JEC COMPOSITES MAGAZINE - Issue #109 - November/December 2016 - 63

Structural certification analysis and reports for aircraft interiors

Materials
Stowage units are constructed from flat phenolic glassfibre composite honeycomb panels. The phenolic materials comply with the fire,
smoke and toxicity (FST) regulations. The composite panels comprise of two 0/90 glassfibre skins in a phenolic resin that sandwich a
phenolic honeycomb core. Each skin is approximately 0.4 mm thick.
The honeycomb core material can be either 12.5mm or 19.5mm depending upon which part of the monument the panel thickness is
assigned to.

Fig. 3: Position of feet attachment to seat rails of aircraft

Stowage unit attachment to aircraft seat rails
The four feat attachments are fixed to the underside of the floor panel of the Stowage unit and fastened to the seat rails. In the example,
the two sets of feet attachments are 900mm apart and their aircraft
coordinates are shown in Figure 3. The feet attachments are simulated in the FEA model as 3-triangular TET3 elements. Their common
element node at the apex is connected to a Bar2 element (Table 1).
The other end of the Bar2 element is fixed in all degrees of freedom.
Three Bar2 elements are allocated equal values of translational stiffness in x and y. The Bar2's z value translational stiffness is approximately one third of the stiffness of the x and y.

Fasteners
The composite panels are connected by potted metal threaded inserts sometimes known as a single part ferule. These inserts are located at specific points along the edge of the adjacent panels. Holes
are drilled along the length of the glassfibre panel and near the edges,
through the glassfibre topskin into the honeycomb, stopping short
of the lower skin. The steel threaded insert is bonded into position.

The material properties are allocated to the FEA model by use of
the MAT8 card which has a cross reference number to the PCOMP
card. The minimum Young's Modulus and strength allowables of
the glassfibre skins are given to both 0 and 90 degree material direction on the MAT8 card. This property and strength allocation is
considered to present a conservative approach if error happens during composite panel orientation during manufacture. The glassfibre
skin, core thickness and stacking sequence with orientation angle of
the composite panel are entered into the PCOMP card.

Load balance,
model quality control
Model quality control is established by the results of load balance.
Hand (classical) calculation is used to determine the combined
centre of gravity of the Stowage unit structure including its contents
defined in the x, y and z directions from an arbitrarily chosen point
on the structure. The calculated x coordinate value (Equation 1) is
165.86mm (Table 1) from a reference corner point selected on the
Stowage unit (Figure3).
xbar = (Σ(w*x))/(Σw)

(Equ. 1)

A possible template for calculating the centre of gravity calculations in
MS-Excel is shown in Table 1, The centre of gravity coordinates derived at this stage need to be extremely similar to those obtained from

An FEA model fastener simulation of the steel threaded inserts is
made by using mpc-elements. In this
case an RBE2 type is used (purple Tab. 1: Centre of gravity derivation by hand calculation
colour) at these particular locaDATUM
tions (Figure 6). The mpc-elements
X
10000
Y
647.7
connect one single (independent)
-140.5
Z
node on the panel's element mesh
Description
Weight Kg X (mm)
Y (mm)
to its corresponding (dependent) Item n°
node on the adjacent panel. Only
Floor stowage
1
24.9
165.859
328.71
the translation degrees of freedom
Floor stowage
2
24.9
165.859
966.69
of UX, UY and UZ may be assigned
3
Coats
17.9
165.859
328.70
to the dependent node. To simulate
17.9
165.859
966.69
4
Coats
the door mechanisms, mpc's that are
associated with the door hinges have
Internal contents
85.6
165.859
647.70
all degrees of freedom fixed except
Structural allowance
84.00
165.859
647.70
for the one rotation about the Z-axTotal contents Kgs
169.60
is. The door latch is modelled with
all degrees of freedom fixed except
mm
Local centre of gravity
Local centre of gravity
Xbar
Xbar
165.86
translation in the Y-direction. The
Ybar
Ybar
647.70
hinge mpc's are at a regular pitch.
Zbar

643.17

Z (mm)

W*X

W*Y

W*Z

151.18

4130

8185

3764.41

151.18

4130

24071

3764.41

907.13

2969

5884

16237.63

907.13

2969

17304

16237.63

467.34

14198

55443

40004.07

822.35

13932

54407

69077

28130

109850

109081

Zbar

No109 November-December 2016

/ jec composites magazine

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #109 - November/December 2016