Numerical analysis of adhesively bonded T-joints with structural sandwiches
and study of design parameters
, A. Ghaznavi
Centre of Excellence for Research in Advanced Materials and Structures, Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran, Iran
Available online 26 February 2011
Finite element stress analysis
Adhesively bonded T-joints are extensively used in assembling sandwich structures. The advantage of
adhesive bonded joints over bolted or riveted joints is that the use of fastener holes in mechanical joints
inherently results in micro and local damages to the composite laminate during their fabrication. One
type of adhesive joint in such structures is the T-joint between sandwich panels. The aim of this
research paper is to study, by numerical analysis, the effect of ﬁllet geometry and core material of
sandwich panels on the performance of T-joints. The base angle of the core triangle (ﬁllet) is the most
important geometry parameter of the triangular T-joint. Nine geometrical models with different base
angles of the core triangle are made to investigate the effect of the base angle on the performance of the
T-joints. It should be mentioned that the base angle in the triangular foam is changed, so that the ﬁnal
volume of the ﬁller is kept constant in all the cases. Different foams with different stiffness are used to
model the core of the panels to study the effect of the core material of sandwich panels. To model the
adhesive between joint components, contact elements and cohesive zone material models are used.
Therefore, failure of adhesive and separation of joint elements can be modeled. Damage and core shear
failure of the base panel are modeled by using a written macro-code in the ANSYS ﬁnite element
method (FEM) program. The ultimate strength of the joint in each case is calculated by modeling
adhesive failure and core shear failure of the sandwich panels. Finally, the results of FEM are validated
by experimental results available in the literature. In general, the failure load predicted by the FEM is
within 5% of the experimental results. The best angle of the core triangle was found to be 451. Also, the
results showed that by changing the core material of the sandwich panel, the joint failure load is also
& 2011 Elsevier Ltd. All rights reserved.
Structural sandwich elements have gained widespread accep-
tance within the automotive, marine, aerospace and sustainable-
energy industries. This is primarily due to their low weight
combined with high bending stiffness, high buckling resistance
and adequate strength . Although sandwich constructions pos-
sess high bending rigidities, they are locally quite ﬂexible and
weak, because of their very high strength or stiffness to weight
ratios. They are especially susceptible to damage inﬂicted by
concentrated loads such as impact of hard objects. For the same
reason, joining sandwich panels presents a great challenge .
Banea and da Silva  reviewed comprehensively investigations on
adhesively bonded joints of ﬁber-reinforced plastic (FRP) compo-
site structures (single skin and sandwich construction). The effects
of surface preparation, joint conﬁguration, adhesive properties and
environmental factors on the joint behavior were described brieﬂy
for adhesively bonded FRP composite structures. The analytical and
numerical methods of stress analysis required before failure pre-
diction were discussed. The numerical approaches covered both
linear and non-linear models. They showed that an accurate
strength prediction of the adhesively bonded joints was essential
to decrease the amount of expensive testing at the design stage .
Several types of joints and joining methods are prevalent in
industry. Typical joint designs include single lap, scarf, double lap
and T-joints, and typical joining methods include adhesive bonding
and structural mechanical fastening .
One of the most common adhesive joints between sandwich
panels is the sandwich T-joint that consists of the base sandwich
panel, the leg panel, ﬁllets and ﬁller, as shown in Fig. 1. The
function of a T-joint is to transmit ﬂexural, compressive, shear
and tensile loads between the leg panel and the base panel .
Many authors have investigated the single composite skin
T-joint [4–9]. T-joints with transverse stitching using the Resin
Transfer Molding (RTM) process and Ciba–Geigy epoxy resin were
evaluated by Shenoi et al. . They showed that transverse
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International Journal of Adhesion & Adhesives
0143-7496/$ - see front matter & 2011 Elsevier Ltd. All rights reserved.
E-mail address: firstname.lastname@example.org (S.M.R. Khalili).
International Journal of Adhesion & Adhesives 31 (2011) 347–356