Process for the manufacture of a ballistic-resistant moulded article
The invention relates to a process for the manufacture of a ballistic-resistant moulded article in which a stack of monolayers is formed, each monolayer containing unidirectionally oriented reinforcing fibres and at most 30 mass % of a plastic matrix material, the reinforcing fibres being highly-drawn polyethylene fibres, and with the fibre direction in each monolayer being rotated with respect to the fibre direction in an adjacent monolayer, the stack then being compressed at a pressure of more than 25 MPa and a temperature between 125 and 150° C., and the plastic matrix material having a 100% modulus of at least 3 MPa.
1. Process for the manufacture of ballistic-resistant moulded article comprising the steps of forming a stack of monolayers in which each monolayer contains unidirectionally oriented reinforcing fibres and at most 30 mass % of a polyurethane matrix material having a 100% modulus of at least 3 MPa, the reinforcing fibres being highly-drawn polyethylene fibres, wherein said step of forming the stack of monolayers includes rotating the fibre direction in each monolayer with respect to the fibre direction in an adjacent monolayer, and thereafter compressing the stack of monolayers at an elevated temperature between 125 and 150° C. and at a compression pressure of more than 25 MPa.
2. Process according to claim 1 , wherein the step of compressing the stack of monolayers is practiced by compressing the stack for at least 60 minutes at a temperature between 125 and 135° C.
3. Process according to claim 1 , wherein the step of compressing the stack of monolayers is practiced by compressing the stack for 20 minutes at a temperature between 135 and 150° C.
4. Ballistic-resistant moulded article comprising a stack of monolayers, each monolayer containing unidirectionally oriented reinforcing fibers and at most 30 mass % of a polyurethane matrix material having a 100% modulus of at least 3 MPa, the reinforcing fibres being highly-drawn polyethylene fibres, and with the fibre direction in each monolayer being rotated with respect to the fibre direction in an adjacent monolayer, wherein the moulded article has an SEA at 80° against AK47 bullets that is at least 100 J/(kg/m 2 ).
5. Ballistic-resistant moulded article according to claim 4 , with an acoustic damping, measured at 0.5 MHz, of less than 20 dB/cm.