Functionally graded joints by dielectric heating
Visualitza/Obre
Estadístiques de LA Referencia / Recolecta
Inclou dades d'ús des de 2022
Cita com:
hdl:2099.1/25211
Tutor / directorMartins da Silva, Lucas Filipe
Realitzat a/ambUniversidade do Porto
Tipus de documentProjecte/Treball Final de Carrera
Data2013
Condicions d'accésAccés obert
Llevat que s'hi indiqui el contrari, els
continguts d'aquesta obra estan subjectes a la llicència de Creative Commons
:
Reconeixement-NoComercial-SenseObraDerivada 3.0 Espanya
Abstract
The most traditional methods of fastening such as bolts or rivets have been used for
decades. However, these cause stress concentrations and premature failure in materials,
while adhesive bonds spread the load more evenly over the surface, facilitating a lighter
and cheaper overall structure. That is the main reason why adhesively bonded joints are
increasingly used in aerospace and automotive industries.
The single lap joint (SLJ) with metallic or composite flat plates is the most common
mainly due to its simplicity and efficiency. However, one major drawback associated to
this joint is the occurrence of shear and peel stress concentrations at the end of the
adhesive layer. This leads to joint premature failures at the ends of the overlap.
The main objective of the present project is to use an adhesive functionally modified
and cured by dielectric heating. This allows a more uniform stress distribution along the
overlap and would permit to work with much smaller areas, reducing considerably the
weight of the structure and give more reliable joints.
In the present project two ways to obtain graded joints were tested. The first way was to
obtain a graded cure of the adhesive using different local concentrations of microwave
absorbing particles (carbon black) along the overlap. The particles interact with the
magnetic field and heat the adhesive. The second way was to use the carbon black to
reinforce the adhesive and obtain graded mechanical properties along the overlap and
cure isothermally by dielectric heating.
Then, a preliminary experimentation was done in order to determine the viability of
main objectives. The results proved the impossibility to perform a graded joint by a
graded cure of the adhesive. This is due to several factors such as the conductivity of the
adherends or the non uniformity of the magnetic field. Therefore, the second
methodology proposed to achieve a graded joint was followed. The effect of carbon
black in the adhesive properties was studied and graded joints were manufactured and
tested.
Finally, the results obtained were discussed and analyzed. Bulk tensile tests showed an
improvement of the ductility as function of carbon black concentrations. Thus, graded SLJs were manufactured using a high local concentration of carbon black at the end of
the overlap. This made the adhesive more ductile and a higher joint strength was
obtained due to the lower stress concentrations.
Also, a failure prediction was done. For graded joints the analytical model used gave
accurate predictions. However, for the joints with uniform properties the predictions
were too much different and several hypotheses were proposed to explain this.
TitulacióENGINYERIA INDUSTRIAL (Pla 1994)
Fitxers | Descripció | Mida | Format | Visualitza |
---|---|---|---|---|
Functionally gr ... by dielectric heating.pdf | Report | 4,327Mb | Visualitza/Obre |