Fastening composite structures using braided thermoplastic composite rivets

2019 ◽  
Vol 54 (6) ◽  
pp. 801-812 ◽  
Author(s):  
Vincent Fortier ◽  
Jean-E Brunel ◽  
Louis L Lebel
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Joint Strength ◽  
Breaking Load ◽  
Bolted Joints ◽  
Thermoplastic Composite ◽  
Lap Shear ◽  
Riveted Joints ◽  
Manufacturing Performance ◽  
Unbalanced Load

Aerospace composite material components are currently joined using heavy titanium bolts. This joining method is not ideal when considering its weight, thermal expansion, electrical conductivity, and risk of unbalanced load distribution. We propose here an innovative fastening technology using thermoplastic composite rivets. A rivet blank is heated above its melting temperature using Joule heating and is formed directly in the composite laminates by an automated process. Carbon fiber and polyamide blanks were used with two fiber architecture: 2D braid and unidirectional. The braided architecture showed superior manufacturing performance and repeatability. Joints were riveted in less than 40 s per rivet. The temperature measured in the riveted composite laminate in the vicinity of formed rivet reached only 136℃ during riveting. Double fastener lap shear testing showed breaking load of 6146 N per fastener. This joint strength is higher than comparable aluminum-riveted joints, and the specific joint strength is higher than titanium-bolted joints. With these advantages, the technology could be developed and used in the next generations of lighter, cleaner, and safer aircraft.

Manufacturing procedure to make flat thermoplastic composite laminates by automated fibre placement and their mechanical properties

2016 ◽  
Vol 30 (12) ◽  
pp. 1693-1712 ◽  
Author(s):  
Suong Van Hoa ◽  
Minh Duc Hoang ◽  
Jeff Simpson
Keyword(s):  
Mechanical Properties ◽  
Composite Laminates ◽  
Composite Structures ◽  
High Speed ◽  
Thermoplastic Composite ◽  
Thermoplastic Composites ◽  
Thermoset Composites ◽  
Material Deposition ◽  
Manufacturing Procedure ◽  
Composites Processing

Automated fibre placement (AFP) is a relatively new process for the manufacturing of composite structures. Among many attractive features, it provides high-speed of material deposition, more repeatability in terms of quality of the part, less labour intensive (as compared with traditional methods of manufacturing such as Hand Lay-Up), less waste and the ability to transition more seamlessly from design to manufacturing. AFP can be used to process both thermoset composites and thermoplastic composites. Thermoplastic composites processing holds many potential benefits. This is because if the process is done right in producing parts with good quality, it is fast since it does not require a second process such as curing in an autoclave or oven. For the purpose of comparison of performance and for design, it is necessary to determine the mechanical properties of laminates made using this process. However, there are challenges in making flat coupons for the purpose of testing for mechanical properties. This article presents these challenges and the procedure developed to make flat laminates using a simple AFP machine. Mechanical properties of these laminates are also determined and compared with those obtained from laminates made using conventional autoclave moulding.

scholarly journals Progressive Damage Numerical Modelling and Simulation of Aircraft Composite Bolted Joints Bearing Response

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5606
Author(s):  
Guoqiang Gao ◽  
Luling An ◽  
Ioannis K. Giannopoulos ◽  
Ning Han ◽  
Ende Ge ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Composite Laminates ◽  
Composite Structures ◽  
Failure Modes ◽  
Composite Plates ◽  
Failure Criteria ◽  
Bolted Joints ◽  
Progressive Damage ◽  
User Input ◽  
Product Cycles

Finite element numerical progressive damage modelling and simulations applied to the strength prediction of airframe bolted joints on composite laminates can lead to shorter and more efficient product cycles in terms of design, analysis and certification, while benefiting the economic manufacturing of composite structures. In the study herein, experimental bolted joint bearing tests were carried out to study the strength and failure modes of fastened composite plates under static tensile loads. The experimental results were subsequently benchmarked against various progressive damage numerical modelling simulations where the effects of different failure criteria, damage variables and subroutines were considered. Evidence was produced that indicated that both the accuracy of the simulation results and the speed of calculation were affected by the choice of user input and numerical scheme.

An Experimental and Numerical Investigation on Bolted Joints of Woven Glass Fabric/Epoxy Composites

2020 ◽  
Vol 05 (03) ◽  
Keyword(s):  
Numerical Modelling ◽  
Composite Laminates ◽  
Joint Strength ◽  
Mechanical Response ◽  
Failure Load ◽  
Bolted Joints ◽  
Glass Fabric ◽  
Element Analysis ◽  
Bearing Strength ◽  
Fabric Composites

In the present work, an attempt is made to study the mechanical response of woven glass fabric/epoxy composite laminates using numerical modelling and experimentation. For this two different configurations namely double lap joined with single and double bolts are chosen. These laminates are subjected to numerical modelling using finite element analysis to study the joint strength and stress analysis. The joint strength of woven glass fabric composites is studied experimentally by conducting tensile test. Along with this the effect of varying edge distance to diameter ratios are studied both numerically and experimentally to arrive at safe design. Both numerical analysis and experimentally obtained bearing strength of composite laminated bolted joints are correlated. This is done in order to predict the the failure load and failure mechanisms in the composite laminate bolted joints. The variation in the numerically and experimentally obtained bearing strength values were well within 5% diference for both cases of single and double bolted joints.

scholarly journals An investigation of the stitching effect on single lap shear joints in laminated composites

2019 ◽  
Vol 26 (1) ◽  
pp. 509-516
Author(s):  
Wang Peiyan ◽  
Geng Xiaoliang ◽  
Zhao Chen ◽  
Zhang Rongshuo
Keyword(s):  
Elevated Temperature ◽  
Bond Strength ◽  
Composite Laminates ◽  
Composite Structures ◽  
Failure Modes ◽  
Epoxy Adhesive ◽  
Lap Joints ◽  
Single Lap Joints ◽  
Working Environments ◽  
Lap Shear

Abstract This paper aimed to investigate the stitching effect on the bond strength of single lap shear joints in carbon/epoxy composite laminates using experimental and simulation methods. Stitched and unstitched single lap shear joints were bonded using the EC-3448 epoxy adhesive and tested under different working environments, including room temperature/dry (RTD), elevated temperature/wet (ETW) and cold temperature/dry (CTD). The results showed that stitching improved the bond strength of the stitched single lap joints, with approximately 60% higher strength for stitched compared to unstitched lap joints under RTD and CTD environments and 10% higher strength under an ETW environment. The increase was smaller under ETW conditions because the adhesive recured under elevated temperature. Embedded interactions connected the lapping plates and the stitch line, and the maximum stress failure criterion was adopted for the stitch line. As the predicted failure modes are consistent with the experimental results, the progressive damage mode can be applied to simulate stitched composite structures.

Experimental study and finite element analysis on the joining performance of GF/PP rivets

2020 ◽  
pp. 089270572093914
Author(s):  
Yuan Wang ◽  
Yong Li ◽  
Dajun Huan ◽  
Lisha Li ◽  
Li Liu ◽  
...  
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Joint Strength ◽  
Simulation Analysis ◽  
Lap Joints ◽  
Thermoplastic Composite ◽  
Failure Behavior ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Riveted Joints

To improve the performance of thermoplastic composite joints and reduce the weight of joints, glass fiber (GF)/polypropylene (PP) thermoplastic composite rivets (GF/PP rivets) were prepared and tensile test and simulation analysis of GF/PP-riveted single-lap joints were carried out. Based on the tensile test, the optimum extension length of GF/PP rod with different diameters was determined by taking the specific joint strength (the ratio of joint strength to the weight of fasteners) as the evaluation index. The effects of the rivet diameter and the thickness of composite laminates on the specific joint strength and the weight reduction of GF/PP-riveted single-lap joints were studied. The joining mechanism and the failure behavior of GF/PP-riveted joints were analyzed by finite element simulation. The experimental results indicate that the specific joint strength of GF/PP-riveted joints decreased with increasing rivet diameter and laminate thickness. For the same specific joint strength, the weight of fasteners at joints could be reduced by 81.4% and 73.9%, respectively, by using GF/PP rivets instead of steel bolts and aluminum blind rivets. The simulation results show that the change of inclination angle of rivet body would cause the change of failure mode of joints.

scholarly journals Evaluation of Single-Lap and Block Shear Test Methods in Adhesively Bonded Composite Joints

2021 ◽  
Vol 5 (1) ◽  
pp. 27
Author(s):  
Alec Redmann ◽  
Vinay Damodaran ◽  
Felix Tischer ◽  
Pavana Prabhakar ◽  
Tim A. Osswald
Keyword(s):  
Composite Structures ◽  
Joint Strength ◽  
Adhesive Bonding ◽  
Failure Modes ◽  
Shear Loading ◽  
Analytical Models ◽  
Normal Stresses ◽  
Block Shear ◽  
Lap Shear ◽  
Shear Joint

Adhesive bonding is increasingly being used for composite structures, especially in aerospace and automotive industries. One common joint configuration used to test adhesive strength is the single-lap shear joint, which has been widely studied and shown to produce significant normal (peeling) stresses. When bonding composite structures, the normal stresses are capable of causing delamination before the adhesive bond fails, providing inconclusive engineering data regarding the bonding strength. An alternative test is the block shear joint, which uses a shorter sample geometry and a compressive-shear loading to reduce normal stresses. Analytical models proposed by Goland and Reissner and Hart-Smith are used to compare the edge-bending moment for the two joint configurations. The stress distributions along the bondline are also compared using finite element analysis. Experimental tests are conducted to evaluate these analyses and the failure modes of each configuration are recorded. Block shear samples demonstrate a joint strength over 100% higher than single-lap shear specimen bonded with the same adhesive material. The lower joint strength measured in single-lap shear is found to be potentially misleading due to delamination of the composite adherend.

Influence of surface roughness, friction coefficient, and wrap angle on clinching joint strength and its correlation with belt friction phenomenon

2021 ◽  
pp. 135065012110253
Author(s):  
Santosh Kumar ◽  
Vimal Edachery ◽  
Swamybabu Velpula ◽  
Avinash Govindaraju ◽  
Sounak K. Choudhury ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Joint Strength ◽  
Joint Interface ◽  
Cross Sectional ◽  
Lap Shear ◽  
Mathematical Correlation ◽  
Mechanical Clinching ◽  
Wrap Angle

Clinching is an economical sheet joining technique that does not require any consumables. Besides, after its usage, the joints can be recycled without much difficulty, making clinching one of the most sustainable and eco-friendly manufacturing processes and a topic of high research potential. In this work, the influence of surface roughness on the load-bearing capacity (strength) of joints made by the mechanical clinching method in cross-tensile and lap-shear configuration is explored. Additionally, a correlating mathematical model is established between the joint strength and its surface parameters, namely, friction coefficient and wrap angle, based on the belt friction phenomenon. This correlation also explains the generally observed higher strength in lap-shear configuration compared to cross-tensile in clinching joints. From the mathematical correlation, through friction by increasing the average surface roughness, it is possible to increase the strength of the joint. The quality of the thus produced joint is analyzed by cross-sectional examination and comparison with simulation results. Experimentally, it is shown that an increment of >50% in the joint strength is achieved in lap-shear configuration by modifying the surface roughness and increasing the friction coefficient at the joint interface. Further, the same surface modification does not significantly affect the strength in cross-tensile configuration.

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