Pultrusion Process for Flexible Spinal Implants
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Solution Overview
Problem
Existing pultrusion processes produce thermoplastic composite materials with high percentages of continuous fibers, resulting in rigid materials unsuitable for flexible spinal implants due to the high fiber content required for the process.
Innovation Solution
A pultrusion process that braids or wraps reinforcing fibers with strands of matrix material having a lower melting point, allowing for a reduced percentage of continuous fibers (10-45% by volume) to produce a more flexible composite material, enabling the composite to be pulled through a heated die while maintaining sufficient strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high percentage of continuous reinforcing fibers is used in the pultrusion process, then the composite material has sufficient strength to be pulled through the heated die, but the composite material becomes too rigid for spinal implant applications
Solution Approach 1:
The reinforcing fiber structure is segmented into discrete bundles spaced at intervals along the composite, rather than using continuous high-volume fibers. This segmentation allows the composite to maintain strength at fiber pull-out points while enabling flexibility between bundles, resolving the contradiction between strength and flexibility for spinal implant applications.
Solution Approach 2:
The invention uses a composite structure combining discrete fiber bundles with a thermoplastic matrix material. This composite approach allows optimization of both phases: the fiber bundles provide localized strength while the thermoplastic matrix provides flexibility and ductility, achieving both strength and flexibility requirements simultaneously.
2Ease of operation
If a low percentage of continuous fibers is used in the composite, then the composite material has increased flexibility, but the composite material lacks sufficient strength to be pulled through the heated die
Solution Approach 1:
The fiber bundles are pre-formed and positioned at specific intervals before the pultrusion process. This preliminary arrangement ensures that strength is provided exactly where needed (at pull-out points) without requiring high overall fiber volume, enabling both flexibility in the bulk material and sufficient strength for processing.
Solution Approach 2:
The invention changes the parameter of fiber distribution from continuous high-volume to discrete low-volume bundles. This parameter change transforms the mechanical properties: the composite gains flexibility due to lower overall fiber content while maintaining processing strength through strategic bundle placement at intervals along the length.
3Strength
If continuous reinforcing fibers are used throughout the composite, then the composite material has high tensile strength, but the material becomes unsuitable for flexible spinal implants
Solution Approach 1:
The continuous fiber reinforcement is segmented into discrete bundles spaced at intervals rather than distributed continuously throughout the composite. This segmentation provides tensile strength at specific locations (where bundles are placed) while allowing the thermoplastic matrix to provide flexibility and adaptability in regions between bundles, making the material suitable for spinal implant applications requiring both strength and flexibility.
Solution Approach 2:
The reinforcement is applied with local quality: discrete fiber bundles are positioned at specific locations along the composite rather than uniformly distributed. This allows different regions of the composite to have different properties - high strength at bundle locations and high flexibility in matrix-dominated regions - enabling adaptability for spinal implants while maintaining necessary tensile strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process results in a more flexible composite material suitable for spinal implants, offering increased flexibility and controlled mechanical properties, such as strength and flexibility profiles, essential for medical applications like spinal implants.
Implementation Method 1
strands of matrix material having a lower melting point than a melting point of the continuous reinforcing fibers... heated curing die that melts the matrix material wrapped about the reinforcing fibers
Implementation Method 2
directed through a heated curing die that melts the matrix material wrapped about the reinforcing fibers
Data Source
AI summary
An improved pultrusion process for preparing composite materials having about 10 percent to about 45 percent by volume of reinforcing fibers so as to produce a composite material having enhanced flexibility as compared with composite materials having a higher percent of reinforcing fibers by volume. Articles of manufacture made from composite material produced by the improved pultrusion process, specifically spinal implants, are also provided.