Claims:We claim
1) A hybrid composite material,
Comprising primarily of 3 parts with total thickness of 32 mm wherein multilayer sandwich composite structure which is blast proof can be employed in aircrafts, surface ships and land vessels and the three segments viz. high temperature ceramic matrix composite (sintered silicon carbide with 6 mm thickness), aluminium honeycomb plate with hexagonal configuration and 10 mm thickness and high temperature thermoplastic polymer composite such polyether ketone (PEK) with PBO fiber reinforced composite with 10 mm thickness were used which are bonded by high temperature epoxy adhesive bonding
2) The hybrid composite material as claimed in claim 1,
wherein, it offered resistance and withstood a blast equivalent to 34 Kg TNT at a stand off distance of 0.6 m with the standard test prescribed by NATO and further, approx. 60 kg TNT at a stand off distance of 0.6 m, in the case of explosive directly kept on the composite face and the weight of the hybrid composite with dimension 150 mm x 150 mm x 32mm is app 900 gm which is five times lighter than Armored Steel (App 5.6 Kgs) of equivalent dimensions
3) A method for fabricating and manufacturing of a hybrid composite material for offering blast proof , fire retardant and impact resisting properties, achieved through making of 3 parts with total thickness of 32 mm wherein multilayer sandwich composite structure which is blast proof can be employed in aircrafts, surface ships and land vessels and the three segments viz. high temperature ceramic matrix composite (sintered silicon carbide with 6 mm thickness), aluminium honeycomb plate with hexagonal configuration and 10 mm thickness and high temperature thermoplastic polymer composite such polyether ketone (PEK) with PBO fiber reinforced composite with 10 mm thickness were used which are bonded by high temperature epoxy adhesive bonding
4) 6 mm SiC plate along with aluminium honeycomb and PEK-PBO fiber composite withstood a blast equivalent to 60 Kg TNT at a stand off distance of 0.6 m with the standard test prescribed by NATO.
5) 10 mm SiC plate along with aluminium honeycomb and PEK-Carbon fiber composite withstood a blast equivalent to 80 Kg TNT at a stand off distance of 0.6 m with the standard test prescribed by NATO.
6) 10 mm SiC plate along with aluminium honeycomb and PEK-PBO fiber composite withstood a blast equivalent to 120 Kg TNT at a stand off distance of 0.6 m with the standard test prescribed by NATO.
7) 10 mm SiC plate along with aluminium honeycomb and PEK-PBO fiber composite withstood a blast equivalent to 200 Kg TNT at a stand off distance of 0.6 m with the standard test prescribed by NATO.
8) The light weight, impact proof and fire retardant composite material as claimed in claim 1, can be used in many strategic applications like civil structures, bunkers, hypersonic aircrafts, light weight choppers (helicopters) light tare weight vehicles used for security and defence purposes etc.
, Description:The advanced hybrid composite consists of primarily 3 parts with total thickness of 32 mm. The multilayer sandwich composite structure which is blast proof can be employed in aircrafts, surface ships and land vessels. The three segments viz. high temperature ceramic matrix composite (sintered silicon carbide with 6 mm thickness), aluminium honeycomb plate with hexagonal configuration and 10 mm thickness and high temperature thermoplastic polymer composite such polyether ketone (PEK) with PBO fiber reinforced composite with 10 mm thickness were used. These are bonded by high temperature epoxy adhesive bonding.

Prototype Manufacturing and Pre-Testing Activities. various threat levels prescribed in STANAG 4569-Mine Threat. Considering the test bed setup, the mass of explosives and stand off distance was scaled down in accordance withCranz-Hopkinson Scaling Law. The explosive used were TNT and PEK 1 whose blast effect are quite similar. The test parameters are as tabulated ( See tabular column 1)
The prototype plate is of dimensions 150 mm x 150 mm x 32mm is used during testing. Weight of this plate is app 900 gm. In total four test blasts were conducted.

Test Blast 1. In this initial test blast a MS plate of same dimensions as that of prototype plate was used in order to set the parameters for actual composite plate test. The test was performed with 5.8gm of TNT with stand off distance of 5cm.The MS plate was observed to be in intact condition without any cracks/ damages. However, it was also observed that the blast set up was inappropriate for conduct of further test.
Test Blast 2. Post improving the test conditions, NATO level 4 blast parameters which is highest level as specified in STANAG i.e 5.8gm of TNT with stand off distance of 5cm was carried out which is equivalent to 10 kg TNT with 0.6 m distance. During this testing it was observed that the prototype plate was intact with minor damage at corners of ceramic layer. Post gaining this confidence the next test was performed on different prototype plate.
Test Blast 3. This test blast was performed with use of PEK-1 (Tetryl + masticated rubber + paraffin oil (90:5:5) which has almost similar properties to that of TNT. 12gm of PEK-1 explosive was directly placed on face of Hybrid Composite (ceramic side) to justify whether this composite can withstand higher level of blast. Post test blast it was observed that the ceramic layer was completely damaged with adhesive becoming brittle in nature. Honeycomb top plate and middle cells layer was found damaged. However a plastic deformation on bottom honeycomb layer and polymer layer was observed. It was concluded that the prototype plate is capable of absorbing approx. 60 Kg TNT blast with stand off distance of 0.6 m.
Test Blast 4. After seeing these promising results, final test blast i.e. custom trial test blast for stand off distance of 50 mm with 17gm of PEK-1 was carried out which is equivalent to 34 Kg TNT blast with stand off distance of 0.6 m. During this blast it was observed that the ceramic layer has been completely damaged however the honeycomb top layer has undergone plastic deformation and honeycomb cells have been crushed at various locations. The polymer layer was found to be intact. However, the adhesion between all three layers namely, ceramic, honeycomb and polymer were absent.

The result of the blast test revealed that the hybrid composite successfully withstood a blast equivalent to 34 Kg TNT at a stand off distance of 0.6m with the standard test prescribed by NATO and further, approx. 60 kg TNT at a stand off distance 0.6 m, in the case of explosive directly kept on the composite face. The weight of the hybrid composite with dimension 150 mm x 150mmx 32mm is app 900 gm which is five times lighter than Armored Steel (App 5.6 Kgs) of equivalent dimensions. Further improvements in its composition and dimensions to achieve higher blast resistance would be carried out in due course of time. The light weight blast proof composite would be highly beneficial for the military and paramilitary forces for blast proofing of any structure, equipment or vehicle.

In continuation with the first prototype second set of tests were carried out with much higher explosive. The mass of explosive and standoff distance was scaled down in accordance with Cranz-Hopkinson Scaling Law. In order to establish the upper limit of blast resistance of the material, blast tests with higher amounts of explosive (PEK) was carried out and details of test carried out are as tabulated in Table 1.

Conclusion. The result of the blast test revealed that the hybrid composite successfully withstands a blast equivalent to 200 Kg TNT at a standoff distance of 0.6 m with the standard test prescribed by NATO. The weight of the hybrid composite with dimension 150 mm x 150 mm x 32 mm is app 900 gm which is 5 times lighter than Armored Steel (App 5.6 Kgs) of equivalent dimensions. The use of Carbon Fiber in one of the sample materials also proved successful. NSAM LLP, Vadodra, Gujarat owns the legal right of this technology under the name ‘Chatrapati Shivaji Armour’.