In order to determine the effect of water uptake on the mechanical properties of the composites, different specimen dimensions were required. Specimens were cut from the belt-pressed (12-ply) all-PP laminates, GMT and NMT sheets into 210 × 15 mm rectangular bars. Three specimens from each material were taken after immersion in water for 40 days at 65 °C and frozen at −18 °C for 24 h. These specimens were then thawed and tested in tension to determine if the expansion of the absorbed water during freezing had affected the tensile performance of the composites.