Layered Composite Spinal Brace Rod for MRI-Safe Rigidity
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Solution Overview
Problem
Metal fixture rods for spinal fixation suffer from magnetic interference during MRI imaging, image disturbance, reduced rigidity, and safety concerns due to exposed fibers upon breaking.
Innovation Solution
A fixture rod composed of alternating layers of reinforcing fiber layers and resin layers, utilizing carbon, glass, boron, SiC, or aramid fibers with epoxy, phenol, unsaturated polyester, etc., and aligned or randomly oriented fibers to enhance rigidity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metal is used for fixture rod, then fixing force and strength are improved, but magnetic field interference occurs during MRI imaging
Solution Approach 1:
The fixture rod uses a composite structure with a polymer core and polymer coating, replacing metal materials. This composite material approach maintains mechanical strength while eliminating magnetic field interference during MRI imaging, as polymers are non-magnetic materials that do not affect magnetic field distribution.
2Ease of manufacture
If fiber density is lowered in polymer rod, then manufacturing is easier, but rigidity and durability are reduced
Solution Approach 1:
The invention optimizes the fiber density parameter within a specific range (30-70 wt%) to balance manufacturing ease with mechanical performance. By controlling fiber content and distribution parameters, the rod achieves sufficient rigidity and durability while maintaining manufacturability through standard composite processing techniques.
Solution Approach 2:
The polymer coating layer provides localized protection and functional properties on the surface, while the core contains fibers for structural strength. This local quality differentiation allows the outer layer to protect the fiber structure while the inner core provides mechanical rigidity, optimizing both manufacturing and performance.
3Ease of manufacture
If fiber density is lowered in polymer rod, then manufacturing is easier, but spinate fibers are exposed at breaking time
Solution Approach 1:
The composite structure with polymer coating encapsulating the fiber-containing core prevents fiber exposure upon breaking. The polymer matrix and coating layer act as containment structures that hold fibers together even when the rod fractures, eliminating the safety hazard of exposed sharp fibers while maintaining ease of manufacturing.
4Strength
If alternating layers of reinforcing fiber and resin are used, then rigidity and durability are improved, but device complexity increases
Solution Approach 1:
The rod is segmented into alternating layers of reinforcing fiber and resin, with each layer having a thickness of 0.01-0.5 mm. This segmentation allows each layer to contribute specific mechanical properties, achieving high rigidity and durability through the cumulative effect of multiple thin layers while using standard lamination manufacturing processes.
Solution Approach 2:
The multi-layer composite structure combines different materials (reinforcing fibers and resin) in alternating layers to achieve superior mechanical properties. This composite approach distributes stress across multiple interfaces and materials, enhancing overall strength and rigidity while using established composite manufacturing techniques.
Data Source
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AI summary
A fixture rod that reduces damage at the time of fixing with a screw, has high rigidity and high durability against a deformation load, and has greatly improved safety even at the time of breaking, is to be provided. A fixture rod according to one embodiment of the present invention comprises a plurality of layers of a reinforcing fiber layer and a plurality of layers of any one of a resin layer, a reinforcing fiber layer having fibers different from those of the reinforcing fiber layer, and a reinforcing fiber layer having fibers obliquely oriented with respect to a fiber direction of the reinforcing fiber layer, in which the plurality of layers are each alternately formed as viewed in a cross-section.