If possible, please elaborate a bit more on the details of your system. Otherwise, I can only offer a general answer - the most common sources of poor mechanical properties of laminates:

1) Insufficient amount of reinforcement (typically, reinforcing layers) or poor mechanical properties of the reinforcement.

2) Lack of penetration of your resin into the reinforcing material or poor adhesion to that material. If the former is the case, you should see your reinforcing material appearing to be "dry" even after prolonged soaking in the resin. If the latter is the case, a drop of cured resin placed on a bit of the reinforcing material should be easily separated after curing.

3) Insufficient amount of the resin to properly soak all of the reinforcing material. This will result in reinforcing layers that can be peeled away from one another.

4) Insufficient degree of curing, due to side reactions, issues with resin/curing agent mixing or hindered curing within the mixture that soaked into the reinforcing material.In this case, I would expect you to be able to "squeeze out" some uncured resin from the laminate.

5) Poor mechanical properties of the cured resin - in some (rare) cases, most often for cured elastomers, the cured resin may not have the stiffness to bind the different sections of the reinforcing material together.

Thank you Tomasz for your kind inputs.

I will consider your suggestions and will get back with more updates. Its wetted properly and as you said there might be chance of less reinforcement. Its like a flapping wing or flexible cardboard.

But has it got to do anything with the mix ratio of resin:hardner?.

yes, the ratio of epoxy and hardener also play important role.