Composites Manufacturing最新文献

When designing filament-wound parts, use of an integrated strategy is recommended to take advantage of the benefits of composites despite limitations of the filament winding process. This paper describes a computer-integrated methodology for the design of filament-wound parts which includes: (1) initial part design using a computer-aided design system; (2) preliminary finite element analysis to determine ideal fibre orientations; (3) fibre path generation, including non-geodesics, to obtain feasible fibre paths; (4) choice of final lay-up sequence; and (5) composite finite element analysis to adapt the final lay-up until strength and stiffness requirements are met. The proposed methodology, embodied in the computer code CAWAR, is illustrated by application to a conical filament-wound part.

An important issue in sheet forming of continuous fibre-reinforced thermoplastic composites is the tendency of the laminates to buckle out of plane under rapid forming conditions. This paper outlines a method used to predict the stress patterns responsible for buckling, and presents experimental results that correspond with the predictions. A finite element formulation for ideal fibre-reinforced Newtonian fluids, featuring the twin kinematic constraints of material incompressibility and fibre inextensibility, is used. A mixed penalty finite element approach is adopted, with independent interpolation of tension and velocity solution fields. An analysis model consistent with an assumption of plane stress is used. For multi-ply lay-ups, each ply is analysed individually, and average stress predictions for the laminate are obtained on this basis. A detailed comparison between numerical stress predictions and experimental buckling patterns is presented for central indentation of circular unidirectional, cross-ply and quasi-isotropic preforms. Parameters influencing the magnitude and location of peak tangential stresses include tangential fibre lengths and diaphragm/composite viscosity ratios. The effect of sheet width and shape on the instability patterns is investigated for quasi-isotropic laminates of different shapes, using both numerical and experimental techniques.

In order to optimize the diaphragm forming process, forming and heating studies have been carried out for continuous fibre-reinforced poly(ether imide) laminates and polyimide diaphragms. Different tooling concepts have been evaluated with respect to the reduction of manufacturing time. Based on these experimental results, a new machine has been designed and built for the automated manufacturing of advanced thermoplastic composite parts.

Diaphragm forming offers several advantages over other forming techniques in the manufacture of advanced thermoplastic composites. The technique can be used in the forming of parts with complex curvature and can produce excellent surface finish. This work investigates the effect of buckling in both single- and double-curvature moulds, while forming carbon fibre-reinforced poly(ether ether ketone) (APC-2). A control system was set up to provide linear displacement of parts at rates of 1–100 mm min⁻¹. Buckling was established for both cross-ply and quasi-isotropic lay-ups in a double-curvature elliptical dish mould. Forming rate experiments were also carried out on a single-curvature 90° mould, with no buckling occurring at forming rates up to 100 mm min⁻¹ The conditions likely to cause buckling were calculated for the 90° female mould, using both the tensile properties of the diaphragm material and interply shear data for APC-2 laminates. An investigation was also made into the spring-forward effect on 90° parts formed using male and female tools for both APC-2 and carbon fibre-reinforced poly(ether imide) materials. The parts made from the male tool using these materials had a larger spring-forward effect in each case. The influence of part thickness was investigated and found to reduce the spring forward which occurred. The effect of mould radius of curvature was also investigated and found to be negligible. The effect on part quality when varying the consolidation pressure was investigated for [0°/90°]_2S and [0°/±45°/90°]_S APC-2 lay-ups in the male 90° mould. The parts were ultrasonically C-scanned to assess their quality; interlaminar shear tests were also carried out to validate the ultrasonic tests. It was found that a consolidation pressure in excess of 200 kPa was required to fully consolidate these parts.