Pre-Heating of Thermoplastic Sandwich Materials for Rapid Thermoforming

Abstract

The thermoforming of thermoplastic sandwich structures based on the same matrix polymer for the face sheets and the core requires precise temperature control both before and during forming. Two opposing requirements must be satisfied: the face sheets must be heated to above the glass transition temperature of the polymer, Tg, whereas the temperature of the core should not approach Tg in order to avoid the collapse of the foam cells. A numerical model was used to determine the optimal thermal parameters for thermoforming using an inverse method. The conductivities of the skins, the interface, and the foam were first calculated by the inverse method and then implemented in a thermal analysis. It was shown that the thermal requirements for the skins and the foam cannot all be fulfilled using a classic one-step heating route; therefore, a two-step procedure was proposed. The numerical tool allowed the principal heating parameters, namely the temperature of the heating plates and the holding and transfer times, to be determined.

Manufacturing of thermoplastic composite sandwich structures

“…Concerning highperformance thermoplastic polymers, polyethersulfone (PES) and especially PEI cores find application. [34][35][36][37][38][39]44 With an operation temperature up to 180 C and excellent Fire, Smoke, Toxicity (FST) properties, PEI is an interesting material for the aerospace industry. 52,53 In comparison with other core materials, PEI cores often originate during the production (in situ) of the sandwich structure.…”

“…TPC sandwich structures can also be joined with similar exopy-based adhesive materials. Rozant et al 36,37 applied a 150 g/m 2 epoxy film to combine glass fibre-reinforced PEI skins with a PEI foam core. Offringa 16,55 reports about TPC sandwich applications for an aircraft floor panel, where PEI fibre-reinforced laminates are adhesively bonded to a Nomex 1 honeycomb core.…”

Foam injection molding of glass fiber reinforced polypropylene composites with laminate skins

“…A continuous‐fiber reinforced thermoplastic laminate is a candidate for the face skins because it has high specific modulus and strength . Two manufacturing routes have often been taken to bond a thermoplastic foam core and thermoplastic composite face skins: (1) compression molding of a stack of a pre‐made thermoplastic foam core and pre‐made thermoplastic composite face skins and (2) joining of a pre‐made thermoplastic foam core and pre‐made thermoplastic composite face skins with an adhesive . Although sandwich panels can be manufactured successfully through the two manufacturing methods, it is preferable to streamline the manufacturing process in an industrial setting, especially the bonding process of a foam core and face skins.…”

A model predictive controller of plastic sheet temperature for a thermoforming process

“…This encourages researchers to develop cost-effective and accurate controllers for polymer forming processes [1][2][3][4][5][6]. The thermoforming process consists of three phases, namely heating, forming, and solidification.…”