Papers by Keyword: Double Cantilever Beam

Abstract: Earlier presented the geometrically nonlinear model of a flexible beam (cylindrical bending of a plate) was used for analysis of post-buckling behavior of the layered composite with delamination at compression. In this paper the model is used for more details nonlinear analysis of double cantilever beam (DCB) that used in standard test for determination of the interlaminar fracture toughness composites with delamination-type damage. The main advantage of the model is a precise description of the curved axis of the beam (plate) without linearization or other higher order approximations. The exact solution of bending differential equation finally can be expressed in terms of the incomplete elliptic integrals of the first and second kind. The model describes only geometrically nonlinear effect of DCB arms bending (global effect) and should be combined with the procedure of effective delamination extension to correct DCB arms rotation at delamination front (local effect). First of all the nonlinear model can serve as a tool to estimate the possible error due the geometrical nonlinearity in comparison with linear solution. On the other hand, this model can be effectively used to determine interlaminar fracture toughness using DCB samples at large deflections. Validation of the model is made using data of standard tests of glass/epoxy DCB samples.

Abstract: Carbon fiber reinforced polymer matrix composites have been widely used in many fields. It is necessary to test the performance of interlaminar fracture toughness of composites and provide useful information for product development and material selection. In this paper polymer matrix films embedding with carbon fiber reinforced composite laminates curing at high temperature were used to study the performance of model I inter-laminar fracture toughness. Mode I interlaminar fracture toughness of composites reinforced by carbon fiber was measured according to ASTM D5528 standard. Three groups of samples cut into double cantilever beam (DCB) specimens were measured to compare their performance. The results showed that there was no fiber-bridging in multidirectional composite laminations. The delamination for all specimens extended slowly and stably. All of three groups of carbon fiber composites had strong model I interlaminar fracture toughness and high delamination tolerances. The sensitive to delamination is different because of different composition of these three carbon fiber reinforced composites.

Abstract: The double cantilever beam (DCB) test method and the modified beam theory are adopted to investigate the Mode I interlaminar fracture toughness of multi-directional composite laminates. The test procedure was developed by using a stereoscopic microscope to observe the delamination front tip and a testing machine to record the displacement and load data. A dial indicator was used to eliminate the error due to initial clearance in the clamp. A modified beam theory and a compliance calibration method were used to calculate the interlaminar fracture toughness. The Mode I interlaminar fracture toughness of carbon fiber reinforced bismaleimide resin matrix (BMI) composite laminates with four different interface patterns ( 0/0, 45/-45, 0/-45 and 0/90, respectively) was obtained. The results show that the patterns of interface ply angles have an obvious influence on Mode I interlaminar fracture toughness of composite laminates.