Laval sought to replace the existing injection-moulded cargo box with a lighter, stronger GMT composite part capable of reducing chassis reinforcements, and hold heavier cargo without damaging. The material also needed to meet flame resistance, full UV protection and Class “A” appearance requirements.

GMT RD30 was selected as the starting material, but the required flame-retardant additive restricted material flow and made it difficult to fill the complex part geometry. Multiple formulations were evaluated by changing the flame-retardant component and resin system to improve flow and mouldability.

Systematic trials varied material temperature from approximately 400°F to 455°F and mould temperature from 150°F to 200°F. Repeated trial runs established that approximately 450–455°F material temperature and 200°F mould temperature provided the most effective flow conditions.

One-piece, two-ply, three-ply and four-ply charge patterns were tested at different sizes and locations. The trials demonstrated that charge thickness, position and the orientation of the material’s cut edges had a significant effect on filling, surface appearance and scrap.

The mould was progressively offset within the press to align the pressure centre with the material charge. A six-inch offset improved material distribution, reducing scrap from approximately 90% during early trials to 5% during a sustained 50-part production run.

Testing confirmed that exposed cut edges caused unacceptable white lines. A six-ply, package-folded charge measuring 1,250 mm × 1,000 mm placed all cut edges on the B-side, producing an improved Class “A” surface with less than 5% scrap. The parts subsequently failed flame testing, confirming that further material formulation was required. Additional flame retardant was added to the material and achieved performance without sacrificing flow, strength or appearance.