Effect of Rivet Structure on Friction Riveting Process and Mechanical Behavior of CFRP/Titanium Alloy Joints

doi:10.3969/j.issn.1004-132X.2026.09.026

Abstract

Abstract:

A C-PDFR process was proposed for pre-drilled CFRP/titanium alloy stacks using semi-tubular rivets. A titanium rivet was driven into a CFRP pre-hole， then rotated at high speed against a titanium alloy plate to achieve friction welding between the tubular rivet and the plate， while the rivet head locked the CFRP， forming high-performance joints. The effects of outward-inclined， symmetrical， and inward-inclined rivet tips on material flow direction and rivet/Ti-plate interfacial bonding quality were investigated. The microstructure， hardness distribution， and tensile-shear performance of typical joints were analyzed. The results show that a fine-grained stirred zone is formed at the rivet/Ti-plate interface. Under the rotational feed of the rivet， metal flash is generated from the stirred zone and flows toward both the inner and outer sides of the rivet. Outward-inclined/symmetrical rivets cause significant inward flash flow， degrading bonding， whereas inward-inclined rivets suppress inward flow， enhancing bonding quality. Tensile-shear tests demonstrate low-strength interfacial failure for outward-inclined rivets versus high-strength rivet shear fracture for inward-inclined variants， with peak force and energy absorption increasing by 137.0% and 159.1%， respectively.

Key words: composite-pre-drilled friction riveting （C-PDFR）, carbon fiber reinforced polymer （CFRP）, titanium alloy, semi-tubular rivet, failure mechanism

摘要：

针对预制孔复合材料与钛合金叠层构件，提出基于半空心铆钉的复材单层制孔摩擦铆焊（C-PDFR）工艺：驱动钛合金铆钉进入CFRP板材预制孔，铆钉高速旋转与钛合金板材相互作用，实现管状铆钉体与板材的摩擦焊连接，并通过钉帽锁紧CFRP板材，实现CFRP与钛合金的高性能连接。研究了外倾型、对称型、内倾型铆钉尖端结构对摩擦焊过程中材料流动方向、铆钉/钛板界面焊合质量的影响规律，分析了典型接头的微观组织特征、硬度分布及拉剪性能。结果表明，铆钉/钛板界面形成了细晶搅拌区，在铆钉的旋转进给作用下，细晶区形成金属飞边，并向铆钉内外侧流动。采用外倾型或对称型铆钉时，大量金属飞边流向铆钉内部，造成界面焊合质量降低。而内倾型铆钉能够有效抑制金属飞边向内部流动，进而改善界面焊合质量。外倾型铆钉获得的接头在拉剪测试中呈现低强度界面失效，而内倾型铆钉的接头呈现高强度铆钉剪切断裂，拉剪峰值力和能量吸收分别提高了137.0%和159.1%。

关键词: 复材单层制孔摩擦铆焊, 碳纤维增强复合材料, 钛合金, 半空心铆钉, 失效机理

CLC Number:

TG44

ZHU Feng, YU Feilong, ZHOU Entao, WAN Hailang, MA Yunwu, GE Ende, ZHAO Yixi, LI Yongbing. Effect of Rivet Structure on Friction Riveting Process and Mechanical Behavior of CFRP/Titanium Alloy Joints[J]. China Mechanical Engineering, 2026, 37(9): 2334-2342.

朱峰, 余飞龙, 周恩涛, 万海浪, 马运五, 葛恩德, 赵亦希, 李永兵. 铆钉结构对CFRP/钛合金摩擦铆焊工艺及接头力学行为的影响[J]. 中国机械工程, 2026, 37(9): 2334-2342.

Figures/Tables 19

Fig.1 The appearance and dimension of different rivets

Tab.1 The chemical composition of TC4 titanium alloy （mass fraction）

材料牌号	w（Ti）	w（Al）	w（V）	w（Fe）	w（Si）	w（C）	w（N）	w（H）	w（O）
TC4	余量	5.5∼6.8	3.5∼4.5	0.30	0.10	0.10	0.05	0.015	0.015

Tab.2 The mechanical properties of CFRP-T300 and TC4 titanium alloy

材料	弹性模量/GPa	屈服强度/MPa	极限抗拉强度/MPa	延伸率/%
CFRP-T300	230		911	2.0
TC4（板材）	110	860	996	12.0
TC4（铆钉）	110	825	932	18.0

Fig.2 SEM and EBSD results of TC4 base material

Fig.3 Schematic diagram of C-PDFR process

Fig.4 Friction self-piercing riveting experimental system

Fig.5 The schematic showing geometrical features of C-PDFR

Fig.6 The sample size of tensile-shear specimens for joint mechanics performance testing

Fig.7 The comparative macro-metallography for different riveting joints

Tab.3 The residual joint height of different riveting joints

铆钉类型	铆钉剩余高度 $H r e s$
铆钉类型	$χ$ =1.0 mm	$χ$ =1.5 mm	$χ$ =2.0 mm
铆钉A	5.21 mm	4.71 mm	4.24 mm
铆钉B	5.13 mm	4.59 mm	4.19 mm
铆钉C	5.10 mm	4.55 mm	4.17 mm

Tab.3 The residual joint height of different riveting joints

铆钉类型	铆钉剩余高度 $H r e s$
铆钉类型	$χ$ =1.0 mm	$χ$ =1.5 mm	$χ$ =2.0 mm
铆钉A	5.21 mm	4.71 mm	4.24 mm
铆钉B	5.13 mm	4.59 mm	4.19 mm
铆钉C	5.10 mm	4.55 mm	4.17 mm

Fig.8 The welding area for different riveting joints（χ=1.0，1.5，2.0 mm）

Fig.9 The interface joining characteristics of C-PDFR joint（rivet B）

Fig.10 EBSD results of different sections for rivet B joint

Tab.4 Grain size and low-angle grain boundary fraction in different regions（rivet B）

区域	平均晶粒尺寸/μm	晶粒尺寸中位数/μm	小角度晶界占比/%
Ⅰ区	2.30	1.65	22.9
Ⅱ区	0.93	0.65	14.3
Ⅲ区	2.68	1.48	65.2
Ⅳ区	3.26	2.35	49.4
Ⅴ区	1.07	0.92	19.0
Ⅵ区	1.16	0.87	23.1

Fig.11 The hardness characteristic and affected zone partition of different rivet joints

Fig.12 The tensile-shear fracture section of different rivet joints

Fig.13 The SEM images of fracture surface for different rivet joints

Fig.14 The tensile-shear load-displacement curves of different riveted joints

Fig.15 The tensile-shear peak load， fracture surface area， tensile-shear strength， and fracture energy absorption of different rivet joints

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