title_body: What is a good alternative to carbon fibre for a quadcopter frame? I am making a diy quadcopter and I need a strong and light material for its frame.
  
  Carbon fibre is not available in my area. I have tried aluminium but it's too soft and so needs repairs. What alternatives are recommended?
upvoted_answer: There's no denying the fact that when it comes to materials that are both strong and light, carbon fiber is king. If you're looking for performance, there's no way around it. If performance is not the most important thing in the world, however... Well, there are several options.
  
  Before I start listing these, I must point out that all frames break. Some break more easily than others, but you can't have an unbreakable frame. The question is how you repair it when it breaks, and the answer depends on the material.
  
  
  Plastic frames are actually a very popular in micro-sized quadcopters that only weigh tens of grams. These frames usually feature a non-flat shape, prop guards and other features built into them. A subset of those, 3D printed frames, are also quite widely used in DIY designs of larger sizes, and, as everything 3D printed, are a good way of prototyping your design before moving on to other materials. In some cases, where performance is not a concern (for example, if your main focus is having a platform for testing algorithms for which flight time or range is not important at the time, or just want to play around with a design) you may even never move on from a 3D printed frame. While these tend to be heavy and/or brittle compared to other materials, there are some exceptionally light designs, and depending on the intended applications, durability might not be a concern. Besides, if you do break one of these, you can always just print a new one.
  Wood and metal/fiberglass is a staple of "oldschool", large (8"+) DIY drones from the KK2/Naze era. As the drone gets larger, heavier frames tend to impede it less, and any crash could easily break an arm just due to the sheer weight of the drone, no matter what the arm is made of. So this kind of design focuses on repairability instead: one can easily make tens of wooden arms in their workshop for very cheap and swap them when they break. Potentially, one could try to make a smaller wooden frame as well, although at this point lightness becomes important, so I'd advise to stick to lighter woods if you do, maybe even balsa. 
  
  
  Full-metal frames are not unheard of as well; Aluminium and titanium are widely-accepted building materials in aviation and actually tend to have better performance than wood. You'll have to use tubes/other non-flat shapes, though.  
  Even though you've ruled out carbon fiber, you may be referring specifically to CNC machining of frames out of flat sheets. Premade carbon fiber elements such as strips and tubing are readily available for order online and are easy to work with using basic tools. A lot of larger drones today are made using the same basic technologies as the wood/metal drones of old, but with arms out of carbon fiber tubes instead of wooden planks. If you're building a large drone, this is a very feasible yet high-performance option.
  
  Finally, Pure fiberglass composite. Glass fiber composites are significantly less stiff than their carbon fiber counterparts, and heavier as well, but there are a few niche uses even in performance designs. 
  
  
  The first of them is very large drones, which tend not to care as much about neither weight nor aerobatic performance. Here, glass fiber can shine if you've got the facilities to manufacture it. That said, if you're building a very large drone, the frame is likely to be a very small fraction of its cost, so you might just as well order a custom carbon design (or use premade carbon parts like the previous option).
  The more interesting option, however, is a PCB frame, in which the frame is
  not just a structural component, but also carries all the electronics
  that the drone needs to fly. Some fantastically lightweight designs
  have been made using this technique: even though the glass fiber
  itself is heavier than carbon, the design makes up for it by ditching
  all the other PCB and wiring weight that would otherwise be carried
  on top of the frame in a traditional design. While not optimal for sporty flying, this is the perfect option for a long-range/long
  flight time autonomous design... if you can lay out the PCB, as all
  of the components (flight controller, ESCs, vTX, etc) have to be
  integrated into it.
  
  
  
  
  
  Some examples for inspiration:
  
  Plastic frames
  
  Brushed micro quadcopter (tiny whoop) with molded plastic frame:
  
  
  2" brushless copter with molded frame:
  
  
  Brushless quadcopters with 3D printed frame:
  
  
  
  Foldable brushed 3D printed frame:
  
  
  Wood/metal homemade frames:
  
  Typical fully wooden H frames of the KK2/Naze era:
  
  
  
  
  Classic X frame with metal/plastic center plate and wooden arms: 
  
  
  Very simple wooden X frame:
  
  
  Small drone with laser cut wooden frame:
  
  
  Frame with metal arms:
  
  
  Full-metal frame:
  
  
  H frame out of carbon tubing with 3D printed brackets holding it together:
  
  
  Glass fiber frames
  
  Molded fiberglass tricopter:
  
  
  PCB frames: