Powershell: Add objects to an array of objects
To append to an array, just use the += operator.
$Target += $TargetObject
Also, you need to declare $Target = @() before your loop because otherwise, it will empty the array every loop.
Typically people do this without using the inefficient "+=" that makes a new copy of the array every time:
$Target = foreach ($Machine in $Machines)
{
$TargetProperties = @{Name=$Machine}
$TargetObject = New-Object PSObject –Property $TargetProperties
}