OF A COMPOSITE CRUCIFORM SPECIMEN UNDER BI-DIRECTIONAL
R. Soni, Mohan Balan, Charles Cross
and Glass/AMB-21 woven fabric, polymer matrix
composites (PMCs), are potential high temperature
materials being considered for aircraft engine
applications. Both of these material systems
have been subjected to a considerable amount
of mechanical testing, including bi-directional
combined tension and bending as well as bi-directional
in plane loading. For both material systems,
the 12-ply laminate orientation is (0/45)3S.
All the effective properties (compressive, tensile
and shear) of these materials have been measured
by AdTech (1), and these properties are utilized
for predicting the laminate behavior.
paper deals with the stress and strength analysis
of cruciform specimen shown in Figures 1 and
2. Both analytical and experimental studies
are conducted. A general purpose FEA software
(SDRC I-DEAS) is used to develop a finite element
model shown in Figures 7 and 8 to conduct the
stress analysis of a composite specimen under
bi-directional loading conditions. The loading
is in the x and y directions of the specimen.
At the intersection of the cruciform legs, two
types of curvatures are considered to create
different stress concentrations. One increases
the stress concentration while the second decreases
the stress concentration at the intersection.
The representative case finite element results
for maximum stress components for both kinds
of specimens are given in bar chart form. These
results give an indication of the possible mode
and location of failure. The experimental results
are compared with the FEA predictions. Failure
loads for specific loading is calculated by
using the computer code (2) called, “Automated
System for Composite Analysis”, (ASCA).
The newly developed unique multi-axial testing
system in the Turbine Engine Fatigue Facility
of the Propulsion Laboratory, Air Force Research
Laboratory (AFRL/PRTC) at Wright Patterson Air
Force Base is used. There exists a good agreement
between experimental and predicted results.