Effects of cure‐hold‐temperature and step‐wise cool‐down path on the service strength of fiber‐mat reinforced composites

The study considered the influence of the cure hold temperature and the techniques applied in cooling to room temperature on the strength of random fiber reinforced thermoset composites. Tensile and Charpy impact tests were carried‐out on chopped strand mat E‐glass fiber reinforced‐polyester composites cured at temperatures ranging between 30°C and 150°C and subsequently cooled through different paths. The composites contained 3 plies for the tensile test specimens, and 10 plies for the Charpy impact test specimens. The matrix was prepared from the same bulk and formulation. From the tests, samples oven cured at 85°C/3 hr and cooled under natural convection cool‐down path were found to give the highest tensile strength of 96 MPa while the laminate cured at 30°C room temperature produced the lowest strength of 69 MPa. Also, samples cured at 85°C under natural convection cooling gave an average impact strength value of 550 kJ/m², which is second to fridge cooled samples of 650 kJ/m² average value. There is therefore need for oven‐cure followed by quenching to obtain maximum strength in polyester laminate applications. POLYM. COMPOS., 39:3935–3943, 2018. © 2017 Society of Plastics Engineers