UWE Bristol Engineering showcase 2015

Sophie Tredwell
BEng (Hons) Motorsport Engineering
Project Supervisor
Ramin Amali
Analysis of the mechanical properties of sandwich panels when subjected to
moisture
Introduction
Sandwich panels are increasingly becoming a popular choice and are used for
many applications in different industries. Favoured because of their light weight,
durability and high strength to weight ratio, they are being used for applications as
varied as the survival shell of a Formula One car, to being used in the deck of a
ship.
Experimental Analysis
Experiments were conducted to find out whether different types of foam samples
were able to absorb moisture. The saturated foam samples were then subjected to
a three-point bending test to determine if the moisture had any effect on the
maximum deflection of the beam. The decrease in maximum deflection increases
the modulus of elasticity of each foam sample.
Theoretical Analysis
Using a series of matrices, including stress and strain transformations, the factor of
safety of each layer of the composite can be calculated and the overall minimum
value can be found as the factor of safety of the whole panel. By changing the
modulus of elasticity used from the original value to the value calculated after 90
minutes of moisture subjection the change in factor of safety can be calculated.
FEA Analysis
FEA software Abaqus/CAE was used to simulate a pressure load acting on the
panel with the same dimensions as the theoretical analysis. The simulation was
used to determine if the moistures effect on the modulus of elasticity had any
effect on the maximum stress on the panel and also its maximum deflection.
Conclusion
The results showed that the factor of safety for the whole panel remained the
same after moisture had been absorbed, but the factor of safety of just the foam
decreased from 6.0 to 5.7. The FEA results showed that the panel subjected to
moisture had a smaller maximum deflection and the stresses in both the direction
of the fibers and the perpendicular direction were reduced. The overall stress of
the panel remained the same however, which is unsurprising as the force and area
were constant.
The deflection of the plate before moisture
absorption (m)
The deflection of the plate after moisture
absorption (m)
Project Summary
The project was carried out to determine
what effects, if any, moisture absorption had
on the mechanical properties of foam cored
sandwich panels.
Project Objectives
The main objectives of the project were;
• To conduct experiments, including
moisture absorption and a three-point
bending test, on a range of different type
of foams that can be used as the cores of
the panels.
• To determine if the moisture absorbed by
the panels had any effect on the
mechanical properties of the foam.
• To use matrices to calculate the factor of
safety of the panels both before and after
moisture absorption.
• To simulate these changes in Abaqus/CAE
to determine whether the moisture has
any effect on how the panels perform.
Project Conclusion
The results showed that the moisture
increased the modulus of elasticity of the
three samples of foam as after moisture
absorption the foam had a smaller maximum
deflection. It was found that the moisture
reduced the factor of safety of the foam, but
this wont have an effect on the panel as the
factor of safety of the laminas was lower.