JEC COMPOSITES MAGAZINE - Issue #74 - July 2012 - 31

Material selection For the study, Ticona supplied 0.25-mm thick PP/glass UD tapes (Celstran CFRTP PP-GF70 with 70 wt-% glass) in a variety of widths. Although such tapes are available in a variety of thicknesses, in practice, they are not stiff enough to handle easily, particularly in an automated or semi-automated moulding process, making it more likely the tapes will move during moulding and end up in locations other than those needing property improvements. Hence, such tapes are generally converted into an intermediate form like a fabric or a tailored laminate before use. Oxeon converted them into tape fabrics (TeXtreme plain weaves that were 0.50mm thick per ply and were laid up two plies thick in either a 0°/90° = (0/90) or a ± 45° = (± 45) configuration). These double plies were used to build stacked configurations in specific thicknesses that were not preconsolidated. Fiberforge also used the tapes to produce tailored laminates (consolidated tailored blanks). For Part 1 (the plaque study), the laminates were supplied in single sheets (to be cut as needed) and several thicknesses and configurations, e.g. 0°/90° = (0/90) with a thickness of 0.5, 1.0 or 2.0 mm, or a quasi-isotropic (0°/90°/+45°/-45°)s where “s” represents a symmetric layup of eight plies. For Part 2 (the engine-shield study), both partshape tailored laminates and large sheets of laminate were produced, which were then cut to size and shape as needed. In both cases, the tape laminates were preconsolidated. Preheating and moulding conditions The tape fabrics and tailored laminates were used alone or paired with a D-LFT composite produced by Fraunhofer, with an ILC unit supplied by Dieffenbacher GmbH Maschinen- und Anlagenbau, PP resin from Dow Chemical, an additives package from Addcomp Holland BV, and chopped-glass fibre by Johns Manville. For the plaque study, glass loading was 30 wt-% (a common automotive formulation), but for the shield study, 20 wt-% was used to enhance fill of more complex geometry.

Both plaque and shield tools were moulded on a Dieffenbacher 36,000kN Compress Plus hydraulic press with parallel levelling control. In all cases where hybrid combinations of D-LFT charge, tape fabric and/or tailored laminate were used, the D-LFT charge was always placed in the tool last and laid on top of tape fabric and/or tape laminate. To ensure good fusion between the D-LFT charge (which exits the ILC unit near 200°C) and the tape fabric and/or tailored laminates, the latter were preheated in an infrared oven close to 200°C. For unconsolidated fabrics, individual plies were pre-stacked (without additional pressure) in the oven prior to heating. Since a range of thicknesses were investigated in the plaque study, preheating times ranged from 30-140 seconds, while materials for the shield tool took 60 seconds. Heating times were governed by the oven, whose power was set so as not to degrade the surface of UD-tape products before resin at the core reached processing temperatures. Use of optimized heating setups could lower preheat times significantly.

Phase 1: plaque moulding trials and impact testing For Phase 1, a total of 20 material/layup combinations were successfully produced, the most representative of which are shown in Table 1 (pure D-LFT, pure tape laminate, pure tape fabric and several hybrid configurations). Plaques were moulded at ≈3,200 kN pressure for 45 seconds at 75°C. Since many plaques were 3.0-mm thick, a longer dwell time was needed to chill parts sufficiently for demoulding. Although thinner layups could have been moulded faster, researchers felt it best to keep process conditions the same, so left all plaques in the tool 45 seconds. At least one plaque was produced for each combination (for hybrid layups, two plaques were produced). After moulding, test coupons were cut from plaques and subjected to instrumented puncture impact testing as per EN ISO 6603-2 “Determination of multiaxial impact behaviour of rigid plastics – Part 2: Instrumented puncture test.” For each configuration, at least 5 samples were impacted

Tab. 1: Selected materials/layup/orientation/thicknesses used to mould flat test plaques in the first section of the study (n/a = not applicable for this sample)

Hybrid layup combinations

Materials used
Pure tape fabric Pure tape laminate Pure D-LFT Pure D-LFT Pure D-LFT Hybrid of tape fabric + D-LFT Hybrid of tape laminate + D-LFT Hybrid of tape fabric + D-LFT Hybrid of tape laminate+ D-LFT Hybrid of tape fabric + tape laminate + D-LFT Hybrid of tape laminate + tape fabric + D-LFT

Nominal wall (mm)
2.0 2.0 2.0 2.5 3.0 0.5 + 2.5 0.5 + 2.5 1.0 + 2.0 1.0 + 2.0

No. of plies/ layers 4 1
n/a n/a n/a 1 1 2 1

Fibre orientation of each ply (o) (0/90) (0/90)2s
D-LFT D-LFT

V1 V2
V3 V4 V5 V6 V7 V8 V9 V10

Feature Automotive

D-LFT (0/90) + D-LFT (0/90) + D-LFT 2x(0/90) + D-LFT (0/90)s + D-LFT (0/90) + (0/90) + D-LFT (0/90) + (0/90) + D-LFT

2 x 0.5 + 2.0

1+1

V11

2 x 0.5 + 2.0

1+1

No74 July 2012 /

jec composites magazine 31

JEC COMPOSITES MAGAZINE - Issue #74 - July 2012

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