Polymer matrix woven fabric composites subjected to low velocity impact. I. Damage initiation studies

An investigation was undertaken to study the damage initiation behavior in polymer matrix laminated composite plates subjected to a transverse central low velocity point impact load. Inplane failure of the layers in the form of matrix cracking/lamina splitting and delaminations were the primary objectives of the study. The study has been carried out using modified Hertz contact law and an inhouse three-dimensonal transient finite element analysis (FEA) code. The inplane failure functions and the interlaminar failure functions have been predicted using quadratic failure criteria. The inhouse FEA code was validated with other analytical studies and the experimental results in our earlier owrk. The present studies have been carried out on different plain weave fabric laminated composite plates, simply supported on all four sides. For comparison, impact behavior of balanced symmetric crossply (CP) laminates made of undirectional (UD) layers and UD composites has been included. The studies have been carried out with plate dimensions of 150x150 mm with different plate thicknesses. Incident impact velocity in the range of 1 m/sec to 3 m/sec and impactor mass of 50 gm are considered. General observations on the distribution of failure functions and the initiation of damage are presented. Materials used are glass/epoxy and carbon/epoxy composites.