Anthony K. Pickett

Numerical and experimental investigation of some press forming parameters of two fibre reinforced thermoplastics: APC2-AS4 and PEI-CETEX

Abstract Continuous fibre reinforced thermoplastic sheets (CFRTP) are a promising material for light-weight structural components. Unfortunately, their medium to high processing and temperature-dependent properties, and the complex deformations mechanisms that occur within the composite sheet during the forming have all presented problems in the practical production of parts. This has contributed to a reluctance by industry to accept these materials. This paper shows how numerical simulation may be usefully applied in order to obtain a better understanding of the press forming of CFRTP. Detailed investigation using both experimental and numerical techniques of the press forming of an CFRTP component are presented. The part under investigation is a ‘sikken’ (half-cylinder with quarter spheres at both ends). Forming parameters such as the choice of the holding system, the use of a blank holder, the punch velocity, the stacking sequence are all investigated. Both UD material (APC-2AS4) and woven fabrics (PEI-CETEX) are studied.

An explicit finite element solution for the forming prediction of continuous fibre-reinforced thermoplastic sheets

Abstract The pressure forming, or thermoforming, of preconsolidated continuous fibre-reinforced thermoplastic sheets offers a promising fabrication option for structural composite components. Modern thermoplastic polymers have improved mechanical and physical properties compared with their thermoset counterparts and, perhaps most important for industry, offer the possibility for rapid part production. As in tradational metal stamping, the current process and part design for thermoforming rely heavily on ‘trial and error’ practices which are costly, inefficient and provide little scope for optimization and understanding of the forming process. For efficient thermoforming information regarding temperature and pressure distribution, part thickness distribution, fibre orientations and potential regions of material defects must be determined. This paper presents some first results of an explicit finite element solution to simulate the forming process. At present a constant temperature process is assumed, however work is presently underway to include this effect.

Simplified and advanced simulation methods for prediction of fabric draping

Three principle methods are available for fabric draping analysis; namely, simplified “mapping” and Finite Element methods applied at the macro- and meso- levels. The mapping method was first introduced in the 1950’s and due to its simplicity is still the preferred technique for industrial work. During the past decade Finite Element methods have evolved that offer significant improvements in terms of accuracy and range of application. This method can allow definition of the forming system, friction and permit material laws valid for a wide range of fabric types. Two levels of fabric modelling are possible; first, macro-models which approximate the fabric as a homogeneous continuum and, second, more complex meso- models that accurately represent fabric architecture and thereby the complex deformation mechanisms. This paper gives an overview of these techniques, their limitations and the state-of-the-art.

NUMERICAL SIMULATION AS A TOOL FOR MANUFACTURING, FAILURE AND IMPACT PREDICTION OF TEXTILE REINFORCED COMPOSITES

During the past two decades Finite Element (FE) simulation techniques have been developed and are now an invaluable tool for the design and optimisation of various manufacturing processes and structural analysis. These techniques have primarily been developed for metals which are relatively simple materials to characterise. Advanced composite materials are also of great interest to a wide range of industries, including the civil engineering sector, and simulation tools to represent these materials in various forming and impact-crash situations are required. Unfortunately the complex nature of these materials makes their numerical simulation a comparatively more difficult task. This paper gives a brief overview of the current state-of-the-art for numerical simulation of draping and impact analysis and presents some new results for advanced composites applications.