STUDY OF FATIGUE BEHAVIOUR OF COMPOSITES
UNDER GUIDANCE OF-
Mrs.M.S.DURGAKAR
Metallurgical and Materials Engineering Department,
Visvesvaraya National Institute of Technology,
Nagpur (M.H.) -440010
India
1.INTRODUCTION
Composite materials are widely used in numerous aerospace, automotive, and construction applications because of high specific strength compared to metallic materials. Many of this applications involve components that are subjected to cyclic loading which desires a good fatigue-resistance. Fatigue damage of composites is a complex process that involves many different damage mechanisms, such as matrix cracking, fiber breakage, fiber-matrix debonding and delamination.
Most of the tests dealt with fatigue of composites under constant amplitude loading. However, in service loadings on aircraft structures are random in nature.
The test deals with the variable amplitude loadings, this type of condition is simulated in the laboratory and the specimen tested.
The aim of this work is to study the effect of block loading sequence and low energy impact damage on fatigue behavior of CFC composites. Experiments were conducted on CFC specimens under a typical flight block loading. The residual stiffness was monitored at regular intervals. Three different maximum stress/strain levels were employed in this investigation. The present investigation also aims to collecting the relevant observations for plydrop composite laminates manufactured by a special technique called VERITy and relate them to the life/probable failure mechanism.
2.EXPERIMENT
For studying the effect of block loading the material used in this investigation is T300/913C carbon fiber composite laminate. The nominal ply thickness is about 0.15mm and the fiber volume is about 0.6mm3. The laminate was prepared with a lay-up sequence of [(+45/-45/90/0/90/-45/+45)s]s. Static tensile tests were conducted in the beginning to the determine the stress levels used in fatigue. All the tensile test were conducted using standard test specimens and as per ASTM D 3039 specifications. Fatigue test specimens were prepared from the laminate specimens were 140mm(length) and 35(width),Fatigue test were done on undamaged and low energy impact damaged CFC specimens,for low energy impact damaged specimens the 5j impacts were given in the center of the specimen on Dynatup impact testing machine.
SHASHANK CHHAJER
