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A novel thermoplastic programmable preforming process, TP-P4, has been used to manufacture preforms for non-isothermal compression molding. Commingled glass and polypropylene yarns are deposited by robot onto a vacuum screen, followed by a heat-setting operation to stabilize the as-placed yarns for subsequent handling. After an optional additional preconsolidation stage, the preforms are molded by preheating and subsequent press forming in a shear edge tool. The in- and out-of-plane flow capabilities of the material were investigated, and compared to those of 40 wt% Glass Mat Thermoplastics (GMTs). Although the TP-P4 material has a fiber fraction of 60 wt%, the material could be processed to fill 77 mm deep ribs with a thickness of 3 mm, indicative of complex part production. The pressure requirements for out-of-plane flow were shown to depend on the fiber length and fiber alignment. Segregation phenomena were found to be less severe with TP-P4 than with GMT material.

A process has been developed where multiple yarns of commingled glass and polypropylene are heated and placed to a desired geometry. The placed unidirectional (UD) tow is then encapsulated by over-moulding with glass mat thermoplastics (GMTs). The effects of both force (20–80 N), with an equivalent pressure range of 8–46 bar, and the displacement rate (20–100 mm/s) during tow placement on void content and flexural modulus were investigated for nine placement conditions. Placement rate affected the tow quality measured before overmoulding. Void contents were reduced after over-moulding. The volume fraction of UD tow (vol. O8 composite/vol. total composite) in the manufactured multi-material structure was 21.5%. Corresponding tensile tests showed a factor of 2 increase in modulus and a factor of 3 increase in strength relative to GMT. Tow placement rate had no significant effect on tensile properties after over-moulding. Tensile behaviour as a function of the UD tow volume fraction was modelled and predicted values agreed with the experimental results. Additionally, the predicted tensile performance of UD tow reinforced GMT has been compared with possible competitive materials using merit indices.

Two resin transfer moulding (RTM) processes have been examined for automotive body-in-white (BIW) structures. An epoxy system was compared with a novel reactive polyamide 12 (PA12) system via characterisation of reaction kinetics and the production of carbon fibre floor pan quadrant demonstrators incorporating typical geometrical features. Cost modelling tools were used to compare the two RTM variants for full floor-pan production at volumes of 12,500-60,000 parts per year. A 22% increase occurred for the standard TP-RTM cycle versus the epoxy system, principally due to thermal cycling of the tool that dominated the in-mould cycle time. Study of alternate preforming strategies showed that a reduction in non-crimp fabric scrap yielded major cost savings.

A systematic study of the effects of charge composition and process parameters is presented for a prototype automotive part (a door cassette) produced by compression moulding from glass fibre and polypropylene composites. This follows previous studies (Parts I–III) of the process-property relations for commingled glass and polypropylene fabrics, glass-mat thermoplastics (GMTs) and sandwiched structures of commingled fabric shins with a GMT core. The scope and function of the component is described together with details of the moulding experiments with GMT and fabric combined as a pre-laminated sandwich and a GMT charge with local areas of fabric to provide selective stiffening. Process parameters were varied to study the effects on proportional mould fill, pressure distributions, microstructure and flexural modulus. Statistical process models were generated from the results and these were used to define process windows. Of the parameters studied, the consolidation time dominated the flexural modulus and void content whilst increased press force and material temperature increased proportional mould fill.

The co-moulding of random-reinforced GMTs with commingled E-glass and polypropylene fabrics was investigated in a series of experiments which were designed statistically. Materials were heated in an infra-red oven prior to non-isothermal compression moulding. Maximum preheat times and temperatures were determined by gel permeation chromatography to monitor the onset of degradation of the polymer matrix. Laminate properties were mapped according to the processing parameters and optimum conditions for consolidation were identified. The process parameters were ranked in order of importance for maximum flexural modulus and time at pressure proved the most significant factor. Microscopy was used to investigate the impregnation mechanisms and the subsequent removal of voidage.

The present work is aimed at assessing the feasibility of integrating thermoplastic polypropylene nanocomposite matrices into conventional fiber-reinforced composites based on hybrid textiles that incorporate both the matrix and glass-fiber yarns, in order to reduce impregnation times. The focus is on the preparation and properties of the polypropylene nanocomposite fiber precursors and the implications for composite processing in general. However, preliminary results are also given that demonstrate satisfactory impregnation and consolidation of simple textiles produced by co-weaving the nanocomposite yarns with glass-fibers, given suitable processing conditions.

The deformation and fracture behaviour of a generic injection moulded structure reinforced by a robotically placed commingled glass fibre/polypropylene UD-tow (uni-directional) was simulated by finite elements. The suitability of modelling hybrid structures using features available within commercial finite element programs and standard material properties was assessed. Two different 2D modelling approaches based on shell and beam elements, which were computationally less intensive, were evaluated against 3D solid element models in both bending and flexure. It was shown that all three approaches predict the global deformation behaviour in both tension and bending compared with experimental data. Differences between the 2D and 3D approaches were mainly in the predicted stress distribution around the load introduction points.

Using an integrated processing methodology, an injection or compression moulded thermoplastic structure can be locally reinforced, for example, with textile structures or uni-directional fibre tows. Netshape components can be produced with cycle times typical for injection or compression moulding but with higher mechanical properties. As the inclusion of local reinforcements adds complexity to the design process, both in the terms of amounts and location, mathematical optimization techniques in conjunction with finite element simulations can be a useful tool to design weight and cost effective structures. This work evaluates approximation models used in conjunction with genetic algorithms by using a generic but industry relevant beam structure as an example problem. The underlying finite element model is based on layered shell elements with up to four different materials through the thickness and with nine design variables controlling the material thicknesses in different areas. Material non-linear behaviour is included for the over-moulding polymer and for the compressive response of one specific fabric material. The accuracy of four different approximation methods was assessed, polynomial models with and without term selection, radial basis functions and Kriging. Rather than solely examine the mean approximation error, a method is proposed of how to treat single large approximation errors. It is shown that a Multi-Island Genetic algorithm can be successfully used to optimize the structural weight under 64 constraints with continuous and mixed continuous-discrete design variables.

Processing of glass-mat thermoplastics (GMTs) by hot-Pow compression moulding represents a complex physical process with non-isothermal and non-Newtonian conditions. To increase the understanding of process and property interactions, a series of statistically designed experiments have been conducted on Pat plaques. Processing variables were ranked in order of importance for increased laminate properties. Processing models were generated using regression techniques describing the e€ect of processing variables on void content measured from the microstructure and laminate mechanical properties. Time at pressure had the greatest e€ect on strength and moduli.

The aim of this work is to integrate polypropylene/montmorillonite (MMT) nanocomposite matrices into conventional fibre-reinforced composites. Two types of composite have been considered: long fibre-reinforced composites from co-woven glass fibre and nanocomposite yarns, and glass mat reinforced thermoplastic (GMT) composites. The melt spun polypropylene precursor yarns contained up to 6 wt% MMT, leading to a 2 to 3 fold increase in axial stiffness, but more modest increases were observed in extruded films and compression moulded specimens. Corresponding stiffness improvements were obtained in GMT samples. However, significantly higher temperatures and pressures were required during preimpregnation to that observed with the unmodified matrix for a given processing time.

Two forms of carbon fibre reinforced polyamide 12 (PA12) were compared during non-isothermal stamp forming. The first was a stretch broken commingled yarn woven into a fabric, studied at three initial preconsolidation levels. The second was produced by in situ anionic polymerisation of lactam 12 (APLC12) in a carbon fibre textile, using a thermoplastic resin transfer moulding (TP-RTM) process. A processing window was defined for TP-RTM based upon non-isothermal polymerisation kinetics. For each material form, the effects of stamping parameters on flat plaque properties were examined. For commingled materials, the influence of preheat temperature and the initial preconsolidation level dominated, with preconsolidated materials deconsolidating strongly during the preheat cycle. For CF/APLC12 materials, the effect of material temperature and tool temperature dominated and reduced deconsolidation occurred. Hemisphere forming was enabled by stretch-broken yarn but was possible for both material classes. Over-injection moulding of recompounded CF/APLC12 composite onto stamped CF/APLC12 plate was performed, demonstrating a closed-loop recycling process.

The feasibility of integrating thermoplastic isotactic polypropylene/ montmorillonite nanocomposite matrices into conventional fiber-reinforced composites has been investigated. Two basic processing routes were considered: long glass fiber (GF)-reinforced composites based on co-wound or co-woven yarns and glass mat reinforced composites. In each case satisfactory impregnation and consolidation were demonstrated, although at high fiber contents, this required increased pressures and/or temperatures in the presence of the montmorillonite. Flexural tests on the glass mat reinforced composites, containing relatively low GF contents, showed the use of a nanocomposite matrix to lead to the significant improvements in bending stiffness and strength.