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1-3 Random Fiber composites

Manufactured by Smart Material

Smart Material manufactures 1-3 composites using piezo ceramic fibers as the active rods, distributed at random across the active area. The composite is made by infiltrating fiber bundles with epoxy and then dicing the resulting cube shaped blocks perpendicular to the fibers. This patented method is known as Arrange and Fill. The random distribution suppresses lateral frequency modes very effectively.

Fiber composites are a cost effective alternative to the Dice and Fill method. Fibers of 105, 250 and 800 µm diameter give fill factors of roughly 35, 65 and 80 per cent in a randomly distributed cross section.

The material performs well in ultrasound transduction thanks to its low acoustic impedance and high coupling factor, and the random spacing of the elements suppresses spurious modes better than a regular array.

Frequencies from 80 kHz to 8 MHz
PZT Navy type II
Fill factors of 35, 65 and 80 per cent
Maximum size 8 cm by 8 cm, larger and curved parts on request
A choice of epoxy and polyurethane interstitial materials
Operating temperatures up to 135 ℃
Gold or copper tin electrodes

Product specifications and options

Property	Range
Resonance frequencies	80 kHz to 8 MHz
Fill factors	35, 65 and 80 per cent
PZT materials	PZT Navy type II
Acoustic impedance	12 to 27 MRayl
Electrodes	CuSn (copper with a tin flash layer) or Au (gold)
Dimensions	Up to 100 x 100 mm, and a range of round diameters
Coupling coefficient kt	0.61 to 0.68, subject to the fiber diameter and frequency aspect ratio
Operating temperatures	Typically 95 ℃, or 135 ℃ on request
Interstitial materials	A range of epoxy systems

By frequency

Frequency	Fiber diameter	Fill factor	Dimensions (mm²)
80 kHz to 1 MHz	105, 250 and 800 µm	35, 65, 80%	max. 100 x 100
1 to 5 MHz	105 and 250 µm	35, 65%	max. 100 x 100
5 to 8 MHz	105 µm	35%	max. 100 x 100

Frequency tolerance is typically ±10 per cent, and ±5 per cent on request. All sizes are made to order.

By fill factor

Fill factor	Fiber diameter	Frequency range
35%	105 µm	80 kHz to 8 MHz
65%	250 µm	80 kHz to 5 MHz
80%	800 µm	80 kHz to 1 MHz

Acoustic impedance

Fill factor	Acoustic impedance
35%	12 MRayl
65%	22 MRayl
80%	27 MRayl

Electrodes

Electrode	Frequency range
CuSn	80 kHz to 1 MHz
CuSn or Au	1 to 8 MHz

Maximum dimensions

Maximum size	Frequency range
100 x 100 mm	80 kHz to 5 MHz
65 x 65 mm	5 to 8 MHz

Mechanical tolerances: ±0.1 mm below 6 mm, ±0.2 mm below 30 mm, ±0.3 mm above 30 mm.

Best coupling coefficient by fiber diameter

Fiber diameter	Maximum frequency for the best kt
105 µm	8 MHz
250 µm	4 MHz
800 µm	1 MHz

Available diameters

Diameter	Inches	Diameter	Inches
3.18 mm	0.125″	12.70 mm	0.500″
5.12 mm	0.202″	14.20 mm	0.559″
5.18 mm	0.204″	15.90 mm	0.626″
5.68 mm	0.224″	17.50 mm	0.689″
6.00 mm	0.236″	18.00 mm	0.709″
6.50 mm	0.256″	19.05 mm	0.750″
8.20 mm	0.323″	20.00 mm	0.787″
9.00 mm	0.354″	24.00 mm	0.945″
9.50 mm	0.374″	25.40 mm	1″
10.00 mm	0.394″	30.00 mm	1.181″
10.20 mm	0.402″	35.00 mm	1.378″
12.00 mm	0.472″	37.7 mm	1.48″

Typical ultrasound applications

Non destructive testing
Sonar, single element transducers
Air ultrasound transducers
Flow control and measurement

Because of the Arrange and Fill method, the raw material arrives as blocks up to 10 cm long with the lateral dimensions of the target element.

Shaped composites

As well as slicing elements to the resonance frequency you need, the Arrange and Fill method allows the raw block to be machined into other shapes, including precise concave and convex contours for broadband ultrasound receivers.

The method scales easily to volume, which keeps lead times short. That is a significant advantage over the more common Dice and Fill method.

Smart Material offers a range of standard epoxy and polyurethane systems as the interstitial material, allowing operating temperatures between 95 and 135 ℃.

A plano concave element.

Specify a composite with us

Send us your frequency, fill factor and size and Smart Material will quote for a composite built to that specification.

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