Bi-metal Z-pin thermal locking for composite delamination
Solution Overview
Problem
Traditional Z-pins, including both cylindrical and shaped types, face difficulties in insertion into composite laminate structures without damaging the fibers, which affects the structural integrity due to their shape and size, and existing solutions do not effectively address the need for enhanced mechanical locking in the z-direction.
Innovation Solution
A Z-pin featuring bi-metal structures with differing coefficients of thermal expansion, which deform during the curing process of the composite laminate structure, transforming from a traditional geometry to a mechanically locking shape, thereby enhancing the locking mechanism within the composite matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shaped Z-pins are used to increase mechanical locking performance, then the locking capability in the z-direction is improved, but the insertion process causes fiber damage affecting structural integrity
Solution Approach 1:
The Z-pin is inserted in a preliminary straight configuration when the composite is in pre-preg state with soft pliable resin, avoiding fiber damage. After curing, thermal expansion transforms the pin into a shaped configuration that provides mechanical locking. This preliminary action allows insertion without damage while achieving the desired locking capability.
Solution Approach 2:
The invention changes the physical state and shape of the Z-pin through temperature parameter changes. During curing, thermal energy causes the pin to expand and transform from a straight inserted shape to a shaped locking configuration, thereby achieving enhanced mechanical locking without causing fiber damage during insertion.
2Ease of manufacture
If traditional cylindrical Z-pins are used for insertion, then the insertion process is simpler, but the mechanical locking performance in the z-direction is insufficient
Solution Approach 1:
The Z-pin transitions from a static cylindrical shape to a dynamic shape-changing component. During curing, the pin dynamically transforms from a straight configuration (easy to insert) to a shaped configuration (provides locking), combining the advantages of both simple insertion and enhanced mechanical locking performance.
Solution Approach 2:
Temperature parameter changes during the curing process trigger the transformation of the Z-pin from a simple cylindrical shape to a complex shaped configuration, enabling the pin to achieve enhanced mechanical locking capability while maintaining ease of insertion in its initial state.
3Strength
If shaped Z-pins are inserted into pre-preg laminate, then mechanical locking is improved, but fiber damage occurs during insertion affecting structural integrity
Solution Approach 1:
The Z-pin is inserted in a preliminary straight configuration when the composite is in pre-preg state with soft pliable resin, avoiding fiber damage. After curing, thermal expansion transforms the pin into a shaped configuration that provides mechanical locking. This preliminary action allows insertion without damage while achieving the desired locking capability.
Solution Approach 2:
The invention converts the potential harm of shaped pin insertion (fiber damage) into a benefit by using the curing heat to transform the pin shape after insertion. The thermal energy that could cause unwanted effects is instead utilized to create the locking shape, eliminating fiber damage while maintaining mechanical locking capability.
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 bi-metal Z-pin effectively increases the mechanical locking performance in the z-direction by deforming and locking into the composite matrix during curing, improving the structural integrity and resistance to delamination without causing fiber damage during insertion.
Implementation Method 1
where curing the composite structure causes the Z-pin to bend as a result of the difference in the coefficient of thermal expansion between metal strips in the structures
Data Source
Figure 1~4
AI summary
A Z-pin (10) including a first bi-metal structure (12) having a first metal strip (18) and a second metal strip (16) bonded together, where the first and second metal strips (18,16) have different coefficients of thermal expansion, and a second bi-metal structure (14) having a third metal strip (22) and fourth metal strip (20) bonded together, where the third metal strip (22) and the fourth metal strip (20) have different coefficients of thermal expansion. The first and third metal strips (18,22) are selectively secured together at at least one discrete location (24) so that heating of the Z-pin (10) causes the first and second bi-metal structures (12,14) to deform relative to each other. The Z-pin (10) is inserted into a composite laminate structure (40) while it is in its uncured state, where curing of the composite structure (40) causes the first and second bi-metal structures (12,14) to deform relative to each other to lock the laminate layers (42) together.