63	71.13	67.34	69.40	1.280	1.84
	0.82	68.17	70.83	68.82	72.42	68.71	66.69	69.27	2.038	2.94
	1.01	64.01	61.60	62.92	61.75	61.90	60.19	62.06	1.295	2.09
	1.08	61.00	62.66	62.64	60.83	60.84	61.04	61.50	0.892	1.45
	1.52	50.50	51.04	55.66	62.29	61.23	52.39	55.52	5.169	9.31
	1.69	53.87	55.34	54.80	54.56	54.28	56.36	54.87	0.882	1.61
	2.35	37.22	35.02	37.91	35.17	31.71	37.83	35.81	2.173	6.07
	2.89	11.04	9.826	9.618	9.779	10.10	8.874	9.873	0.705	7.14

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