Case Study: An Investigation into Composite Joints

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Introduction
Intrinsys prides itself on its understanding and practical experience of the very latest industrial processes, techniques and leading edge design, development and manufacturing practices. It does this by maintaining strong links with leading research universities, opening the door to some of the best engineering research facilities available anywhere in the world.

Intrinsys’ customers often operate in hi-tech or world class environments. They are frequently called upon to produce products using materials and manufacturing processes that are often innovative but may or may not be unique to their particular industry to maintain their competitive advantage.

When supporting its customers Intrinsys can often apply its knowledge and experience of a similar industry but when innovation and new research are required Intrinsys are more than happy to take on the challenge. Should fresh investigative research be required Intrinsys are delighted to be able to call on institutions like Cranfield University, renowned for their expertise, facilities and excellence in research, to maintain their well deserved reputation at the forefront of industrial design consultancy.

Cranfield University
Cranfield has a global reputation for inspirational teaching and research, industrial-scale facilities and superior links with industry and commerce. Their mission to transform knowledge into ingenious solutions in science, technology and management places them at the forefront of some of the world’s most practical, cutting-edge projects.

From unique cabin evacuation research to finding life on Mars, from a frost blanket for racecourses to zero-emission cars, Cranfield’s focus is squarely on the application of its research. It’s clear to see that the university’s passion for the areas of expertise they operate in - aerospace, automotive, defence, energy, environment, healthcare, management, manufacturing and security – makes them uniquely placed for both students and corporate partners alike. Their aim is to transform all its knowledge to practical application.
 

Project - On a need to know basis
During a number of resent client programmes Intrinsys have been challenged to solve a variety of composite structural problems.

Within the aerospace industry, where composites are coming to the forefront as the material of choice, design optimisation for strength and weight is critical. One of the main factors within the design of composite panels is the transferring of load into and between composite panels. These regions of the design are often the weakest area of construction and are frequently re-enforced at the cost of additional mass.

Traditional methods of re-enforcing connections involve the use of secondary structural elements like aluminium struts or preformed solid laminates. These elements are then bonded and riveted to the panels adding an increased mass penalty to the design.

Preformed panels are typically machined to create an interconnecting joint called Castellation. Upon reviewing the application of these joints it became apparent that minimal design optimisation research had been carried out to determine the effects and failures of the joints in both a tensile and bending load applications and that the required knowledge for effective and efficient design did not exist.
 

 
At the forefront of composite engineering
Intrinsys is always keen to acquire new knowledge and develop its services through research, thus ensuring that they remain at the forefront of the latest technologies and manufacturing developments. As a result it allows them to support their customers as they solve critical design issues, building competitive advantage by exploiting unique research.

Intrinsys took on this critical research element as part of its design solution. It started working with Cranfield University to investigate the jointing method to provide a set of design rules that could be used to optimise the load carrying capacity whilst achieving the lowest possible weight.

Cranfield University’s specialist resources were called on to investigate the following:

  • Creation of a definitive Abaqus finite element model to replicate the castellated joint, proven via comprehensive test results.
  • Determine the effect of manufacturing clearances and variability e.g. manufactures like the largest clearance possible to aid assembly.
  • Set the physical size and design of the castellation, pitch / end clearance etc.
  • Determine if the design rules need to change as the panel thickness is varied.
Results that take composite use within aerospace a step further on
The end result of this unique investigation has had the following benefits:
  • It enabled Intrinsys to create preliminary designs with the confidence that the joints would meet loading requirements.
  • Allowed the optimisation of a variety of designs that minimised weight while still meeting load capacities.
  • Determined the effect of manufacturing clearance and variability.

Completing this project has been a rewarding experience for Intrinsys and keeps them at the forefront of composite engineering. “We have enjoyed working with the researchers at Cranfield University,” says Darren Cairns the director responsible for Intrinsys’ design consultancy and PLM business. “We must have the capability to offer the very best services to our customers if they are to continue to lead their particular industry sector. Our links to leading research facilities, such as those at Cranfield University, are essential to maintaining our edge and ability to offer world class services.”

The link between Intrinsys and Cranfield
Intrinsys often find themselves working with clients that lead their particular industry which calls for not only an appreciation for the standards and requirements pertinent to the work, it requires an end result that pushes the boundaries of accepted design and modern materials and practices. “Our day to day working environment has a close synergy to the innovation, investigative and academic thrust of Cranfield University,” adds Darren Cairns. “Their forward looking approach to today’s most demanding design and manufacturing issues closely matches our own, making them an ideal partner for this type of work.

The working partnership has not only been a success on this particular project it has opened up a line of similar work applied to other industries with similar issues to solve. For Cranfield the benefits of pushing limits continue to attract bright students and additional industrial partner projects.