An Experimental Study About Dropped-ply Region Of Laminate Under Compression

In this paper, a micromechanical investigation for laminates composites with internally-dropped plies (T300/5208) has been performed by means of micro-moiréinterferometry under compression. The mechanical behaviors in the dropped-ply region were observed .The observed regions were about 2.0×2.4mm2. The high sensitive moiréfringes were obtained in very fine resolution and high quality. The resolution of moiréfringes was about 10μm, similar to the diameter of carbon fiber. And direct micro-measurement for the composite with dropped-ply region was achieved in this experiment.The mechanical behavior of dropped-ply region has also been numerically simulated using the finite element software --- MSC.MARC. The distribution of stress and strain in the dropped-ply region was measured. And the experimental results and the finite element simulation are discussed.There is a high-stress region in the dropped-ply region when the composite material specimen was pressed. There is stress concentration in this region that mainly happened at three corners of the dropped-ply region. The experimental results and the finite element simulation show that the dropped-ply region is the vulnerable area of the composite material. It is the origin of failure.