No abstract

When polyethylene terephthalate (PET) is stretched, it exhibits strain-hardening properties, which are temperature and strain-rate dependent. In this paper, two grades of PET are experimentally characterized using biaxial tests. A visco-hyperelastic model is used to describe the stretching behavior for the polymer. A biaxial characterization method is employed to determine the model parameters using a robust nonlinear curve-fitting program. This model can represent adequately well the stretching behavior of PET. Based on this model, the membrane finite element formulation is developed to simulate the stretch blow molding process. Two bottles of different designs, produced based on the single-stage injection blow molding process, are used to validate the model. Good agreement with the bottle thickness profile is observed.

The resin flow through fiber reinforcements in Compression Resin Transfer Molding (CRTMI has been modeled by Pham et aL (1). First the preform is partially filled by resin during the injection phase. Then it is compressed by the mobile part of the mold. The resin flow in the fiber bed is governed by Darcy's law. The consolidation of the saturated preform is described by the total mass conservation. A mathematical model is developed for thin curved composite parts. A filling algorithm based on resin conservation on a deformable grid is used to advance the flow front at each time step. Resin pressure and velocity are calculated by the finite element method. Several control parameters of the CRTM process are investigated in this study, such as the compaction speed of the mold upper wall, the injection pressure and the closing/opening of the injection gate. The numerical model allows the calculation of pressure distribution in the mold, which is compared with analytical solutions and experimental results. . schematics of the c m process. U m p art \ DisplacementU method. Shell elements are used to discretize the domain. The resin flow occurs in a two-dimensional space. The consolidation of the preform happens in the thickness, which is considered an independent parameter of each element.First, the experimental results of Wirth et aL (4) are compared with analytical and numerical solutions. Regular and non regular meshes with conforming and non conforming triangular elements are employed to study the sensitivity of the solution. Then, the results of 2D Cartesian numerical simulation is compared with the exact solution obtained in the cylindrical coordinate system. Finally, the numerical model allows studying the effect of compression on the filling of a composite part for different compaction speeds, injection pressures or injection flow rates. , JUNE 1999, V d . 20, No. 3 POLYMER COMPOSITES

Predicting failure stress and failure modes in composite laminates is very difficult. The choice between failure criteria is complex and there is a lack of experimental study to validate the results obtained. In this paper, a theoretical and experimental study of damage progression and failure modes of graphite-epoxy laminates in three points bending tests is presented. A quasi-isotropic [(± 45/9010)]5 graphite-epoxy composite is investigated. C-scan method and microscopic sectioning permit to monitor damage progression and failure modes during the experiment. Specimens at different failure levels are used to determine damage progression and the effect of geometrical parameters on the successive failures and on failure modes is studied. The progression of damage has been followed experimentally and identified in detail. The theoretical study is based on the classical laminate theory in the case of in-plane loads. A software program has been elaborated for post-failure treatment and experimental results are compared with numerical predictions.

Quality control is an important factor for manufacturing companies looking to prosper in an era of globalization, market pressures, and technological advance. The functionality and product quality cannot be guaranteed without this important aspect. Manufactured parts have deviations from their nominal (CAD) shape caused by the manufacturing process. Thus, geometric inspection is a very important element in the quality control of mechanical parts. We have focused here on the profile inspection of non-rigid parts which are widely used in the aeronautic and automotive industries. Non-rigid parts can have different forms in a freestate condition compared with their nominal models due to residual stress and gravity loads. To solve this problem, dedicated inspection fixtures are generally used in industry to compensate for the displacement of such parts for simulating the use state in order to perform geometric inspections. These fixtures and the inspection process are expensive and time-consuming. Our aim is therefore to develop an inspection method which eliminates the need for specialized fixtures by acquiring a point cloud from the displaced part using a contactless measuring system such as optical scanning and comparing it with the CAD model for the identification of deviations. Using a non-rigid registration method and finite element analysis, we will numerically inspect the profile of a non-rigid part. To do so, a simulated displacement is performed using an improved definition of boundary conditions for simulating unfixed parts. In this paper, we will apply an improved method on two industrial non-rigid parts with free-form surfaces simulated with different types of displacement, defect, and measurement noise.