Composite Shear Testing Device with Adjustable Shear Plane
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining the interlaminar shear strength of composite materials, such as the short bending test, often result in impermissible stress concentrations and bending failures due to compression stresses, limiting the ability to select shear planes and compare different materials effectively, and require specific sample geometries.
Innovation Solution
A device with a movable upper base body and stationary lower base body, coupled by guide rods, allows for adjustable shearing planes and sample sizes, enabling the application of a test force while measuring displacement to determine interlaminar shear strength and shear modulus, with support plates and pressure plates ensuring even force distribution and sample alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the short bending test is used to determine interlaminar shear strength, then a standardized method is available for quality assurance, but compression stresses from support fins and fixtures generate impermissible stress concentrations and bending moments that exceed material strength before interlaminar shearing occurs
Solution Approach 1:
The invention extracts and removes the harmful support fins and fixtures from the testing system. Instead of using traditional three-point bending fixtures with support fins that generate compressive stresses, the patent employs a pure shear configuration where the specimen is loaded directly in shear between two parallel plates, eliminating the source of stress concentrations and bending moments that cause premature failure
Solution Approach 2:
The invention inverts the loading approach by applying pure shear loading directly to the specimen rather than using indirect bending loading. Instead of bending the specimen and hoping for shear failure, the system directly applies shear forces through parallel plate loading, reversing the conventional approach to achieve the desired failure mode without harmful side effects
2Measurement precision
If the short bending test is used with fixed sample geometry ratios, then consistent comparison between materials is possible, but the sample geometry is restricted and cannot be freely selected
Solution Approach 1:
The invention creates a universal testing system that can accommodate various sample geometries and configurations. The parallel plate shear fixture design allows testing of specimens with different dimensions, orientations, and configurations without requiring specific geometry ratios, making the system multi-functional and adaptable to different material types and sample preparations while maintaining measurement consistency
3Adaptability or versatility
If the Compression Shear Test (CST) is used with adjustable cutting edges, then any sample size can be tested, but the ratio of sample height to sample width cannot be arbitrary or too large to avoid pressure failure instead of shear failure
Solution Approach 1:
The invention removes the lever arm mechanism and cutting edge configuration from the CST that creates compressive pressure zones. By using direct parallel plate shear loading without mechanical leverage, the system eliminates the pressure concentration that causes compressive failure, allowing any sample height-to-width ratio to fail in shear rather than compression
Solution Approach 2:
The invention changes the fundamental loading parameter from compressive shear (CST) to direct shear loading. By altering the stress state from a combination of compression and shear to pure shear, the system changes the failure criterion, allowing specimens with various dimensions to fail in shear without the compressive stress component that causes pressure failure in traditional CST
Data Source
Figure 1a
Figure 1b
AI summary
Apparatus and method for determining the interlaminar shear strength and shear modulus of fiber-reinforced plastic laminates, comprising a movable upper base body and a stationary lower base body, wherein a sample is positioned in a sample chamber and support plates are provided laterally to the sample and parallel to the shear plane, wherein the shear plane is arbitrarily adjustable over the entire thickness (d) of the sample, wherein the support plates are movable independently of the upper base body or the lower base body by means of guide rails.